Roof problem attaching to party wall.

[Chreag]

Hi
Hopefully someone can help me with a design problem I have.

My builders have built 2 walls for my extension. The other 2 walls will be the existing external house wall and the party wall with next door.

The roof be warm EDPM flat roof construction, but will fall away from the house at an angle of about 6 or 7 degrees to clear the soil pipe from the upstairs toilet as I don't think there is room to fit the roof in below the soil pipe and I'd rather not mess around with that.

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• Chreag
• 27 Apr 2014
• 1

I'm not sure how to finish this off with the party wall, which is single story with a parapet for next door's extension.

At the point where the roof hits the party wall near the house it will be higher than the party wall, and at the other end it will be about 3 courses of bricks lower.

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• Chreag
• 27 Apr 2014
• 1

Does anyone have any idea how I would deal with this in terms of ensuring I don't have water ingress issues?

Thanks
Chreag

 

[catlad]

I would advise you to remove the soil stack before you continue.

 

[Chreag]

I considered moving the soil stack but assuming I want to keep the toilet where it is, I can't see how it would help especially as I've no idea where I would move it to

 

[ree]

If you post some more pics, from a further back view, showing all the "walls" you perhaps could be helped a bit?

And Pics of whats to the left and right?
How did your party wall neighbour deal with this issue?

From what can be seen you could get away with a 10 or 11 degree pitched roof, but you would have to drop the horizontal soil pipe below the finished ceiling line. The WC discharge could be altered to come out of the wall at a lower point.

Without the above requested pics i dont know but it seems that even with a flat roof you will hit the soil pipe and stack.

Dealing with the parapet will probably need a bit of ingenuity and your neighbour's permission.



Whatever, the parapet is minus a lead saddle, and splash (the green stuff) is soaking your wall.

The parapet and party wall would have to be investigated for any existing cavity fill, blockages or top DPC.

Read the post from a week ago "Flat Roof Leak", to get an idea of what difficulties attempting to build or flash around a soil pipe can cause.

 

[Chreag]

Thanks Ree. It is a bit tricky to get a photo showing it all, but here are a few extra ones;

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• Chreag
• 27 Apr 2014
• 1

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• Chreag
• 27 Apr 2014
• 1

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• Chreag
• 27 Apr 2014
• 1

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• Chreag
• 27 Apr 2014
• 1

The neighbour doesn't have the issue as their soil stack is round the side of the house.
I've not got the height to get up beyond about 8 or 9 degrees, which would clear the horizontal pipe, but be higher than the parapet. I think the soil stack is going to have to go through the roof as it is a long way to the side of the house and I don't want to have to dig a new drain.

The neighbour has given me permission to do whatever i need to (within reason) as long as I don't negatively impact their side.

 

[ree]

Thanks for the extra info and pics.

Ignore for the moment the parapet and p/wall.

If you pitch a roof just one course below the bedroom window cill, you could come in at 11 degrees.

Pitching your roof this way, you could cut the stack just above the tee and swing the upper vent portion away from the wall, and then swing back above the roof line.
That is, after piercing the roof far enough away from the wall to correctly fit a collar, and not interfere with the cover flashing.

A flat roof, based on what i can figure out from the pics, & with an eight foot ceiling, will give you many difficulties.

There are a few other possible issues i've noticed on the pics. If you want further suggestions, just ask.

 

[xfr]

What does the drawings say in getting around the soil stack.
What do you intend to do with the manhole.
That's one monster extension your building.

 

[Chreag]

That's a great idea swinging the soil stack vent pipe away from the wall to fit a proper collar thanks!

That's an improved version of my original plan to fit a "flat" roof with a pitch of about 8 or 9 degrees. I hadn't thought about swinging the soil stack out.

Even at 11 degrees I'd still construct it like a flat roof, as we get quite a lot of wind and the lowest pitch rating for tiles I've seen is 10 degrees and I wouldn't feel comfortable fitting tiles right at the end of their specification.

The reason I started considering a non-pitched flat roof was because I've got no idea what to do at the bit you've asked me to ignore! I figured it'd be easiest if the top of the roof was lower than this level, so I could just flash up that wall.
Any further ideas/issues spotted would be gratefully received thanks.

 

[Chreag]

Hi XFR
I've not got an architect involved and am designing around the issues as I come to them.
Ideally I'd move the drains, but my budget is going to be stretched as it is, so I'm planning on shuttering the manhole when I insulate/concrete the floor, then fit a trapdoor in the floor for access, strategically covered by a rug.
Yes it is a monster and has escalated massively from the original plan of a small conservatory!

 

[xfr]

Good luck with your project.Im also in the middle of a extension
I had to move my manhole as it was in direct line of founds..

 

[Chreag]

Good luck with yours too.

I can't believe how much this has taken over my life already and I've barely got going!

 

[xfr]

Im a little further on.Just fitted velux windows and started slating roof today,Yes it does take over your life organising everything. I just keep telling myself it will get done sooner or later. Oh and got soaked in this great British weather of ours.

 

[noseall]

Is this being built under Building Control Reg's? I ask because your glazed area seems to exceed the minimum, the large lintel looks like there is not enough (150mm) bearing and there is no provision for tieing in the dpm.

How do you know whether the large lintel is adequate? We have had to jump through hoops recently regarding large span lintels and roof loads etc. The most recent one we fitted was an extra heavy duty beast with 200mm bearings.

Very risky proceeding without a designer.

 

[ree]

I know Oxford and dont recall any strong winds - Cambridge yes, but Oxford?
Anyhow, you will have to take some specialist roof advice for your "flat" roof coverings.

I'm assuming that your ceiling will also be pitched to miss high the horizontal soil pipe because you cannot go below the pipe - your ceiling would be too low.

Other issues:

The manhole cover could be raised to FFL - google sealed, interior manhole covers. You can "in-fill" some of them with tile or wood etc.
A small diameter inspection chamber would suffice but it would mean more groundwork.
Hiding any access position for anything is a bad idea.

Is the floor insulation already installed? Whats below the sand?

Cover the exposed cav insulation from rain.

How do you intend to supply pipework and elec cables?

Do you plan any knock-through's?

Remove all trace of ivy etc. and all impedimenta off the house wall.

Check that alls well with the rear roof and guttering.

Is your whole house solid flooring?

I dont like that method of sealing the parapet - but if it works then leave it alone except where you may have some flashing detailing to do.

 

[noseall]

Hi XFR
I've not got an architect involved and am designing around the issues as I come to them.
Ideally I'd move the drains, but my budget is going to be stretched as it is, so I'm planning on shuttering the manhole when I insulate/concrete the floor, then fit a trapdoor in the floor for access, strategically covered by a rug.
Yes it is a monster and has escalated massively from the original plan of a small conservatory!

Christ on a bike, you don't have a clue!

STOP. NOW!