Is a dormer possible with thin attic party wall?

[timber]

I'm in the middle of a loft conversion, and would really like to add a rear dormer if possible. However, the house is a standard 1920's Victorian end-of-terrace, and the party wall is not very thick. It's 9" solid brick up to the ceilings of the first floor, but then above that changes to 4.5" brick at the front and rear to support the purlins, and the middle was originally straight through to next door but has since been filled with what must be 100mm cinder blocks. 

Next door have converted their loft (no dormer) and have plaster boarded straight onto the other side. 

Does anyone think a dormer will still be possible due to the additional beam needed in the ridge? Will I have enough bearing if I cut into the cinder blocks? If not, are there any workarounds?

[JohnMo]

Aren't there rules about party walls and noise mitigation that requires a load of insulation adding to your side of the cinder blocks?

 

Don't you have plans?

Wouldn't you need planning for a loft conversion and to add a dormer?

[timber]

1 hour ago, JohnMo said:

Aren't there rules about party walls and noise mitigation that requires a load of insulation adding to your side of the cinder blocks?

I'll likely be sand and cementing the wall to ensure there's no direct pathways for sound, then adding an isolated stud wall in front of it to get around the noise.

 

1 hour ago, JohnMo said:

Don't you have plans?

Wouldn't you need planning for a loft conversion and to add a dormer?

 

There's no need for planning permission to build a rear dormer - it's permitted development: https://ecab.planningportal.co.uk/uploads/miniguides/lofts/Lofts.pdf

 

I'm assuming I don't have enough bearing on a load bearing wall to make it possible, but I'm asking just in case anybody knows otherwise. I'll also be speaking to a structural engineer and I'll report back their opinion here. 

[timber]

Speaking to a structural engineer, he confirmed the party wall in the attic would not be suitable for supporting the end of a steel ridge beam. But it seems there's a way forward.

 

This is a typical no-frills 3.6m wide Victorian terrace with a staircase going across the house in the middle, with brick walls either side of the stairs going right up to the roof ties. There are wooden lintels over the doorways at either side at the top of the stairs, that are supported by the party wall at one end and the stairway walls at the other. He's suggested replacing them with concrete lintels subject to calculations, placing a short beam along the party wall bridging the two lintels, and using this beam to support a post that will support the party wall end of the new ridge beam. 

 

He also suggested a beam running from each side of the house directly a floor below the steel ridge beam (i.e. first floor ceiling level) and support the support post on that which would be useful for houses in a similar party wall situation that don't have the 2-storey brick walls across their middle.

[joe90]

30 minutes ago, timber said:

He's suggested replacing them with concrete lintels

Be careful, I had concrete lintels over doorways to support vertical steels to hold the ridge beam on a hip roof, however the BCO told us concrete lintels should not take point loads so we had to change them out for steels. Best to ask before you go ahead.

[Canski]

42 minutes ago, joe90 said:

Be careful, I had concrete lintels over doorways to support vertical steels to hold the ridge beam on a hip roof, however the BCO told us concrete lintels should not take point loads so we had to change them out for steels. Best to ask before you go ahead.

 

[timber]

1 hour ago, joe90 said:

Be careful, I had concrete lintels over doorways to support vertical steels to hold the ridge beam on a hip roof, however the BCO told us concrete lintels should not take point loads so we had to change them out for steels. Best to ask before you go ahead.

 

 

Thanks for pointing this out.

 

It makes sense - his first detailed suggestion was to build up the party wall with brick from the new concrete lintels, which I guess would avoid the point loads. It was my probably wrong assumption that the same concrete lintels would be used for the second idea he came up with that I described in my post.