How To Obtain Layout Approval And Building Plan Permit For Your Estate - Engr. Osaz’ ENOBAKHARE

Having a Global C of O for an estate is not the same as an approval for that estate as unsuspecting property shoppers are often cajoled to believe. The Global C of O like every other land titles actually pertains to the land not necessarily the structures or activities on that land. Some estate owners are either unaware of this fact or choose to deliberately ignore it thereby putting subscribers at a great financial and ownership risk. There are reported cases where built-up Estates have been demolished due to lack of estate layout approval and building permits and people have lost millions and their beautiful homes. To secure a full estate layout approval and building permit for your estate (especially in Lagos), follow these simple steps;

-         Get a perimeter survey – a perimeter survey will capture the distance round that estate from a reference point back to that point. It will ultimately show the total area of the estate as well as the length, breadth and overall shape of the estate land including adjourning features like roads, water bodies, etc. The survey is prepared by a Land Surveyor. Traditionally all survey plans are lodged at the office of the surveyor-general. In order to regularize this survey, you will be required to pay certain processing fees; part of which will be used to obtain the beacon sheet from the relevant office. The perimeter survey is needed for the next stage which is to plot out the estate layout.

-         Plot the estate layout – every estate should have a layout. This layout shows the entire positioning and arrangement of structures and infrastructure on the estate land together with the topography and other essential features. It is traditionally the function of a Town Planner to prepare this document. The Estate Layout is different from an Estate Plan which is prepared by an architect. In a typical layout drawing, you see various blocks carrying different colors each having a distinct meaning. Medium-density zones are so identified, so are low-density and high-density areas. The same also applies to core residential zones, commercial and mixed areas. After preparing the layout, the next phase will be to submit the layout for government approval.

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-         Submit the layout drawings for approval – Once the layout is submitted for approval, it goes through a process of scrutiny to determine whether the purpose of use of the land is in sync with the already established zoning requirement. The arrangement of spaces within the estate is also checked for consistencies with established planning regulations in that city. If there are discrepancies, it might not be approved. Occasionally, it is returned for corrections or adjustments. If successful, the estate is now officially recognized. Next line of action will be to apply for building approval/permit. To get this process underway, you would have to prepare the required designs.

-         Prepare the architectural and engineering drawings – You would have to engage a registered architect in preparing the architectural drawings of the entire buildings in the estate. He would be required to apply his/her ARCON stamp and seal to the drawings as so required. Then the structural engineer will prepare the structural drawings. He would present it along with a letter of supervision or engineering report where applicable. A professional builder can also present a letter of supervision with regards to building projects with his/her CORBON seal affixed. The other engineering drawings are prepared by the relevant engineers usually the Mechanical and Electrical Engineers. A comprehensive soil test report from which the structural design would derive basic foundation design parameters would also be required.

-         Submit your building drawings for approval - Armed with all the relevant building drawings, signed, stamped and sealed, you approach the planning authority to obtain approvals. You will be required to pay processing and approval fees. In the course of this approval, all the drawings would be scrutinized for consistencies with the relevant codes of practice and statutory regulations. A physical inspection of the site would also be carried out. The aim will be to compare the paper work with actual site conditions. If satisfied, an approval will be given with an approval number issued. Where the estate has been partially or fully developed prior to filing for approvals, an engineering report will be required which will certify that the buildings are fit for habitation after a non-destructive integrity test ‘’NDT’’ has been carried out. 

It is very important to obtain the layout and building drawings and approvals for your estate in order to avert the risk of losing your property. You can contact the author for further discussions.

Why It Is Important To Conduct A Soil Test (Investigation) Before Construction - Engr. Osaz’ ENOBAKHARE

Most structures are earth-laid and it’s in your best interest to know what the earth feels about what you are about to construct over it. If you really don’t care and the earth doesn’t feel good about your ideas, you are heading for disaster. Investigating the condition of the sub-soil upon which a structure will be built is a process that should not be undermined and must be carried out diligently. Every building is supported by a foundation, making it about the most important component of a building. The foundation itself, no matter how strong could be unreliable if it does not sit firm on the ground hence the need to understand where and how best to place it.

