Recognised Construction Detail for Gable

[Jammy5]

My SAP calc assumes I follow the recognised construction details. On the gable end of the property, I am expected to installation insulation above the fire socks and flowing it into the soffits and fascia. The sketch is below showing this:

 

https://www.recognisedconstructiondetails.co.uk/library/document/mpf-150-e13-02-gable-insulation-at-rafter-level.pdf

 

The question here is, do I really have to install the insulation in this area? 

 

Looking at the guidance photos, the SAP assessor does not receive a photo of anything other than inside the wall looking at the insulation between the truss/joist and internal leaf of the gable wall.

 

I was advised by someone else they didn't think it was best practice to fill the soffit/fascia with rock wool?

 

Any thoughts please?

[Big Jimbo]

The drawing seems to show a non ventilated flat roof on top of a cavity wall. There is no reason not to fill it all with mineral wool in my opinion. You should atleast fill it to above the cavity closer as that is a week point. You did well to find any detail for what to do as accepted practice. I couldn't find any for my funny detail bits.

Edited yesterday at 07:55 by Big Jimbo

[ADLIan]

@Big Jimbo the detail is a pitched roof gable as viewed looking up the roof slope. Not applicable to flat roofs.

 

@Jammy5 the psi-value is based on the exact construction shown so should be built strictly in accordance with it. If required for clarity and confirmation more photos should be taken. Both BCO and SAP assessor will need this info.

[Jammy5]

10 hours ago, ADLIan said:

@Big Jimbo the detail is a pitched roof gable as viewed looking up the roof slope. Not applicable to flat roofs.

 

@Jammy5 the psi-value is based on the exact construction shown so should be built strictly in accordance with it. If required for clarity and confirmation more photos should be taken. Both BCO and SAP assessor will need this info.

 

It is certainly a pitched roof gable.

 

 @ADLIan this is what I currently have. Is it a case of running some insulation between the ladders and down into the soffits?

 

Slight issue is the blockwork, especially on the inner leaf, is potentially too high as it's flush with the top of the top of the truss.

 

Just for clarity, the socks nearer the top aren't actually fitted yet, where it looks like it's protruding from the cavity

 

Edited 14 hours ago by Jammy5

[ETC]

The detail is for a situation where there is a room-in-the-roof. Do you have this?

[Jammy5]

42 minutes ago, ETC said:

The detail is for a situation where there is a room-in-the-roof. Do you have this?

Unfortunately yes I do

Edited 11 hours ago by Jammy5

[Jammy5]

With the block work being higher than planned, this stops me laying a 100mm rockwool over the blockwork as it would protrude past the top of the truss.

 

If I'm correct, this would then cause an issue where the insulation touches the underside of the breathable felt and removed any air gap?

[Jammy5]

Or is it a case of lay the insulation and let the felt compress it if needed? No air gap needed? This is purely on the gable blockwork and ladders.

 

The rest of the roof would have PIR between trusses and I'll ensure there is an air gap