How do I stop draughts from a loft hatch?

A loft hatch is a small hole in the most important insulated surface in the house, sitting exactly where warm air collects. It is one of the cheapest and most effective jobs available.

Safety

What you'll need

• Compression draught seal — P-strip or E-strip, or foam gasket tape
• Rigid insulation board, 50 to 100mm
• Turn-buckle catches or a barrel bolt
• Adhesive, a knife, and a tape measure

Step by step

1. Understand why it matters.Warm air rises and collects at ceiling level, so a loose hatch leaks continuously rather than only when it is windy. It also carries moisture into the loft, where it condenses on the cold roof.
2. Check what you have.A drop-in board, a hinged hatch, or a loft ladder assembly. Each is sealed slightly differently, and a loft ladder frame is the hardest because the frame itself is a leak path.
3. Fit compression seal, not foam tape.A rubber P-strip or E-strip in the rebate. It compresses when the hatch closes and recovers. Cheap open-cell foam tape crushes flat and comes unstuck within a season.
4. Clean the rebate first.Dust and old paint stop the adhesive holding. Wipe with methylated spirit and let it dry before applying the strip.
5. Run the seal in one continuous piece.Round all four sides with joins only at the corners. Gaps at joins are where the air goes, and it does not take much.
6. Insulate the hatch itself.Rigid insulation board cut to fit and glued to the loft side, 50 to 100mm thick. An uninsulated hatch is a cold patch in the ceiling and a condensation point.
7. Check the hatch still closes.Insulation adds weight and thickness. Test it before finishing, and make sure the board does not foul the frame or the ceiling.
8. Fit catches to pull it closed.Turn-buckles or a barrel bolt. A hatch resting on a compression seal is held up by it and does not seal — the catch is what makes the seal work, and it is the step usually missed.
9. Deal with a loft ladder differently.The ladder frame itself leaks. An insulated loft hatch box that sits over the whole opening in the loft is the usual answer, or a purpose-made insulated hatch assembly.
10. Check for gaps around the frame.Between the hatch liner and the ceiling plasterboard there is often a gap into the void. Seal it with a flexible sealant or expanding foam trimmed flush.
11. Do the loft insulation at the same time.Check the depth — 270mm of mineral wool is the current recommendation and many lofts have far less. Insulation over the hatch surround should not obstruct it.
12. Keep the eaves ventilation clear.Insulation pushed tight into the eaves blocks the airflow that keeps the roof space dry. Leave a clear gap, or fit eaves vent trays.
13. Do not seal the loft as a whole.The loft above the insulation is meant to be cold and ventilated. Sealing the hatch stops warm moist air getting in; sealing the roof vents would cause condensation.
14. Check it afterwards.On a windy day, run a hand round the closed hatch. Any draught means the seal is not compressing evenly, usually because the catch needs adjusting.

Tips

• The catch matters as much as the seal. Without something pulling it down, the hatch rests on the strip and does not compress it.
• Compression seal, not foam tape. Foam crushes flat within a season and the draught returns.
• Do the eaves check while you are up there. Insulation stuffed into the eaves blocks the ventilation the roof needs.

Common mistakes

• Fitting draught strip with no catch — The hatch sits on top of the seal rather than compressing it, so it seals no better than before and may sit proud.
• Blocking the eaves ventilation with insulation — The roof space needs airflow to stay dry. Blocking the eaves causes condensation and eventually rot in the roof timbers.

If it doesn't work

Questions people ask