The process of determining how the earth would accommodate the foundation first begins with carrying out a sub-soil investigation. It goes by the saying ‘what you don’t know can kill you’; for instance, if you don’t know that at 1-metre depth the subsoil on your land is too weak to support your proposed structure and you go ahead to place your foundation there, the result is likely going to be disastrous. 

Soil test for construction purposes, otherwise referred to as sub-soil investigation is different from the process carried out to test the biological and chemical properties of a soil in order to know if it can accommodate the growth of certain plant species; ofcourse not! It actually involves the physical examination of the soil from layer to layer to determine its type, density, strength characteristics (bearing capacities), consolidation potentials, rate of soil settlement, water table and other relevant data. This information is useful to guide the structural Engineer in determining the most suitable type of foundation to support the proposed structure, the most suitable depth to terminate it and the overall design of the foundation. The test also helps predict problems that may arise during and after construction and how they can be properly dealt with.

Usually as the major scientific step before construction, geotechnical information from soil investigation also helps in determining a more reliable construction cost estimate for a proposed project. On live projects, a simple soil investigation can influence a foundation design that can put the cost of construction significantly in excess of what was originally budgeted; hence the need to conduct a soil investigation before arriving at any meaningful construction budget especially in a joint venture (JV) or concession arrangement. 

In Nigeria, a standard soil test report prepared by geotechnical personnel is a pre-requisite for structural design approval especially for buildings that consist of more than one floor. The most common soil tests for building projects back here are the Dutch-Cone Penetrometer Test (DCPT) and the Cone Penetrometer Test (CPT). While the former is quite simple; can be concluded on-the-spot within a few hour and is mostly useful for buildings not more than two-floors, in the latter a rig is deployed, it is more comprehensive and would normally require laboratory analysis of samples taken from site. It is standard practice to test at least two points per plot of land for DCPT and at least one trial pit and borehole of CPT on the same size of land. 

A standard soil test report consists of a soil profile showing the various layers of soil and their physical and geotechnical characteristics. It would normally show the procedure adopted in the carrying out the test together with graphical and numerical data both from on- the-field results and those computed based on established empirical formulae. In the end, the geotechnical personnel or structural engineer is able to ascertain whether or not a shallow or deep foundation is okay to sustain the proposed structure. Most report would enlist a range of suitable foundation types based on the information available on the size and load characteristics of the proposed structure. 

Combining Raft And Pile Foundation On The Same Structure Can Save Cost - Engr. Osaz’ ENOBAKHARE

Anything to reduce cost and still maximize benefits goes in today’s world. Sometimes we find ourselves with only a few options but we can still explore them. Unlike short bored piles, constructing deep piles are normally expensive compared to raft foundations because not only would the piles be installed using various machines or equipment they usually will have large caps and beams constructed over and connecting them respectively. Therefore when cost becomes an issue you can find an acceptable way to run the race and win the prize. Where practically possible and technically okay, a combination of two or more foundation types can be adopted. In practice both raft and pile foundation can be used together on the same structure to achieve a foundation that performs excellently under load and still reduce overall cost and when you choose this option, there are several factors to take into consideration.

For instance you intend to put up a block of 8 flats on four floors; 2 flats per floor and your soil test report allows you to combine pile and raft foundations dependently or independently without necessarily specifying where either of the two should be used, you can in agreement with your engineer/builder opt to use pile on one wing and raft on the other. In other cases, project owners who intends to build semi-detached duplex and bungalow together or semi-detached duplexes or terrace houses or even two separate buildings lying side by side to each other can use a combination of pile and raft foundations perfectly. The type of foundation arrangement discussed here is not the same as combined Pile Raft Foundations (CPRF) which is achieved by constructing raft over existing piles instead it is about the use of two different foundation types in different locations on the same building or buildings sitting close to each other on the same land.  However in any case, it is important to follow the lead of the soil investigation before venturing.

