So I have this damp wall...

It's a damp corner of the building attached to our house - art studio. 120 year old building with 400mm thick walls. The ground level outside is about one metre higher than the concrete floor of that building, hence the dampness.
I'm wondering whether to try and seal the wall before repainting, or just not paint it so it can breathe - though it will be moisture laden breath, which isn't ideal.
If I seal it, what might work? My preference would be to seal and paint.
Now is the time to do it with Sydney going through such a dry spell.
Scott

 

@Depreciator - you're battling hydrostatic pressure, simply sealing it will trap the moisture and force it up higher in the wall.

Application of a membrane to the inside is just asking for trouble (the pressure will eventually cause the membrane to lift and the problem still be there).

Typical treatment - do nothing, repaint frequently. May lead to salt attack in the brickwork, degradation of mortar, building failure .

Part 1 If possible, excavate outside, tank the wall, install a damp proof course (dpc) above ground level, protect the membrane with fibro then backfill. That will reduce moisture from external sources and stop it beyond the dpc. That's not going to happen (5#!+load of work for very little payback).

Part 2 (option 1) - strip the render internally to 1m above affected area, install dpc 2 courses above external ground level, allow wall to dry out (about a month or so with forced ventillation) apply Krystol to bare brickwork, then cement render with more Krystol additive. Paint when cured.

Part 2 (option 2) - Use a product like "No More Rising Damp" (liquid siloxane). This will involve stripping the paint to get the wall to a dryer state (not just surface dry). Drill the c@rp out of the wall - in this case you'd probably need to do it above ground level as well as into the hob (and also from outside if the brickwork has no cavity). Let it dry out. Re-apply. Let it dry out. Letting it dry is important (apart from the VOCs in the silicone, you have now trapped all of the moisture in the wall by forming a horizontal (silicone based) dpc, this moisture has to come out of the wall. Once tested with a moisture meter (several times over including after rain/good soaking with hose with a trigger nozzle between 10.00am and 4.00pm - you can't be seen to be wasting water ) and you're satisfied that no more ill effects due to rising or horizontal damp, then you can repaint.

Part 3 - Spray your exterior wall with siloxane to repel rain etc on the surface.

Part 4 - Monitor and Pray. Send daily sacrifices to the water dragons.





This wall had rising damp up to 2m above FFL - I was lazy and didn't remove skirtings or the paint (which traps the moisture for longer), wall drilled at 125 mm intervals.. Wall needed repainting after 6-8 months - I missed part 4 for 1 day .






This place is as best as I can date it 1880-1890 based on subdivision & sales information from govt website.

Linky - State Library Records
Petersham Estate - in the days before the roads had names

 

Thanks for all that.
Impressive drilling.
There is another building butting up to this one, so excavation or getting to the outside of the wall is not possible.
No cavity - solid 400m brick.
I think that wall can stay unpainted - I'll scrape the existing paint off as it lifts and call it 'patina'.
There is a dehumidifier down that end of the studio, so I reckon that might have to suffice.

 

Sounds like 'do nothing' (at the least, a coat of Krystol will probably improve things - have used it on heritage lift pits where no access is possible externally).

 

Krystol won't force the damp upwards?

 

That's a pity both the external wall's are one,otherwise a few vents along the bottom sections maybe would reduce the damp effect ..Myself i would just seal it off and paint the entire section ,and that may have to be done quite often..imho..

 

Krystol is a cementaceous product, as it's name implies it is crystalline. It forms a water resistant surface by growing towards the moisture and forming a plug (of sorts).

You'd probably look at KMA (K-309) or K-321

Brochure

 

It was boring. Next time I'll leave it to someone younger.

Just get a 450mm long x 10mm dia drill bit and treat the full depth.

 

A $90 solid carbibe masonary head by Hilti would fix the problem ,and they will drill straight through the rebar and very hard to break.. imho...

 

I know that I went through a dozen or so TC drill bits and I was only doing single skin (for most part).

The wall in question appears to be 230-250 brick with an extra skin at the bottom. I wouldn't expect to hit reo. If you do, shift the drill another 2" and start again.

A wall that thick will take a very long time to dry out too, so trying to use a liquid membrane may not be too effective if the brickwork is already saturated.

 

The wall is thick and the hob down the bottom is an extra 200mm. It's a pretty solid building.
Outside ground level is one metre higher than inside, so not much point drilling holes at floor level inside. And given there is a metre of dirt and a building against that wall, it's never going to be completely dry.

 

I measured the thickness of that wall. The hob is 250 and the rest of the wall 350mm. So at its thickest point, it's 600mm. And at that point it is below the level of the ground outside.
Treating the outside of the wall is not an option. And injecting is not an option. So that leaves getting as much paint off as possible, leaving it to dry as much as possible, and trying to seal it.
I suspect it will never be 100% dry before sealing.

 

Krystol it is then, it will grow into the existing brickwork/render to form a watertight(ish) seal.

 

Zinsser Watertite?

 

I'll check them both out. The thinking behind the Krystol one sounds interesting.

 

So I spoke on the phone to a very helpful bloke at Krystol. He said because I'll be leaving the existing render there, the best product is KGM-500. It's a two part epoxy primer sealer. He knew we weren't talking about a big commercial job and asked where I lived. He told me about a company near me called Enviro. He said they are good and will have their own version of a KGM-500 type product.

 

I know the crowd, they've rebuilt their offices, showroom & factory (they have an on site industrial chemist who formulates all of their products).