Ideas please for my Motorhome garage. (1 Viewer)

[CazPaul]

I’m not that confident in him to be honest, he has made a good job of digging out and the foundations but I’m not confident that water won’t penetrate the walls. He just want to use the black damp proof sheet sat up against the walls, then backfill

I think once the damp proof sheet has punctured water will pour through it rains for fun up here in winter.

I would sooner get ideas etc before it’s back filled or tell him I will backfill it.

 

[CazPaul]

PermaSEAL 8 Eco Cavity Drain Membrane for Floors & Walls 40m²

A high quality recycled cavity drain membrane manufactured from 100% recycled HDPE, suitable for walls and floors, internally and externally, above and below ground.

www.permagard.co.uk

Thanks, that needs fixing to the walls I can get access at the back wall but not the side, would it work just stood against the sidewalls without fixing do you think.

 

[Landy Andy]

You don’t need to fix it to the walls if you are back filling with stone as that will keep it in place.
If you are wood cladding the top part of the structure you can just lean up against wall, back fill with stone then cut off the top as required and hide the top by cladding over the top if that makes sense. That way the membrane stays high above ground level.

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[CazPaul]

You don’t need to fix it to the walls if you are back filling with stone as that will keep it in place.
If you are wood cladding the top part of the structure you can just lean up against wall, back fill with stone then cut off the top as required and hide the top by cladding over the top if that makes sense. That way the membrane stays high above ground level.

Yes I see what you mean, I wonder if it’s flexible enough to wrap around at the top and then sit over the wall so the timber spars of the garage sits on it?

 

[Landy Andy]

I wouldn’t, just keep it above ground level and sit timber on DPC

 

[dunnah01]

Just get your builder to show you what he's intending to do and then pop them on here for another round with the popcorn. So far he's not covering himself in glory. I hope you're not expected to pay for that ornamental black plastic stuff

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[Minxy]

As a layperson I think your builder has cocked up to some extent ... if you want it to be damp-proof you should NOT put holes in the membrane ... I understand why he's put the pegs in so he could level the footings but in doing so he has compromised the waterproofing. Short of him removing the blocks and laying a new membrane across the whole thing then laying the blocks again and taking the membrane up the outer of them above the height of the land, you're gonna get an issue with damp through the floor/walls.

As has been suggested by others I'd make a 'tub' so that no damp can enter whatsoever, ie put a full membrane internally across the floor and up the walls, then onto the top of the wall blocks which should be taken at least 1, ideally 2, blocks above the highest point of the surrounding land - it would likely be easier to have the block walls all raised to this height and then the timber garage 'top' structure would just sit on it rather than having to be at different levels to match stepped blocks (more pratty to make and likely more expensive too); aesthetically you could just render or paint the outside of the blocks to make them look better. Internally you'd need to cover the membrane to protect it from damage and make it look better too so you could panel it with something or put in a rubberised floor and take it up the walls to form a continuous easily cleaned area.

 

[CazPaul]

I wouldn’t, just keep it above ground level and sit timber on DPC

Yes it’s going to be too unstable doing that with all those 8 mm dimples in it, but wouldn’t water get in at the top and run down behind it?

As a layperson I think your builder has cocked up to some extent ... if you want it to be damp-proof you should NOT put holes in the membrane ... I understand why he's put the pegs in so he could level the footings but in doing so he has compromised the waterproofing. Short of him removing the blocks and laying a new membrane across the whole thing then laying the blocks again and taking the membrane up the outer of them above the height of the land, you're gonna get an issue with damp through the floor/walls.

As has been suggested by others I'd make a 'tub' so that no damp can enter whatsoever, ie put a full membrane internally across the floor and up the walls, then onto the top of the wall blocks which should be taken at least 1, ideally 2, blocks above the highest point of the surrounding land - it would likely be easier to have the block walls all raised to this height and then the timber garage 'top' structure would just sit on it rather than having to be at different levels to match stepped blocks (more pratty to make and likely more expensive too); aesthetically you could just render or paint the outside of the blocks to make them look better. Internally you'd need to cover the membrane to protect it from damage and make it look better too so you could panel it with something or put in a rubberised floor and take it up the walls to form a continuous easily cleaned area.

im not sure about that the membrane sits below the foundations and the floor will be about 10 inches or more above that so with the damp proof membrane in the floor and dpc in the walls above ground level I can’t see what you mean.