To get the procedure right, basically obtain a geotechnical report (soil test) to know the soil strata and bearing capacities at various depths. Pre-inform the geologist or structural engineer handling your soil test of the type of structure and your intention to combine raft and pile foundation so they can compute various strength characteristics in line with your option. A lot of technicalities are involved in the combination of these two types of foundation especially for the same building but engaging a professional structural engineer will make the work look very easy and the resultant cost reduction is amazing!  For instance the interaction between both foundation elements and the subsoil to achieve maximum functionality are primarily hinged on the characteristic pile and base resistance to load and against settlement hence the foundation must achieve resistance that is sufficient enough not to fail or settle excessively or inordinately at any given time. Also, the internal and external bearing capacities of both foundation elements which border largely on strength of materials used and bearing pressures exerted on, by and around the foundation respectively should be properly analyzed. If you get your procedure right you would have cut some 20% off your foundation cost and that’s huge savings especially on a large scale.

Converting an Office Complex to an Enveloped Shopping Mall: Thinking Aloud!

      Converting an Office Complex to an Enveloped Shopping Mall: Thinking Aloud!

                                                                                  Engr. Osaz’ ENOBAKHARE

As towns metamorphose into cities and cities develop into mega cities, the quest to create decent shopping malls continue to rise. The advantages a shopping mall over a regular market is huge ranging from the presence of co-ordinated ample parking spaces to giving shoppers the extra opportunity to shop and get entertained at the same time. Truly, the ever soaring mall culture has made owning a mall a big business not only in Nigeria but the world over. Most shopping malls have a collection of shops, stores, restaurants, cinemas, services outlets (e.g. e-banking outlets), etc. offering a wide range of affordable products and services to a vast number of people in a more convenient ’cashless’ manner and fit perfectly into densely populated residential as well as commercial areas. Modern (enveloped) shopping malls class themselves higher than the traditional open shopping complexes because of their envelope design that allows for central cooling of all the shops or outlets throughout the day as well as proximity advantage for quick shopping in the building.  Generally shoppers feel a sense of peaceful ambience and safety in enveloped shopping malls than the traditional type.  

There is still a huge shortage of enveloped shopping malls across towns and cities in Nigeria and the demand is relatively high. Viral pictures taken and shared by mall users during weekends and festive seasons which normally show crowd rush only provide more evidence to this assertion.

 

Recent industry estimates have showed that the financial returns developers derive from owning classy multi-occupier shopping malls are now scaling higher than what obtains from an office complex of the same size in the same location. This is forcing more and more developers to think aloud on converting existing office buildings or spaces existing in shopping hotspots into ultra-modern shopping malls.

Converting an office building into an enveloped mall like other conversion projects would first require that a thorough assessment is carried out on the building to identify its load-bearing and non-load bearing components. Sometimes, it becomes imperative to conduct an integrity test on the major structural components of the building to ascertain their current strength parameters (especially if it is an old structure) as naturally, shopping malls are designed to accommodate more live loads due to heavy human traffic and movement of heavyweight goods and furniture than typical office buildings.

The way office buildings are partitioned is quite different too, hence the need for very detailed conversion architectural and engineering designs which may compel the use of shoring techniques to reposition some load-bearing columns, beams and walls.  Attention must equally be given to the use of high quality aesthetic interior and exterior finishes as a selling point. For enveloped malls, there is often the need to redesign and reconfigure the entire lighting and cooling systems as well as the transport mechanism within the building too. The conversion process demands paying attention to a lot of details but once the mall is set, everybody smiles.

Roofing: When The Roof Load Becomes An Issue - Engr. Osaz’ Enobakhare

‘Wear the cap on whom it fits’ so the saying goes. There is a lot of sense in this one and a real good line of thought too.  Although caps cannot stop you from getting wet under the rain, your roof can. Caps are better worn on whom they fit and so should roofs be. The passion for sky-scrapping roofs suddenly envelope nearly all classes of players and participants in the built environment back here and the aesthetic impression it gives to a building quickly blindfolded many to its structural implications. Now some bungalows have roofs that are five times as high as the building frame itself.  Likewise, the crave for curvy, straight-stepped and composite parapets built mostly of reinforced concrete made a mockery of traditional wooden fascia that normally flushes with external asbestos ceiling that was the norm up to the mid 90’s.

Apart from preventing direct exposure to external weather conditions, roofs are important structural elements of buildings. They constitute a significant fraction of the entire load of the structure and must be well designed so that they do not portend danger to the overall strength and stability of the building. For instance, roofs are designed to be structurally able to withstand wind loads (weight imposed on the roof from wind pressure forces) and ice load too (in country where this is applicable). Hence they have to be strong enough to perform these functions but that should not mean that a roof should become too heavy.

