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A few weeks ago, I paid a visit to one of my very good friends – Tony. He had just moved into a new apartment in Lokoja (it is a town which sits on the confluence of Rivers Benue and Niger and is the capital of Kogi state in Nigeria.). The house looked quite new as though it had been constructed only a few years back probably within the past two to five years and if not, had just been recently renovated.
Although it was a very nice property and situated on a large plot with lots of space around, something sad caught my attention and that was the presence of damp on the lower walls of the building- way above the foundation and rising towards the level of the window seal.
For those who know Lokoja quite well, you’d know that during the rainy season, some parts of the town, especially those close to the river Niger and not placed on a very high ground are always flooded and for such areas, proper care ought to be taken in the construction of such buildings with emphasis on the strength and durability of the foundations. Hence the reason for this write-up.
A lot of things are involved in the construction of foundations. However the one simple fact I wish to lay emphasis on in the course of this write-up is the DPC/DPM (Damp proof Course/Membrane) and polythene sheets in particular.
Damp Proof Course
DPC is a stage/level where damp-proofing of the structure is done while the DPM is the material used for damp-proofing. It is a layer of material laid over the foundation walls some distance above the ground during construction to prevent moisture from rising from the ground into the walls and floor of the building.
A variety of materials can be used for this purpose such as bitumen felt, mastic, asphalt, cement concrete, polythene sheets and a host of others.
In our part of the world, polythene sheets are the most go-to for damp-proofing reasons being that they are flexible, water and chemical resistant, cheap, readily available and can be used in almost all conditions except in severe cases.
Use
For use, they come in a standard size of 4mm by 25-30mm sheets (except you’re going for recycled sheets which is not advisable because there could be holes in them) and should be spread over a leveled surface (blinding of sand over hardcore). Where the edges meet, they should be overlapped by at least 6inches and sealed. The sheets should exceed the edges of the external walls by at least 3inches (this will be turned up against the wall and covered up during plaster).
Ensure the sheets are well in place and free from dirt before pouring a layer of concrete (oversite) over it. This should be allowed to cure (dry) before erection of the superstructure continues.
Effects
The presence of DPC actively prevents the rise of moisture through capillary action and would help keep your wall and floor finishes intact and free from damp unlike in buildings without it - in which case you see physical damages to your walls and floors such as paint peeling from the walls of the building, swell and cracks on the floors and walls etc. which is a definite no no
In conclusion...
Be you a prospective houseowner, a bricklayer/mason or construction professional, always take care to ensure the presence and proper placement of DPC during costruction because although it sounds minute, it is actually a very crucial of a structure and could save you lots of money and worry over time in terms of repairs to moisture damaged walls...
Ever a Steemian
@ bennyjay