EWI & cladding

[LSB]

I'm using EWI on our single skin conversion, but everything I find about it talks about the top coat being render.

The last bits being fibreglass mesh & basecoat on top of the insulation, then the render.

But we are mixing Render & Cedar cladding.

It doesn't seem right to put the cladding battens directly onto the insulation as there will be cold bridging issues around every insulation board, but is the basecoat / mesh just for render.

 

Thanks

 

[Iceverge]

Yes. Mesh is there to reinforce the render. The only benefit otherwise I can think of is pest/insect proofing the the insulation.

 

What is the insulation material?

 

Do you have a detail for the cladding installation? You shouldn't have any bridging of done correctly. 

 

[LSB]

2 minutes ago, Iceverge said:

Yes. Mesh is there to reinforce the render. The only benefit otherwise I can think of is pest/insect proofing the the insulation.

 

What is the insulation material?

 

Do you have a detail for the cladding installation? You shouldn't have any bridging of done correctly. 

 

The instructions we have been given are to attached the insulation with dot and dab adhesive and 5 screws per board.

We have not been instructed to tape the board joins as the adhesive & render will stop any cold bridging.

Obviously we can tape if we can attached the battens direct to the insulation with very long screws through to the block.

I was also wondering about DPM / vapour mesh (breathable)

 

The insulation is  

Kingspan K5 external wall board 70mm thick

 

[Iceverge]

Am I right in thinking your wall build up will be 

 

1.Existing wall

2. Kooltherm K5 dot dab and screwed. 

3. Basecoat of render with reinforcing mesh about

4. Top coat of coloured render 

 

or

 

1. Existing wall

2. Kooltherm k5 dot dab and screwed

3. Breather membrane. 

4. Treated battens fixed through the kooltherm into the wall. 

5. Cedar cladding.  

 

Cold bridging shouldn't be a problem if   the boards are fitted tightly to each other. Mesh and render won't do much to improve this. 

You may be able to omit the plastic fixings under the cedar cladding as your battens will have the same effect. 

Have you thought about how you will join your membrane under the cedar to the render. This should be continuous as it is your weatherproof layer. 

7 hours ago, LSB said:

Obviously we can tape if we can attached the battens direct to the insulation with very long screws through to the block.

I was also wondering about DPM / vapour mesh (breathable)

 

You've lost me a bit here I'm afraid. Is it a contractor you expect to carry out the work or DIY? 

 

 

 

[LSB]

3 minutes ago, Iceverge said:

Am I right in thinking your wall build up will be 

 

1.Existing wall

2. Kooltherm K5 dot dab and screwed. 

3. Basecoat of render with reinforcing mesh about

4. Top coat of coloured render 

 

or

 

1. Existing wall

2. Kooltherm k5 dot dab and screwed

3. Breather membrane. 

4. Treated battens fixed through the kooltherm into the wall. 

5. Cedar cladding.  

 

Cold bridging shouldn't be a problem if   the boards are fitted tightly to each other. Mesh and render won't do much to improve this. 

You may be able to omit the plastic fixings under the cedar cladding as your battens will have the same effect. 

Have you thought about how you will join your membrane under the cedar to the render. This should be continuous as it is your weatherproof layer. 

 

You've lost me a bit here I'm afraid. Is it a contractor you expect to carry out the work or DIY? 

 

 

 

Hi, it's DIY and the above is how I understand it needs to be.  

I was happy with the render path, I just wasn't quite so sure about the cladding as I was worried about the join between the insulation sheets, but you seem to be saying that it isn't an issue.

 

The build is an L shape so 6 walls, 3 are render and 3 cladding so the join will be corners, there will be cladding to cladding, render to render and cladding to render,  and I haven't yet thought about joining, makes my brain hurt ?

Suggestions welcomed, it will be a year or slightly more before we are doing this, I'm just planning it out at the moment.

Our planning permission just agreed with our statement of 'render or cladding'.

 

[Iceverge]

What condition is the building in as we speak? Do you know the current wall build up? 

 

How did you arrive at 70mm kooltherm? It's an expensive insulation. The only justification I could see for it is if you were really limited by existing overhangs. My preference would be to use 2*100mm layers of Graphite EPS, with all joints staggered. It'll cost roughly the same per m2 and reduce heat loss by 40% albeit with thicker walls. Bin the cladding and use render everywhere. 

