How to build parapet wall here....

[DC1977]

Hi

Looking to build a parapet wall and box gutter above the frameless glass window seat that will be installed here. Do we need to add another course of bricks or two to the existing parapet wall between us and the neighbour (on right hand side of photo)? Although we get on well it might be contentious.....

We have a party wall agreement in place as we have done the loft but it probably wouldnt cover building into may not cover going into the parapet wall?

 

[DC1977]

Here is a view of parapet between us and neighbours I suppose we would need a couple of courses if bricks added to this if she agrees to do roof properly, it’s on the left hand side of this photo...

 

[sxturbo]

The neighbours parapet wall can stay the same height.

When building not though I would recommend ditching the coping stones and going for aluminium coping, this would have to be carried over the shared parapet between you and your neighbors however.

The stones have a tendency to move, and the mortar base doesn't last long in the weather.

Ideally they should be mechanically fixed in place as well as mortar pointed, but it's labour intensive.

Aluminium is dearer to buy but man hours saved cancels the additional cost, also you are much less likely to have damp issues using aluminium coping than you are with using stones.

I would also advise the roofing material goes up and under the aluminium coping.

 

[DC1977]

The neighbours parapet wall can stay the same height.

When building not though I would recommend ditching the coping stones and going for aluminium coping, this would have to be carried over the shared parapet between you and your neighbors however.

The stones have a tendency to move, and the mortar base doesn't last long in the weather.

Ideally they should be mechanically fixed in place as well as mortar pointed, but it's labour intensive.

Aluminium is dearer to buy but man hours saved cancels the additional cost, also you are much less likely to have damp issues using aluminium coping than you are with using stones.

I would also advise the roofing material goes up and under the aluminium coping.

As the wall is solid underneath there is not need for the parapet wall to have a cavity is there? On the extension we were going to build the parapet as a solid wall above the cavity wall too?
I cant see the neighbour allowing us to take off the current tiles on the parapet wall and putting aluminium coping on but I think we will use that on the rest of the parapet. The builder is going to construct the box gutter out of timber I believe and then felt it...

 

[sxturbo]

The box gutter out of timber is fine, but it should be covered in the same material as the rest of the roof which I presume will be EPDM or fibre glass, neither will stick to felt, and the roofing membrane has to go through the box gutter

A solid wall above the cavity wall is fine, however you will need to make sure cavity trays and DPM is installed where the cavity will be bridged.

 

[sxturbo]

Also I presume that your neighbours parapet will be joined to yours, and I don't know how you will be able to install the aluminium coping with the tiled coping they have already, unless the tiles are replaced.

If you don't join the parapets I can't see how you will be able to ensure water tightness

 

[DC1977]

The box gutter out of timber is fine, but it should be covered in the same material as the rest of the roof which I presume will be EPDM or fibre glass, neither will stick to felt, and the roofing membrane has to go through the box gutter

A solid wall above the cavity wall is fine, however you will need to make sure cavity trays and DPM is installed where the cavity will be bridged.

Was going to use 3 layer felt on the roof.....

 

[DC1977]

Also I presume that your neighbours parapet will be joined to yours, and I don't know how you will be able to install the aluminium coping with the tiled coping they have already, unless the tiles are replaced.

If you don't join the parapets I can't see how you will be able to ensure water tightness

Yes will need to think about that one good point....

 

[sxturbo]

Was going to use 3 layer felt on the roof.....

Is it a cost factor?

EPDM generally isn't much more expensive but lasts a lot longer

 

[DC1977]

Is it a cost factor?

EPDM generally isn't much more expensive but lasts a lot longer

Ive been told that the 3 layer felt nowadays if looked after could last 25 years. I know EPDM lasts longer, but the roofer I know doesn't use it. So at the moment Im going with him....