I recently moved into a house with a garage at the bottom of the garden which has a damp proof membrane (DPM) that protrudes out at the base of every wall by approx 4 to 5 inches.

Can I safely trim this off without affecting the damp proofing?

I want to fit some interlocking garage floor tiles to make the space less dusty and cleaner but currently can't do this as the DPM will stop me getting the tiles tight to the walls.

Photo of the DPM protruding from base of wall: photo of damp proof membrane DPM around door

Around the single door frame and garage roller door entrance the DPM is already trimmed down to be flush with the ground, so I believe I should be able to trim this off but this is my first time ever having to look into doing this so I want to be sure.

Link to the floor tiles: Rolson garage floor tiles

  • It's hard to answer not knowing why the membrane was installed. Maybe add information and/or photos explaining that. Your photo is so close up it's hard to get context.
    – isherwood
    Jul 19, 2019 at 15:38
  • Also, how old is the home? New build?
    – J Crosby
    Jul 19, 2019 at 17:17
  • Old house, relatively new garage. I believe the garage (not attached to house) was built some time in the last 15 years. I'll try and get some better photos. Jul 24, 2019 at 16:09
  • 1
    Considering the missing material and holes that already exist, go right ahead. I think Iggy is correct.
    – isherwood
    Jul 24, 2019 at 18:59

1 Answer 1


If the garage isn't below grade, doesn't have a sump pump on its level, there's no drain pipe open to daylight out in the yard and you don't have holes drilled at the base of the walls. Then yes, you can cut it down, as it's just newer concrete of this century that normally requires a water and vapor barrier...typically it's clear or black 6-mil polyvinyl sheeting required by code.

If yours were a very minor part of a proper drying or water handling system it would be hard and stiff plastic that's bubbled or ridged, like the picture below. Drain Tile Connector.jpg

  • Thanks for the info, I've added another photo of where the previous owner has cut the DPM away around the door frame and this sounds like the polyvinyl you describe, I think Jul 24, 2019 at 18:52
  • 1
    Yep, that 2nd shot looks more like the normal stuff of just a vapor barrier that can be trimmed right off. FYI, it's usually left out so The Inspector can approve that it's properly present and of adequate thickness.
    – Iggy
    Jul 24, 2019 at 19:41

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