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Damp Proof Membrane between Flowerbed and Garage Wall

We are landscaping the garden with artifical grass after leveling it quite a lot. The area next the the neighbours walls is a bit of concer as with the level we are coming quite high up the damp proof course. I am concerned that the flower bed will cause the damp to go into the neighbours. Our landscaper insists that he will put the damp proof membrane next to the wall which will go below the DPC and will be higher than the flowering bed.

Do you think this will be enough to prevent damp to penetrate the wall or do we need to do something else to for it. I have asked them about the sleeper (4 walls) but they insist that the damp proof membrane would be enough.

Can anyone please suggest?


  • FairygirlFairygirl Posts: 52,027
    Hi @junaid.mukhtarXB7CRlms. If you're concerned at all, and I can understand that, why not just tell the chap you want the sleepers right round your planting area, leaving a small gap as well between it and the wall.  :)

    Is it a big area you're making? Obviously it could be a fair bit more expensive if it is, but it can be worth it for the peace of mind.  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • These are the images; red line in the pic1 is the DPC of wall. @Fairygirl I have absolutely no idea about this, can you suggest if the damp proof membrane would work if it goes 2 bricks under the DPC and all the way above the soil?

  • FairygirlFairygirl Posts: 52,027
    Not something I've ever done unfortunately. I would always put in something more solid between a planted area and a wall, but I expect the damp proof membrane would be ok  if it's the right stuff. In a previous house we built a raised deck when we did an extension. We left an area about four feet by 2 at one end, where it met the kitchen wall, to create a planted border. We used a specialist waterproof paint on the wall which my then hubby got through his work - he was a surveyor. That bed never caused a problem  :)

    However, is that the size of bed you're planting up? It's very narrow. You couldn't really get another sleeper in there anyway. 
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • I agree with you on the width, but they have kept it to this width as the plan is to put in the damp proof membrane at the bank and we don't want too wide flowering bed.
  • JennyJJennyJ Posts: 8,786
    If I were your neighbour I don't think I'd want to rely on just a membrane between the soil and the wall. It would maybe be worth the risk if it was your own property.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • LoxleyLoxley Posts: 5,222
    I am not sure a damp proof membrane will work, moisture could track up behind it if the soil gets wet. I think the wall needs to be tanked (with neighbour's permission), or else pull the planter back off the adjacent wall, leaving a gap where the soil level is 150mm below dpc
  • zugeniezugenie Posts: 784
    I agree, it’s not really worth taking the risk with your neighbours house, you don’t want to be paying for any problems caused if the membrane does fail.

    Has the fence at the back also got soil sitting up against it? 
  • StephenSouthwestStephenSouthwest Posts: 488
    edited May 2022
    I'd not be happy with that arrangement. Ground level needs to be kept below the house's dpc.
  • I am thinking of asking them to put a sleeper wall a bit away from the wall (150/200mm) all the way down below the dpc. This sits on a porous ground anyway so should be OK. 

    @zugenie no we have a type 1 mot compacted next to the fence and over it will be artificial grass with sloping away from the fence
  • WilderbeastWilderbeast Posts: 1,413
    Building control states you shouldn't have any material closer than 150mm of the damp course (in height so 6 inch below), where this isn't possible a french drain (gravel trench) must be put in place though I must not go above the damp course. I'm a small builder and there's no way I'd be raising the ground level above a neighbours damp course as you are unless I had 1. A specific design and materials list from a qualified person 2. Had in writing permission from the owner of the property. Damp course's are an integral part of building design and shouldn't be be built over as you are planning on, any issues caused by it will be straight back to you which means all costs for repairs 
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