Some people do not take cognizance of the roof load implication on the foundation to which it is transmitted and with time, the roof load begin to take its toll on the foundation causing it to experience excessive settlement or failure. The roof carcass and parapet are very integral parts of the roof load that have heavy members. The combined load of a timber roof carcass and parapet for a residential building can reach up to 1kN/sqM. That is almost equivalent to 2 bags of 50kg cement on every square meter of the roof. Now that’s a lot!

An overweight roof is often a disaster! It is therefore generally advisable to reduce the load of the roof so as not to impede on the structural efficiency of the building. To achieve this, the use of light-weight yet rugged parapet fascia (e.g. wired polystyrene, aluminum, etc.) as well as using light-weight roof carcass (like treated timber, light steel, etc.) and fitting them in such a way as to deliberately reduce the weight on the structure. Where reinforced concrete is to be used, light-weight (aggregate-less) concrete with damp-proof membrane could be used.       

The Danger of open excavation near your foundation - Engr. Osaz' Enobakhare

There is naturally a danger of having an open excavation anywhere at all; from being a dirt trap to becoming a death trap hence protection of open excavation is a compulsory item in basic construction practice. On typical construction sites, it is often the responsibility of the Safety Engineer to enforce such vital regulation on site. They would go hard on any worker who do not obey this regulation due to the numerous potential dangers; but what happens when the site is now built up, handed over, the ‘dreaded’ safety Engineers are gone, and someone excavates close to the foundation and leaves it open? No doubt, there is equally a latent danger in having an open excavation near a foundation. Here is why –Foundations relate with the subsoil on which they are built and around them by constantly pushing against the active soil pressure in a relatively balanced manner in order to remain stable throughout their life span. If there is a substantial counter balance from either of the foundation itself or the supporting earth at any point, it will impede on the stability of the foundation and might cause it to settle (or sink) rapidly.

The rapid settlement of some defective buildings studied over the years is a result of fully or partially-open excavation at close distance to the foundation. Open excavations up to 4-metres from the foundation line can still affect your foundation depending on the soil strata. When there is an excavation near a foundation, the active soil pressure acting on the foundation at that region reduces, causing the soil to slip. Subsequently when there is natural earth movement, it drops further, making the foundation not to hold firm to the ground. If not checked on time, the vertical load of the building acting on it would cause the building to settle at that region and further apart. Although there is nothing particularly wrong in having an excavation close to a foundation but care must be taken to ensure that the walls of the excavated areas are protected or embarked to stay the adjourning earth and prevent the devastating impact on the neighboring structure especially if such structures are on shallow foundations (i.e. foundations of 5-metres or less in depth from natural ground level mostly raft, strip, pad, etc.). Such impact could also include poor resistance against ground vibrations and burrowing by small animals that may attack foundation walls.  

Reinforced Concrete can be used in protecting the walls of an excavation close to a foundation but it is important to construct them properly else they fail to serve the purpose intended. Where a tree is fell close to a foundation, it is important to refill the excavated portion and stabilize the earth firmly at that point. Leaving an open excavation close to a foundation unattended to also allows it to collect surface water which might constantly soak-away into the foundation and damage its fabric rapidly. This is particularly the case where due to low water table a traditional ‘block’ strip foundation was used. Whichever way it is advisable not to allow especially deep open excavation close to your foundations to prevent foundation cracks and the attendant regrets!

Pile Foundation: What Can Make A Pile Fail - Engr. Osaz’ ENOBAKHARE

Foundations are vital elements of earth-laid structures because they support and transmit the entire load of that structure to the earth. Of all foundation types, deep foundations are often considered the safest and most appropriate especially where cost factor cannot be allowed to take prominence. Pile foundations are the commonest of all deep foundation types and they are very critical because of their depth and size; they are relatively slender compared to the overall size of the structure and they go as far below the natural ground level as where there is suitable bearing capacity –reaching beyond 50-metres for some high-rise buildings. Piles with circular cross-section are very popular in the industry and the usual width (or diameter) lies between 300 – 600mm.  In Nigeria, reinforced concrete cast in-situ (bored) piles are common compared to driven piles because it is considered less expensive. The cost involved in driving a pre-cast reinforced concrete pile into earth is about a quarter times higher than for cast in-situ piles and then the technicalities involved.

