Room with external concrete render, internal gypsum walls

[Sikes]

Hi

New to the forum and to period properties.

I bought an end of terrace house dating from around 1918. It has stone on the outside (judging by the neighbours) and brick internally. The previous owners have concrete rendered the outside.

Before I knew any better, I had the walls and ceilings of the upstairs rooms covered with gypsum plaster. There are no damp issues upstairs.

Now I've started on the downstairs and have since learnt that this type of house needs to breathe. The first downstairs room I'm tackling has slight damp issues. Probably due to the previous owner not opening the windows for 10 years and the drips from the guttering were hitting the external wall. The previous owner(s) had a chemical injection put into the ground floor (judging by the holes along the side of the house). In the front downstairs room they've put in a concrete floor (as opposed to a red clay tile floor which is in the hallway) and plastered 1m up the wall. I believe this 'tanking'? The plaster above this, which is not gypsum, not sure what it is, has some damp spots.

Finally got round to my question , my budget is tight, is it worth replacing the internal gypsum and taking it all back to the brick to replace with lime? While keeping the external concrete render until I can afford to replace it?

Section of the wall:

 

[livias]

As your budget is tight, then concentrate on
Sorting the gutters
Open windows more regularly than the previous owner did
Unblock air vents
Make sure there is no earth banked up outside
Tart up the interior walls with a coat of paint and get on with your life for a bit

By the end of next summer it should be obvious if there is a major damp problem that you need to address properly

 

[MikeG]

......In the front downstairs room they've ...... plastered 1m up the wall. I believe this 'tanking'?.....

Unlikely. It is almost certainly part of the injected damp-course work. These companies typically strip plaster off the walls a metre high all round, drill their pointless holes and fill with their pointless chemicals, then re-plaster. This has two effects: it removes the damp plaster they encountered when starting work, and it allows them to hide their damage.

 

[Sikes]

Thanks both. Currently sorting the gutters . I suppose the best short term solution is to make all the simple issues are addressed and plaster around?

Worry about lime if I get a serious damp issue? :? The gable end is south facing and has plenty of sun

 

[Abi Cott]

I'm no expert, but the previous treatment of your house sounds like a recipe of actions intended to remedy damp which long term will have exactly the opposite effect. Depending on how long ago the "remedies" were done, you could be the recipient of the unintended consequences.

I'm in a similar situation. Gypsum on the top floor wouldn't worry me unduly now I've got my roof and gutters in good shape, but I've got the opportunity to use lime on the external and party walls so I'm going for it.

On the ground floor I've got serious damp issues. I can't change the ground levels. I have "tanked" walls and a suspected concrete floor.

Based on the research I've done so far I will be looking at creating a Limecrete trench around the perimeter of the room and stripping off the "tanking " plaster and replacing it with ventilated panelling up to 1.2m high. All remaining plaster will be in lime and painted with breathable paint. It might not work, but it's the most cost effective solution I've come across that has a hope in hell of working.

 

[steveb]

We've been through similar pain. One of the constraints would be that the work to remove and re-do is going to be pretty disruptive so internally if you have any plans to decorate the room before you make this decision you are potentially throwing away money. If you can live with it for a while, fix any obvious problems such as the guttering and see what happens first there is an awful lot to say for it. This would depends a lot on your lifestyle and also you need patience as well as heat and ventilation for the damp to dry.

In our case we had cement render externally and "dry lining" internally - so a plasterboard face built on a timber stud wall intended as a cure for damp (most of our neighbours believe that this is the cure) however we know the dry lining was only 10 years old from the previous owner and the damp smell and the peeling paint told us that this wasn't working, in the same way that it doesn't work for our neighbours either :roll:

Removing the plasterboard was simple as it was so soft you could use a spoon which revealed behind a nice brick and stone wall, soaking wet (pictures in some other thread somewhere). Over the next several weeks you could watch the tide mark as the wet area receded up the wall. We hadn't removed the external cement at that point, so just allowing the moisture out of one of the sides was good enough to start the wall drying.

On the top floors we didn't have much gypsum however we did have woodchip wallpaper in the bedrooms coated with about five layers of gloss which probably has similar properties. The original lime underneath had started to crumble and quite a lot came off when we removed the paper but we re-patched it in lime. Like Abi I would be less concerned with gypsum upstairs as long as the wall can breathe on at least one side

-Steve

 

[Lithgae]

I have a ~150-200 year old house, with sandstone ashlar block on the front and irregular stone on the other 3 walls - bought two years ago and lots of damp problems. The ashlar block was exposed but the other 3 walls were covered in cement render.

I have just finished getting all of the cement render off and repointed, and along with 2 stack rebuilds has parted me with tens of thousands of pounds. My render was cracked in places and I was concerned about bits falling off etc, but I don't think it contributed to the dampness so I wouldn't have done it for that reason.

My take on the cement render is that it won't cause much of an issue upstairs because unless a lot of humidity its probably keeping as much water out as its keeping in. I think the problem with cement render downstairs can be if it runs right down to the ground level, because then the damp rising up from the ground can only breath to the inside. If this is the case it could be taken off to expose the stone say up to a foot off the ground or so and that would probably be enough to let the rising damp breath out to the outside.

I also don't think that the gypsum makes a huge amount of difference either, especially upstairs, because unless the wall was damp to begin with if it is vapour impermeable from the outside and from the inside then water can't get into the wall. Maybe more so if it was downstairs because if cement is stopping the rising damp breathing to the outside, and it can't escape on the outside then it will build up and find a way through somewhere. Having said that I don't think it is usually gypsum that is the problem, i think its more likely to be the modern paint that is the bigger factor in preventing vapour transmission.

As others have said, concentrate on the cheap and easy stuff first. My cast gutters were broken and blocked and pouring water down the walls. Its taken over a year since repairing them to dry out but the walls look in much better shape now and a lot less green! I also found a broken rainwater drain just under the ground and right beside a wall which was visibly damp on the outside and had a few mushrooms growing on the inside!

 

[mm289]

As above, fix the obvious stuff first, gutters, soil levels etc.

We have a C18 brick built farmhouse that was "renovated" in the 80's AKA cement rendered on weather wall, 1" cement render on all internal walls then plastered, oh and also injected with damp proof chemical magic :roll:

We have treated ground floor and 1st floor separately as the upstairs doesn't suffer from any damp so TBH isn't worth stripping back.

Downstairs we removed the cement render where we could (plinth at base of wall about 3ft), the wall was literally dissolving as it was so damp. We also removed all the render internally then repaired all brickwork. Where external brick walls had been repointed in cement we also stripped out and repointed in lime.

They had also laid a 3ft concrete path all the way around the house which we also dug up

End result, after creating a billion tons of hardcore and spending a lot of dosh and effort is a bone dry house. Was it worth it? Yes, the house is dry and TBH I don't think it would have surviced another 20 years without serious structural issues from the damp. Would I do it again, no, 'cause now I know what not to buy when I look at an old house :shock:

Cheers,

MM