Planning approval granted… now conflicted over build method because it’ll be 100% timber clad

[fatgus]

We’ve finally been granted permission for our extension and hope to get started in the spring, subject to discharging a few pre-commencement conditions.

 

Our plan was to go for block build with 300mm cavity (a bit like Denby Dale), with EWI on the existing (block) building, but we’re now considering a pivot to twin-wall timber frame, mostly because of speed and precision.

 

The original design had wood cladding on the ground floor and metal on the first. Planners didn’t like the aesthetic so we switched to 100% wood. On the intended block build, that seems to be fine, but on a timber frame I understand that insurance can be problematic and, if we were to sell, mortgagability might be an issue. Obviously, some of the building will be the old block structure, but the surface area of the extension walls is something like 3x that of the retained exterior walls.

 

It would be great to know if anyone has faced a similar choice, built a 100% wood clad timber frame house or have any other insight on the subject  Thanks!

 

 

 

 

 

 

[Nickfromwales]

This would require a LOT of EWI, to get these two sections (old and new) to be anywhere close in comparison. 
 

Have you included increasing the soffit and roof overhang to accommodate this properly?

 

Seems the new extension will massively out-perform existing, eg you’re in Passivhaus territory with the new, so without airtightness and MVHR (assuming this?) are you sure this isn’t just a little OTT? 

[Gone West]

1 hour ago, fatgus said:

built a 100% wood clad timber frame house

We moved into our new timber frame, timber clad, self build in 2018. We had no problems insuring it, neither did the new owners in 2021 have any problems obtaining a mortgage or insurance when we sold it. Regulations may have changed in the meantime though.

 

 

Edited yesterday at 13:02 by Gone West
Update

[saveasteading]

Timber building is standard, but some insurers don't know anything about construction and rule out cover on a whim or misunderstanding. 

If you get building regs you will get insurance.

 

But timber cladding on a timber building? Of course there is more risk.  You would want a fire barrier between them, but would still have to tick the insurance boxes for timber structure and timber facing.

On what basis are you choosing the construction? Why twin wall?

[fatgus]

3 hours ago, Nickfromwales said:

This would require a LOT of EWI, to get these two sections (old and new) to be anywhere close in comparison. 
 

Have you included increasing the soffit and roof overhang to accommodate this properly?

 

Seems the new extension will massively out-perform existing, eg you’re in Passivhaus territory with the new, so without airtightness and MVHR (assuming this?) are you sure this isn’t just a little OTT? 

The existing roof is flat and will be removed entirely, so the overhang can be tailored to match whatever we do with the existing walls. We’re considering larsen trusses on the existing walls so we can maximise the insulation and try to maintain a kind of continuous envelope of insulation around the entire building.

 

We’re aiming for passive-ish levels and airtightness is a priority, along with the insulation. We’ll have MVHR, ASHP, UFH, triple glazed windows/rooflights. 
 

Incidentally, despite the username I am also Nick and am in Wales 😁

 

 

1 hour ago, saveasteading said:

But timber cladding on a timber building? Of course there is more risk.  You would want a fire barrier between them, but would still have to tick the insurance boxes for timber structure and timber facing.

On what basis are you choosing the construction? Why twin wall?

We were going for block construction, but it’s taken a long time to get to this stage and timber frame would appear likely to make the process quicker and easier in so many ways. Twin wall isn’t definite, but seems appealing… more insulation, easier to blow said insulation, less cold bridging and thicker walls. We’ve had a few quotes that seem reasonable, although we’re still looking at the details. We’ve discussed the fire risk with one of the TF suppliers and their suggestion was to use cement board behind the cladding.

 

I can’t help feeling that the original plan of block build would make more sense 🤔

 

 

[fatgus]

3 hours ago, Gone West said:

We moved into our new timber frame, timber clad, self build in 2018. We had no problems insuring it, neither did the new owners in 2021 have any problems obtaining a mortgage or insurance when we sold it. Regulations may have changed in the meantime though.

Thanks

[Gone West]

34 minutes ago, fatgus said:

We’ve discussed the fire risk with one of the TF suppliers and their suggestion was to use cement board behind the cladding.

You could use Cedral Click cladding instead of timber cladding. I have recently used it and if you want a painted timber effect it's very good.

[Alan Ambrose]

>>> We had no problems insuring it

 

Us neither on a barn conversion, entirely timber.

[fatgus]

38 minutes ago, Gone West said:

You could use Cedral Click cladding instead of timber cladding. I have recently used it and if you want a painted timber effect it's very good.

We’ve had some samples of cedral and a few composite alternatives. Other than possibly millboard, there are none that really appeal, which is a shame 🫤

[G and J]

We are building timber frame and had planned a render on board and circa 70% larch cladding.

 

Because of the type of people we are, and you never know, we did some research to ensure the result was mortgageable, by either as as a equity release in years to come or by others should we decide to sell.

 

We found several instances in mainstream lenders of more than 50% cladding being a no go, and other requiring more than 50% block. In the end we have a block skin to the ground floor and less than 50% wood cladding backed by cement board on our boundaries.

[Nickfromwales]

5 hours ago, fatgus said:

I can’t help feeling that the original plan of block build would make more sense 🤔

Or ICF  

 

5 hours ago, fatgus said:

Incidentally, despite the username I am also Nick and am in Wales 😁

Sorry mate, there's only room for one.  

 

5 hours ago, fatgus said:

We’re aiming for passive-ish levels and airtightness is a priority, along with the insulation. We’ll have MVHR, ASHP, UFH, triple glazed windows/rooflights.

10/10. Consider AeroBarrier for the airtightness of the existing. Just done a hybrid masonry / posi joist roof refurb, and got the AT score down to <0.20ach as I am a fecking wizard lol. Norrsken doors and windows, blown cellulose in the roof + AVCL and the parge and liquid airtight membranes where necessary to get the results. ASHP and UFH now operate at crazy low temps, tres bien!