 

 

 

 

 

 

 

[Gus Potter]

5 hours ago, LSB said:

Hi, it's DIY and the above is how I understand it needs to be.  

I was happy with the render path, I just wasn't quite so sure about the cladding as I was worried about the join between the insulation sheets, but you seem to be saying that it isn't an issue.

 

The build is an L shape so 6 walls, 3 are render and 3 cladding so the join will be corners, there will be cladding to cladding, render to render and cladding to render,  and I haven't yet thought about joining, makes my brain hurt ?

Suggestions welcomed, it will be a year or slightly more before we are doing this, I'm just planning it out at the moment.

Our planning permission just agreed with our statement of 'render or cladding'.

 

Hi LSB.

 

If you are DIY then experiment with the fixings and what you have to work with.. this is they key. If they fail then you have wasted your money. Make a mockup and see what it "feels" like (when you are screwing the fixings) and how you do the ingoes to the windows etc" . Make sure you get the right fixing, when they are long you are almost fixing "blind" if you are not used to doing it. Maybe go for a higher fixing density.. reduces the U value but best to be safe. Remember that that you may be fixing into old brick / hitting uneven / weak / weathered mortar joints that have a lower capacity than what the manufacturer declares in their spec. 

 

Go for the least complex fixing you can and put plenty in!

 

 

[LSB]

16 hours ago, Iceverge said:

What condition is the building in as we speak? Do you know the current wall build up? 

 

How did you arrive at 70mm kooltherm? It's an expensive insulation. The only justification I could see for it is if you were really limited by existing overhangs. My preference would be to use 2*100mm layers of Graphite EPS, with all joints staggered. It'll cost roughly the same per m2 and reduce heat loss by 40% albeit with thicker walls. Bin the cladding and use render everywhere. 

 

 

 

 

 

 

 

Currently the walls are one block thick, it's a barn, I can easily use Graphite EPS.

Cladding is a planning constraint, we can use some render where the walls are bare block, but as part of the barn currently has wood cladding we have to replace it so it looks the same.

The choice of Kooltherm was a suggestion by someone, can't remember who, I think it was one of our local builders, but I don't have any particular affinity with the product.

We don't have any overhangs now as the roof is being replaced.

Thanks for the details.

 

[LSB]

16 hours ago, Gus Potter said:

Hi LSB.

 

If you are DIY then experiment with the fixings and what you have to work with.. this is they key. If they fail then you have wasted your money. Make a mockup and see what it "feels" like (when you are screwing the fixings) and how you do the ingoes to the windows etc" . Make sure you get the right fixing, when they are long you are almost fixing "blind" if you are not used to doing it. Maybe go for a higher fixing density.. reduces the U value but best to be safe. Remember that that you may be fixing into old brick / hitting uneven / weak / weathered mortar joints that have a lower capacity than what the manufacturer declares in their spec. 

 

Go for the least complex fixing you can and put plenty in!

 

 

Thanks, good idea to try it out and see how we get on.

Current walls are block, no brick at all, but some of the mortar joints are not very good and there are definitely some parts of the wall that need to be reduced to about 1m and rebuilt due to some sort of metal support frame that has rusted.  I think this frame was the fixings for the pig pens that were in there.

Old barns have limitations, but we have to use the walls as part of our planning.

[MikeGrahamT21]

If your having to do wood cladding, how about using a 200mm Larsen truss/I beam, then pack in between with rock wool insulation. It won’t be as effective at stopping cold bridging but you will have a solid surface to work with for the cladding. 
 

just another idea to throw into the mix

[Iceverge]

I think @MikeGrahamT21 is onto a good idea here.

 

IF your structure is only single story have you considered erecting a timber frame internally and treating the existing wall as cladding? 

 

[Iceverge]

@LSBhaving had time to read your blog I've seen that you've already had the internal structure suggested. 

 

I assume you're completely committed to the external wall insulation at this stage?

 

On another note have you decided on a roofing finish? Might I suggest using insulated cladding like this.

 

https://www.kingspan.com/irl/en-ie/product-groups/insulated-panel-systems/insulated-roof-panels/sinusoidal-roof-panel-ks1000-srw

 

It would make a super thin roof profile and can be used in pitches as low as 4 degrees. 

