Damp-proofing for garage floors
What it looks like
Omission of a DPM where necessary leads to dampness or efflorescence on the garage floor, potentially affecting adjoining habitable spaces.
Why it happens
While a damp-proof membrane (DPM) is not universally required for all garage floors, it is essential where dampness could transfer into an adjoining habitable area, or where the floor needs protection from chemical attack originating from the ground. For floors below ground level, robust waterproofing or tanking measures are necessary to prevent groundwater ingress.
What it costs if it is missed
While a damp-proof membrane (DPM) is not universally required for all garage floors, it is essential where dampness could transfer into an adjoining habitable area, or where the floor needs protection from chemical attack originating from the ground. For floors below ground level, robust waterproofing or tanking measures are necessary to prevent groundwater ingress.
How to inspect for it
Confirm DPM installation if the garage is attached to a dwelling or if chemical attack from the ground is a risk, and verify tanking for below-ground garages.
How to prevent it
While a damp-proof membrane (DPM) is not universally required for all garage floors, it is essential where dampness could transfer into an adjoining habitable area, or where the floor needs protection from chemical attack originating from the ground. For floors below ground level, robust waterproofing or tanking measures are necessary to prevent groundwater ingress.
Basis in regulation
BS 8102
Read the sourceBS 8103-1
Read the source
Last updated 23 August 2026. This is our editorial summary of publicly available regulation and site practice, not building control approval or a warranty determination.