Patchwork wall — what's my next move?

[wah_fish]

Hi all, my first post of many no doubt!

While preparing to have this wall replastered in lime, I uncovered this patchwork of materials behind thick layers of gypsum plaster and cement. Not sure what needs further investigation, what needs fixing, what needs removing and what can be left as is. Any advice appreciated!

Building dates from ~1790s in Surrey. Ground floor is brick and first floor is timber framed with brick infill. At some point a small fireplace was blocked up with breezeblock, several inches of cement and some reinforcing metal bars. I think the corrosion and expansion of the metal caused a significant horizontal crack through the modern blockwork/cement and resulted in a noticeable damp line in the plaster. One of the brick infill panels has been displaced outward. The spring sash window is being replaced with a more traditional corded sash.

Thanks for taking a look!



Interior context



Exterior context (room top right)


Detail of displaced infill



Detail of breezeblock and thickness of cement that I've partially removed.

 

[Cubist]

Hi there and welcome,
The things I would be concerned about and feel would need further investigation would be;

• Differential movement due to the use of Portland cement blocks and mortars with steel re-enforcing bars within the timber frame panel(s) versus the neighbouring panels which are likely to have been constructed with lime mortars.
• Decayed and absent timbers of that frame panel that may in turn have weakened the structural integrity of the panel and the wall.
• The nature and condition of the timbers used in the top of the wall to support the first floor structure above.
• Rain-water ingress to the old flue that may have been sited in that wall.

Bluntly I think you should consider getting rid of all the OPC block-work and mortars and replacing with comparable bricks to the rest of the house and using lime mortars. The embedded timbers will also perhaps need to be replaced or repaired if at all possible.

Sorry for this gloomy outlook but I think you've found a large sin of a previous owner.

Good luck, I'm sure other members will be along soon to offer their thoughts too.

Cheers,
Cubist

 

[malcolm]

That's a horrible job. Not sure what I would do. The younger and more enthusiastic me would have wanted to replace the concrete block with brick and lime mortar. The old and weary me would still be keen to remove the cement render but would probably leave the concrete blocks and just lime plaster over them.

Main thing worry about with concrete is what wood it can rot at it's boundaries. It's only a small area that doesn't go down to the floor, there is a good thickness for lime plaster to dry the new window frame, and the remaining timber frame isn't supporting anything anyway. I would leave it be.

 

[stuart45]

Ideally you should avoid using different types of masonry units in a wall because they move, such as expand and contract, differently as Cubist stated. They look like Thermalite AAC blocks, which really suck out the moisture from the plaster or render on a wall.

 

[88v8]

Hi all, my first post of many no doubt!

While preparing to have this wall replastered in lime, I uncovered this patchwork of materials behind thick layers of gypsum plaster and cement. Not sure what needs further investigation, what needs fixing, what needs removing and what can be left as is. Any advice appreciated!

Lordy, what a mess.
Differential materials, embedded timbers.

But a remarkable curved wall.

I presume that flue is open at bottom and top so it's dry, or can be made so?

OK, here's a thought... it's upstairs so breathability is not really important. The external boarding is presumably watertight?

So if you cover the wall internally with well-secured stainless mesh, that will provide some structural integrity to the coating, then it can be plastered with gypsum+fibres.

A non-period thought.