New shed - wet floor

Jamesfinlay26 · 18 May 2017

Hi folks,

Recently put up a new shed which is 10 x 8 in size. I built a concrete pad to place it on which is 10 x 10 in size so there is a 1ft overlap on either side of the shed. Toaday after some heavy rain i noticed water seeping through the floor around the edges of the shed, im guessing this is because i made the pad too big and the concrete is holding the water and allow it to seep through? any suggestions on how to fix this? would guttering fix it or should i just hre a sthil saw and cut the base to size? Thanks

Chud · 18 May 2017

Pictures would help but are you saying the shed floor is directly on the concrete pad (i.e. it has no runners etc on the underside of the shed?)

Jamesfinlay26 · 18 May 2017

here are a couple of photos of the base, the shed floor had runners, so its prob approx 40ml off the ground, the water seems to be seeping through on the inside where the runners are on the outside.

Jamesfinlay26 · 18 May 2017

and here is a pic on the inside of the water seeping through the wood.

JohnD · 18 May 2017

Jamesfinlay26 said:
the shed floor had runners, so its prob approx 40ml off the ground

you mean 40mm?

very neat looking slab. I suppose it's perfectly flat?

I suppose it would be a lot of work to lift it and put something under the bearers. A single course of bricks would be ideal, with a dpc on top, or concrete strips, or those long thin paving slabs, assuming that whatever you put down will get wet so a wooden object will rot. If you used slabs you could jack up one side of the shed or use a lever, and slide them under.

I'd start with gutters. Easiest option, and you need them anyway as the bottoms of the shed will get splashed and rot.

Jamesfinlay26 · 19 May 2017

Thanks for your reply, ye i meant 40mm, not perfectly flat its got a slight gradient, i think the issue is with the rain hitting the pad and splashing up under the shed, will try source some guttering and hopefully that fixes the issue! was talking on placing the shed base on some 4 x 2 runner but decided against it, wish i went ahead and done it now! thanks

John D v2.0 · 21 May 2017

As said above gutters will probably solve the main problem, but for the record any base shouldn't extend beyont the walls due to this problem. If water is sitting on the slab you can cut a groove close to the shed and run it off the edge at the lowest point if it's easier than cutting the slab to size.

Jamesfinlay26 · 21 May 2017

Ye thinking on it that makes sense, the original idea of the overlap was to bolt some anchors on to attach ratchet straps as i live on the isle of Lewis and its not uncommon for 80 mph winds here! would it be worth renting a stihl saw and cutting away the overlap and replace with a shingle as i want to preserve the life of the shed as long as possible. Thanks for your reply.

T6 KFR · 16 Feb 2019

Hi! Trying to solve the same problem you had. My base is similar to your own and the side of shed is hit bad with wind and rain (NE Scotland!). I have guttering which makes no difference as the rain soaks the shed wall.

Any ideas?

conny · 16 Feb 2019

If you are considering raising the shed on slabs or higher runners you will have to make them the same length as the current runners or your floor will sag in the unsupported areas.
The groove idea is a possibility but it would need to be more than a blade thickness, maybe about the width of 3 blades and at least 6-8mm deep.
Along with the groove you could try putting and extra board along the bottom to try and prevent 'splash back' but this will reduce the ventilation flowing underneath.

T6 KFR · 16 Feb 2019

conny said:
If you are considering raising the shed on slabs or higher runners you will have to make them the same length as the current runners or your floor will sag in the unsupported areas.
The groove idea is a possibility but it would need to be more than a blade thickness, maybe about the width of 3 blades and at least 6-8mm deep.
Along with the groove you could try putting and extra board along the bottom to try and prevent 'splash back' but this will reduce the ventilation flowing underneath.

Do you think its splashback though? I was more of the opinion the outer walls were consistently wet and seeping down into the dry floor base?

Its a large shed (9000x3700) so jacking isn’t easy although i was keen to try.

conny · 16 Feb 2019

When you think, a dpc on a house is recommended to be 6" (150mm) above ground level to prevent bridging and splash up, the same would naturally apply to a shed.
A easy way to prevent splash back is to take the gravel right up to the edge of the shed to a depth of at least 30mm, but this would obviously cover the O/P's flags and cover 3/4 of the ventilation area underneath unless he trimmed the flags back flush with the shed walls.

T6 KFR · 17 Feb 2019

Yeh i see your point, thank you.

I could try layering with stones/ gravel along that side that’s affected to gauge improvement- I guess the purpose is draining and reduces splashing?

conny · 17 Feb 2019

Yes, the gravel will help prevent splash back and may help.

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