 

If you had exposed purlins you could end up with a nice high ceiling. 

[LSB]

11 hours ago, Iceverge said:

I think @MikeGrahamT21 is onto a good idea here.

 

IF your structure is only single story have you considered erecting a timber frame internally and treating the existing wall as cladding? 

 

Thanks for your suggestion, but we decided on EWI because of how much space we would lose internally.

 

[LSB]

10 hours ago, Iceverge said:

@LSBhaving had time to read your blog I've seen that you've already had the internal structure suggested. 

 

I assume you're completely committed to the external wall insulation at this stage?

 

On another note have you decided on a roofing finish? Might I suggest using insulated cladding like this.

 

https://www.kingspan.com/irl/en-ie/product-groups/insulated-panel-systems/insulated-roof-panels/sinusoidal-roof-panel-ks1000-srw

 

It would make a super thin roof profile and can be used in pitches as low as 4 degrees. 

 

If you had exposed purlins you could end up with a nice high ceiling. 

our roof has to be metal, ideally zinc, but that's pretty expensive so I'm looking at steel.

It's a single story barn of 240sqm so a lot of roof.  We are also going to have Solar PV.

But, the above does link does look like a viable option as it looks very similar to the existing steel roof.  We can't reuse that as it is rusted in a lot of places and has no insulation.

It was a barn for an intensive pig rearing unit, only stopped when the regulations changed.

I  must say that I'm happy about that, looking at it when we first purchased the site it can't have been very pleasant for the pigs who would never get to see any daylight.

 

 

[MikeGrahamT21]

1 hour ago, LSB said:

Thanks for your suggestion, but we decided on EWI because of how much space we would lose internally.

 

My idea is a form of EWI

[Iceverge]

6 hours ago, LSB said:

our roof has to be metal, ideally zinc, but that's pretty expensive so I'm looking at steel.

It's a single story barn of 240sqm so a lot of roof.  We are also going to have Solar PV.

But, the above does link does look like a viable option as it looks very similar to the existing steel roof.  We can't reuse that as it is rusted in a lot of places and has no insulation.

It was a barn for an intensive pig rearing unit, only stopped when the regulations changed.

I  must say that I'm happy about that, looking at it when we first purchased the site it can't have been very pleasant for the pigs who would never get to see any daylight.

 

Do you have any idea of the total cost of a standing seam total construction for comparison?  Panels are available with build in roof-lights as per the site below, to avoid the lack of sun afforded to those poor pigs. I have no affiliation or experience of this company but they were good enough to put their prices online. They can be had for about £45 per m2 for a u value  of 0.14 which is very cheap. Not to mention the speed and ease of fitting as they are a commercial/agricultural product.  If you can live with the aesthetic I'd be tempted.  

 

https://www.steelroofsheets.co.uk/categories/insulated-cladding/

 

Without putting myself into the same camp as the knuckle dragging misogynist who was so dismissive to you on that site visit solar PV doesn't have to go on the roof, indeed it might not be ideal given your low roof pitch. Have you seen @ProDaves beautiful solar chalet for a cool example. 

 

Also reading backwards you have had approval for building an external wall as cavity wall. I know you dismissed this initially due to the cost of blockwork but before you commit to the EWI route please price up the render systems for it as they are expensive and not completely robust. I dismissed EWI on our new build due to this and opted for wide cavity walls with sand cement render as it has a great track record locally. (70 years + on my parents house with no problems next door) 

 

[LSB]

48 minutes ago, Iceverge said:

 

Do you have any idea of the total cost of a standing seam total construction for comparison?  Panels are available with build in roof-lights as per the site below, to avoid the lack of sun afforded to those poor pigs. I have no affiliation or experience of this company but they were good enough to put their prices online. They can be had for about £45 per m2 for a u value  of 0.14 which is very cheap. Not to mention the speed and ease of fitting as they are a commercial/agricultural product.  If you can live with the aesthetic I'd be tempted.  

 

https://www.steelroofsheets.co.uk/categories/insulated-cladding/

 

Without putting myself into the same camp as the knuckle dragging misogynist who was so dismissive to you on that site visit solar PV doesn't have to go on the roof, indeed it might not be ideal given your low roof pitch. Have you seen @ProDaves beautiful solar chalet for a cool example. 

