Damp Proof Measures In A House
A house has some inbuilt or inherent measures designed to keep moisture out. There are several features that help keep our homes warm, dry and comfortable for us and our families.
If moisture gets into the property it could cause dampness, mould and general mustiness in the house.
Here is a list of the features that are built into a home to keep out moisture.
1. A roof
Very simple and totally obvious but a roof is one of the first barriers a home has to stop moisture entering the property. A well built and regularly maintained roof stops rain water coming into the property and causing issues in the attic space and upper levels.
2. Pointing in brick or stone work
The pointing (the cement in between the bricks of the outside of the house) should be neatly done, unbroken and checked frequently to make sure rain water isn’t accessing the property from the driving rain.
Well maintained pointing will stop driving rain entering the property.
3. A damp proof course
A damp proof course (DPC) is a vapour barrier that is installed in the outer leaf of the house (external walls) to stop moisture from wicking up through the ground into the house.
It is usually but not always around 2 levels (courses) of brickwork above the ground and it stops water from coming from the ground into the house.
The DPC itself is usually a thin strip of plastic that is laid on the 2nd level of bricks and then cemented in place. In older homes you can see a thick black layer which is usually either tar or bitumen. Both are oil based and stop moisture coming through.
Not all properties have a damp proof course.
4. A damp proof membrane
A damp proof membrane is a vapour barrier that is applied directly to or under the concrete floor.
In newer homes where concrete floor or slab is laid a polythene sheet (often referred to as visqueen) is laid down first and then the concrete is poured on top. This prevents moisture from the earth below and around the slab from affecting it. The polythene sheet creates a vapour barrier and protects the slab from the surrounding damp. In addition, a secondary damp proof membrane is usually lain on top to prevent any construction moisture from the concrete itself entering the property. This can be a polythene sheet or sometimes foil backed insulation if a floating chipboard floor is installed. Where solid oak floor is being laid directly on top of the concrete floor we would always recommend that a DPM is installed.
In older homes you often see a concrete floor with a black covering (it looks like paint). This black paint is often bitumen or a type of bitumastic layer and it is applied as a liquid to the concrete floor. Once dry it sets hard and prevents any moisture entering the house from the earth surrounding the floor.
In older properties there isn’t a DPM below the concrete slab so they retrospectively used bitumen in later years. In some cases you will see plastic tiles on the concrete floor and they also act as a DPM. They are glued to the floor and are put together tightly to stop moisture entering the house from the concrete slab which can be wet.
If your DPM has been compromised for whatever reason please get this reinstated ASAP. The amount of moisture coming through the floor could have adverse effects on floor coverings especially if wooden floors laid on top. Always make sure your flooring contractor checks the moisture content of the slab first before fitting either carpet, lino or wooden floors.
5. Air bricks and Air Grates
Where the property is on a suspended floor (wooden or block and beam) the property has air bricks to allow any moisture underneath the floor to escape outside.
Air bricks allow for a constant flow of air under the property which helps carry away moisture vapour under the floor.
Air bricks must not be covered up or allowed to fall into disrepair. If the air bricks become blocked it can lead to a build up of moisture in the solum (void under the floor) which can lead to damp walls.
6. Windows
A window allows plenty of natural light to enter the property but also prevents rain from getting into the house too.
Make sure that the silicone sealant around the edges of the windows is in tact and isn’t allowing water to enter the property. If you have a trickle or air vents keep them open to allow any build up of moisture in the property to escape.
7. Gutters, drainpipes and drains
Guttering is a crucial feature which allows the property to divert rain water away from the roof, through drainpipes and into the rain water drains.
A blocked gutter will allow moisture to pool and drip out of the gutter onto the walls of the house.
Gutters, drainpipes and drains have to be maintained regularly and kept clean and clear of any obstructions.
8. Cavity Walls
We have written an article in this blog about the issues with cavity wall insulation. You can find that is you need more detailed information about them (click here)
Very old properties were built with a single this wall which spanned the outside to the inside of the house. More modern homes are built with a double skin construction. This means that the house effectively has two walls to it. The outer wall which is usually brick or stone and the inner wall which can be brick or block. In between these two walls there is an air gap called a cavity. This cavity is there to prevent moisture from entering the inner wall of the house from driving rain or damp.
Effectively the sir barrier to moisture and as long as it is maintained and not filled, the moisture cannot move from the outer wall to the inner wall.
The cavity prevents moisture from entering the house.
Summary
There you have it. These are some of the most popular water proofing measure that are inherent to a house. Maintaining these will allow you to have a dry home which is comfortable for you and your family.
However, if you are experiencing rising or penetrating damp issues and need some advice please contact Rainbow International on 01274 588011