Draught marks (also known as filtration marks or filtration soiling) are darkened areas of heavy soiling most commonly found areas around the edges of fitted carpets like the first picture and in internal doorways. But what causes them and what can you do about them?

As most readers will know from their school days, heat rises. Therefore inside your home or office, warmed air will make its way upwards. Where there are small gaps in floorboards or skirting boards the rising air is replaced by cooler air being drawn through those gaps at floor level, creating a draught.

The problem is that the air entering the room is not clean. It contains microscopic contaminants, such as dust, pollen, soot etc. These airborne contaminants are carried through the small gaps by the movement of the air and as it passes through, some of the contaminants get trapped by the carpet fibres, which act as an air filter. Over time the contamination builds up and if left unchecked, dark areas can appear round the edges of the room. These are draught marks.

But they are not confined to the edge of the room. They often form in doorways where the door is mostly kept closed and one room is kept at a different temperature to the other, such as between halls and lounges or bedrooms, but especially airing cupboards which are usually much warmer than the adjoining room.

If you have full length curtains, especially in older houses without double glazing, draught marks can form where cold air trapped between the curtains and the window falls to floor level and finds its way into the warm room through tiny gaps at the foot of the curtains.

In this case the draught marks will follow the zig zag profile of the closed curtain, as in the second picture. The thicker the curtains, the greater the temperature difference and the greater the problem. Unfortunately it’s worse with made to measure curtains as they are made very precisely so that they hang correctly and leave only the smallest of gaps at the bottom which concentrates the air movement.

Historically, older properties were more susceptible to draught marks as they tend to have more gaps for the air to flow through, but it’s a problem we’re seeing more and more of in newer houses these days. It’s partly down to the finishing quality in some new builds in the rush to complete construction, with small gaps left unsealed. Equally, a side-effect of the drive for ever greater energy efficiency has resulted in automatic door closers being installed as a matter of course in most new builds, meaning that temperature differentials between rooms are greater as internal doors are kept closed virtually the whole time, leading to more draught marks in doorways.

How to deal with draught marks

First of all, prevention is better than cure. If you’re about to replace a carpet you can go round the room sealing up any gaps between floorboards and round the edges with a proprietary sealant or decorator’s caulk (the type that you apply with a special applicator gun). Don’t fill the gap between the front edge of the skirting and the floor – the fitter will need that gap to tuck the edge of the carpet into for a neat finish, it’s gaps further back you should be looking for, and make sure you allow plenty of time for the sealant to fully cure before the new carpet is laid.

Again, if you’re replacing the carpet, replace the underlay too and get a good quality one. A thicker one will be better able to prevent draughts getting through (as well as feeling more luxurious under foot).

For ongoing maintenance, regular vacuuming is a must, at least once a week, preferably more often. Make sure you get right into to all the edges using a crevice nozzle attachment, moving furniture out of the way where necessary, even if you can’t see any visible soiling. Once draught marks have built up they are really difficult to remove so preventing the build-up is the best option.

If you already have visible draught marks, a professional carpet cleaner can treat them with specialist products and the right equipment. However, the longer they are allowed to build up the harder they are to remove and if left for too long there comes a point when they become permanent. Once they reach that point, the appearance can usually be improved but they cannot be fully removed.