Ideas please for my Motorhome garage.

[CazPaul]

The builders have dug so much out as the drive is sloping as you can see.

Size planners have agreed to is 8.7 metres long, 3.6 metres wide, door height 3.3 metres, door width 2.9 metres, total height 4.1 metres.

Now as you can see they have really dug into the sides and especially rear, the builder reckons the plastic damp proof will stop any damp coming through the walls, which are 11 inch thick(Concrete block laid sideways on for solidness)

There is plenty of room at the back wall to get access and wonder if that tanking solution or tanking membrane would also help, before he backfills it

They have got some of the blocks down and think the wall would be better stepped now part way down I think that’s a good idea as part of the timber garage would be below ground otherwise.

He says he is putting a field drain in as well around the back and side.

What about a drain down the centre of the floor obviously need to know before the concrete floor gets done.

Any other ideas anyone?

 

[Just smiffy]

Can’t help with the drains, but I was thinking the trees on the right, will they interfere with the garage once it’s up..? Trimming them would be a problem too...

 

[Ivory55]

I have seen some sort of corrugated plastic down the outside with a land drain at the bottom, back filled with a load of shingle. How it works I have no idea, only took the shingle there.

 

[CazPaul]

Can’t help with the drains, but I was thinking the trees on the right, will they interfere with the garage once it’s up..? Trimming them would be a problem too...

They are thankfully not very high and are not the fast growing Leylandi but they will hopefully be coming down before the garage it plonked on the top, which won’t be while end of June.

 

[CazPaul]

I have seen some sort of corrugated plastic down the outside with a land drain at the bottom, back filled with a load of shingle. How it works I have no idea, only took the shingle there.

Yes I think that’s what he’s fitting it’s like corrugated plastic pipe with holes all along it.

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[63720]

It doesn't look much now but you have to imagine it with the carpets down and curtains up.

 

[tribalbrit]

A land drain around the perimeter and covered with pea gravel will re-route much of the water in the ground. A 2000 gauge polythene membrane to the internal floor should be placed on a well consolidated hardcore base prior to concreting. This should be turned up the internal sides of the block work and onto the top, then trapped with an additional course of brickwork prior to placing the garage on it. All joints should be taped. The polythene already in place is all but useless as the timber levelling pegs appear to have punctured it. Polythene externally will also rot over a period of time especially if exposed to UV rays.

 

[CazPaul]

A land drain around the perimeter and covered with pea gravel will re-route much of the water in the ground. A 2000 gauge polythene membrane to the internal floor should be placed on a well consolidated hardcore base prior to concreting. This should be turned up the internal sides of the block work and onto the top, then trapped with an additional course of brickwork prior to placing the garage on it. All joints should be taped. The polythene already in place is all but useless as the timber levelling pegs appear to have punctured it. Polythene externally will also rot over a period of time especially if exposed to UV rays.

Thanks, the polythene in place was placed before the concrete foundations were put in, the punctures are from wooden stakes to get the correct level of concrete in the foundations. It was wrapped around underneath and up the wall so was only punctured beneath the foundations.

Yes when the floor is laid he will use the polythene as you suggest. The damp proof polythene will be back filled he said with hardcore and gravel I was thinking about trying to get some tank membrane glued to the rear wall as well?

 

[Landy Andy]

I wouldn’t put plastic up against the walls on the outside. It stops any air getting to it, and you can guarantee that somewhere it will get a small hole in it and then it will just trap the water against the brick work. There are proper membranes for this, or paint with bitumen to keep water out. I would then lay perforated pipe around wall base then back fill with stone, so water can pass through it. I also wouldn’t have a din in the middle of the garage floor as I can just see it being a pain, and not required

 

[tribalbrit]

Don't thing its necessary, if polythene is fixed as said internally. You would only be protecting the blocks themselves and as these are designed for use in the ground there's not much point. It would also be impossible to make a watertight joint between the tanking and polythene already in place.

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[CazPaul]

Don't thing its necessary, if polythene is fixed as said internally. You would only be protecting the blocks themselves and as these are designed for use in the ground there's not much point. It would also be impossible to make a watertight joint between the tanking and polythene already in place.

Sorry don’t think what is necessary?

Tank membrane glued to the concrete block exterior?

When it’s back filled would water not penetrate the wall and trickle in?

 

[tribalbrit]

Tanking externally not necessary. You will not make a water tight seal between the polythene and any tanking material used. So any moisture that may get in will track under the blocks and into floor area.
Do the waterproofing internally with one piece of good quality DPM.
The blocks may become damp but nothing can get in because the DPM membrane fixed internally will prevent it.

 

[Landy Andy]

But wouldnt you be better to keep the blocks at the rear of the garage as dry as possible?

My garage is set in to the ground and no stone behind wall just concrete. The wall is soaking wet, and anything store in front of it also becomes wet, and then mouldy. I didnt install the garage, I just have to live with it unfortunately. So I would membran, or paint outside, then have only stone touching the external brick/block work.

 

[CazPaul]

Tanking externally not necessary. You will not make a water tight seal between the polythene and any tanking material used. So any moisture that may get in will track under the blocks and into floor area.
Do the waterproofing internally with one piece of good quality DPM.
The blocks may become damp but nothing can get in because the DPM membrane fixed internally will prevent it.

Thanks, when the DPM is fixed before the concrete floor goes down how do you fix it in position as it drapes up the sides WHEN the wall has already been built?

