Leak in new brick and block building

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We had a “shed” built last year; base is concrete and then 4 courses of blue engineering bricks, followed by concrete blocks covered with render.

The shed leaks near the bottom through some of the engineering bricks, the water stains the floor but you can see the damp on the mortar. The roof is flat (rubber) and I identified that rain water was coming off the sides rather than flowing to the gutter at the back (problem 1).

The builder thought that the leak could be a combination of the water coming off the side of the roof and a small overhang from the base. He still sawed off the overhang today. When I cleaned off the dust from render and bricks the leak has happened still.

I’ve had a few issues with this builder and want to be clued up when I talk to him. I suppose fixing the roof might stop some of the water getting to these bricks but my suspicion is there is something up with the mortar and would be more comfortable if that were done.

Any views please?

Thanks
Paul.
 

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blue bricks

peraps the mortar is gappy

show us the gutter and downpipe please

I think the mortar is gappy, did a few experiments with a watering can and it does come through the mortar in the suspect places. It looks like that is the issue. What are the options - obviously repointing but would need to check all areas of leakage have been identified. Or is there something you can paint on to do it that won’t cause condensation inside (it’s not heated or lined as just used as a garage type storage).

The gutter is at the rear as is the down pipe. The issues are at the sides where there are no gutters, the builder says there is a “lip” to channel the water down the roof but the seal has failed.

Is there any issue with blue bricks?
 

JohnD

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Blue bricks don't seem to be working John or didn't you read the post?

i did read it

blue bricks are a fine product and make an effective dpm if used correctly

in this case I suspect shoddy jointing, plus either water is running down the wall, or the concrete base (floor) is below surface level allowing water to run in, rather than out.

in view of water running off the sides of the shed, I suspect the builder may not be very good at building.

At the back of my mind I am thinking about laying a DPM inside the shed, turned up the walls into a tray, and pouring a dry floor slab inside it. you could even add insulation if you wanted.
 

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I think the mortar is gappy, did a few experiments with a watering can and it does come through the mortar in the suspect places. It looks like that is the issue.

water should not be running down the walls. even if the walls were beautifully built, this would cause damp, at least in ordinary brickwork.
 
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water should not be running down the walls. even if the walls were beautifully built, this would cause damp, at least in ordinary brickwork.
Is that a problem with the roof then?? If water hit the walls eg driving rain it would have to run down it?
 

JohnD

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yes.

an ordinary brick wall can cope with ordinary driving rain. it gets a bit wet, then dries out when the rain stops

a single-skin wall has little capacity to do that

and if there are building defects allowing water to penetrate, damp is likely.

such driving rain is infrequent or uncommon in most parts of the UK. Some exposed areas can be unsuitable for CWI without extra precautions. I have a coastal house where the weather side is slate-hung, and in storms water pours off it like a waterfall.

Is your slab above ground level?
 
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yes.

an ordinary brick wall can cope with ordinary driving rain. it gets a bit wet, then dries out when the rain stops

a single-skin wall has little capacity to do that

and if there are building defects allowing water to penetrate, damp is likely.

such driving rain is infrequent or uncommon in most parts of the UK. Some exposed areas can be unsuitable for CWI without extra precautions. I have a coastal house where the weather side is slate-hung, and in storms water pours off it like a waterfall.

Is your slab above ground level?

Yes slab is above ground level and they cut out the overhang to rule that out. I’m sure the problem is a combination of water running down the walls and the dodgy joints. I say that because I experimented with a watering can (spout only), water drained away when pouring on the ground and came through the said dodgy joints when poured on them. Admittedly unrealistic conditions pouring 10 litres of water on a joint but seemed a good way to isolate the issue!!

So I think the answer is (1) stop water running off the roof down the walls - builder is going to resell the edges of the rubber roof and (2) fix the dodgy joints eg by repointing them or painting something waterproof over them all. If it helps I think it’s the vertical joints which are dodgy (based on the experiment above). I’m wondering if (2) is essential or a safety net - basically because I want to be sure the thing is watertight as I owe the builder money which I will use to sort this (as an absolute last resort).

Sorry to sound daft but what’s the difference between an “ordinary wall” and a “single skin wall”? And what’s CMI? It’s unlikely indeed that we have the conditions mentioned as the shed is sheltered on the 2 leaking sides.
 

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houses usually have cavity walls, and unless there is a fault or abnormal condition, rain on the outer skin will not make the inner skin damp, even if there is CWI (Cavity Wall Insulation). Solid (nine-inch walls) have less resistance, but are not usually damp unless there is a broken gutter or something making the wall wet. Either of these is an ordinary wall if built of ordinary bricks (or rendered blocks)

blue engineering bricks are impervious to water and damp should not pass through if they have been well built with strong mortar. They are considerably more expensive and would suggest a high-class job unless the builder is incompetent.

sheds and garages often have walls about four inches thick with a single leaf of brick or block. This is called "half a brick thick" because a brick is about 9 inches long. These have much less resistance to damp and water penetration. It is a cheaper build but adequate for an outbuilding. Sometimes a lining will be added later if it is to be treated as habitable space.

painted-on sealants should not be necessary. The actual fault should be found and rectified

photos would be very useful.

I don't think "sealing the edges" is right. I think it has been built wrong. Try a large spirit level side to side.

consider the possibility that your builder is an incompetent half-wit and is not capable of building a shed properly

in which case you would be better off with someone else.
 
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houses usually have cavity walls, and unless there is a fault or abnormal condition, rain on the outer skin will not make the inner skin damp, even if there is CWI (Cavity Wall Insulation). Solid (nine-inch walls) have less resistance, but are not usually damp unless there is a broken gutter or something making the wall wet. Either of these is an ordinary wall if built of ordinary bricks (or rendered blocks)

blue engineering bricks are impervious to water and damp should not pass through if they have been well built with strong mortar. They are considerably more expensive and would suggest a high-class job unless the builder is incompetent.

sheds and garages often have walls about four inches thick with a single leaf of brick or block. This is called "half a brick thick" because a brick is about 9 inches long. These have much less resistance to damp and water penetration. It is a cheaper build but adequate for an outbuilding. Sometimes a lining will be added later if it is to be treated as habitable space.

painted-on sealants should not be necessary. The actual fault should be found and rectified

photos would be very useful.

I don't think "sealing the edges" is right. I think it has been built wrong. Try a large spirit level side to side.

consider the possibility that your builder is an incompetent half-wit and is not capable of building a shed properly

in which case you would be better off with someone else.
Ok massive thanks for helping by the way. I’ve taken loads of photos and rerun the watering can test.

Firstly the roof. There was a bit of rain last night hence slightly wet. Hopefully you can see that the sides have a “lip” to prevent water run off, this is sealed with some sort of rubbery sealant. The gutter is at the back.

If you look at the fascia you can see where water has run through in one place, this is near where the water penetrates the building. It happens on the other side but you can’t see the water as well so no picture.
 

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