Because piles are a sort of stand-alone foundation and are mostly designed to carry very heavy loads, it is often advisable to test their load bearing capacities before building over them. The common tests for piles are the Pile Load (PLT) and Pile Integrity Tests (PIT). These tests are not only relevant for the purpose of structural analysis; they also provide useful information about the composition of the pile throughout its length. The construction of pile foundations and testing of same are best carried out by professional structural engineers. However, due to ignorance or negligence, some project owners either outsource their piling works to random borehole drillers who are mostly skilled in water works with little or no idea on the dynamics of piles or do not carry out appropriate tests on their piles even after taking such unreasonable risk.

Shit happens and piles fail too. There are many reasons why this occurs but of all, poor construction and faulty arrangement of piles are the commonest. If a pile is not constructed properly, for instance the mix ratio or provision for reinforcement in a reinforced concrete pile is not in tandem with what was stated in the structural design; the end result might be a weaker pile. Also, if the mix ratio is adequate but the concrete was not properly loaded into the borehole, the pile may have sizable gaps and pores and lines of weaknesses may result from it. Likewise if a pile is designed as a friction pile but constructed as end-bearing, it might become surplus to requirement. There are reported cases where deliberate attempts were made by unscrupulous constructors not to reach the specified depth in a bid to cut corners. This is not a healthy practice and might not help the pile reach its desired strength. When constructing bored piles without casement and sufficient care is not taken to avoid excessive backfilling before loading concrete, the result might be a shorter or a soiled pile and that is not a good one. There are other factors like faulty designs, poor supervision, poor mixing of concrete and the use of sub-standard materials especially with regards to the tensile strength of steel rebars, dirty aggregates and foul water etc. 

For driven piles, if the blow (hit) from the pile hammer on the pile head generates excessive vibrations and stresses down the pile, the pile may lose strength.   Pile failures can be devastating to a structure as failure of a single pile can lead to a partial collapse of a building, hence the need to build it right all the time

How To Construct Floating Helical Staircase In Buildings - Engr.Osaz' Enobakhare

You can beat this only if you can. It’s staircase on a whole new level – the floating helical stairs; with long splay bearing and virtually no support in between. An amazing piece for style and functionality; helical staircases can redefine a space and give it the meaning and respect it truly deserves. There is not much of a big deal in the construction of this fanciful type of staircase but if you miss it somewhere, down it goes and it takes the user with it to the ground and that’s a disaster! The rate of failure of helical stairs is known to be higher than several other types of stairs and this is because they are mostly self-supporting or ‘floating’.

Helical stairs are made from several types of materials, mostly reinforced concrete, metal, glass, timber or a combination of any of these. Whichever primary material is used, the principle remains the same. Most helical stairs are fixed at both ends with beams running from end to end throughout the splay and the other sides into a load-bearing element which transfers load from the thread on to the beams and then to the fixed ends.

Essentially, stairs help as a transit line from one floor/level in a building or structure to another. In order to effectively perform this function; they must be strong and stable. They must be able to support users well enough without excessive vibration and shear throughout the effective life span of the structure. The finishes on stairs should be non-slip and able to withstand various temperature changes, moisture, impact, wear and tear, and provide good resistance to fire as they are preferred over typical spiral stairs in cases of emergency. The expected traffic on a stair technically affects its design; helical stairs designed for residential buildings are quite different in structural design than those for public use. For instance, the provisions for reinforcement will be at par with loading requirements which are normally higher for public facilities than private ones. Generally stairs are designed to be rigid.

The process of constructing a reinforced concrete helical stairs involves first carrying out a design where this has not been done prior. The architectural design shows the form and pattern of the stairs and guides in the construction of the formwork while the structural design and analysis shows the provision for and arrangement of reinforcement as well as required concrete mix.

Next the base of the staircase is marked out at the point of installation for cast in-situ and any given point within a work area for pre-cast. The carpenter builds the formwork from end to end; supporting them securely with props and bracing. In order to get the curves perfectly, flexible plywood or thin sheets are used; attached to timber or steel frameworks so they stay firm in position.

