Damp Under The Stairs Cupboard

What's happening?

The space under the stairs sits on the ground floor, often on a thin, old or missing slab, with solid walls on two or three sides and no air movement. That makes it a natural spot for damp. Four causes cover most cases. Ground moisture comes up through a floor with no damp proof membrane, or an earth floor in an old house. Rising damp or penetrating damp travels in through the outer or party wall. A leaking water pipe, waste pipe or drain, often with the meter and stopcock in this cupboard, wets the floor. Or there is simply condensation in a cold, closed space. A musty smell often comes first, then damp on the floor and the bottom of the walls. Find out which is the cause before treating it.

What usually causes it?

• Ground moisture through a floor with no damp proof membrane, or a solid or earth floor in an older house
• Rising damp or a failed damp proof course in the outer wall
• A leak from a water pipe, stopcock, waste or drain under or near the floor
• Condensation in a closed, cold, unventilated space
• A bridged damp proof course where a stair string, a stud or a render touches the ground
• Penetrating damp through the outer wall or from a leaking gutter or downpipe outside

Is it dangerous?

Low in itself, but a damp cupboard grows mould and can rot the stair timbers and anything stored in it. If a gas or electricity meter is in the cupboard, keep it clear and do not block ventilation around it.

Can I fix it myself?

Empty the cupboard, lift anything stored on the floor and look for pipes, drips and the damp pattern. Check the stopcock and meter and look for a wet spot below them. Leave the door open and ventilate it for a few days and see whether the damp shifts. Store things on a rack off the floor. Do not paint it with damp-proof paint or seal the floor until the cause is clear.

When should you call a damp proofer?

Call a plumber if there is a leak or a wet spot below a pipe or the stopcock. Call a damp proofer if the damp is on the walls or floor with no leak. Ask them to treat the floor and the wall base if needed, and to say whether ventilation will cure a condensation problem.

What will the damp proofer actually do?

• Survey the cupboard, floor and walls for moisture and note the pattern
• Check pipes, drains and the stopcock for leaks with the water on and off
• Check the outer wall, ground levels, gutters and the damp proof course
• Fit a damp proof membrane or lay a vented raised floor where ground moisture is the cause
• Treat the wall base for rising damp or fit a ventilator for condensation
• Make good plaster and timber damaged by the damp

Who fixes this

• Damp survey
• Internal damp proof membrane
• Rising damp treatment

Questions people ask

Sources & References

1. Property Care Association: rising damp
2. Designing Buildings: rising damp
3. Designing Buildings: damp proof membrane
4. Designing Buildings: condensation