Water in garden Shed, how to stop?

Forums › Home Workshop DIY › Water in garden Shed, how to stop?

1 | 2

SepticSceptic

2186 posts

Uber Geek

Trusted

#1563980 2-Jun-2016 09:31

Tape up the outside rim where the wall meets the floor, and then on the inside, use a can of expanding foam run under the gap.

The tape around the outside will keep the foam from expanding outwards. You can always trim up with a sharp knife.

Once the foam has set, and you have trimmed it tidy, you may then need to seal the foam - just to stop the slow deterioration by sunlight, but it will probably last for years even if you dont.

mdf

3512 posts

Uber Geek

Trusted

#1564220 2-Jun-2016 13:16

Is there enough clearance inside the shed to build a floor? Ideally you want the floor inside the perimeter of the walls, so water runs down the walls and under the floor. If you jack it up and build the floor beyond the perimeter of the walls in order to support them, you run the risk that water runs down the walls and into/across the new floor.

If there was enough clearance (i.e. your height plus about 75 mm), and assuming there is a relatively solid concrete base, I'd run lengths of 100x50 F4 sideways (i.e. 50mm up from the concrete) parallel with the direction of the water flow at 400mm centres. Drill recessed holes and dynabolt to the concrete. I'd layer this with another moisture barrier to stop moisture rising up inside the shed, then run smooth(ish) boards/fence palings across to act as the new floor.

Disclaimer: I am not a builder and this may well represent *terrible* practice, but is what I'd do. I'd use 100x50 sideways as you can't get F4 50x50 at my local Bunnings, nor F5 100x50, either of which would actually be better. 400mm centers is probably overkill too but I like a firm floor.

Pro tip: securely nail the outside two floorboards. Then lay the remainder out from the outside into the center. If necessary, over trim the last board by 50mm or so, then "tent" the middle two boards and stomp. This will get the gaps nice and tight.

Pro pro tip: always measure the diagonals (distances to outside corners) before fastening to check that whatever you're doing is square, *before* you so securely fasten it that it will never move again.

Disclaimer 2: some or all of these lessons may have been learned by yours truly the hard way.

frankv

5680 posts

Uber Geek

Lifetime subscriber

#1564251 2-Jun-2016 13:27

Pour a concrete floor inside the shed. Maybe 10mm deep should do? Maybe put some grooves/slots in it in the direction of the slope to allow any water that does get in to get out again without making puddles.

tchart

2379 posts

Uber Geek

ID Verified

Trusted

#1564256 2-Jun-2016 13:32

frankv:

Pour a concrete floor inside the shed. Maybe 10mm deep should do? Maybe put some grooves/slots in it in the direction of the slope to allow any water that does get in to get out again without making puddles.

gzt

17104 posts

Uber Geek

Lifetime subscriber

#1564282 2-Jun-2016 14:02

Adding a false or real floor with some ply and h3 runners is the simplest and best option imho but here's some other random thoughts.

I cannot see the exact roof angle but I am wondering if adding a gutter to the rear of the shed roof will solve 85-95% of the problem.

Btw the weight of these sheds is virtually nothing when the bolts are removed.

The sealing option is actually realistic and cheap with the possibility of lift, seal, replace gently.

In the back of my mind I'm thinking there is a premade adhesive strip like a door seal you could apply to the concrete and drop the shed on. Could be wrong about that. Ideally add a few more dynabolts to seal the deal.

In fact another layer or two of malthoid and some dynabolts might even do it alone.

robcreid

243 posts

Master Geek

#1564291 2-Jun-2016 14:13

MikeB4: Build a false floor or put a pallet in it maybe

My mum's shed had the same problem and that is what I did.

Got some treated fence rails and the cheapest grade treated decking they had and built a false floor. I built it in a few sections so I could pull it out to dry if it got really bad but it seems to still be working ok and drying out after rain after more than a year.

One stupid thing I didn't think of until after I did it was if you raise the floor by a couple of inches you may also need to raise any hooks you have for long handled tools. :)

MikeAqua

7773 posts

Uber Geek

#1564295 2-Jun-2016 14:18

This what I would do. Laying small areas of concrete is easy.

A couple of bays of premix, quick float and trowel and job done.

frankv:

Pour a concrete floor inside the shed. Maybe 10mm deep should do? Maybe put some grooves/slots in it in the direction of the slope to allow any water that does get in to get out again without making puddles.

Mike

Equinox IT

Cloud spending continues to surge globally, but most organisations haven’t made the changes necessary to maximise the value and cost-efficiency benefits of their cloud investments. Download the whitepaper From Overspend to Advantage now.

tdgeek

29740 posts

Uber Geek

Trusted

Lifetime subscriber

#1564601 2-Jun-2016 21:05

SepticSceptic:

Tape up the outside rim where the wall meets the floor, and then on the inside, use a can of expanding foam run under the gap.

The tape around the outside will keep the foam from expanding outwards. You can always trim up with a sharp knife.

Once the foam has set, and you have trimmed it tidy, you may then need to seal the foam - just to stop the slow deterioration by sunlight, but it will probably last for years even if you dont.

There isn't really a gap as such, the wood frame sits on the concrete. The wood is more or less smooth, the concrete isn't, plus the malthoid that was used as the "sealer" is failing Good option, but not sure it will work

tdgeek

29740 posts

Uber Geek

Trusted

Lifetime subscriber

#1564605 2-Jun-2016 21:12

mdf: Is there enough clearance inside the shed to build a floor? Ideally you want the floor inside the perimeter of the walls, so water runs down the walls and under the floor. If you jack it up and build the floor beyond the perimeter of the walls in order to support them, you run the risk that water runs down the walls and into/across the new floor.

