External lime render advice, 1830 building

[Lily1991]

Hello,

In June of last year I purchased a building built in 1830 and have been gently stripping the layers of wallpaper back to begin renovation which I am hoping to do myself with a little help from friends and builders - only where necessary.

The house was built in 1830 it’s a 9inch brick single skin construction, but has had very little done to it in the meantime. From around 1970 (ish!) onwards the fireplaces have not been used and there has been no central heating or insulation. The original lime plaster has been buried under layers and layers of wallpaper including some pretty industrial vynl wallpaper that had meant the lime crumbles away completely along with the wallpaper as you remove it.

In an ideal world I would repair the laths, many of which are un-salvageable and redo all of the walls in lime plaster. Unfortunately my budget won’t allow for that for now so hoping to put up insulated plasterboard with a vapour layer straight onto the batons.

My question really (at last! Sorry for the waffle) relates to what I should do about the external wall. The building is end of terrace, the external walls were originally lime but have at some point been re-rendered in cement. The internal walls on these sides are very damp, and when I have stripped them back the lime mortar on the exposed bricks is very deteriorated.

I know the sources of some of the water ingress, cracked window sills etc and there is a large-ish crack on one of the exterior walls that I will need to get some assistance in to tie and patch asap. Should I also be factoring the need to chip off the cement render at the same time, in order to replace with lime render?

I know that in a perfect situation this is what I would do, but given my budget is extremely tight, can I get away with keeping the existing cement render, patching it and repainting, so I can get on with putting up the internal walls?

I’ve done quite a bit of research, but I’m a bit lost at this point and would be immensely grateful for any advice anyone can offer!

 

[Kearn]

Sadly not, the external wall faces are far more important than the internal, in terms of finish. Focus your time and attention here, before the insides as you’ll just end up damaging internal works.
The vapour and insulated plasterboard will make the situation worse, it’s unsuitable for a solid walled building.
Patching lime isn’t too tricky, if you’re willing to try and learn and have patience! You will also be surprised at the resilience of lime once it’s dried back out again.

It’s not just the cracks outside you can see that do the damage, immovable cement render has micro cracks all over as it can’t move as the building does, once moisture gets in, it’s trapped. Then the bricks are continuously wet, and they conduct heat out of the building, as opposed to insulating, as when they’re dry.

There may be other sources of water, not just rain, but broken gutters/downpipes, inadequate roofs, high ground levels, splashback from roads etc which are making the external water ingress worse. Minimise:remove these as you can.

Don’t expect immediate changes, your sodden 9inch wall will take 6-12 month to thoroughly dry.

Don’t patch failed cement, you’re just trapping the existing moisture.
Externally may not have originally been lime rendered, possibly just pointed in lime. Regardless, the biggest gain would be removal of the cement render to stop water being trapped and allow the wall to dry out.

Photos would help further insight.

 

[Lily1991]

Firstly, thank you so much for your response, really enormously helpful!

If you have a moment would be interested to hear your thoughts on the following sort of mid way solution..

The crack in the side of the building I mentioned will need fixing either way as a matter of urgency, as there has been some movement and the wall has bulged out so will need tying back in. If I were to do that as soon as the temperature reaches a level to be able to work with lime - so probably spring/summer. Patch in the repair with lime putty, and repair the existing window sills and gutter etc but then leave the wall as it is (painted cement render) for another year or so, until my budget allows for me to compete the work of stripping back the whole wall.

Then in the meantime if I were to use lime internally (thank you for the guidance on plasterboard and its pitfalls!) so that the walls can at least start to breathe and won’t trap moisture. Would this be a possible solution for the time being to allow for the interior works to be completed?

Many thanks again!

 

[Kearn]

I’d assumed a crack in just the render …!

Adding wall ties isn’t a small undertaking, you’ll be losing some of the cement render there anyway for the pattres I expect. You may find it detaches quite nicely and taking it all off while you have scaffold off isn’t a bad idea financially.

It will benefit form some naked time to dry out, if you plan to render in lime.

Internally, same thing applies, but more exaggerated, as the walls won’t dry as quickly. Don’t expect to be able to lime plaster to completion in a hurry if your bricks are sodden. The lime will fail. We had a 14” brick wall which had been tanked in this project, totally soggy and needed to wait the best part of a year before the float coat was dry enough for the top to go on.

Best bet, is to get it all stripped and give it time to slowly dry out. Forced drying with heat and fans won’t actually speed the process.

 

[Lily1991]

Ok, yes that makes sense, hopefully we’ll have a dry summer!

Where the render had failed internally, would it also be worth holding off on repointing (with lime) until the bricks have dried out?

 

[Kearn]

Ok, yes that makes sense, hopefully we’ll have a dry summer!

Where the render had failed internally, would it also be worth holding off on repointing (with lime) until the bricks have dried out?

Yes, that bit I said also… can’t lime plaster successfully onto a wet substrate.