Internal rendering 200 year old stone cottage

[pasty-man]

Could I please have some opinions please.
What would be the best approach to refinishing the downstairs internal walls in a 200 year old stone built cottage. The current 'plasterwork' is in a varied state from solid through to very hollow sounding/ loose.
About a year ago the upstairs rooms were hacked back to the stone where necessary (50% of the area) also crumbling away several inches of the very soft grey ash like mortar. These walls were rendered in a few stages with a sand/cement/waterproofer then plastered. They have a good solid feel however several fine but long cracks have spread across several areas. This doesn't surprise me and I would put it down to either/both the drying out of a thick render layer and the unflexability of the cement mix.
My current thoughts are:

1) The same again and fill cracks as they appear (But will they keep apearing forever???)

2) Some form of lime render prior to plaster?

3) Provide a structurally strong finish? with the cement render then dot n dab boards & skim?

My concerns are that board may hide future damp evidence/problems and
anything other than a cement pointing/rendering may not give sufficient strength to 'hold the stone together '.

 

[marshman]

lime putty render - mortar is always best over stones because stones expand and shrink and crack anything hard that's used on or around them
as you have seen and lime putty render is skimmed with lime putty + silver sand, this does let the wall breathe,
( do read some of the damp posts )
if you go with a waterproof render then your dot and dab might be the best answer,
I really can't advise to how long the cracking will go on for, I have render and set with both over stone but I never really get back to see my work
years later, I get more work from the customer's friends that tell me how nice it all looks but as the buildings are old and many are listed
there are no new add on's to go back to.

do a google on lime putty render and its uses that may help you.

 

[doormouse1]

My house is 180 years old and solid random stone (550mm thick). I had the walls rendered internally 19 years ago. Some cracks (max 1mm wide) appeared over the first 18 months but haven't changed since. My plaster advised widening the cracks with a blunt srewdriver and filling with the stuff they use for 'dot and dabbing'. He thinks the stuff is flexible enough not to recrack.
I've been to lazy to test if this works.

 

[pasty-man]

Thanks for your responses!

Both great answers. Marshman - I suspected a lime putty render would poss be the way however I have enormous faith in good old cement. Can you tell me if working with lime based products is any harder than conventional sand/cement & multifinish? How does its strength compare to a cement based render or is this not an issue? Do you think I may be creating future problems if I opted for the cement render & dot n dab board? I will search for damp related posts.

Doormouse- Sounds good from a homeowners point of view. The cracking shouldn't continue forever then! Can I ask if this was both up & downstairs. Assuming the house wasnt built on foundations as such has there been any problems with damp either before or after??

 

[doormouse1]

I'm pretty sure there's no foundations.

There was some evidence of damp before internal rendering. None afterwards, except where a skip driver took out a down pipe. I killed all my drills and bits trying to put a new one up (very hard stone).

I've just walked round for you.

All my ceilings are 2.35m high.
The four upstairs rooms with extrnal walls under 3m wide have no cracks at all.
An upstairs room with an external, south facing wall 4.6m wide has a crack above and below the window. (presumably weakest point / maximum expansion).
The longest wall (downstairs lounge - staitcase - upstairs landing) has a diagonal of about 15m. This has two cracks, one by the stairs where it's narrowest and one by a window.
The shorter (<4m) downstairs external walls show no cracks.
A south facing 5m wall has a crack - again near a window.
Three walls that don't face south 5m, 4.5m, 4.5m are crack free

The cracks are less than 1mm, are covered from painting and not that visible.

Hope this is of help.

 

[pasty-man]

Thanks for the effort doormouse! Most appreciated.
So it would seem in your case that there has been little really apart from minor cosmetic issues as a 'problem'. In fact as you say damp has been less of a prob. Are you sure they are solid stone walls or are they of the 'rubble/dirt' filled cavity construction?

 

[doormouse1]

Oh they are definitely solid. Enlarged a few windows when I moved in and some of the stones go all the way through the wall. Taking out 250lbs+ stones from 10 feet up, with just a ladder is scary (and stupid).

Stone are random - some large, some small - but theres no dirt in there. The mortar is white/grey. I assume it's lime based.

 

[pasty-man]

Thankyou so much for your input doormouse. Feeling OK about cement render now. That is of course unless anyone else has their tuppence worth that might steer me back to lime based? I'm quite happy with crack patching. Feel happier with the strength of cement. Does anyone have any good arguments for not using cement??

 

[marshman]

lime putty render is soft, flexible and fatty or if you like sticky when you apply it, it needs time to dry between coats and much harder
to get the final skim good compared to gypsum plaster, its not strong like cement render, you have to fix through it if you want a shelf to stay up.
I would go with cement render, I've never had any come backs from past jobs were the cement render has come away.
After reading doormouse 1 posts, I would be happy with a few small cracks and at 1mm wide I would fill with artex, mix a little in a mug, apply
with a 2 inch scraper and wipe over with a damp sponge,
if you've got central heating turn it on low and warm the house up slowly this first winter.

 

[pasty-man]

Agreed then. All I gotta do now then is find a good plasterer in Bristol. I've had experience of several in the past who all claimed to be good but their work wasn't all that.
If anyone in the area wants to drop me a message feel free.
Thanks all!!!