What’s wrong with this? (Clue - It's to do with the damp proof membrane)

This is a photo looking down at the floor to a patio door opening and is a relatively common detail where the concrete carries over the internal blockwork to close the cavity.

Using damp proof membranes correctly

The damp proof membrane (DPM) has been cut too short to extend across the cavity and form a continuous link with the damp proof course (DPC) to the door threshold. This DPC is also missing and needs to be added to the outer leaf and made continuous with the external brickwork DPC. If left, water may track underneath the door.

It could easily have been solved before the floor concrete was poured.

Also missing is the perimeter insulation. It’s just visible where the floor meets the internal blockwork but this should have been continued around the reveal and between the floor slab and external brickwork to prevent a cold bridge.

If built like this mould growth would almost certainly occur at skirting board level in the door reveal and at the floor finish with the door.

Involving your building control surveyor at every key stage in your construction will help you identify such problems before it becomes too late and too costly to put them right.

Find your local LABC team here

Further information

Browse our How to get it right articles for tips on avoiding common construction problems.

Please Note: Every care was taken to ensure the information was correct at the time of publication. Any written guidance provided does not replace the user’s professional judgement. It is the responsibility of the dutyholder or person carrying out the work to ensure compliance with relevant building regulations or applicable technical standards.

^{This article was updated on 24 November 2022}