Damp coming up under DPC?

[dllive]

Hi all
We have had a utility room built on an existing concrete garage floor. (the garage was demolished). The builder put plastic DPC at about 2 bricks high and put lead flashing around the bottom. When it rains the water pools against the walls:

This water then seems to get inside and rise up. Could it be absorbing through under the DPC and lead flashing and emerging inside? How can this be fixed?

 

[noseall]

Oh dear.

Little thought has been given (in your case) to the reason we have a DPC. The floor and walls should be united in repelling damp via a membrane which is tied into a DPC. This should have occurred at 150mm above external floor level.

Hi all
The builder put plastic DPC at about 2 bricks high

How? You have blockwork showing internally with a door sitting a third of the way up that block???

You may be able to remedy it with DPM visqueen and a screed but I'd beat the builder with the roll first.

 

[dllive]

I *think* this is what the builder did: A strip of lead flashing with DPC on top.

Can you explain how it SHOULD have been done? (So I can meet with the builder forearmed).

Perhaps a fillet of mortar all the way along that edge of the room will suffice?

 

[John D v2.0]

Mortar won't do anything, it's not water proof. That's why we need a dpc.
There probably is a dpc in the block work but obviously it won't prevent the wall below it from getting wet. That is exactly what is happening and is normal for a garage. For a habitable room damp coming in like that is not acceptable, nor is a lack on insulation. I assume that t this wasn't done with building regulations approval.

 

[Notch7]

So is the concrete slab outside, the same one we can see inside?

If so, any water on the outside will soak in and the damp will travel horizontally and travel up through anything porous it touches

 

[dllive]

So is the concrete slab outside, the same one we can see inside?

If so, any water on the outside will soak in and the damp will travel horizontally and travel up through anything porous it touches

Yes, the same blocks.

The room is only ever going to be used as a plant room (ie its where the boiler is, bike, firewood etc...). Do you think this issue is acceptable or should I complain? Should they have put a DPC at ground level? I would have thought the lead flashing they put in would have prevented damp travelling horizontally (unless they didnt put the lead flashing touching down to ground level).

 

[Notch7]

Yes, the same blocks.

By slab, I meant the concrete floor you can see outside and inside. If that is the same then the damp will travel across. Im not sure what the lead would do in that context.

 

[dllive]

Ah yes, the slab is the same.
What should the builder have done? Obviously put in a new floor with DPC in. I think its too late for that as the water cylinder and pipe work is all in. Whats the best way to fix this?

 

[noseall]

What should the builder have done?

Building off a larger footprint slab is asking for trouble in any case, ask any pre-fab garage owner. But working with what he's got he should have:
Laid two courses of engineering brick.
Sand blinded the slab and fitted a DPM lapped onto the engineering bricks.
Fitted some insulation and screeded or concreted the floor level with engineers.
Laid DPC onto the engineers and over the lapped DPM.
Built blockwork and fitted frame.

 

[Notch7]

Whats the best way to fix this?

I wish there was an easy solution. Unfortunately I cant think of a retro solution.

Dpm, insulation and screed is the best you could do now -but that cant be done without moving your water cylinder is in place.

I supposr you could paint the external concrete with a liquid waterproofer, extending up to the dpc. Maybe you could hide it externally with a few paving slabs bedded on sand. Thats proably a rubbish idea but it may keep the concrete near the wall more on the dry side.

https://www.roofingmegastore.co.uk/...kDhmYkYI_SGfHTSTB0Mhuxe5rk6o7lMhoCp4oQAvD_BwE

 

[dllive]

I wish there was an easy solution. Unfortunately I cant think of a retro solution.

Dpm, insulation and screed is the best you could do now -but that cant be done without moving your water cylinder is in place.

I supposr you could paint the external concrete with a liquid waterproofer, extending up to the dpc. Maybe you could hide it externally with a few paving slabs bedded on sand. Thats proably a rubbish idea but it may keep the concrete near the wall more on the dry side.

https://www.roofingmegastore.co.uk/...kDhmYkYI_SGfHTSTB0Mhuxe5rk6o7lMhoCp4oQAvD_BwE

Thanks. As you say, it woul dbe a massive job and inconvenience to move cylinder and pipework.

Painting the external section of slab with a waterproofer sounds good.

I was thinking (not that I know anything!!!) about a beveled edge of concrete which keeps the water away from the wall, like this:

How far away from the wall would you suggest I need to keep the standing water away from. IE: How far do you think the water can absorb through the slab - 100mm? 300mm?

Or perhaps I could dig a little channel with some plastic perforated pipe in it so any standing water gets drained away. (Im clutching at straws).

 

[John D v2.0]

Draining away standing water would certainly help. But water can even absorb through concrete from below, so nothing will be perfect. You will always have to keep the floor area well ventilated and the humidity will always be high in the room.

 

[dllive]

Draining away standing water would certainly help. But water can even absorb through concrete from below, so nothing will be perfect. You will always have to keep the floor area well ventilated and the humidity will always be high in the room.

Perhaps like a gully like this:

Perhaps the builder can

Dpm, insulation and screed is the best you could do now -but that cant be done without moving your water cylinder is in place.

Can he do as you say but leave the cylinder in place, IE: DPM/insulate/screed 75% of the floor area. (I know - complete bodge, Im clutching at straws).

 

[cdbe]

My prefab concrete garage is built on a slab below the external ground level. Water used to pour in - standing water over most of the floor. I put in a fillet of sand/cement/SBR after priming the join with SBR cement slurry. It's been dry for 3 years now. I didn't think it would make that much difference but it was a huge improvement. Bitumen paint on top and up the first course of block would help as well.

 

[dllive]

My prefab concrete garage is built on a slab below the external ground level. Water used to pour in - standing water over most of the floor. I put in a fillet of sand/cement/SBR after priming the join with SBR cement slurry. It's been dry for 3 years now. I didn't think it would make that much difference but it was a huge improvement. Bitumen paint on top and up the first course of block would help as well.

Wow - that sounds just the ticket! What is SBR? How wide was the 'fillet'? This is a big ask, but can you take a photo of it? (Dont worry if not)