Damp in workshop wall

[Morris]

I have section of wall in my garage/workshop that has a damp issue. The construction is rubbish in this area due to some strange DPC positioning.

The sketch shows it as it was, I removed the inner course of three bricks high years ago as it did nothing. As you can see the next door ground level is below the DPC but that is three courses above my floor level. Those three courses are damp and wringing in winter.
There is no access down the side as my wall is the boundary and there is a shed close to it on next door's land (so no french drain). Also the inner layer of bricks at floor level are damp because whoever built it used commons for the foundation's.
Any ideas from the collective for stopping the damp?

 

[bricol]

I used tanking slurry to stop similar in my garage pit.

I have no idea it that means the blocks will fail and the pit collapse in 5, 10, 100 years time due to holding the damp in the wall.

 

[Olderisbetter]

Pardon our interruption...

I have used this kind of tanking slurry many times to stop damp

 

[Agroshield]

Look up 'cavity drain'. It is like an egg-crate that fixes to the wall. The inside (your garage) is separated by an impermeable membrane from the outside (the face of the brickwork). Apply on your side, seal well top and bottom and make provision to drain the cavity (maybe a sloped channel in the floor with a small sump from which you can pump any water).

 

[gaz1]

I have section of wall in my garage/workshop that has a damp issue. The construction is rubbish in this area due to some strange DPC positioning.

The sketch shows it as it was, I removed the inner course of three bricks high years ago as it did nothing. As you can see the next door ground level is below the DPC but that is three courses above my floor level. Those three courses are damp and wringing in winter.
There is no access down the side as my wall is the boundary and there is a shed close to it on next door's land (so no french drain). Also the inner layer of bricks at floor level are damp because whoever built it used commons for the foundation's.
Any ideas from the collective for stopping the damp?

does the intenernal dpc touch the outer wall ?

as goes for the outer wall that will remain wet and if you seal it in years to come they will be destroyed

Look up 'cavity drain'. It is like an egg-crate that fixes to the wall. The inside (your garage) is separated by an impermeable membrane from the outside (the face of the brickwork). Apply on your side, seal well top and bottom and make provision to drain the cavity (maybe a sloped channel in the floor with a small sump from which you can pump any water).

a cavity drain is what was there but someone removed the inner bricks therefore removed the cavity drain

 

[Morris]

a cavity drain is what was there but someone removed the inner bricks therefore removed the cavity drain

about as wrong as you can be.
There was no cavity drain,I removed the bricks which were attached to nothing, just sitting on plastic DPC soaking wet.
EDIT the drawing looks like there is a cavity,in reality it doesn't exist,just my crappy drawing.

 

[Morris]

does the intenernal dpc touch the outer wall ?

There is no "internal dpc", it's just a piece of dpc sitting on bricks level with the floor,see the sketch.

 

[brightspark]

use taking slurry mixed with a bit of sbr bonding agent and tank up to above the dpc as long as its ok.if it isnt drill 10mm holes along it roughly 4 inch apart and inject it with damp proof jelly in a caulk gun. job done

 

[winchman]

As I see it the only solution is a French drain.
Yes other methods will hide the problem but it may well ruin the brickwork behind the stuff you cover it with

 

[GraemeVW]

When I built my workshop, I dug it down into the sloping garden. Floor is up to 3 foot below outside soil level. Single thickness wall in concrete block. Membrane under 3" thick concrete floor poured after the walls were built. Dpc 6-12" above outside ground level.
I bitumen painted the wall inside the workshop from dpc to floor, and just piled the soil back to the wall on the outside.

I realise about every aspect of this is completely wrong.

It's been up 12 years and ive never had a trace of damp inside and bare steel doesnt rust.

I've no idea how come, unless the bitumen paint is some kind of miracle substance. Flat timber roof, insulated now but didnt used to be. Double glazed windows, no ventilation apart from the log burner which is rarely lit.

So, my recommendation is bitumen paint!

 

[Agroshield]

As I see it the only solution is a French drain.

If, as the OP, the outside is inaccessible, that is difficult to install.

How impossible or impractical would it be to remove alternate bricks in the bottom course and work from inside the garage to install a perforated pipe? Call the first three removed Tom, Dick and Harry.