Concurrently, the welder fixes the rebars in place. For stairs in private residences, a provision of 4Y16 to 6Y16 top and bottom and 10mm stirrups placed at 150 – 200mm centres for the beam on the longer splay of the stairs or both sides as well as 12mm main and distribution reinforcement for thread is common. The rebars in the stair are fixed at the base and at the top landing area. In some cases it is also hinged to beams built into walls along its path to ensure rigidity. Concrete of adequate mix is poured into the formwork and left to set.

Estate Infrastructure: How to construct underground drainage channels - Engr. Osaz’ ENOBAKHARE

                              

The major function of drainage systems on adjourning road is to convey surface water to a collection point. This is to ensure that water is not allowed to collect on the road surface in order to prevent rapid deterioration and inevitable damage. In addition they normally serve to collect waste water from buildings along their path and transport them to the point where they are either treated or dumped. Open drains are common on our roads and streets back here, and unfortunately due to bad (environmental) habits or practices of road users (commuters and passerby), these drainages have become refuse collection channels creating serious blockage problems especially during the rainy season. Constructing underground drainages have the advantage of solving this problem and it generally hold sway as the most efficient and long-lasting drainage type; making it the first choice for developers who are concerned about efficient and cost-effective drainage systems for their estates

In constructing underground drainages, it is important to first study the terrain and slope relative to the ends or final point of disposal; usually this is done by an engineer or a surveyor using certain equipment e.g. leveling equipment. Then a drainage design is developed using suitable software (e.g. HydroCAD). This design although often undermined is very important because it reveals the sizes, composition and position of all the elements of the drainage system (e.g. Manhole, drain blocks, etc) in a very efficient manner based on the anticipated water flow rates, pressure-forces, energy levels and other relevant factors within the system at any given time.

Then you pre-cast the drainage blocks in a factory or yard on or off site. Reinforced concrete drainage blocks are the commonest in town and reinforcing the blocks must be done in accordance with the structural design in order for it not to fail at any time within its estimated life cycle. Most fabricators are increasingly using spiral distribution reinforcement in drainage blocks with circular cross-section. This is believed to provide a better continuous longitudinal support against tension. The drainage blocks are left for about two weeks to set and gain strength before they are transferred to the point of usage by means of a truck.

 Concurrently, setting-out is done on site and points are marked out for all items in the drainage system. Afterwards trench excavation is carried out to the required depth; usually about 2-metres. In case of ground water, adequate effort is made to rid the trench of it, to allow for proper leveling and compacting of the subsoil using a jumper rammer or a good substitute. Depending on subsoil conditions, there may be a need to remove excess poor earth and refill with hardcore and or sharp sand before compaction is done. A layer of concrete blinding up to 75mm is then placed.

The drainage blocks are lowered to their individual points on ground with the aid of a crane and locked into each other at open ends water-tightly and to manholes and other drainage elements. Openings provided on the blocks as entry points are well connected to the surface before the backfilling is done. In some cases, non-return valves and wire filters are installed at those entry points. The earth-fill over and around the blocks are well leveled and compacted to avoid surface depressions. Care must be taken not to allow debris into the drain during construction to avoid blockage.

Signage is placed at surface level to indicate that a drain passes underneath and that’s it!

How To Construct A Slab Culvert Over a Drainage - Engr. Osaz' Enobakhare

How To Construct A Slab Culvert Over a Drainage

Engr. Osaz' Enobakhare

Lagos, Nigeria.

