Water coming through concrete shed floor

The_B_Man · 07-11-2019 7:49pm #1

I have a shed out the back that has gotten flooded twice this week.
The heavy rain is causing flooding down the garden, and there's a big puddle at the front door of the shed, however, no water is getting in the front door.

The water is coming up through a gap in the back wall.

I moved into the house last year and the neighbours either side said that they had to get French drains put in as they had drainage issues. The gardens are slightly on a hill going down towards the shed, so all the water pools down there. This is the first time i've noticed the water coming in. I could hardly miss it since it was a few inches at the deepest part (the floor isn't level. Some parts were bone dry, others were a few inches nuder water!).

I reckon we'll have to get the garden done, and drains put in, but that'll probably just mask the issue. I'd rather get this fixed now, as I can't afford a new garden at the moment.

I've attached some pictures of inside the shed. The wall that is leaking is the boundary wall with the neighbour behind me. Three of the shed walls were existing boundary walls, and a slab of concrete was laid down, and the front shed wall (with door + windows) was built on that. So the gap is between the garden wall and the slab of concrete.
I was out there earlier and noticed when I put weight on the area of the concrete floor, I could see some movement as if the floor was moving. I would have thought it'd be more solid, given its a solid concrete floor!

Anyway, is there something I can pour down this, or paint over? (see attached images)

Cheers

looksee · 07-11-2019 7:57pm

On the one hand, if your neighbours are at a higher elevation than you then their drains drain into your garden. Where can you redirect the water to? Is there more 'downhill' for you to direct into?

On the other hand you are not going to get a lot of sympathy for a flooded shed when you created it by building over three boundary walls. What kind of a roof does it have? Where does the rain run off from the roof go?

The only solution is to fix the drainage, you are at nothing until you have done that.

The_B_Man · 07-11-2019 8:14pm

Ye I know about building it on the 3 boundary walls. The previous owner built it years ago! The roof is steel and tilted back towards my garden so it comes down at the front of the shed. There's no leaks from the roof anyway. It's steel with a layer of felt underneath, which is bone dry.

I'll attach another photo of outside the shed. You'll see what I'm dealing with.

I don't care about that flooding as long as the shed stays dry so I'm just trying to find out what my options are in terms of sealing the cracks. I know I could knock the whole thing and start again but I can't afford that right now.

Would some kind of tec7 sealant work? If it works in a shower, then maybe there's one that sticks to concrete that I could apply around the bottom? Or some kind of polyfilla? Or maybe pouring another layer of concrete?

bfclancy · 07-11-2019 9:46pm

No amount of tec 7 will keep that water out. The level of the water is higher than the floor on all sides by the looks of it until drainage is sorted it will continue to happen. Blocks are porous so water will travel straight through

The_B_Man · 07-11-2019 11:00pm

bfclancy wrote: »

No amount of tec 7 will keep that water out. The level of the water is higher than the floor on all sides by the looks of it until drainage is sorted it will continue to happen. Blocks are porous so water will travel straight through

How about pouring some levelling fluid? Is that waterproof? If it's liquid enough, it'd hopefully seep down to where the water is coming from and seal it.

Lumen · 08-11-2019 7:40am

I would start with a bit of research of BS 8102:2009 and then find appropriate tanking products that will help meet the grade you're aiming for.

https://www.watertightconcrete.basf.co.uk/bs-8102-watertight-solution

This is not like tanking a wetroom because you are dealing with hydrostatic pressure from ingress, not egress. Solutions that work fine holding water in will not hold water out, because the pressure is driving the tanking off the wall. Physics is against you.

Calahonda52 · 08-11-2019 8:26pm

French drain ,with a sump, and a submersible pump with a float: have done many of these

the_pen_turner · 08-11-2019 8:53pm

if you cannot drain it away completely i would put a drain around it and dig a big soak away that can take it.

then i would concrete the floor again to seal the wall to floor joining better and to raise it above the flood line

The_B_Man · 09-11-2019 8:00pm

Lumen wrote: »

I would start with a bit of research of BS 8102:2009 and then find appropriate tanking products that will help meet the grade you're aiming for.

https://www.watertightconcrete.basf.co.uk/bs-8102-watertight-solution

This is not like tanking a wetroom because you are dealing with hydrostatic pressure from ingress, not egress. Solutions that work fine holding water in will not hold water out, because the pressure is driving the tanking off the wall. Physics is against you.

I had a read there and figured I'd be going for a grade 3 type A/B, but it seems all the solutions there are admixtures and stuff done during construction rather than a retrofit.

Calahonda52 wrote: »

French drain ,with a sump, and a submersible pump with a float: have done many of these

What's the typical cost of this? And is it a summer job or year round?

the_pen_turner wrote: »

then i would concrete the floor again to seal the wall to floor joining better and to raise it above the flood line

I'm looking at levelling fluid but how thick do you reckon the concrete would need to be? What I mean is, can I throw a thin layer and that'll make it waterproof, or does it absolutely have to be above the flood line? Actually tbh an inch would probably do it. But I'm no expert here.

the_pen_turner · 09-11-2019 8:08pm

The_B_Man wrote: »

I had a read there and figured I'd be going for a grade 3 type A/B, but it seems all the solutions there are admixtures and stuff done during construction rather than a retrofit.

What's the typical cost of this? And is it a summer job or year round?

I'm looking at levelling fluid but how thick do you reckon the concrete would need to be? What I mean is, can I throw a thin layer and that'll make it waterproof, or does it absolutely have to be above the flood line? Actually tbh an inch would probably do it. But I'm no expert here.

I would put 3 inches minium

GolfNut33 · 09-11-2019 8:25pm

Calahonda52 wrote: »

French drain ,with a sump, and a submersible pump with a float: have done many of these

This.

Water coming through concrete shed floor

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