 

[Landy Andy]

Yes it’s going to be too unstable doing that with all those 8 mm dimples in it, but wouldn’t water get in at the top and run down behind it?

No because you would finish it above ground level and cover the top part with the wood external boards you finishing your garage with.

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[CazPaul]

As a layperson I think your builder has cocked up to some extent ... if you want it to be damp-proof you should NOT put holes in the membrane ... I understand why he's put the pegs in so he could level the footings but in doing so he has compromised the waterproofing. Short of him removing the blocks and laying a new membrane across the whole thing then laying the blocks again and taking the membrane up the outer of them above the height of the land, you're gonna get an issue with damp through the floor/walls.

As has been suggested by others I'd make a 'tub' so that no damp can enter whatsoever, ie put a full membrane internally across the floor and up the walls, then onto the top of the wall blocks which should be taken at least 1, ideally 2, blocks above the highest point of the surrounding land - it would likely be easier to have the block walls all raised to this height and then the timber garage 'top' structure would just sit on it rather than having to be at different levels to match stepped blocks (more pratty to make and likely more expensive too); aesthetically you could just render or paint the outside of the blocks to make them look better. Internally you'd need to cover the membrane to protect it from damage and make it look better too so you could panel it with something or put in a rubberised floor and take it up the walls to form a continuous easily cleaned area.

I’m not sure about that putting the floor membrane up the internal walls all the way to above ground level it won’t look right

 

[M-J]

What did planning say?

Was drainage & damp protection part of the spec on the application?

Are building control involved? What have they said?

 

[Landy Andy]

I assume the builder is going to now put a DPC on the blocks and continue to build up, so the blocks see now will get damp, which is normal, but those above won’t. Then the floor that goes between the blocks (that you can see, and will be damp) will be inside a layer of plastic sheet to protect it from moisture coming up, or through the bricks at the side.

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[CazPaul]

As a layperson I think your builder has cocked up to some extent ... if you want it to be damp-proof you should NOT put holes in the membrane ... I understand why he's put the pegs in so he could level the footings but in doing so he has compromised the waterproofing. Short of him removing the blocks and laying a new membrane across the whole thing then laying the blocks again and taking the membrane up the outer of them above the height of the land, you're gonna get an issue with damp through the floor/walls.

As has been suggested by others I'd make a 'tub' so that no damp can enter whatsoever, ie put a full membrane internally across the floor and up the walls, then onto the top of the wall blocks which should be taken at least 1, ideally 2, blocks above the highest point of the surrounding land - it would likely be easier to have the block walls all raised to this height and then the timber garage 'top' structure would just sit on it rather than having to be at different levels to match stepped blocks (more pratty to make and likely more expensive too); aesthetically you could just render or paint the outside of the blocks to make them look better. Internally you'd need to cover the membrane to protect it from damage and make it look better too so you could panel it with something or put in a rubberised floor and take it up the walls to form a continuous easily cleaned area.

I still don’t get it, even if you removed the blocks the membrane went below the foundations 9 inches of concrete with steel in.

 

[CazPaul]

What did planning say?

Was drainage & damp protection part of the spec on the application?

Are building control involved? What have they said?

Planning only interested in the sizes, reclaimed brick above ground, colour, etc

Building control not required

 

[CazPaul]

I assume the builder is going to now put a DPC on the blocks and continue to build up, so the blocks see now will get damp, which is normal, but those above won’t. Then the floor that goes between the blocks (that you can see, and will be damp) will be inside a layer of plastic sheet to protect it from moisture coming up, or through the bricks at the side.

Yes that’s what he’s doing he said. dpc on the blocks/bricks above ground level then the hardcore then membrane then the reinforced concrete floor.

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[Landy Andy]

This is the norm, but you are single brick, and no wood floor.....

