Retrofit damp course

[bebeboeuf]

We have an attached brick built outhouse/shed (c1900) which has in the past been converted to a kitchen.
It was never built with a damp course and there is one problem wall that has damp rising up a few bricks worth in places.

We have had a few different surveyors over. Some damp specialists and some independent and they all agree that no damp course is in place and one should be retrofitted.

Is the injected chemical damp course the best way to go here or is there any alternatives we should be looking at before getting the work done?

The injection ones don't always work. You could probably remedy it by using lime plaster on the interior of the walls and making sure the exterior ground level is lower than the internal floor level. The lime plaster will let the small amount of moisture coming in through the wall come into the room and evaporate which will stop it building up in the wall.

We have no damp course anywhere in our house and the only damp problems we have are where we haven't got round to fixing the gutters.

Look for the source of water. Most likely a plumbing, drain or gutter leak.

There’s definitely no pipewrok in the wall.

It’s external wall. The outside levels are low.

One thing that probably doesn’t help is that the external side of that wall is considerably shaded so doesn’t get the heat of he sun.

Drainage is good, gutters replaced, ground levels at correct height.

The level of damp doesn’t change, doesn’t decrease or increase at all.

We have had a dehumidifier running and that’s reduced it slightly but generally the humidity reading from my hygrometer in that room is at a steady number and peaks at about 55 at worst.

is there a drain on the outside of that wall?

is it a solid floor?

Do you know the route the incoming water supply pipe takes?

It’s a solid concrete floor but laid directly onto earth with no dpm.

There is a drain about 5ft away. From talking to neighbours the shared drain had issues before we bought the house but they all organised for them to be cleared.

No other drainage issues since we moved in.

Incoming water supply was renewed with poly pipe by water company before we moved in too.

The only other things I have noticed about the wall is that there is no actual damp smell coming from it.
No mildew or mould has ever formed on that wall.
There are salts coming through which I regularly brush off and they reappear

If you have salts coming through at that point, the salts will attract moisture from the atmosphere and make the wall wet.
Try this - it worked for me on a long standing problematic wall.
Wash the salty area with a mix of 50% tap water and 50% white vinegar.
Let it dry and see if your damp patch has gone.
I couldn't believe it when I did it.

"There is a drain about 5ft away. "

In that age of house it will be glazed clay, which is usually cracked and broken at bends, traps and gulies. Can you see any gullies or manholes?

There’s a visible manhole in my patio. I’ve never looked in it. (Not too sure what I’d be looking for though)

What does the drain look like?

I’m a tad embarrassed to say I have no idea if I can even lift the drain cover: it’s heavy and has the brick patio Ladin into it

what did you mean by "There is a drain about 5ft away. "

You won't be able to lift a cover that's inlaid with paving.

Sorry I meant that there is a manhole I can see 5ft away

This indicates a drain is there underneath?

yes

can you draw a sketch plan, and post some photos, including the wall with damp patches?

Include any downpipes from gutters and any drains or pipes

I haven’t drawn a sketch plan yet but I have been doing a bit of investigative exploration on the areas that appear damp.

I’ve removed all the loose bits and what it’s shown is the point that the moisture is coming up the wall is where walls have been removed in the past.

Photo attached showing the junction where the wall and floor meet and the gap between. I poked my finger about and where there isn’t brick underneath is malleable clay type stuff.

I’ve also noticed after clearing that some weird black patches appear.
This feels almost like charcoal and a bit gritty when I poke my finger to it.

Here’s some photos.

Looking down the gap I think I can see something grey. It isn't a lead pipe, is it?

There seem to be gaps between the bricks. I have seen this before where a long-term leak has washed the mortar away, probably where it was lime mortar which is relatively soft.

The bricks don't look particularly wet at the moment.

My thoughts was that it was old lead pipe but I had a plumber out to check it where it connected and he said it was copper.

I’m still in doubt.

I have arranged for that stretch of pipework to be renewed anyway just for peace of mind and whilst everything is visible

Do you think it’s all just down to that?

Have you seen any worms? What colour?

The bricks are feeling so much dryer to the touch now everything is exposed.

I just didn’t want to replanted and find it starts creeping up the wall again

No worms that would totally concern me as I hate anything creepy crawly

Why would there be worms?

The black stuff could be deposits from coal if it was a coalshed previously?
I agree with PJ, that looks like it might be a lead pipe in one of the photos.
Chemical DPCs rarely work and can cause more problems.
Is the external wall half brick thick (102.5mm) or was the wall upgraded when converted to kitchen (i.e. is it now a cavity wall or a thicker brick wall)

Old pipe in the ground is sometimes disused and sometimes carrying water. Copper might have been sweated on to it to fit a new stopcock or to join on extra pipe. Very few plumbers are old enough to work lead pipe. Lead pipe a hundred years old may well leak, especially where it has been jointed to copper.

Red worms are found around broken drains and soil pipes. I presume they like the organic material.