What am I looking at and how shall i fix it?

[frustin]

I'm going to decorate the hallway. The hallway was a bolt on to the main house. The main house is made from timber frame and lime render. The hallway is brick. The wall in the pictures is solid and about 1ft thick.
What am I looking at? rising damp? Dry rot?
What can i do to resolve it? dig it out and plaster?
What about refilling it? should i use lime plaster or can i use gypsum?



These are some close ups of that gap - with and without flash used

 

[Cubist]

Whllst at first glance one might conclude that it's a very poor past repair, the last two pictures suggest that the wall is constructed of aerated concrete blocks rather than bricks and finished with a thin mortar render and plaster skim coat. The blocks appear to have been heavily contaminated with salts and this has resulted in the visible damage to the blocks and the irregular blistering of the render/plaster. The remedy would be to remove the damaged render/plaster to get back to the surface of the block-work, use a stiff brush to remove any remaining salt deposits and treat the blocks with a salt neutraliser and when dry apply a new render and plaster to finish.

There are several possible root causes but the most likely are rainwater penetration from outdoors or rising damp. Sadly aerated concrete blocks are extremely vulnerable to any source of water. Is there any evidence of a DPC?

 

[frustin]

here are several possible root causes but the most likely are rainwater penetration from outdoors or rising damp. Sadly aerated concrete blocks are extremely vulnerable to any source of water. Is there any evidence of a DPC?

I moved in 3 months ago and along the outside wall to where this is, i've added a ditch outside, with ACO channelling to ensure there wont be any standing water along that face of the wall anymore. Attached is the ACO picture and blue line sort of denotes the internal wall.

What's a salt neutraliser? also, stiff brush like this: https://www.toolstation.com/hand-brush/p24880

Shall i buy this: https://bestoflime.co.uk/product/patchcote/ to repair it after removing the damaged render?

 

[Kearn]

As it’s in a corner, I’ll assume it’s the reveal to the external doorway as it doesn’t look like the fireplace.

Two very obvious suspects there, leaking down pipe and possible ingress around the door / wall interface.

Equally, you’ve got external evidence of plastic paint bubbling due to moisture trying to escape, so it looks like quite a saturated wall. Which means you’re a long way from repair, first challenge is uncover and let the wall dry out (internally and externally) and ensure you’ve located and dealt with the source of moisture.

That kind of moisture saturation builds up over a long time, but more importantly won’t dry out for a long time either. Once the bricks are free of modern crap and can start to dry out, you’re looking at approx 1 month per inch of thickness. Very little point like plastering sodden bricks leaching salts as it won’t go off. No point plastering in gypsum as it will continue to suffocate the wall.

 

[Janela]

You've been very restrained not to start picking away at the crumbly area inside the house.
Once you take it back a bit pehaps you will be able to see more clearly what you are dealing with and it can start drying giving you time to plan the next step.
I'm also wondering what a salt neutraliser is as my chimney surround is often about an inch deep in 'fleur de sel'

 

[frustin]

Two very obvious suspects there, leaking down pipe and possible ingress around the door / wall interface.

perhaps this will help a bit. i've added the location of the foul water pipe, though there's no smell and i'm pretty sure that it's not leaking

 

[Cubist]

If I recall the content of you previous post to this forum higher levels of damp had been detected by your surveyor on this side of the house than the other elevations. This was in part suspected to be due to rainwater collecting near the external wall on that driveway. Given the work you have already done to improve external drainage away from the wall there is little more that you may be able to do to improve matters other than to wait for the the brick and block-work to achieve a consistent level across the site.

That history also confirms that this side of the house was, and still is, foot-wet and rising damp from the ground below must remain the chief suspect - unless a break or leak can be detected in the foul water pipe hidden in that wall. Given that the hallway is a late addition to the property it is not unreasonable to suppose that the internal skin of the wall was constructed using aerated concrete blocks as I first suggested - these are notorious for their ability to absorb large amounts of water from their surroundings very quickly and must be protected from rising damp by an effective DPC.

A stiff brush like the one you have already identified will help to remove the loose surface layer of salts as the block-work dries and a Salt Neutraliser such as the one in the link below may help for the future but they key is to allow the masonry to dry as thoroughly as possible - as @Kearn has also suggested.

https://www.screwfix.com/p/sandtex-quick-dry-stabilising-solution-5ltr/295HY?tc=MA8&gclsrc=aw.ds&gad_source=1&gbraid=0AAAAAD8IdPx7qgfTKghiNMmikjAh1ZS5e&gclid=CjwKCAiAgoq7BhBxEiwAVcW0LCngruV_iSwmEHH8cWmKjfI-RCNxfiybQrseRp7kJdkX9VXR-6kzchoCTfoQAvD_BwE

 

[frustin]

must be protected from rising damp by an effective DPC

I cannot see a DPC, you can see that there is render on the outside of the wall, however on the plinth in black, it's bricks on this side. Is it reasonable to assume a DPC was built in when this part was constructed?
Can a DPC be added after the fact? that sounds really expensive.
Given that it's winter, i'm assuming that the blocks will take months to fully dry out. In the mean time:
1. Should I clear out that crumbling plaster down to the blocks?
2. do i need to use lime (some of this)? or will gypsum plaster be ok assuming it really is concreate blocks?
3. if the blocks are dry to the touch when i get back to them, can i fill anyway?

