External insulation to take K Rend Finish

[AChristie]

Hello, we've removed old 1960's tile cladding from our house and intend to have a render finish.

 

Before render,  we'd like to add some external insulation (the cavity walls have an injected foam insulation, but it's not super effective). 

 

The hope for the insulation is that we can also achieve a flush finish with the existing brick piers at either corner of the house. 

 

As per the attached, you can see that the depth is around 190mm (200mm in places).

 

I understand K Rend will have a finished thickness of somewhere between 14 and 18mm.

 

So this means i need to find approximately 180mm of insulation.

 

Does anyone have any ideas on what my options could be for application beneath the render? If i could aod having to do too much wood work to batten out, that would be ideal to reduce cost. So if there were any 'direct fix' solutions. I'm also not sure whether  would need to leave an ar gap, as yo dou with a PIR when inserting into an external cavity.

 

Cheers

 

 

[ProDave]

Are you even sure that blockwork you have exposed is a cavity wall?  It would not surprise me if on a 1960's house that was not just single block then the hanging tiles?

 

I would not want the render to come right out to the face of the piers, I would want some small step back or are you intending to render over the brick pier as well (thus creating a joint in materials just waiting to crack?

[Chanmenie]

Have a look at EWI Store they do external insulation and the silicone render to match and can recommend an installer in your area which would then give the warranty.

I believe their render is up market from K Rend 

 

https://ewistore.co.uk/?gclid=Cj0KCQjwn_OlBhDhARIsAG2y6zNNjisDZYjLv_qO1YE5UXtv1ZiLnyev9BmOg76A-zZaeuGcMcuWIDoaAgtZEALw_wcB

[Redbeard]

EWI does not need a void. It is generally a 'straight-on-the-wall' system. Agree with @ProDave re the blockwork - may well be single skin.

 

I worry about the piers as a thermal bridge. 

 

The foam in your cavities - was it done a long time ago.? A lot of 1960s (and older houses 'done' in the '60s) have urea-formaldehyde foam CWI. Do not, at this stage, worry too much re formaldehyde, but do bear in mind that it can degrade. I took apart parts of a house to replace spalling brickwork and the UF foam was mainly crumbled to dust in the bottom of the cavity. Not everywhere - oddly - but in places. You will know if it is UF. If you find any 'overblow', say in the loft, it will disintegrate as you pick it up.

[AChristie]

9 minutes ago, ProDave said:

Are you even sure that blockwork you have exposed is a cavity wall?  It would not surprise me if on a 1960's house that was not just single block then the hanging tiles?

 

I would not want the render to come right out to the face of the piers, I would want some small step back or are you intending to render over the brick pier as well (thus creating a joint in materials just waiting to crack?

Thanks @ProDave - You have me doubting myself now, we have taken down one of the walls on the leaf of the house which was brick and this did have the pumped insulation inside the cavity - but i will need to double check the blockwork forms part of a cavity.

 

I was looking to hide the piers with the render TBH, as i am not a fan of the colour/type of brick. 

 

I take it you're suggesting that isn't advisable due to having to render over two adjoining different materials?

[AChristie]

5 minutes ago, Redbeard said:

EWI does not need a void. It is generally a 'straight-on-the-wall' system. Agree with @ProDave re the blockwork - may well be single skin.

 

I worry about the piers as a thermal bridge. 

 

The foam in your cavities - was it done a long time ago.? A lot of 1960s (and older houses 'done' in the '60s) have urea-formaldehyde foam CWI. Do not, at this stage, worry too much re formaldehyde, but do bear in mind that it can degrade. I took apart parts of a house to replace spalling brickwork and the UF foam was mainly crumbled to dust in the bottom of the cavity. Not everywhere - oddly - but in places. You will know if it is UF. If you find any 'overblow', say in the loft, it will disintegrate as you pick it up.

This sounds like the stuff i have found in other other wall, i imagine it was done a long time back (can't really tell, only been in the house a couple of years) crumbles to nothing when you hold it. I was able to take it out in fairly large chunks. You can see some of it hiding in this small cavity, it's the white stuff protruding, comes out it largish chunks, but will crumble quite easily.

 

Do I need to worry if it is formaldehyde?

 

There are two piers, they line up with the two ends of the house, possible thermal bridging, but i am hoping to avoid messing around with them. 

 

[nod]

2 hours ago, Chanmenie said:

Have a look at EWI Store they do external insulation and the silicone render to match and can recommend an installer in your area which would then give the warranty.

I believe their render is up market from K Rend 

 

https://ewistore.co.uk/?gclid=Cj0KCQjwn_OlBhDhARIsAG2y6zNNjisDZYjLv_qO1YE5UXtv1ZiLnyev9BmOg76A-zZaeuGcMcuWIDoaAgtZEALw_wcB

If by upmarket you mean more expensive Your right 

I use them all K Rend is by far the best and has better support and warranty 

[Redbeard]

"This sounds like the stuff i have found in other other wall, i imagine it was done a long time back (can't really tell, only been in the house a couple of years) crumbles to nothing when you hold it. I was able to take it out in fairly large chunks. You can see some of it hiding in this small cavity, it's the white stuff protruding, comes out it largish chunks, but will crumble quite easily."

 

Yours looks to have fared a great deal better than my former client's, then. If it is cohesive, as it seems to be, leave it, in my view.

 

Do I need to worry if it is formaldehyde?"

 

As I said, quite possibly not really. Most UF foam was done in '60's and '70's AFAIK and is very likely to have done all the off-gassing it wants to by now. Don't take my word for it; do an internet search.

 

[AChristie]

I did some digging through all the old documents that previous owner left. Looks like the cavity wall insulation was installed by a company called Megafoam (from Kent) back in September 1980. So chances are it is UF Foam, but having done some rudimentary reading as @Redbeard has suggested, enough time has passed.

 

Funnily enough, document also states the Megafoam is guaranteed for the life of the building - ironic, as it doesn't look like Megafoam still exist