Building Construction

[malana-3]

My friend lives in a bungalow built 3 years ago. It has a solid concrete floor. The builder has placed, at intervals around the property plastic air bricks/ ventilation bricks in the brickwork course of the outer skin immediately below the damp proof course (DPC). During recent very heavy rainfall his garden flooded to the extent that these air bricks were under water. What is the purpose of these air bricks and what could be the result of their admitting water?

[reefgal]

Air Bricks are used to ventilate Cavity walls and Suspended floors.

[malana-3]

Thanks reefgal. I understand what you say, but I repeat the property has a solid floor, so when did the Building Regs change to require the cavity to be ventilated? I ask that because an adjacent bungalow built 2 years before my friends ( by the same builder) does not have any cavity ventilation. If these airbricks have been provided for cavity ventilation why put them under the DPC?

[buildersmate]

Cavities do require ventilation. Your friend's DPC is a single thickness of brick (100mm) and it runs across the outer skin only. There will be another DPC also 100mm wide, tied into the DPM that covers the whole of the solid floor, at the same height on the inner skin.
If water drips down the cavity, there has to be a way of it getting out. These ventilation bricks allow it out.
Air bricks under water, and water over the DPC level means both inner and outer bricks skins will take up water. In a severe case, the dampness may have shown itself through to the inside as a damp patch on the plaster surface.
Otherwise, if the water has now subsided, nothing else should happen. It is summer, the air is 20 degrees C or so and there is plenty of time for it to dry back out again before winter.

[malana-3]

Thank you " Buildersmate". Has there been a change of thinking about cavity ventilation in the last few years because as I mentioned an adjacent bungalow built 2 years previously to my friends ( in 2004) is not provided with air bricks into any cavity. Thanks in advance.

[buildersmate]

In England & Wales, it is covered within Part C of Building Regulations document. This document was updated as Part C (2004) which was actually published in 2006. I am not sufficiently well up on it to know what the differences were. However there are several ways of achieving a satisfactory solution to where the excess water goes. For example, if the cavity goes down further, below ground level, then there may be no need to have any weep holes in the first place.
You can trawl your way through the document if you are that interested - see here around p29 onwards.
http://www.planningportal.gov.uk/england/profe ssionals/en/4000000000242.html