Cabling and pipes into walls

Walls tend to have a lot of ‘punctures’ through them

In the UK we build walls and then make holes in them. This is a bit strange when you think about it, but in older houses we are forced to drill through walls in order to install our modern conveniences and technology. So old houses have a range of holes for soil pipes, TV aerials, washing machine drains, phone lines etc. We have also drilling into walls to inject cavity wall insulation, chemical DPCs etc. Take a look at your house and see how many times it has been drilled through.

Surely drilling and placing a cable / pipe through is a simple matter with few risks?!

Oh how wrong we can be. Having just been to a house where incorrectly installed cables and pipes are potentially causing a lot of damp (even on the cavity wall extension).

So where does it go wrong?

Well the most obvious problem is where we encourage water to track into the wall by:

1. Drilling down at an angle rather than horizontally / slightly angled up. A downward slope encourages water to run into the hole especially if it is not properly sealed.

2. It is almost impossible to adequately seal holes / around pipes etc. Most of the time contractors don’t even bother trying to seal around holes.

3. Cabling is not looped around so that all cabling enters from below (if cabling goes down the wall and straight into the hole, water will track down it and into the structure).

4. Many holes are drilled into walls that face the prevailing wind rather than exploring another less risky option of an East or North facing wall. This means that the weak spot of the hole is exposed to the worse of the weather.

Sometimes it is difficult to access the best place on the wall for a hole and this is especially the case with Damp Proof Course injections. These tend to be fitted on the external face of the wall and need to be as close to the ground level as possible (generally). This often means that the drill holes are sloping down into the wall due to the body of the drill being next to the ground. The trouble with this is that rainwater running down walls will enter these holes and put water above the DPC! It is vital therefore that these holes are sealed completely and in a long lasting manner, However, more often than not I see holes unfilled, ill fitting plastic plugs pressed in or a dot of mortar placed roughly over the hole. In the long term these will all let water into the structure and cause damp.

So when faced with having to drill through a wall, remember:

  • Keep the drill level (or sloping up slightly)
  • Seal around the cable / pipe using a good quality sealer and press into the wall as much as possible
  • Ensure that the cabling does not encourage water into the wall
  • Put as much cabling through the lee side of a building (rather than facing the prevailing winds)