 

[Minxy]

im not sure about that the membrane sits below the foundations and the floor will be about 10 inches or more above that so with the damp proof membrane in the floor and dpc in the walls above ground level I can’t see what you mean.

The fact that the membrane has been breached and wooden pegs have been 'enclosed' within the concrete footings could in the future allow damp to penetrate especially once the pegs starts to rot away, it may not happen, but it could.

I’m not sure about that putting the floor membrane up the internal walls all the way to above ground level it won’t look right

Obviously you'd cover the membrane as I suggested, with whatever you wanted really as it would be mainly cosmetic, you'd just have to make sure you didn't puncture the membrane itself whilst doing so so some form of adhesive to stick the membrane to the wall and then again to fix the 'cosmetic' covering over it, no need for nails etc so no risk of piercing it.

The 'tub' I'm suggesting could be done at a later time if you find you have issues with damp inside but if you choose not to do this then you'll have to do something about preventing damp from getting into the exterior walls now, it's either keep it out on the outside or stop it from getting to the inside. I'd go for the internal 'tub' instead as I think it would be an easier, and likely more long-lasting, solution.

 

[M-J]

I would be looking at a creating a gap around the 2 sides and back with drain gullies along the whole run which feed to a soak away at least 3m away.

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[Landy Andy]

The fact that the membrane has been breached and wooden pegs have been 'enclosed' within the concrete footings could in the future allow damp to penetrate especially once the pegs starts to rot away, it may not happen, but it could.

That doesn’t matter as footings aren’t supposed to be kept dry, and the builder will now add the DPC, so everything above that will not transfer the damp higher. The floor will be laid in its own plastic lined hole so that will also stay dry.

 

[CazPaul]

The fact that the membrane has been breached and wooden pegs have been 'enclosed' within the concrete footings could in the future allow damp to penetrate especially once the pegs starts to rot away, it may not happen, but it could.

Obviously you'd cover the membrane as I suggested, with whatever you wanted really as it would be mainly cosmetic, you'd just have to make sure you didn't puncture the membrane itself whilst doing so so some form of adhesive to stick the membrane to the wall and then again to fix the 'cosmetic' covering over it, no need for nails etc so no risk of piercing it.

The 'tub' I'm suggesting could be done at a later time if you find you have issues with damp inside but if you choose not to do this then you'll have to do something about preventing damp from getting into the exterior walls now, it's either keep it out on the outside or stop it from getting to the inside. I'd go for the internal 'tub' instead as I think it would be an easier, and likely more long-lasting, solution.

I think preventing water on the external walls will be the best bet to start with and take it from there, once it p1sses through the external walls you are going to have a problem regarding of what you do internally.

 

[Stoosal]

I would try and avoid tanking/membrane at all costs....unless it is done ‘properly’ (you can read usually expensive). I would dig away wall at rear and side where your trees are and try and leave a proper gap between the garage and ground levels. You would lose a couple of feet of garden at rear and side but it is far better than trying to stop water getting in in the first place via membranes etc. The corrugated pipe builder talks of will route groundwater away from base etc but it probably won’t do anything to stop water trying to get in walls via the earth/gravel against walls.

Other things......conduit for power, water, pedestrian access door, skylights also get a bit of heat into garage via sunlight.

Can’t get individual pics just now but this was mine....it’s a few pages but pics show space left at rear etc. Builder, architect, structural engineer etc all warned me at very start to avoid tanking and make gap away from walls....if you can I would!

My garage build

After years of umming and ahhing about whether or not to build a garage/workshop we’ve finally bit the bullet and decided to give our motorhome an easy life and keep her out of the scottish weather. Building will be in two parts......a garage for motor home (5m x 8.5m) and second part a smaller...

www.motorhomefun.co.uk

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[Minxy]

That doesn’t matter as footings aren’t supposed to be kept dry, and the builder will now add the DPC, so everything above that will not transfer the damp higher. The floor will be laid in its own plastic lined hole so that will also stay dry.

