House re-render BS49

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stevenhunter

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1970's timber frame house alpine rendered directly onto ply sheathing. Some tile cladding on front (first floor only) to be removed. Existing render cracked in a few places. Have had quotes from builders and EWI experts, both very high. Wondering whether we can batten over existing render and then render onto new rib lath to prevent disturbing existing render/sheathing. Currently there is no gap between existing render and sheathing board so thinking this would solve that problem and keep sheathing dry. Can anyone recommend good plasterers/renderers in this area?
 
The qoetes given depends what you consider high! If you have had a few and there all rondabout the same then there you go it aint cheap considering what method you opt for materials labour ect. i would suggest getting a few more qoetes and remember to do a bit of research on whoever you decide to go with. Sure someone will be in touch off here good luck:RpS_thumbsup:
 
Thanks for reply! The quotes provided were roughly as follows: 1) remove existing render, add new timber studwork over existing sheathing, extra insulation between studs, board over new studwork/insulation, render over this:approx £22k + VAT; 2) EWI fixed over the top of existing render and thin-coat finish over this approx £20k + VAT.

The above were requested on basis that we believed existing insulation (70mm mineral wool) would not meet required u-value for renovation of thermal elements as required by building regs. so assumed extra insulation would be needed. It now turns out that existing u-value is better than threshold value requiring improvement so extra insulation not necessary. Therefore now looking for price to remove cladding and re-render to give the house a considerable makeover but without major renovation of walls. Thinking that battens over existing render fixed through to timber frame and then lath/render system over this might be least destructive/disruptive approach.
 
Get some new prices mate for the change in the job , get a few plasterers around and see what they think is best to use etc , also search for any rendering companys rather than builders as they are just going to take a 20-30% cut off the renderers in anyway if your trying to save money ....
 
stevenhunter said:
Thanks for reply! The quotes provided were roughly as follows: 1) remove existing render, add new timber studwork over existing sheathing, extra insulation between studs, board over new studwork/insulation, render over this:approx £22k + VAT; 2) EWI fixed over the top of existing render and thin-coat finish over this approx £20k + VAT.

The above were requested on basis that we believed existing insulation (70mm mineral wool) would not meet required u-value for renovation of thermal elements as required by building regs. so assumed extra insulation would be needed. It now turns out that existing u-value is better than threshold value requiring improvement so extra insulation not necessary. Therefore now looking for price to remove cladding and re-render to give the house a considerable makeover but without major renovation of walls. Thinking that battens over existing render fixed through to timber frame and then lath/render system over this might be least destructive/disruptive approach.
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It will be a lot cheaper this way although it WILL crack within a few years.sand & cement on a timber frame is asking for trouble due to it being very brittle so with the movement of the timber frame and this it will most probably crack.
Timber off then use a carrier board(cement based external render board) then a thin coat render system is the way to go here.
I might be interested as I'm southwest based.
 
bobby said:
It will be a lot cheaper this way although it WILL crack within a few years.sand & cement on a timber frame is asking for trouble due to it being very brittle so with the movement of the timber frame and this it will most probably crack.
Timber off then use a carrier board(cement based external render board) then a thin coat render system is the way to go here.
I might be interested as I'm southwest based.
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Although the existing will need to come off
 
I wouldnt timber stud the new and fill the gaps with insulation over an existing render or a frame with a fullly insulated core. in fact you may not pass BC as the spec for TF is to maintain the cavity, if you go with say a 50mm batten and a 50mm insulant and sandwich this over with a render board with no cavity gap for the frame to breath then I woild almost gaurantee you will move the dew point to an inner surface. @Runswithscissors might be able to explain better than me about that but in short

Building regs for timber frame is to have a 25mm cavity that is ventilated bottom to top to keep the subframe dry of dew and ingressing water as you often get with this type of construction

from what I have read in your post this will pose a problem for you wanting to increase the insulation thickness and it still being effective if it is in front of the cavity and not behind ie, inside the frame.

Do you have a cavity between the current rendered faacade and the subframe ?

a typical build up on today regs would be:

subframe (insulated between studs inside),
sterling osb/plywood sheet, breather membrane like building paper felt etc
vertical 25mm battens,
render carrier board,
render finish
 
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I recon your right there, it wouldn't meet building control doing that.
also I recon around 20 grand is about on the money if your allowing for scaffold materials etc based on a typical detached of around 250 metres ish.
it should only be rated at 5% for vat in any case as its rated at energy related work as a whole incorporating any insulation with the render.
 
