What Could be the Cause of my Draughty home?
Q There’s a cold draught coming up from under the suspended timber ground floor of my lounge. What could be causing this and how should I go about solving this problem? Jane Spriggs
A IAN ROCK SAYS:
Many houses built from the Victorian period onwards had ground floors made of ‘suspended timber’ construction. These comprise a series of structural timber joists supported on short ‘sleeper walls’ or brick piers, and the joists are covered with wooden floorboards or, more rarely, chipboard panels, similar to upstairs floors. Underneath your lounge floor there will be a void probably of at least a couple of feet deep with air flowing through it. If you take a look outside at your lower main walls, just above ground level, you should see a series of small air bricks with holes in, designed to allow air to flow through and ventilate the floor. This helps disperse moisture thereby preventing damp-related problems, such as rot and wood beetle, developing in timber floors. So it’s essential that timber ground floors are kept well ventilated. Unfortunately it’s not
unknown for homeowners to sometimes seal these up in a misguided attempt to prevent draughts.
The solution to draughty floors is to approach the problem from indoors by stripping back any floor covering such as carpets and sealing gaps between floorboards or underneath the skirting.
For this purpose you can buy flexible rubber ‘floorboard gap fillers’ which are sold in three sizes — thin, standard and thick. Larger gaps can be sealed by cutting and gluing matching strips of wood, or where appearance isn’t an issue, expanding foam can be applied or mastic sealant for smaller gaps.
To really make a difference to heat loss through suspended timber floors you need to insulate the floor, by cutting and wedging rigid insulation boards between the joists, for example. However this is quite a labour– intensive job. Alternatively, laying a carpet over a professionally fitted thick underlay (sometimes applied over a thin hardboard base) should boost room warmth as well as helping to block draughts.