Lime render - Please Help

[ziggy1979]

Hi All

We have a 200-odd year old property that needs total renovation.

We just discussed plans with an architect/developer who is quoting for the work and he said that we would need to take all the render/plaster off the walls (he's not yet seen the property) and that we would need to re-render the property in "lime render". The property is not listed and we don't have a massive budget.

We assume that the walls are made of stone, render, rock and anything else the original builders could get their hands on (but definitely not "normal brickwork"- most walls are approx 1-2 feet or so wide.

IS it absolutely necessary on these old walls to use lime render or can a "normal" cement render be used instead (I thought it would be cheaper if we did a cement render instead).

Thank you all so much for any advice you can give us.

Thanks

Zigs

 

[roughcaster]

Cement render onto old stonework would "not" give the best results long term. Lime render allows old walls to breathe and is flexibile. Cement render has no give in it, and would probably crack/come loose. "Cheapest" in this case, is definitely not the best option.
You might even "have" to use authentic materials on an older building, i don't know,, maybe our Richard C might know, and be able to advise you.

 

[ziggy1979]

Hi Roughcaster

Thanks a lot for that. I will look forward to hopefully hearing from Richard C.

Just one other question ... is it possible to build a stud wall e.g. with metal studs with a 10mm gap from the stone wall ... insulate and vapour barrier to stop any moisture coming from the stone wall, through the 10 mm gap and through the plasterboard?

If this is possible, would I have to do anything to the existing wall?

Thanks again!

Zigs

 

[roy c]

I think that you wont get much of a "Vapour Barrier" and insulation with a 10mm gap. I have worked in situations when we have been advised to hack all the plaster and render off the stone wall and build a stud wall (3" or 4"x 2") in front of it and leave the wall to "breathe"...

 

[PikeyDIY]

Cement render is fine until it cracks, which it will. Not enormous gaping obvious cracks, just little tiny ones. The cracks will then let in water which cant get back out again. This will eventually lead to you having damp walls.

Lime render is more flexible, so doesnt crack and therefore retains its waterproofing ability. Which is why if you have a solid stone wall it should always be lime rendered.

 

[Richard C]

I assume were talking internal here. The problem with very old properties is that not only are they subject to movement, the solid wall construction & most probably lack of any damp course means they are prone to damp & need to be able to breath. Sand/cement based render does not flex at all well; you can add lime to make it more resilient & this will help with cracking but does not allow it to breath to any extent. I’m assuming your Architect/builder is referring to lime putty render which, because of it’s make up, can be expensive but as the others have already stated is the correct stuff to use. Have a read of this;
http://www.ecomerchant.co.uk/datasheets/Renderingtheneedtobreathe.pdf

Something you need to bear in mind is that if you remove more than 24% of the existing plaster from external walls, you’re changing a thermal element which puts the work under Building Regulations requiring the walls to meet current thermal insulation standards; assuming your walls don’t already meet them, replacing like for like won’t achieve that. A way of achieving it is to build an internal stud wall as roy c suggests, fit a vapour barrier, install enough insulation to bring the walls up to current thermal standards (assuming they don’t already meet them) & board over using Duplex boards. Another method of achieving it is to use Thermaline boards;
http://www.british-gypsum.com/produ...es/gyproc_thermal/gyproc_thermaline_plus.aspx
These are gypsum based plaster boards that come with different thickness of insulation & incorporate an integral vapour control barrier.

Old buildings can be very expensive to renovate & the method you chose depends on listed status (which you say isn’t relevant) & what you want to achieve for your grand old building in terms of keeping it original.

 

[ziggy1979]

Hi Guys

Thanks a lot for all your help.

The walls in question are internal ... does the external render also have to be lime putty render or will a normal cement render be ok (i'd actually thought of using a polymer render)?

You're absolutely right that old buildings can really set you back more than you'd hope! With thatin mind, I am thinking that, in some rooms at least, we could go down the stud wall path.

Just so that I understand it clealy ... would we leave the existing wall (incl existing wall covering as is) and simply build a stud wall i front of it? Would it be best to use aluminium studs? I am concerned that wooden ones might not like the moisture coming through the stone wall and might eventually rot.

Also, does the vapour barrier go on the "stone wall" side of the studwork or does it go on the room side (ie behind the plasterboard but in front of the insulation)?

Just so you are aware this property is in southern spain - not sure whether the heat out there affects the type of lime render we should use. Also, what is a standard amount per m2 to budget for rendering in lime putty render?

Thank you all so much for your help!!!

Zigs

 

[1john]

Can you actually get lime putty render in spain, you need to speak to people out there, my parents have a villa in spain, new build ish mind and my uncle has a old finca which is really old (wouldnt like to guess) and one thing that comes up alot is that they have very different products and very different way of doing things over there than here. The products react differently too. I dont think I have ever seen a smooth flat wall like we have here from multi finish.

 

[trowelmonkey1]

good points boys!

you might find it easier to get hold of 'quick lime'to which you add water to make your own putty, process called slaking, highly volatile/dangerous process though so must be done with LOTS of care and the resulting putty MUST be left to cure for between 3 & 6 months, the longer the better though.

you wouldn't use putty for external render, for this you would want NHL, Natural Hydraulic Lime as this sets with water like cement or plaster does due to the clays in it, comes in 3 strengths 5, 3.5 and 2, 5 being the strongest and should be used for the most exposed parts of the building i was told but you mustn't have a render stronger than the substrate, same as for normal cement render.

think the internal stud option sounds like the best to me.

 

[1john]

The biggest benefit of the studwork is that you can easily hide all of your services in the void, and ofcourse add insulation, i know all cabling is ran in 22mm flexible conduit in spain and this is alot chunkyer than anything that we need to bury over here, also in stone walls you hardly ever get the depth as they are not uniform.

 

[Richard C]

Just so you are aware this property is in southern spain

Well that does rather change things

 

[Micilin]

Just so you are aware this property is in southern spain

Well that does rather change things

Richard - you mean you are not up to date on the Spanish regs?

 

[Richard C]

Just so you are aware this property is in southern spain

Well that does rather change things

Richard - you mean you are not up to date on the Spanish regs?

Not sure they have any after some of the things I've seen .

We do a 6 week house swap every year with my sister in law who has a vila in Calpe. They had a new gas c/h boiler fitted 2 years ago & I nearly had kittens when I saw the flue had been terminated about a foot below the guest bedroom window! On my advice they got the installer back (supposedly approved) I’ve no idea what the Spanish regs. are regarding combustible appliances but to my astonishment, he said it was not a problem I advised them to pay extra & have the flue extended to the eaves but they’ve chosen to ignore my advice ; now I never sleep in the guest room with the window open

 

[Micilin]

Joking aside, the recent Thomas Cook case should have focussed minds.

 

[Richard C]

Joking aside, the recent Thomas Cook case should have focussed minds.

Absolutely; that’s why I don’t understand how the Spanish gas bloke said it was OK. But what I don’t understand even more is that my sister in law has chosen to go with what he’s saying, ignoring both the Thomas Cook affair & my advice when she knows full well my background & experience. Even if it’s not against their Regs. (which I doubt), plain common sense should tell anyone it’s not right; an accident waiting to happen IMO.