Flooding: Turning Your Perimeter Fence into a Retaining Wall -Osaz' Enobakhare

Security and privacy are common reasons for constructing perimeter fences around a building. Some fences are simply symbolic while others are basically for defense. They also help to prevent land encroachment from neighbors which is not uncommon in this clime. However, fences can be designed to perform yet another critical function of flood control especially for buildings constructed in areas prone to flash floods, run-off waters from faulty drains, erosion, etc. This is the core functions of embankments and retaining walls including the ability to stay earth. Retaining walls hold back or fend off flood waters from entering into your compound. There are a number of designs and technologies suited for this purpose and they can be incorporated into your fence wall and not necessarily constructed separately; saving cost and space in the end.

Generally, aesthetics is valued from outside in, not necessarily inside out. Therefore the perimeter fence and gate of our houses becomes a very vital point for aesthetic reference for the buildings as a whole, being mostly the first point of contact. 

This places a burden on the designer (or architect) to allow for aesthetic considerations for perimeter fences intended to serve as retaining walls or embankments; understanding that these fence types will be under intense water pressure when the weather goes wild compared to ordinary fences. Only suitable color, texture and styles should be used for the finishes of such fence walls. Stone-based finishes are often recommended while some others prefer to use special moisture-resistant paints and coverings. There is also the structural engineering consideration which factors in the strength, stability and durability components. If the fence is beautiful but cannot stand strong against flood pressure adequately, then it may be considered good for nothing. The method of building them is slightly different from the normal ones. One striking difference is that the base for retaining walls are normally higher than those of other fence types usually extending beyond the level of projected flood heights before block walls are introduced. Some are even designed to be trapezoidal rather than rectangular in section.

Perimeter fences are normally designed either as non-load-bearing or partially-load-bearing walls but those intended for retaining walls are essentially load-bearing walls. They do not support their weights alone or small loads from security furniture but also sizable pressure forces from external flood. There are various types of materials that can be used for building special fences of this nature; the most common type is concrete. Other types include a composite of reinforced stabilized earth with bricks or blocks as well as other poly-based substitutes for concrete. Whichever material is used, there is need for it to possess sufficient strength to withstand the pressure forces of water as well as be stable enough not to deflect, crack, fail or over-settle in the process. It should also be able to perform this function throughout the life span of the building or space it was designed to serve.

In areas susceptible to flood, the sub-surface soil conditions are often poor because of the long overbearing effect of stayed water on them, so there is always a need to take cognizance of the nature of the soil during the design of the fence. Well-built solid raft base or a combination of short-bored piles and reinforced concrete strip are good options for the foundation of such walls. Reinforced stabilized earth has also been successfully used for this purpose and is said to be a cheaper option to both polymer-based fences and concrete. 

Flood control is serious business especially in rainy seasons. There is no better way to imagine the devastating effect of flood than to watch a house go partially or completely under water; destroying the building fabric and other valuable properties in the process. Although fencing alone cannot completely take care of flood on a large scale however it is known fact that the retaining wall fence type surely minimizes the effect by helping to redirect water from a property.   

The Red Road: How to construct Estate Roads with Lateritic pavers - Osaz’ ENOBAKHARE

In-tune Developers and Estate Owners with an eye for budget-friendly yet aesthetically-appealing, stable, strong and durable estate infrastructure are already exploring the option of adopting the ‘red road’ technology. With the abundance of cheap and good quality laterite deposits in various parts of the country on the one hand and the prevalent rising cost of construction materials on the other, the use of lateritic pavers for estate road construction in place of concrete interlocks and asphaltic (tarred) roads may just be the real deal.

In structural/highway engineering terms, the Red Road is designed as a light and medium-traffic road with individual unit of paver having the same compressive strength as that of Grade M40 concrete (i.e. 40N/sqMM) as obtainable in concrete pavers for the construction of similar road types. Light and medium traffic roads includes car parks, office driveways, housing estate roads, rural roads, farm houses, office/commercial complexes, boulevards, city streets, small market roads, intersections/rotaries, utility cuts on arteries, service stations, etc. If properly constructed, the red road sufficiently satisfies nearly all known functional requirements for roads with durability potential believed to span beyond 50 years during which only little maintenance is needed. 

