Gypsum plaster issue in 17th C listed building

[jjklu]

Hello all,

looking for some advice please on an issue in our property. We have a ground floor bathroom with the internal side of the external wall that had some cracking and damp marks. I have stripped back the gypsum plaster to reveal a mixmash of brickwork, breezeblock and concrete which I have been drying out for a week or so with a fan heater and dehumidifier.

I have left the plaster on the top half of the wall around the window as you can see as it appears to be fine.

My question is how should I deal with the bottom half?

We had a contractor take a look at it and he suggested we could sand back the bottom part then coat it with a breathable waterproofing substance and paint over it. My concern with this is that it will look like a botch job. My thoughts were to either lime plaster the bottom half or coat it with the waterproofing substance and then clad it.

One thing to bear in mind is the fact that the property is 17th Century Grade 2 Listed.

Excuse my naivety but can anyone see a problem with any of these options?

Any advice would be greatly appreciated!!

 

[stuart45]

What's the exterior of the wall?

 

[vinn]

Its always a good idea to talk to the local conservation officer where work to a listed building is proposed.

As above, pics of the outside would help.
Is the FFL higher than the outside ground level?
Are you on a hillside?
How is your waste drainage arranged after it goes under the external wall?
You presumably have a solid floor but no membrane (DPM) edge can be seen in the pics where the floor meets the wall?

Clean off all the plaster/render to expose the bare masonry.
The contractors suggestions dont appear to be what I would do but more info is needed before suggestions can be offered: eg. do you have external render and do you have waste gullies?

 

[bernardgreen]

Its always a good idea to talk to the local conservation officer where work to a listed building is proposed.

Not just a good idea, it is essential to at least ask if Listed Building Consent will be required BEFORE you start the work. The work you are proposing is similar to that about to be started on my walls. Listed Buildng Consent was necessary for the inside as well as the outside repair and re-pointing.

 

[jjklu]

Thanks for all replies so far. We have had a conservation officer round to ok the work but it is not clear as to the best solution.

I have attached pics of the exterior. As you can see there is a lower decked level immediately outside our back doors, and then a raised decking level outside the bathroom which is at the same level as the garden to the rear. Under the raised decking is a drainage hole directly outside the bathroom underneath the window.

 

[bernardgreen]

I would create an air gap along the full length of the external and thus remove that void under the decking.This would allow the outside wall to breathe into fresh air and not into a dank void. It would also allow steam from the waste pipe to escape to the atmosphere and not be trapped under the decking to condense on the cold stone wall.

At least a foot wide on the raised bit. as shown by green. Or better a few feet wide with a retaining wall along the red line to allow access to the wall without having to squeeze along th narrow path.

 

[stuart45]

The interior would probably benefit from lime plaster.

 

[vinn]

Thanks for the photos.

How a conservation officer(s) passed the whats been going on at the rear of your listed building is hard to imagine?

1. The decks are possibly allowing moisture on to the walls, they also blind the gulley. They should not be in contact with the walls. Is the left hand deck necessary?

2. The garden wall is abutting the house and will be causing penetrating damp. The garden wall needs isolating from the main house wall.

3. What looks like (shiny) plastic paint has been used - my experience is that Listed means no painting if at all possible. Plastic paints cause damp difficulties. Masonry paints are breathable.

4. There is a sand & cement plinth - this would have been installed in hope of eliminating damp, in fact such plinths are a cause of damp. Removing it will be necessary.

5. There are green splash/damp marks just above the gulley. A shoe or a bend is needed to direct water into the gulley. Does the gulley have a grate? Is the gulley trapped and does it run to mains drainage or something else? The gravel surround needs lowering.
What is the stone sill above the gulley the remains of?

6. Further along the rear elevation there is a trellis - perhaps, take it down, you dont want climbing plants on those walls.

7. Where does the down pipe discharge to?