 

[CazPaul]

But wouldnt you be better to keep the blocks at the rear of the garage as dry as possible?

My garage is set in to the ground and no stone behind wall just concrete. The wall is soaking wet, and anything store in front of it also becomes wet, and then mouldy. I didnt install the garage, I just have to live with it unfortunately. So I would membran, or paint outside, then have only stone touching the external brick/block work.

I must say that was my thought too, try to stop any damp material touching the external concrete wall.

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[tribalbrit]

I am assuming the floor level is top of blockwork. ?
So, you have concrete floor, on membrane, thicker the better (2000 gauge). on 25 to 50 mm sand blinding on 150 mm of consolidated hardcore, on the ground you have.
The membrane passes under the concrete, turns up the sides between the concrete and wall, turns onto the top of wall and is trapped with a course of bricks or blocks. This can also trap the one you have externally
The membrane is kept in place by the concrete, which as said I assume is the same height as your blocks.

 

[tribalbrit]

If the external ground is to finish higher than the floor, which is never a good idea, Then any membrane needs to extend higher. 150 mm above the external ground is the norm.
Or do as previously stated but build blockwork up higher than external ground and apply a tanking slurry internally.

 

[GMLS]

Have you thought about security? Maybe time to think about a collapsable bollard? I assume you've got ducting for pulling through power cables from the house?

 

[CazPaul]

Have you thought about security? Maybe time to think about a collapsable bollard? I assume you've got ducting for pulling through power cables from the house?

Thinking more about the general construction at the minute and particularly damp getting in.

 

[CazPaul]

I am assuming the floor level is top of blockwork. ?
So, you have concrete floor, on membrane, thicker the better (2000 gauge). on 25 to 50 mm sand blinding on 150 mm of consolidated hardcore, on the ground you have.
The membrane passes under the concrete, turns up the sides between the concrete and wall, turns onto the top of wall and is trapped with a course of bricks or blocks. This can also trap the one you have externally
The membrane is kept in place by the concrete, which as said I assume is the same height as your blocks.

Floor level will be much lower than top of block work they have really excavated the area to get the ground level as the photos show. There are more blocks to go on yet the photos only show what they have done so far.

So as Landy Andy says the issue I am trying to get ideas for and to prevent is the damp issues that could result because of the walls and ground level externally pressing up against them, particularly rear and the sides at the rear end, getting soaked and leaking through internally.

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[Raul]

I hope this will work for you, but, water can get in at the bottom once it saturated the soil around the plastic. The membrane under the slab would prevent that, if is continuous and lapped at damp course level, 150mm above ground. Field drain is to direct water away so it does not create hydraulic pressure to force it up through the floor. It depends on your landscape and water table.

 

[Littlewheels]

It doesn't look much now but you have to imagine it with the carpets down and curtains up.

Great imagination but its Hardwood floors with underfloor heating and wood shutters to the windows these days.

 

[solaris]

OP made point that at rear, and bit of sides the external ground level will be higher than floor. Dpm under slab will prevent damp rising but for walls tanking and land / french drain round outside is required to stop inside face of walls becoming damp. Dpc in wall should be two courses above external ground level to prevent rising damp so would be stepped front to back as ground rises. Years ago there were various rigid sheet tanking systems. Alternatively cut back soil away from walls all round, but any collapse would risk bridging dpc

 

[Simon Meadwell]

I would use the plastic sheets they use for tanking basements but fixed to the outside approx 6” above ground level and down past damp level . Fix a lead flashing at the top to prevent water getting down behind the plastic. Just google basement damp proofing and it comes up dimpled plastic sheeting .

 

[Ivory55]

Instead of pea shingle, would 20 mm shingle be better. Being bigger the gaps between the stones will be bigger so less chances of silt clogging it up over time. No expert, just thinking out loud.

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[CazPaul]

OP made point that at rear, and bit of sides the external ground level will be higher than floor. Dpm under slab will prevent damp rising but for walls tanking and land / french drain round outside is required to stop inside face of walls becoming damp. Dpc in wall should be two courses above external ground level to prevent rising damp so would be stepped front to back as ground rises. Years ago there were various rigid sheet tanking systems. Alternatively cut back soil away from walls all round, but any collapse would risk bridging dpc

What’s the rigid sheet tanking system please, I thought it would be easy to stand some rigid sheet up against the wall before backfilling, so simple to do as well.

I cannot get access to a lot of the sidewall due to the closeness of the ground. Plenty of room behind the rear wall though.

 

[BouncyBoatFolk]

Instead of pea shingle, would 20 mm shingle be better. Being bigger the gaps between the stones will be bigger so less chances of silt clogging it up over time. No expert, just thinking out loud.

Yes and cheaper. Also reject ballast, that's normally pretty cheap. Tanking the outside wall is the only guaranteed way of keeping ground water out. You need a compression layer of DPM in the brickwork, this expands if becomes wet, thus self sealing., There is a three part fluted vertical membrane that goes straight onto the wall, [ be it brick concrete], then the French drain stone can be laid straight against that. I used this on a project some 20 years ago, that was a basement, it has never leaked.
Mike.

 

[Tombola]

Ive picked up some goods tips here and while not wishing to sound negative, shouldnt your builder already know all this and do whats required ?
Is there an issue wth the builder or something

 

[MisterB]

i would be putting solar pv on the roof. its cheaper to do now whilst its being built and will give you a small return for your investment plus some free electricity when the sun shines !!

 

[Landy Andy]

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

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www.permagard.co.uk

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