Controlling flood is taking new dimensions. Canal-like ‘V’ drainages are taking root in many cities across the country. The advantage of utilizing less quantities of concrete and reinforcement than the regular drainage makes it cost less to construct and relatively flexible. This type of deigns allows the drain to be supported largely by the earth on its sides and bottom than its own weight. Most constructors of this type of drainage use BRC Wire Mesh as the reinforcement material in the concrete mass hence it is relatively light and not safe enough to support drain covers. Although this types of drainage using wire mesh, if not constructed properly are known to fail quickly under intense water pressure-forces. For this reason building a culvert ‘bridge’ over them to allow passage of vehicles become imperative so that the slab do not by any means bear on the drainage to avoid collapse. But the design of slab-culverts is quite different from the usual drain cover supported fully by the drainage because they would have to stand alone. To get it right, you should engage a structural engineer in designing the culvert which takes into account the expected load (or weight) the culvert will bear par functionality. Culverts designed to largely support heavy vehicles, trucks and trailers like those constructed to serve fuel/filling stations, warehouses, heavy duty parking lots and major streets are quite different from those constructed to support cars and light moving loads for small residential apartments hence the special consideration given to them.  Generally in constructing culverts, you have to;

1      Get a structural design. Set-out the area to construct it by its sides on both faces.

1     Excavate the foundation trench to the recommended depth, usually beyond the depth of the drainage.  Ensure that trench excavation is properly done so that the formwork can fit in properly. Let the trench be wide enough up to 500mm to allow for clearance (or extra space) between the earth and the formwork as well as the face of the drainage and the formwork.

     Install the formwork using timber (wood) or steel with adequate bracing. The formwork should neither lean wholly on the drainage nor the earth so that it can be removed once the concrete sets. Build the slab formwork together at once. Brace the soffit (bottom) of the slab properly so it doesn’t collapse during construction.

    Look up the structural design and fix reinforcement accordingly. Usually the foundation is constructed as a solid raft (with main reinforcement and distribution reinforcement spanning from bottom of the trench to the top in all directions) and the slab is constructed like a beam (with top and bottom reinforcement, up and down bound by stirrups) and fixed together, not like typical floor slab ‘mat’ in buildings.

    

   Prepare and place concrete of good mix into the formwork (depending on the strength requirement a mix of 1:1.5:2 is normally recommended). With the aid of a poker vibrator, vibrate the concrete in the formwork properly to avoid pores and void. Then leave to set properly before detaching the formwork. Then you are good to go

Latest Cost Estimates of Building Projects in Nigeria 2018 (Osaz'Index)

Based on popular request, your first choice contractor and construction partner, Engr. Osaz' finally brings you the latest building design and construction cost index valid for towns and cities across Nigeria, sourced from priced bills of quantities/quotes of quite a number of completed and on-going private projects, and based on wide consultations with relevant industry stakeholders especially Contractors, Quantity Surveyors, Builders, Engineers and Architects.

It is important to note that no two projects are exactly the same in scope and extent of work to be done and we hope you also know that we do not reserve the right to determine what fees or bill any contractor or professional handling any project should charge a Client or Project Owner at any time, hence the figures displayed here only serve to guide you so as to make informed decisions. 

This therefore doesn't give any contractor or project handler any particular advantage over the other as sources of estimates for this research remain confidential.  

The cost parameters has been divided into three main categories - Design, Structures & Services and Finishes.

Design - Architectural Drawings, Structural Design, Electrical Services, Mechanical Services Designs and other relevant working drawings.

Structures & Services - Foundation/Substructure works, Columns, beams, stanchions, floors, staircases, Lintel, arch, block/brick wall, steel panel wall systems (where applicable), roof carcass, roof covering, windows, doors, ironmongery, Plumbing and Electrical Installations etc. 

(The rough estimates for Structures & Services is based on the assumption that the parent wall material is made of reinforced concrete, block, brick or steel or a combination of any of them. It is also assumed that a soil test must have being carried out to determine the depth of suitable subsoil for foundation. Plumbing and Electrical installations doesn't include expensive gadgets like AC, Jacuzzi and Bath Cubicles.      

Finishes -Wall Finishes, Floor Finishes, Ceiling Finishes, Fitting, Fixtures and related items of work.

Generally, costs of finishes are largely subjective and differ with individual tastes and preferences, therefore for the purpose of this Index the cost of finishes only represent the cost of regular finishes (i.e. cement-sand rendering, plastering, normal painting, fair quality wall and floor tiles, PVC ceiling or its equivalent etc).  

The rough estimates for External works (e.g. Perimeter fencing, soak-away pit/septic tank. borehole, Interlocks or pavers, beautification, external security furniture, landscaping, etc) are not included anywhere in the list. 