I know footings are not meant to be dry but unless the internal membrane, as in your diagram, is taken above the level of the surrounding ground to above the DPC in the walls (or used to create the DPC), then damp can come through the walls, either from the holes punched in the existing membrane in the ground or through the walls themselves.

I would be looking at a creating a gap around the 2 sides and back with drain gullies along the whole run which feed to a soak away at least 3m away.

Yes, that would be my preference too, it will also allow any dampness to dry out during the year, it would mean the side ground would need permanent retainers putting it to ensure they can't collapse in the future which would be difficult to deal with once the garage is in place.

 

[CazPaul]

I would try and avoid tanking/membrane at all costs....unless it is done ‘properly’ (you can read usually expensive). I would dig away wall at rear and side where your trees are and try and leave a proper gap between the garage and ground levels. You would lose a couple of feet of garden at rear and side but it is far better than trying to stop water getting in in the first place via membranes etc. The corrugated pipe builder talks of will route groundwater away from base etc but it probably won’t do anything to stop water trying to get in walls via the earth/gravel against walls.

Other things......conduit for power, water, pedestrian access door, skylights also get a bit of heat into garage via sunlight.

Can’t get individual pics just now but this was mine....it’s a few pages but pics show space left at rear etc. Builder, architect, structural engineer etc all warned me at very start to avoid tanking and make gap away from walls....if you can I would!

My garage build

After years of umming and ahhing about whether or not to build a garage/workshop we’ve finally bit the bullet and decided to give our motorhome an easy life and keep her out of the scottish weather. Building will be in two parts......a garage for motor home (5m x 8.5m) and second part a smaller...

www.motorhomefun.co.uk

Thank you I agree tanking etc is a poor substitute for a proper build but I can’t do what you suggest, the drive has already been made wider and can’t go any further out either side. We are stuck with this really so I agree anything done now will not be as good as your build but will have to suffice.

A lot of people have the same problem with cellars and rooms below ground etc, to be honest it’s only a timber garage on the second drive to keep the horrendous weather off the van it’s not like it’s the house.

 

[CazPaul]

I would be looking at a creating a gap around the 2 sides and back with drain gullies along the whole run which feed to a soak away at least 3m away.

No can’t do that at the sides not possible there is plenty of room at the rear though for a drain.

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[CazPaul]

I know footings are not meant to be dry but unless the internal membrane, as in your diagram, is taken above the level of the surrounding ground to above the DPC in the walls (or used to create the DPC), then damp can come through the walls, either from the holes punched in the existing membrane in the ground or through the walls themselves.

View attachment 469842


Yes, that would be my preference too, it will also allow any dampness to dry out during the year, it would mean the side ground would need permanent retainers putting it to ensure they can't collapse in the future which would be difficult to deal with once the garage is in place.

I still don’t understand what you mean, when they build houses they don’t put dpc in the foundations do they before the concrete goes in?

 

[Minxy]

I still don’t understand what you mean, when they build houses they don’t put dpc in the foundations do they before the concrete goes in?

No but that is the ONLY thing your building is relying on to protect the interior from the damp which he has 'bridged' by puncturing it, if you look at the above image you'll see how it is done for houses but due to your external ground level the membrane would need to be taken right up the wall which you don't want to do.

I'm just offering suggestions, nothing more.

 

[CazPaul]

No but that is the ONLY thing your building is relying on to protect the interior from the damp which he has 'bridged' by puncturing it, if you look at the above image you'll see how it is done for houses but due to your external ground level the membrane would need to be taken right up the wall which you don't want to do.

I'm just offering suggestions, nothing more.

All suggestions gratefully received thank you, it is always difficult building like this when it’s not an ideal situation and you have to work with what you have.

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[Landy Andy]

So now the black line is the new membrane and the ground line will be higher. The four courses (in the pic) below DPC are not protected from damp but everything else is.
Or lower the ground level, which is ideal, and simpler, but not an option

 

[Stoosal]

If removal of soil to create gap is not an option then bitumen paint outside, cover with black dpm protected by insulation sheets to stop punctures. Backfill with gravel. You are where you are.

 

[sweetie]

Where is ianthebuilder when you need him

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