Because one of the main constituent material, Laterite which usually amounts for more than 50% by volume of the mix in the red pavers normally contains up to 70% clay -which is known to be ‘plastic’ in nature, the thin gaps or voids between interlocking pavers allows for expansion and contraction across various seasons and at different temperatures; although a suitable infill material which does not affect this natural process can also be used to seal the void. Some engineers also lay damp proof membrane (dpm) beneath the bed in areas with high water table. 

As applicable with concrete pavers, pavers for red roads are built on good bedding usually made of highly-draining sand spread uniformly to form a longitudinal bearing throughout the surface area of the road up to a thickness of 100mm or more depending on the subsoil conditions. Stoppers are installed at the edges of the road with protected linkages to the adjourning drainage to prevent the bedding sand from washing off. In areas where highly compressive soils like clay and peat are encountered at near surface levels, the poor soil is first excavated and a more stable earth fill is used to replace it before the bedding is made. The bedding in any case must be properly leveled and compacted before the lateritic pavers are laid to avoid depressions, bulges and over-settlements at various sections as they receive varying degree of stresses from live loads.  

  

Red roads are built from lateritic pavers made of a stable mix of laterite, crushed stone/stone dust and cement. The proportion of each constituent material known as the mix ratio largely depends on the expected bearing capacity of the road. For instance, the percentage by weight of stone dust in the mix is often higher for pavers to be used in main arterial roads (i.e. the road(s) leading from the main estate entrance gate to the streets) than the pavers used on the streets (or branch roads) because the load bearing requirements are relatively different.

Recently (March 2017), a kilometer of dual carriage red-road to be constructed by an indigenous firm in Garki, Abuja has already been estimated to cost some 37% less compared to the use of conventional methods. Interestingly also, for lovers of road ‘black’, the red road can also be sprayed black with hot black soot material at an extra fractional cost and still maintain its functionality. As it stands now, Red-roads may soon become a part of our road life.

Why You Need A Material Schedule For Your Project - Osaz' Enobakhare

Sometimes the use of direct labour in conjunction with supervisory and quality control inputs from one or two professionals is seen as a more budget-friendly approach to the delivery of a project, especially small-scale projects. Other times, the project owner may choose to be engaged directly in purchasing and organizing the supply of construction materials to their site, also in a bid to save cost. Whatever the case may be, whether it’s your personal project or as a group, it is important to know what and what you should expect at completion. You don’t plant grapes and expect to reap blueberries. A project for example, a building development is essentially a product of the use of materials and workmanship. You don’t order for tiles and expect to see epoxy flooring; neither would you see a classic brick wall when you actually paid for blocks.

The usefulness of a material schedule is undoubted. You may never know it until you lose money buying the wrong or a substandard material at the same price as the original or even more. It is that piece of document that shows you the types, sizes, quantities, quality specifications and sometimes current price of all the materials you would need for a project from start to finish. It is not the same as a Bill of Quantities (B.O.Q) or Priced Bill of Quantities which gives brief details of all the items of work in a construction project and cost included respectively, it doesn’t give you the work item or work processes, it only deals with the materials aspect.

The Material Schedule is presented in such a way that the user can easily identify with what materials will be used in the construction of his/her project and it often reveals approximate quantity estimates of all the materials needed with minimal allowance for wastage. Usually the material schedule is a construction document prepared after all the relevant designs/drawings has been completed so that at no point is any material is omitted due to incomplete architectural and engineering details and a thorough market survey has been done to check availability and current prices of the required materials. It is often done in conjunction with the owner’s specifications.

When engaging a contractor, it is important to ask for a material schedule so that you can follow up on the quality of materials used for your work. If the materials used are not those you have agreed on as duly reflected on the material schedule in the absence of a pro-work variation, you can call for a replacement. But if there are no documents to show material specifications, then you can expect anything. Sometimes regret may follow; this is particularly the case when a nominated supplier is engaged without a material schedule to back up your claims on the specs of the materials ordered for. Take for instance, you need a simple timber (wood) to construct your roof carcass, if you don’t specify the product type, size and condition (e.g. Mahogany Hardwood, 50 x 75mm full lengths, new and smooth) but just say supply me ‘wood for roofing’ who is to blame when a truckload of used fragile softwood is brought to your site and workers begin installing them?  Although the material schedule comes at a cost, it is worth it.