Plastered walls ruined by damp

[lostinspace333]

Hi we had an old garage refurbed and we managed to get a leak through the walls somehow which would somehow trickle water through the brick work thanks to the old builder. We managed to seal the leak and every time it rains now there hasn't been an oz of water come through so fingers crossed that is sorted but there is an enormous amount of mould/damp whatever you want to call it.

It's made the plaster all flaky ready to peel off and black. I cleaned the walls previously with some bleach it hasn't really grown back but it looked a lot worse than that. Also on one pillar theres a lot of damp and the metal bits which you put in the corners to plaster over have gone brown orangy.

Basically what I need is some help how to completely sort this out now as I want to put a pool table in there and it looks disgusting at the mo. People have told me about scraping the paint off and sealing it with pva glue then painting over it? could anyone explain if that is a good solution?

Just realised we havn't got one of those air vents so I'll buy one and fit one in to improve the ventilation. I don't know how humid the room is but I'm guessing the room might need a dehumidfier because I don't the pool table to get moist.

If anyone can help me on how to sort the below out I will be forever thankful!


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[flameport]

If the angle beads (metal corner edges) in the plaster have gone rusty, then they will need to be removed and replaced. Otherwise, the rust will show through the wall and whatever decoration you have.

Painting the walls with PVA and then trying to paint over it will be a disaster. Don't do it.
If the room is damp and mouldy, it is either due to condensation (which can be reduced by increasing the ventilation), or damp is getting in through the structure somewhere.

When you say 'we had an old garage refurbed' what exactly was done to it? What construction are the walls / floor / roof?

 

[Richard C]

To reiterate Flameport, what exactly was done in this refurb? Garages are usually single skin brick or block work construction & will always be liable to damp permeation through from outside; the pictures indicate this & it’s why the steel plaster beds on the column have rusted & it takes a serious amount of damp to do that. You cannot just plaster over single skin walls, they have to be lined with a damp membrane & insulated, likewise the floor; moisture will permeate through the brickwork & into the plaster & there is nothing you can do that will stop it. Coating with PVA will do nothing to help either, it will not take paint &, in fact, standard PVA is water soluble not water proof; even a waterproof SBR coating inside will not stop moisture permeating into the plaster; plaster hates damp, it will continue to fester & eventually fall off.

 

[lostinspace333]

To reiterate Flameport, what exactly was done in this refurb? Garages are usually single skin brick or block work construction & will always be liable to damp permeation through from outside; the pictures indicate this & it’s why the steel plaster beds on the column have rusted & it takes a serious amount of damp to do that. You cannot just plaster over single skin walls, they have to be lined with a damp membrane & insulated, likewise the floor; moisture will permeate through the brickwork & into the plaster & there is nothing you can do that will stop it. Coating with PVA will do nothing to help either, it will not take paint &, in fact, standard PVA is water soluble not water proof; even a waterproof SBR coating inside will not stop moisture permeating into the plaster; plaster hates damp, it will continue to fester & eventually fall off.

Thank you for your reply, I'm not the most DIY savvy so I will to answer the best way possible.

We originally had an old garage single skin of combo of brickwork and block work on opposing walls. The corner of the room which surprisingly has the damp is the area where the large garage door used to be, this had a lot of leaks etc when before it was done and what the builder did was fill that square in the wall with new blockwork. 2 of the walls were insulated and plasterboard (don't know if he used DPM) put over whilst the other 2 walls were simply skimmed over with the coarser finish then skimmed with plaster.


Because we had the old brickwork in that corner which was exposed to so much moisture, wetness and dampness. The builder essentially kept that as part of the structure and just extended the wall and insulated/skimmed over. So is the dampness there because of the old crappy damp bricks basically?

When you say the walls have to be lined with DPM do you mean the whole face has to be sheeted with some plastic then wool insulation then plasterboard? There are other small areas in the garage like that but not as bad as that corner.

It initially started because of a water leak that seeped through the plaster. The plaster seems fine and strong, doesn't look like falling off because it's been like that 2 years. It's just the paint work that got affected the most and it got black with those mould spores.

Am I screwed?

 

[Richard C]

We originally had an old garage single skin of combo of brickwork and block work on opposing walls. The corner of the room which surprisingly has the damp is the area where the large garage door used to be, this had a lot of leaks etc when before it was done and what the builder did was fill that square in the wall with new blockwork. 2 of the walls were insulated and plasterboard (don't know if he used DPM) put over whilst the other 2 walls were simply skimmed over with the coarser finish then skimmed with plaster.

