Replacing and modifying extension roof

[MadAlicesDad]

I need to replace the roof on my extension, at the same time raise it slightly to get a full size door and frame in, and get a better slope (currently tiles over felt on a 15deg slope).
The top of the roof forms an apex with a similar structure next door sharing a party wall. Although they have worse roof problems than me, unfortunately they are not in a position to fix it yet so I have to go it alone.
I can see a way of lifting the roof by building up the wall on my side, but this gives me a problem wrt joining with the neighbours roof. Although not to scale I hope the picture is clear. How can I waterproof the gap shown in green?

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• MadAlicesDad
• 18 May 2010
• 2

I wondered about putting a joist along the top of the new wall, fixing timber to it to make up the gap and then using lead flashing to seal to next door's roof (see second picture).

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• MadAlicesDad
• 18 May 2010
• 1

Any thoughts on this and/or alternative suggestions?

TIA
Mike

 

[Regencyroofingipswich]

Looks like you already have it sussed out , thats how it should be done .

Just make sure your lead is covering 150mm down from the top of the tile and going up under the mono ridge 150mm too.

Dont forget to put a rubber washer behind your screw when you fix the monoridge.

 

[Cumbrianroofer30yrsexp]

Sounds about right,use code 4 lead and in sections no longer than 1.5m.Unless you want white stains on next doors roof tiles apply pattination oil to finished lead work immediatly after fitting.

 

[MadAlicesDad]

Excellent, many thanks for the quick responses.
Cheers,
Mike

 

[MadAlicesDad]

There are two rooms in the extension and I'm tackling them one at a time. I've built up front and back walls along the first part of the extension and fitted wallplates and joists at 400mm spacing. I want to put sarking boards down, partly for insulation but also because the pitch is not as steep as I'd have liked - I've got a pitch angle of about 17 deg ie marginally below min for Redland 50 double roman which is what best match the house (on my budget at least!).
My plan for above the joists is for 9mm OSB sarking, breathable membrane, counter battens, tile battens, tiles. Underneath the sarking will be a 50mm airgap, 75mm Kingspan, vapour barrier and plasterboard. The airgap will be vented top and bottom.
Is all this correct, or have I missed something? Should the membrane go above the counter battens?
Any help or (constructive) comments greatly appreciated.
TIA MIke

 

[noseall]

Your remedy looks ok but the position of the 'joist' as you call it (pole plate) looks suspect. You are showing it fixed to the uppermost point of the top course of blocks which may not be a good idea due to strength.

I would be inclined to fix vertical battens that fix lower down the blockwork and up into the rafter ends, or even into the wall plate. Also i would add insulation between the battens before fixing 18mm ply instead of a timber plank then fix your flashing to the ply.

The insulation suggestion may only be relevant if the internal space adjacent is habitable and not loft space, as to avoid cold bridging.

 

[MadAlicesDad]

Do you mean like this?

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• MadAlicesDad
• 26 May 2010
• 2

The internal space is habitable (not a loft space) so the insulation and ply is a good idea, but I can't guarantee getting good access for fixing vertical battens to the outside of the wall. I have secured the wall plate to the wall with 1m straps and the joists to the wall plate with truss clips- is this not sufficient?

Please forgive the terminology used - I've not come across 'pole plate' before, but having looked up the definition, my 'joist' is only there to support the plank/ply and the flashing, not the roof structure itself. Does this change your thoughts ref need for vertical battens?

Mike?

 

[noseall]

My reference to strength was regarding the weakness in the uppermost course of blocks and the likelihood that you may dislodge them and not in the pole plate itself.

 

[MadAlicesDad]

Good point, I'll try fixing vertical battens.
Mike

 

[Static]

Might wanna bear in mind getting planning and party wall stuff as well

 

[MadAlicesDad]

I had assumed that it came within permitted development - no higher than 4m and no bigger than 15% of house volume, or has the law moved on?
Party wall stuff is a good point, although we have no problems with the neighbours and they are happy with what I am doing (and will probably copy it in due course.
Mike