External Rendering

[ragg987]

Do factor in the price - I was surprised (unpleasantly so) at how expensive it is. Love the look, though.

 

The detailing should be done with your render system supplier - each one seems to be slightly different, however attached ours. The fuzzy image (no 3) shows detail under the aluminium cill.

[ryder72]

  On 31/03/2017 at 16:00, Rossek9 said:

 

What is the detail above windows and door for the above?

 

I really would like to get away from a block outer leaf but the traditionalists keep giving me the fear about resale value and also mortgage availability  

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 I suspect this is the expansion joint needed when your render spans multiple floors.

[Russell griffiths]

Why is everybody against having a block outer skin with render. 

 

The amount of agro and cost to use a batten and board with all the taping and cutting. 

 

Our last house was timber frame with a common brick outer that was then rendered with an acrylic render with a texture finish. 

 

I personally believe the risk of movement with a sheet substrate as opposed to a block skin is fairly large. 

[Jeremy Harris]

Lots of good reasons why using a brick or block outer skin is problematic with a timber frame.  The foundation detailing needed to ensure there's no thermal bridging isn't that easy, and adds cost.  A block or brick outer skin consumes a lot of labour cost, probably around double that of a render board skin.  Render board is well-proven and has been used for a long time in other countries, with no problems, as long as it's properly fitted.  Finally, it increases the wall thickness by a lot, for no benefit at all in terms of performance or longevity.

Edited March 31, 2017 by JSHarris

[Roundtuit]

  On 31/03/2017 at 18:24, JSHarris said:

Finally, it increases the wall thickness by a lot, for no benefit at all in terms of performance or longevity.

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Except perhaps decrement delay?  I'd agree, my brick skin is a (very...) expensive rain screen, but I expect it to contribute to the temperature stability inside.  Yes, you can achieve the same thing with alternative insulation types, but then you're back to increasing wall thickness again are you not?

[ProDave]

  On 31/03/2017 at 16:00, Rossek9 said:

 

What is the detail above windows and door for the above?

 

I really would like to get away from a block outer leaf but the traditionalists keep giving me the fear about resale value and also mortgage availability  

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I didn't want a block outer skin. I wanted the whole wall make up to add to the buildings insulation. Hence why I settled on100mm thick wood fibre board. I guess I am lucky I don't need a mortgage, and not planning to sell in a hurry.

 

One advantage of the wood fibre system is there is no cavity, so no need for weep ventilators no expansion joints.

 

The window detail seems to some extent be a local thing. Up here they almost never continue the rough cast top coat into the ingo's, instead leaving those just finished with the base coat. I did insist my garage door ingo's which are much deeper were done with the top coat.

[ProDave]

  On 31/03/2017 at 18:41, Roundtuit said:

 

Except perhaps decrement delay?  I'd agree, my brick skin is a (very...) expensive rain screen, but I expect it to contribute to the temperature stability inside.  Yes, you can achieve the same thing with alternative insulation types, but then you're back to increasing wall thickness again are you not?

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Brick plus cavity =150mm thick for almost no contribution to insulation.

 

Wood fibre board applied direct to (thicker than normal in my case)  timber frame =100mm thick, and adds more insulation to the building. The lack of cavity and hence need to ventilate it will also make the structure more inherently air tight.

 

Battens, counter battens and render board is probably not a lot thinner than the wood fibre board, and does not add the the insulation. Plus, like the block or brick skin needs vents and expansion joints.

[ragg987]

Just to comment on mortgage and insurance with render.

 

Building warranty requested a third party render system warranty on materials and labour before they would sign off. I argued that this is a bba approved system and they had not requested this at proposal time, they relented and issued the warranty.

 

On occupancy, buildings insurance was more problematic due to timber frame rather than render per se. Managed to find a few and got a sensible price.

 

Mortgage company did not question any of the build at all.

 

Resale value ask in a few years. I think not having a brick skin will put some buyers off and reduce the number of interested parties, my feeling is that buyers tend to be conservative in that respect. But we have a 1 in a 10,000 home so perhaps there are buyers out there willing to pay a premium?

 

If you intend to live in the for a while then do it for yourself, is my view. Else we would all just queue up outside the show house in that new estate...

[ragg987]

  On 31/03/2017 at 19:05, ProDave said:

Wood fibre board applied direct to (thicker than normal in my case)  timber frame =100mm thick, and adds more insulation to the building. The lack of cavity and hence need to ventilate it will also make the structure more inherently air tight.

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This was a technique we saw in one German kit-house supplier. Quite a neat solution. We decided to go with MBC in the end and played safe with having the cavity as per TRADA recommendations rather than risk warranty issues at a later date. Our MBC house external walls were not level enough to fix fibreboard tight to the timberframe - we had to use spacers (you can see this in the image I posted earlier) beneath the battens to achieve a square face to render on. Don't know if this is typical or just our build.

[ProDave]

  On 31/03/2017 at 19:43, ragg987 said:

This was a technique we saw in one German kit-house supplier. Quite a neat solution. We decided to go with MBC in the end and played safe with having the cavity as per TRADA recommendations rather than risk warranty issues at a later date. Our MBC house external walls were not level enough to fix fibreboard tight to the timberframe - we had to use spacers (you can see this in the image I posted earlier) beneath the battens to achieve a square face to render on. Don't know if this is typical or just our build.

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Our Timber Frame was perfectly flat enough to fix the wood fibre direct to it with long screws and big plastic washers (the pictures just shows a few scres, a lot more were added later)

[ryder72]

We have finally settled for 47*50 treated battens and counterbattens to create a 94mm cavity. As per TRADA guidelines, battened and counterbattened cavities dont require tapered horizontal timbers.

 

I cant find definitely guidance on the type of fixings to use. Are ordinary nail gun nails sufficient or is it essential to use stainless steel nails for battening and counterbattening given that they are very unlikely to get wet. We will be using annular SS nails for the cladding.

[Crofter]

I just used ordinary nail gun nails on my counterbattens, but I used long screws on the battens. This was because I wanted to fix right through to the stud, and you can feel whether a screw has bitten or not, plus a 90mm nail wouldn't have been long enough.

[MrP]

I would always recommend use of non corrosive fixings for external applications. Even though they are unlikely to get 'wet' there is always going to be risk of some moisture penetrating over long periods. Stainless steel nails are freely available for nail guns, a little more expensive but definately worth the extra in this case.