Is this a fully detached garage or are any internal house walls involved? What sort of insulation was used & how was it fixed? What sort of plasterboard was used, standard wallboard or Moisture Resistant (green)? Are you saying he closed up the garage door opening with single skin blockwork, what sort of blockwork was it? Did he render the outside? Did he put any damp course into the new wall he built? Sounds like he’s used a base coat & skim but even a sand/cement render base with water proofer in it won’t hold back the moisture penetration on a single skin wall, as soon as it gets to the plaster that’s it.

Because we had the old brickwork in that corner which was exposed to so much moisture, wetness and dampness. The builder essentially kept that as part of the structure and just extended the wall and insulated/skimmed over. So is the dampness there because of the old crappy damp bricks basically?

The dampness is there because moisture is getting through from the outside & brickwork in poor condition won’t help matters at all. Unless you cure the damp it will be a recurring problem unless you take more effective measures to keep it out but on a single skin block wall, you’re wasting your time anyway, it’s always going to be doomed to failure.

When you say the walls have to be lined with DPM do you mean the whole face has to be sheeted with some plastic then wool insulation then plasterboard? There are other small areas in the garage like that but not as bad as that corner.

Basically yes but you can use insulated plasterboard some of which has an integral moisture barrier. Rigid foam insulation is more suitable in these sorts of situations; mineral wool insulation is not a good idea unless you’re going to build a new inner skin, effectively creating a cavity wall. But that won’t take care of the floor & unless it was laid with an integral DPM, damp will still come up through the floor.

It initially started because of a water leak that seeped through the plaster. The plaster seems fine and strong, doesn't look like falling off because it's been like that 2 years. It's just the paint work that got affected the most and it got black with those mould spores.

But where was the water coming from? If you’ve cured the leak it may be salvageable for a short time but if it’s rain seeping in through a crappy single skin brickwork, then there is very little you can do short of knocking it down & starting again. I’m getting the impression that this is a conversion done at minimal cost with little regard to the limitations of single skin construction.

Am I screwed?

Difficult to say without giving it an eyeball survey but probably.

 

[lostinspace333]

Is this a fully detached garage or are any internal house walls involved? What sort of insulation was used & how was it fixed? What sort of plasterboard was used, standard wallboard or Moisture Resistant (green)? Are you saying he closed up the garage door opening with single skin blockwork, what sort of blockwork was it? Did he render the outside? Did he put any damp course into the new wall he built? Sounds like he’s used a base coat & skim but even a sand/cement render base with water proofer in it won’t hold back the moisture penetration on a single skin wall, as soon as it gets to the plaster that’s it.

Fully detached in the back garden but one wall is adjacent to a neighbours garage. Insulation he used was the wool stuff with baton rails? and normal plasterboard over on top. Yes he closed it up with single skin blockwork. I'm not sure what he used but it must have just been normal entry level stuff.

No he didn't render it outside, from the outside you can see the different bricks old and new. (My guess is poor construction/pointing is a contributer to the conditions of moisture getting inside). I don't know/think he did use dpm in the walls but the existing ones were pretty damp and messed up anyway so the damp was always there ? am i right.Yes he used a base coat and skim inside for 2 walls.

The dampness is there because moisture is getting through from the outside & brickwork in poor condition won’t help matters at all. Unless you cure the damp it will be a recurring problem unless you take more effective measures to keep it out but on a single skin block wall, you’re wasting your time anyway, it’s always going to be doomed to failure.

What do you mean by getting effective measures to fix it but it's a waste of time?

But where was the water coming from? If you’ve cured the leak it may be salvageable for a short time but if it’s rain seeping in through a crappy single skin brickwork, then there is very little you can do short of knocking it down & starting again. I’m getting the impression that this is a conversion done at minimal cost with little regard to the limitations of single skin construction.

I believe there was a crack in the brickwork somewhere, the builder patched this up and it hasn't had any wetness/damp/leak since.

I really want this corner of the garage sorted. How much money am I looking at, people have told us use this spray or use this glue etc but you guys on here are saying the opposite and I trust you lot more. Would any builder be willing to come a look at it and give us a quote? What would the best measure be to getting it fixed?