Air bricks are bricks with holes through them, designed to allow air to pass though. They are inserted in exterior walls to provide ventilation of Cavity Walls and spaces below floors so as to prevent the build-up of damp, mould and unwanted and hazardous gases (such as Radon).
Air bricks must not be allowed to become blocked. A survey will show if this has happened, and what remedial work is required. Often this will be fairly simple, such as removing a build-up of soil, but if later building work has blocked an air brick then more extensive work may be required.
The ground floor of older houses frequently consists of a timber floor suspended on joists, with a space or void beneath. Ventilation to this area by means of air bricks is essential, as otherwise the timber joists and flooring will be prone to rot and fungal infection.
Air bricks are also frequently found in older properties to provide room ventilation. Such ventilators are often blocked with paper to stop draughts. This can cause problems with damp. especially in bathrooms and kitchens.