Because of the level of discrepancies observed in construction bills from location to location, handlers to handlers and with differences in designs and site conditions, it was only reasonable to present Osaz'Index in a range value format as seen below.

If you need clarification about any item listed here, askEngineerOsaz'. 


Rough Estimate of 1-Bedroom Apartment (Detached Bungalow)
Spaces: 1 Bedroom, 1 Living room, 1 Toilet/Bath, 1 Terrace, 1 kitchen
Max Building Area: 50sqM
Max Height: 4m
Soil Condition: Dry Land, Suitable subsoil within 5-metres depth

Rough Estimate of 1-Bedroom Apartment (Detached Bungalow)
Spaces: 1 Bedroom, 1 Living room, 1 Toilet/Bath, 1 Terrace, 1 kitchen
Max Building Area: 50sqM
Max Height: 4m (Detached Bungalow)
Soil Condition: Water-Logged Land, Suitable subsoil within 5-metres depth

Rough Estimate of 1-Bedroom Apartment (Semi-Detached Twin Bungalow)
Spaces: 1 Bedroom, 1 Living room, 1 Toilet/Bath, 1 Terrace, 1 kitchen (Per Unit)
Max Building Area: 120sqM
Max Height: 4m (Detached Bungalow)
Soil Condition: Dry Land, Suitable subsoil within 5-metres depth

Rough Estimate of 1-Bedroom Apartment (Semi-Detached Twin Bungalow)
Spaces: 1 Bedroom, 1 Living room, 1 Toilet/Bath, 1 Terrace, 1 kitchen (Per Unit)

Max Building Area: 120sqM

Max Height: 4m (Detached Bungalow)
Soil Condition: Water-logged Land, Suitable subsoil within 5-metres depth

        

Rough Estimate of 2-Bedroom Apartment (Detached Bungalow)
Spaces: 2 Bedrooms, 1 Living room, 1 Ante-room,2 Toilet/Bath, 1 Visitor's Toilet, 1 Terrace, 1 kitchen
Max Building Area: 180sqM
Max Height: 4m (Detached Bungalow)
Soil Condition: Dry Land, Suitable subsoil within 5-metres depth

        

Rough Estimate of 2-Bedroom Apartment (Detached Bungalow)

Spaces: 2 Bedrooms, 1 Living room, 1 Ante-room, 2 Toilet/Bath, 1 Visitor's Toilet, 1 Terrace, 1 kitchen

Max Building Area: 180sqM

Max Height: 4m (Bungalow)
Soil Condition: Water-Logged Land, Suitable subsoil within 5-metres depth

   

Rough Estimate of 2-Bedroom Apartment (Semi-Detached Twin Bungalow)

Spaces: 2 Bedrooms, 2 Living rooms, 2 Ante-rooms,2 Toilet/Baths, 2 Visitor's Toilets,2 Terraces, 2 kitchens (Per unit)
Max Building Area: 250sqM
Max Height: 4m (Detached Bungalow)
Soil Condition: Dry Land, Suitable subsoil within 5-metres depth

Rough Estimate of 2-Bedroom Apartment (Semi-Detached Twin Bungalow)


Spaces: 2 Bedrooms, 2 Living rooms, 2 Ante-rooms,2 Toilet/Baths, 2 Visitor's Toilets,2 Terraces, 2 kitchens (Per unit)

Max Building Area: 250sqM

Max Height: 4m (Bungalow)
Soil Condition: Water-Logged Land, Suitable subsoil within 5-metres depth

Rough Estimate of 3-bedroom Apartment (Detached Bungalow)

Spaces: 3 Bedrooms, 1 Living room, 1 Ante-room, 3 Toilet/Bath, 1 Visitor's Toilet, 1 Terrace, 1 kitchen

Max Building Area: 150sqM

Max Height: 4m
Soil Condition: Dry Land, Suitable subsoil within 5-metres depth

        

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Rough Estimate of 3-bedroom Apartment 

Spaces: 3 Bedrooms, 1 Living room, 1 Ante-room, 3 Toilet/Bath, 1 Visitor's Toilet, 1 Terrace, 1 kitchen

Max Building Area: 150sqM

Max Height: 4m (Bungalow)
Soil Condition: Water-Logged Land, Suitable subsoil within 5-metres depth

         

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