Warm Flat Roof with Parapet Detail

[Ay8452]

Hi Folks,

 

I am doing a single storey extension which was originally specified for a cold flat roof/parapet wall detail. I want to change this to a warm flat roof/parapet wall detail partly because I am going to be adding EWI to the old wall the roof is going to be attached to. Just so I can figure out if I have the correct spec/thickness of everything - is this diagram broadly correct? I am hoping I have enough height to change to a warm flat roof. Will take this to my roofer and designer next week to ask if we make this work over a cold flat roof. (building to current building reg's, foundations in and walls up to DPC currently)

 

- Am I correct in understanding the minimum height f the parapet wall from the external roof deck/GRP is 150mm?

- I have going with timber frame for the inner leaf for the parapet wall to eliminate the cold bridge, is this sensible?

 

Thanks

 

Ali

[mistake_not]

Not an expert by any stretch, but detail library lets you buy BR compliant cad drawings for something likely £3 a go that is good for checking:

 

https://detail-library.co.uk/product/mr7/

[SBMS]

On 22/02/2025 at 19:21, Ay8452 said:

Hi Folks,

 

I am doing a single storey extension which was originally specified for a cold flat roof/parapet wall detail. I want to change this to a warm flat roof/parapet wall detail partly because I am going to be adding EWI to the old wall the roof is going to be attached to. Just so I can figure out if I have the correct spec/thickness of everything - is this diagram broadly correct? I am hoping I have enough height to change to a warm flat roof. Will take this to my roofer and designer next week to ask if we make this work over a cold flat roof. (building to current building reg's, foundations in and walls up to DPC currently)

 

- Am I correct in understanding the minimum height f the parapet wall from the external roof deck/GRP is 150mm?

- I have going with timber frame for the inner leaf for the parapet wall to eliminate the cold bridge, is this sensible?

 

Thanks

 

Ali

Think you need/would recommend a cavity tray in the parapet across the cavity. 

[ETC]

Where’s your gutter?

[goodbyegti]

For the thermal break you can use a marmox thermoblock or similar and then carry on upwards with the blocks when above the roof PIR. You can attach OSB to the blocks for the GRP.