Composite roof class q

[S J H]

I wondered if anyone had used composite roofing on a class q recently, and if so what thickness was used please? It’s just for a re cladding of an existing building and was trying to future proof as much as possible. TIA.

 

[George from SJM Planning]

I wondered if anyone had used composite roofing on a class q recently, and if so what thickness was used please? It’s just for a re cladding of an existing building and was trying to future proof as much as possible. TIA.

Is this as part of an approved Class Q or for cladding a building with a future Class Q in mind?

 

[S J H]

Is this as part of an approved Class Q or for cladding a building with a future Class Q in mind?

Only cladding for it in mind for the future, I expect regs will change and we’ll be out of date anyway but thought it was worth thinking about.

 

[George from SJM Planning]

Only cladding for it in mind for the future, I expect regs will change and we’ll be out of date anyway but thought it was worth thinking about.

That's ok then, I have had people come to me after they replaced the roof panels as part of a Class Q conversion and Planning Enforcement had been informed. We had to apply for retrospective planning for the whole build just because of the extra 220mm height caused by the thicker panels.

 

[flinty123]

I wondered if anyone had used composite roofing on a class q recently, and if so what thickness was used please? It’s just for a re cladding of an existing building and was trying to future proof as much as possible. TIA.

You can over clad existing roofs using a built up system

 

[HatsOff]

You'd want to go as thick as possible really.

It's a bit complicated - for refurbishment of roofs the target u-value is 0.15W/m²K, but if it is 0.16W/m²K already then it can stay as is.

However a 80mm Briarwood panel has a u-value of 0.28W/m²K so you'd have to do some upgrading anyway. You can get thicker panels but there's space between the purlins that can be used to insulate.

Composite panels are non-fragile which helps a bit too.

 

[S J H]

You'd want to go as thick as possible really.

It's a bit complicated - for refurbishment of roofs the target u-value is 0.15W/m²K, but if it is 0.16W/m²K already then it can stay as is.

However a 80mm Briarwood panel has a u-value of 0.28W/m²K so you'd have to do some upgrading anyway. You can get thicker panels but there's space between the purlins that can be used to insulate.

Composite panels are non-fragile which helps a bit too.

Thank you, I was basing it on 80mm, so we’d be under spec anyway, do you know roughly what thickness the regs would equate to?

 

[HatsOff]

Thank you, I was basing it on 80mm, so we’d be under spec anyway, do you know roughly what thickness the regs would equate to?

A 120mm Kingspan KS1000RW has a u-value of 0.15.

Although I would bother too much because in a conversion you'd need to put a ceiling up so adding some mineral wool in the depth of the purlin wouldn't be a major issue. So, worth comparing prices but if the Kingspan is too expensive then there's a get out down the road.

 

[S J H]

A 120mm Kingspan KS1000RW has a u-value of 0.15.

Although I would bother too much because in a conversion you'd need to put a ceiling up so adding some mineral wool in the depth of the purlin wouldn't be a major issue. So, worth comparing prices but if the Kingspan is too expensive then there's a get out down the road.

I think you’re right, will just stick to 80mm and least it will be a good roof for other uses. Thank you for your reply.

 

[bobk]

I think you’re right, will just stick to 80mm and least it will be a good roof for other uses. Thank you for your reply.

I put 150mm kingspan in the roof as they were cheaper than the 125mm that is obligatory