 

[Morris]

Thanks for the advice guys, I'll have to consider the options.

 

[bricol]

Pardon our interruption...

I have used this kind of tanking slurry many times to stop damp

Same stuff I used.

 

[brightspark]

Same stuff I used.

i dug round a punters garage and put a land drain in but was still getting water coming in from cracks in the floor, tanked the floor and the walls with a few coats of ka tanking slurry and sbr and cured the leaks worked a treat been done 3 years now

 

[gaz1]

As I see it the only solution is a French drain.
Yes other methods will hide the problem but it may well ruin the brickwork behind the stuff you cover it with

yes the french drain would work but so will a drain channel cut out with a grinder

i wouldnt advise sealing the water in on the brick but i would allow it to breath even if that means taking some pointing ( preps ) out so it drains better into the channels the lower down you do it the better it will drain out from behind the wall

but remember its still a boundary wall

 

[Pigeon_Droppings2]

Probably a silly question...does the neighbours shed roof have a gutter?

It's hard to make suggestions without understanding the land...here in London for example we're on a hill and oh boy is the ground wet!

 

[Dapph2]

I had a similar problem, we live on a steep slope so much of the time lazy brickies do a quick cut and fill with out compacting properly then digging foundations correctly , painted my internal outer wall to 12 inches above the outside DPC and painted a a foot wide margin of the floor ( 2 coats of fibre reinforce bitumen waterproofing paint .
I also discovered a few old anchor bolt holes in the floor that wept in rainy weather , they got stuffed with the bitumen and fibre WPM treatment too.

Along the back wall I found that all of my side of the back wall was sat on a DPC level with the floor slab . The builders had cast a double garage slab then before it was dry dropped the DPC on the slab so there is no sensible foundation wall to work with .

There was still heavy moisture ingress on my internal wall ,so in the end I cleared the outside back wall almost as deep as the base was thick and used 10 ,15 and 22mm SDS drills to puncture the cavity from the outside . Painted up some 20 mm conduit and slipped it in the hole as a drain tube . So far four years on no further water ingress.
Could you angle down a 22 mm bore hole to pick up the cavity and also go through the slab floor as well as doing the waterproofing exercises .

 

[jmp49]

I had a breezeblock workshop in a rented property that had similar ground above the dpc, I painted it with water sealant paint on the inside to stop ingress and it seemed to work for the years I was there.
Current workshop is also underground at one end (which is actually great for temperature stability...) and is a centuries stone/mud constructed wall so its a case of forget being able to dpc or injecting it.
I dug in a french drain from the inside just inboard of the wall at the edge of the slab near the underpinning I had to do also, & that leads out the drain at the front because the levels worked, and cut a seperate sump in under the bench where it isnt in the way and is covered with a metal cover, with a lift pump actuated by a float inside.
Mostly the french drain copes with ligher rainfall, and when its torrential rain for days on end, the sump pump kicks in because the french drain doesnt seem to flow fast enough.
Its not perfect, but its never going to be with a stone building with no foundations and the garden next door banked up against the lower part, but its managed the situation, and I dont find 4 inches of water slopping round the floor after monsoon level rain now..

 

[Gareth J]

There wasn't a cavity drain, but could there be? I.e, if you lifted some more bricks out from below your workshop floor, and you have fall to allow a cavity to drain somewhere, you could build a protecting cavity.

Something like surecav 25 would allow you to maintain a good cavity with a relatively narrow gap. Then rebuild another stubby wall against the surecav. It's using the surecav kind of the opposite way around to normal but seeing as the outside isn't yours, probably has to be something like that.

 

[Morris]

Probably a silly question...does the neighbours shed roof have a gutter?

It's hard to make suggestions without understanding the land...here in London for example we're on a hill and oh boy is the ground wet!

It doesn't have a gutter. I know that this is part of the problem. Bit of history. There was an old couple lived next door, Cliff used the shed (it's actually an asbestos garage of poor quality) for his hobby. It housed his r/c model aircraft. He died a few years ago and his widow passed two years ago. There's a youngish couple in now updating and sorting the place. The shed is is used for storing building materials now. He has plans to remove it when it's of no further use and has said that a French drain is not a problem.
We are at the lower end of a gentle slope but it's not part of the problem imo.
Sorry to ramble on.