 

Also reading backwards you have had approval for building an external wall as cavity wall. I know you dismissed this initially due to the cost of blockwork but before you commit to the EWI route please price up the render systems for it as they are expensive and not completely robust. I dismissed EWI on our new build due to this and opted for wide cavity walls with sand cement render as it has a great track record locally. (70 years + on my parents house with no problems next door) 

 

They can be had for about £45 per m2 for a u value  of 0.14 which is very cheap.

 

That is cheap, we have been quoted between 25 & 40 for standing seam zinc, house is 240sqm so between 100 & 166 per sqm.  This is what has put us off as it eats so much of our budget.  Other steel is cheaper, totals about 20, but that's still quite a lot, but I do prefer the look of standing seam.

 

As far as the cavity versus EWI, we have permission for EWI, but not to build a second cavity, planners being what they are they have their idiosyncrasies.

 

I'm beginning to understand that it is impossible to understand all the different build methods, planning,  conversions.

If I could do what I want I would attack the barn with the tractor, dig up the site and start again, but when I spoke to the planner it was made very very clear that this would not be allowed.

There have been all sort of comments on this forum about building one wall then another etc., but if I got caught then I would lose out big time and it's just not worth it.

 

I will stick to what I'm allowed, including using the existing walls, openings and the roof structure. 

 

 

[Mr Punter]

With the EWI, if you use graphite XPS it will need to be quite a bit thicker than the Kingspan to get the same insulation value.

 

You will need to work out or have assessed what insulation value needed to pass building regs, then work out which product will be easiest / least expensive.  You will need a SAP assessment for Building Regs in any case, and the assessor should be able to guide you.

 

With the render finish you can fix the insulation with a combination of adhesive dabs and mechanical fixings and finish with mesh coat / render system.

 

With the timber cladding you can cover the boards with non-flammable breather membrane holding it all on with 25 x 50 vertical battens (screwed through the insulation into your existing walls) onto which you fix the cladding.

 

In both cases, the insulation boards are closely butted together.

 

The thicker the insulation, the more expensive the fixings.

 

Make sure there is provision for fixing downpipes, aerials etc.

 

 

[phatboy]

Hi @LSB,

 

What did you do with this in the end?  I have 1 wall which will be clad over K5 EWI, and I am as lost as you were in this thread!

 

Thanks

Tim

[LSB]

On 01/01/2023 at 20:35, phatboy said:

Hi @LSB,

 

What did you do with this in the end?  I have 1 wall which will be clad over K5 EWI, and I am as lost as you were in this thread!

 

Thanks

Tim

Hi Tim

nothing, various circumstances stopped our build, just planning to get going again this year.

 

[LiamJones]

Any updates to this thread, I too am now considering cladding over 100mm EPS EWI, but not much information is available online, relative to thin coat render. Got quoted £75/m2+vat for render. Weighing up alternatives such as cladding and brick slips.

[phatboy]

I did it in probably not the optimal way, but I'm OK with it.

 

- 4x2 timbers attached to the block wall with large L brackets

- Insulation packed between them (70mm K5)

- Breather membrane cover

- Battens 15mm thick over the top, nailed onto the 4x2s

- Counter battens 2x1, painted up with Black Jack

- Millboard vertical cladding

[Iceverge]

On 22/05/2024 at 10:11, phatboy said:

I did it in probably not the optimal way, but I'm OK with it.

 

- 4x2 timbers attached to the block wall with large L brackets

- Insulation packed between them (70mm K5)

- Breather membrane cover

- Battens 15mm thick over the top, nailed onto the 4x2s

- Counter battens 2x1, painted up with Black Jack

- Millboard vertical cladding

 

Any pics of these L brackets?

 

Why not just fix the 4x2s directly to the wall?

 

 

[LiamJones]

I wonder if you could have gone standard PIR in this kind of buildup, rather than the more expensive k5? What even is the difference? 

[MikeGrahamT21]

2 hours ago, LiamJones said:

I wonder if you could have gone standard PIR in this kind of buildup, rather than the more expensive k5? What even is the difference? 

K5 has a fabric coating to accept render/adhesive on both sides, and is also made from phenolic foam rather than polyisocyanurate, which is marginally better at insulating