If there was enough clearance (i.e. your height plus about 75 mm), and assuming there is a relatively solid concrete base, I'd run lengths of 100x50 F4 sideways (i.e. 50mm up from the concrete) parallel with the direction of the water flow at 400mm centres. Drill recessed holes and dynabolt to the concrete. I'd layer this with another moisture barrier to stop moisture rising up inside the shed, then run smooth(ish) boards/fence palings across to act as the new floor.

Disclaimer: I am not a builder and this may well represent *terrible* practice, but is what I'd do. I'd use 100x50 sideways as you can't get F4 50x50 at my local Bunnings, nor F5 100x50, either of which would actually be better. 400mm centers is probably overkill too but I like a firm floor.

Pro tip: securely nail the outside two floorboards. Then lay the remainder out from the outside into the center. If necessary, over trim the last board by 50mm or so, then "tent" the middle two boards and stomp. This will get the gaps nice and tight.

Pro pro tip: always measure the diagonals (distances to outside corners) before fastening to check that whatever you're doing is square, *before* you so securely fasten it that it will never move again.

Disclaimer 2: some or all of these lessons may have been learned by yours truly the hard way.

The clearance is good now, if I added a floor internally that will decrease which I'd prefer not to.

There is no water running down the walls. Picture this. Slabs are goos and sloped for runoff. The shed is good, internal wood framed, but no floor, the slab is the floor. {revioous owner laid the shed on malthoid. Ugh. Great option for the first year. So the rain runs to the shed and seeps inside. Big seeps after a good fall.

Im tempted to put an external, perimeter, say 50x 5mm treated, glued if there is a nailbond epoxy type of glue to the slab. Seal that with external Bostik, so the rain will just run down the slope of the slab /sealer.

tdgeek

29740 posts

Uber Geek

Trusted

Lifetime subscriber

#1564608 2-Jun-2016 21:16

frankv:

Pour a concrete floor inside the shed. Maybe 10mm deep should do? Maybe put some grooves/slots in it in the direction of the slope to allow any water that does get in to get out again without making puddles.

Not thought of that, thanks. The water only gets in under the front of the shed at ground level, due t the slope of the slab. so a concrete floor would eliminate that as it will just build up and run off. The slab runs front to back and also right to left in the photo.

tdgeek

29740 posts

Uber Geek

Trusted

Lifetime subscriber

#1564613 2-Jun-2016 21:21

gzt: Adding a false or real floor with some ply and h3 runners is the simplest and best option imho but here's some other random thoughts.

That a definite option, the water will still seep under but will be under the raised floor, so that will work. Lose some headroom though.

I cannot see the exact roof angle but I am wondering if adding a gutter to the rear of the shed roof will solve 85-95% of the problem.

No, the only issue is rain run off from the slab to the shed, seeping into the shed

Btw the weight of these sheds is virtually nothing when the bolts are removed.

For some reason I imagines it was heavy, but the more I think of it, they must be light. Which would make it easier to gradually raise without warping

The sealing option is actually realistic and cheap with the possibility of lift, seal, replace gently.

If I realised and sealed then dropped, will the seal that takes up some space, maybe 2mm will fail over time? then leave a gap? But painting may be good idea.

In the back of my mind I'm thinking there is a premade adhesive strip like a door seal you could apply to the concrete and drop the shed on. Could be wrong about that. Ideally add a few more dynabolts to seal the deal.

Rubber? Will look into a layer of strip

In fact another layer or two of malthoid and some dynabolts might even do it alone.

tdgeek

29740 posts

Uber Geek

Trusted

Lifetime subscriber

#1564617 2-Jun-2016 21:26

robcreid:

MikeB4: Build a false floor or put a pallet in it maybe

My mum's shed had the same problem and that is what I did.

Got some treated fence rails and the cheapest grade treated decking they had and built a false floor. I built it in a few sections so I could pull it out to dry if it got really bad but it seems to still be working ok and drying out after rain after more than a year.

One stupid thing I didn't think of until after I did it was if you raise the floor by a couple of inches you may also need to raise any hooks you have for long handled tools. :)

An internal floor as you say is easy, but I will lose the height of the runners and decking.

nickb800

2715 posts

Uber Geek

Trusted

#1564632 2-Jun-2016 22:15

I'd be weary about a 10mm thick concrete topping, not sure if there would be enough internal strength to hold a thin slab together. You could apply concrete bonder to the original slab first, but that costs $$. If going the concrete route I'd go with 50mm thick minimum, although again that would get expensive just through the number of premix concrete bags.

All in all, timber subfloor sounds like a good option. Goes with the principle of working with the water rather than trying to 100% stop it - which is rarely successful. Ideally you want H4 treated for the runners against the slab and perimeter, then you can get away with H3 for the false floor. Yes H4 is more expensive and narrower range but is a must when the timber may be constantly wet. Judging by the wheelibins, the OP is in Christchurch? Check out an independent timber place (e.g. Musgroves, Baier, Onestopdeck shop, Kenneally), should save you quite a lot over Bunnings/etc

gzt

17104 posts

Uber Geek

Lifetime subscriber

#1564655 2-Jun-2016 23:20

Can go with a real floor & keep the same height if there is a bottom plate sounds like there is:
1. Flip shed
2. Fasten 19mm ply (poss h3 but maybe not needed) to bottom of shed
3. Fasten h3/h4 runners to bottom of ply
4. Maybe a malthoid moisture break between the two.
5. To be nice seal the edge of the ply with something even paint

Edit: or 5b push a flash between bottom plate and the cladding but that is probably just overkill for this if you have h3 ply etc.

1 | 2