I dont recon scaff is in that TBH

Its prob gonna need stripping back, need a vapour membrane and probably a load of render board.

he could look at the EWI RAIL systems but for me I cant see how they provide the values with the cavity being behind the insulant, still some manufacturer still spec it some dont
 
Thanks for the replies.

To clarify, there is not currently an air gap. I guess in the 70's you could get away with that!

So build up inside -> outside is currently: plasterboard - vapour membrane - studwork (70mm) with mineral wool between studs - plywood - membrane - render. Based on 70mm mineral wool we believe current u-value is around 0.55 so less than 0.70 threshold requiring improvement under building regs.

So assuming no additional insulation is required, I was hoping to bring into line with current building regs by introducing a cavity over what is already there. This was why I was thinking battens with gap and then some kind of lath/panels with render over that.

Alternatively, removing existing render then vertical battens over ply, cement boards and render over that sounds workable.

Any suggestions on approx. cost for this? House is detached, two storey, 10m wide, 7m front to back, big windows. I calculated approx 150 m2 area to be rendered.
 
With regards to likely cracking of sand/cement render, does this justify extra cost of K-rend or similar? I've read mixed reports that K-rend isn't all that it's cracked up to (excuse the pun), and that lime added to sand/cement render would give it flexibility to cope with some movement. What I find interesting is that house has been standing near 40 years and render isn't in a terrible state, only a few significant cracks. Also, the existing render would have been added over a timber frame that was new at the time and has no doubt shrunk somewhat since. So on an old timber frame which won't be subject to anywhere near as much shrinkage now, I would have thought I could assume it would be less prone to cracking now than it was then with all other things being equal?

Sorry for all the questions, help and advice very much appreciated!
 
Hi Steve

As Plasterjfe said above would be the most sensible.

I look after the Knauf Aquapanel Exterior Cement Board as a directly applied render carrier board for timber frame and SIP systems. There are lots of options, but your thin current insulation and poor U Value needs to be addressed... I am not sure that adding all the insulation on the outside will help - you will only have so much space under your soffit board on the roof and will need to more services (down pipes, etc) - but this is common issues with EWI....

Also, adding insulation to the outside of a TF wall may cause issues if you use closed cell insulation (the most common EWI material), it will trap moisture in the TF and may cause rotting in the longer term....

If you want to add more insulation outside, fit some horizontal battens and insulate between them with some rock or mineral wool insulation (this will breath outside), then vertical batten with 25mm cavity before board and render... Then add thermal laminate drywall to the inside of the house as well....

None of this will be very cheap, but there may be some grants if you talk to insulation companies (try Knauf Insulation)

Good Luck
 
Renderking said:
How many metres?
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stevenhunter said:
Thanks for the replies.

To clarify, there is not currently an air gap. I guess in the 70's you could get away with that!

So build up inside -> outside is currently: plasterboard - vapour membrane - studwork (70mm) with mineral wool between studs - plywood - membrane - render. Based on 70mm mineral wool we believe current u-value is around 0.55 so less than 0.70 threshold requiring improvement under building regs.

So assuming no additional insulation is required, I was hoping to bring into line with current building regs by introducing a cavity over what is already there. This was why I was thinking battens with gap and then some kind of lath/panels with render over that.

Alternatively, removing existing render then vertical battens over ply, cement boards and render over that sounds workable.

Any suggestions on approx. cost for this? House is detached, two storey, 10m wide, 7m front to back, big windows. I calculated approx 150 m2 area to be rendered.
Click to expand...

Long thread I know but its all there
 
Give this bloke a ring, he will probably point you in the right direction, lives near Clevedon too.

Pete 07973377807.
 
No joy

Not getting much joy with this - a couple of no shows after messages via this forum. Can anyone provide recommendations of trustworthy reliable contacts in this area e.g. Bristol, Clevedon, North Somerset?
 
Bit big for me that to be honest buddy, as i mainly work on my own. Will have a think if i know anyone, and not much experience in EWI either :)
 
HI steven I live in Bridgwater but im in London until April 3rd I can come and see when im back or you can send me a message at Celestial interiors @Hotmail.com or 07946177827 Andy
 
stevenhunter said:
No joy

Not getting much joy with this - a couple of no shows after messages via this forum. Can anyone provide recommendations of trustworthy reliable contacts in this area e.g. Bristol, Clevedon, North Somerset?
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I live in Portishead steve give me a call on 07877263772 and I'll come around and have a look
 
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