 

[frustin]

No rot behind skirt, that looks like gypsum plaster (it's pink), however that metal angle bead is rusted to hell.

The material (where that hole is) is like sand-stone texture. is that aerated concrete blocks? I shone a light down the hole, it goes about an 20mm deep but still just same material so it's not render.

 

[Cubist]

Your latest photos seem to confirm that a gypsum plaster was used to finish the walls surface but shed little extra light on its construction. The porous holes, like those seen in a sponge, are still evident in the damaged area but these could have mislead me into thinking the inner skin is of aerated concrete but I cannot think of another material that exhibit a similar texture. The remedy in my view remains the same; remove the plaster and render to expose the underlying brick or block-work, clean and treat, re-plaster.

I'm intrigued by the steel angle bead you've exposed. Blessed if I can think what its purpose may be, are there any other clues?

 

[frustin]

remove the plaster and render to expose the underlying brick or block-work, clean and treat, re-plaster.

Can i use gypsum?

Blessed if I can think what its purpose may be, are there any other clues?

My guess it's to protect the corner of the wall. I think that because it's metal and rusted it's wicked moisture up and blown the plaster. The rest of the wall, is ok, just that patch and on the other side of that corner. If i remove the plaster as you said, cut away the angle bead and replace that with plastic that should fix it.

 

[Cubist]

Can i use gypsum?

You could, and it would achieve a better bond to the remaining plaster than a lime equivalent.

My guess it's to protect the corner of the wall. I think that because it's metal and rusted it's wicked moisture up and blown the plaster. The rest of the wall, is ok, just that patch and on the other side of that corner. If i remove the plaster as you said, cut away the angle bead and replace that with plastic that should fix it.

I misunderstood, I thought the metal was running horizontally at the foot of the wall. Galvanised steel mesh folded with a 90 degree corner was/is often used to form and strengthen the corners of wall returns and its use confirms that this section of wall is a fairly recent addition. That said, the rusting of the steel will be a direct result of the salts in the brick/block-work. The rust alone has the capacity to blow small sections of plaster lying immediately over the steel but the salts will produce identical and perhaps more significant and widespread. It would be wise to replace this with a plastic equivalent as you propose.

 

[frustin]

I dont have any experience using plaster.
This is what i intend on doing:
1. remove render up to the level of the blown plaster
2. hacksaw off the metal bead
3. replace bead with plastic
4. paint on Sandtex Stabilising Solution directly on wall
5. add plaster, will this do (link)?
6. do i need to add tape or anything at this point?
7. Fine Surface Ready Mixed Filler to give it a smooth finish
8. Sand it

 

[Cubist]

This is what i intend on doing:
1. remove render up to the level of the blown plaster

Remove all salt damaged plaster and render back to the brick or block-work. I'm not sure what 'brown' plaster you're referring to but will assume the top skim coat.

2. hacksaw off the metal bead

Not a good idea. These mesh steel corner beadings are typically held in place using galvanised flat head nails. Cutting anywhere along its length will leave the wanted end with no support. Best to remove all or none of it along the full length.

3. replace bead with plastic - Only of necessary.
4. paint on Sandtex Stabilising Solution directly on wall - Make sure you follow the directions concerning how long it must be left to work and how many times to apply it.
5. add plaster, will this do (link)? - Yes, but better to buy more than you think you'll need. Use a 'float' to apply the plaster a spatular will produce poor results.https://www.toolstation.com/gyproc-easifiller-ready-mixed-filler/p34950

6. do i need to add tape or anything at this point? - No
7. Fine Surface Ready Mixed Filler to give it a smooth finish - No need for this. Use the product at step 5 to achieve the required finish level during that step, the material will it claims produce the desired finish.
8. Sand it - By hand only and using a sanding block and be ready for the mess.

 

[malcolm]

Isn't the problem that the wall is full of water that is pushing modern waterproof plasters off? Ideally you'd figure out why that water isn't evaporating away before it gets above internal floor level, but even without doing that it will help a lot to provide some way for the water to get out of the wall rather than bunging it up again.

There often isn't a lot of water that needs to get out and making the plaster breathable might help a lot. I would knock off all the plaster back to the structure up to just above where it is falling off and replace with lime plaster. Then paint with a breathable paint such as clay paint so that water can get out. Lime plaster is totally DIYable. The working time is so long you can get fed up and throw a trowel at it then come back and finish it in the morning.

The metal corner edgings are a modern thing that makes plastering cheap and easy. I chop off the rusted remains re-plaster without them.

 

[stuart45]

The metal corner edgings are a modern thing that makes plastering cheap and easy. I chop off the rusted remains re-plaster without them.

I normally do the same. When I built our extension, I used straight edges to form the reveals. This method was used up to the 70's, but when Carlite took over the metal angle beads came in.
When using straight edges do the reveals first, as you can fix them to the wall, and then remove them and strut the timbers for the walls off them.