does warm roof insulation require planning permission.

[Dannyboyski]

We are planning a new roof on our house renovation, leaks badly and has been tarred countless times.

Planning to utilise our top floor space, it's not really a loft conversion because it already has a structural floor and some windows, so thinking about insulating the underside of the roof:

Considering using the foil insulation and breather membrane on top of the rafters, for a warm roof construction. This obviously needs counter battening so the roof height will change by the thickness of the batten plus the product.

Does this need planning permission? It is a detached rural house if that matters.

Many thanks

Dan

 

[Notch7]

do you mean superfoil
or do you mean foil faced rigid board like celetex?

it needs building regs. Planning maybe in theory, I cant see another few inches being worth the fuss TBH

 

[Dannyboyski]

Hi Notch, The foil stuff, actis boost or tlx gold type stuff. Breathable vapour barrier and Insulation layer in one.

As I understand it this above the rafter Insulation uses the counter batten as the air gap meaning I can completely fill the rafters with insulation meaning less Battening down into the room to achieve the desired u values.

 

[DevilDamo]

Below is a link to roof alterations under PD...

https://www.planningportal.co.uk/info/200130/common_projects/47/roof

Although the alterations would comply with the first bullet point, they wouldn’t comply with the second. In that respect, I would be of the impression that you would require formal Planning approval.

 

[tony1851]

Would definitely need Building Regs approval.
Any roof enlargement less than 150mm above the original roof surface is permitted development (as long as it doesn't go above the ridge).
But if its a detached, how/why would anyone know?
Save yourslf the £206 planniing application fee.

 

[IT Minion]

Hi Notch, The foil stuff, actis boost or tlx gold type stuff. Breathable vapour barrier and Insulation layer in one.

As I understand it this above the rafter Insulation uses the counter batten as the air gap meaning I can completely fill the rafters with insulation meaning less Battening down into the room to achieve the desired u values.

I'm struggling to picture your plan but it doesn't sound right to me. If you're doing a warm roof then you don't need to put anything between the rafters, everything goes on top.

The foil stuff normally needs a lot of care and attention to ensure its well sealed and not in contact with anything, as it relies on the air gap on both sides to get it's published R value.

Have you checked on the possibility of going with the more traditional warm roof of lots of celotex?

 

[Dannyboyski]

Thanks for your reply IT Minion, you are correct. It was a while ago I researched this, and I appear to have got a bit muddled. A single layer of the foil stuff is sufficient with nothing between the rafters.

The alternative would be 175mm of celotex, which would need a 50mm air gap, so 225mm depth in total. Our rafters are only circa 87mm deep so it would mean a lot of battening into the space.

Have got building control coming out later in the week, so we will see what they say.

 

[IT Minion]

Thanks for your reply IT Minion, you are correct. It was a while ago I researched this, and I appear to have got a bit muddled. A single layer of the foil stuff is sufficient with nothing between the rafters.

The alternative would be 175mm of celotex, which would need a 50mm air gap, so 225mm depth in total. Our rafters are only circa 87mm deep so it would mean a lot of battening into the space.

Have got building control coming out later in the week, so we will see what they say.

Those numbers still don't sound right to me. If you were doing a cold roof you'd normally have 50mm air gap, 100mm in the rafters, then 20mm or so underneath the rafters to hit current regs (more or less).

With a warm roof then I'd expect no more than 120mm Celotex would be needed. No air gap or impingement into the room as it'd be all on top.

 

[DevilDamo]

Those numbers still don't sound right to me. If you were doing a cold roof you'd normally have 50mm air gap, 100mm in the rafters, then 20mm or so underneath the rafters to hit current regs (more or less).

With a warm roof then I'd expect no more than 120mm Celotex would be needed. No air gap or impingement into the room as it'd be all on top.

Yes, more or less. To achieve 0.18 for a pitched roof, you’d expect to see 100mm Celotex between and 62.5mm Celotex below (insulation and board). I know for a flat roof, you’ll get away with a 120mm Celotex on top. Can’t remember the build up for a warm pitched roof as it’s something I just don’t normally specify.

@Dannyboyski I assume you’ll be looking to upgrade or replace the soffits, fascia and gutters with a retro fit warm roof build up?

 

[Dannyboyski]

Thanks for the replies, this is very much in the early stages of planning, just considering options as our slate roof is in need of replacement anyway. seems sensible to explore the warm roof option.