Underfloor vents are required to allow airflow to the underside of a ground floor structure. Ventilation prevents build up of condensation and dries out any water that may find its way to the underfloor due to leaks or spills.
Many issues develop from poor design of vents, blockages or changes of external condition.
Insufficient number of vents is commonly seen on older properties. They are often found blocked; further reducing the air intake.
Ground adjacent to older properties is often paved and the levels of the ground increased reducing the distance between the underfloor vent airbricks and the ground level externally. During heavy rain, rainwater ricochets from the hardstanding into the airbrick; increasing the humidity within the underfloor void. During wet season, the amount of damp finding its way into the void can be greater then going out, which may settle on the timbers and make timber decay.
There are a number of ways to deal with all of the issues. A detailed survey normally lists all details of the building construction and external elements. It takes into the account ground clearance, number of vents and the airbrick condition.
Depending on the conditions, the recommendations can include:
- Clearing/unblocking the existing vents;
- Reducing the ground levels externally and removing materials abutting the walls;
- Cutting back hardstanding and installation of French drains;
- Replacing of existing vents with a "periscope" type vents;
- Cutting out and installation of additional vents.
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