EPDM membrane creases

[omph]

I am adding a box gutter into my flat roof design and intend to use a single EPDM membrane to cover the entire roof (including the gutter). The main roof will having firrings leading to the box gutter, and the gutter will have it's own slope which leads to the drainage point.
My question is how will I lay a single EPDM membrane with such a configuration ? My concern is it will crease and not sit properly due to the different slopes.
I could "fix" this by laying two membranes but I would like to keep it as one membrane.

 

[Deluks]

You might be better off patchworking it, a crease may be unavoidable and then might create problems of directing water in the wrong direction.
It's obviously not as an attractive proposition as doing it in one sheet, but if you use the right materials and do the job properly, the join should be fine.
Use the correct adhesive under the correct conditions with the correct amount of overlap.
Your supplier should be able to advise.

 

[phatboy]

I've done exactly this. I created the box gutter, and applied a couple of coats of fibreglass resin. I then used offcuts of EDPM, contact adhesived to the box gutter on the sides and bottom. Held a piece of 2x2 in the box gutter and cut the roof EDPM against it. Then held it down, and drew with chalk the line of the EDPM into the gutter. Then contact adhesive on the gutter and the roof EDPM, and rollered together.

Seems absolutely fine, and the joins are all in the right direction to shed water. Had no issues to date.

Trying to use a single piece will be a nightmare, and possibly involve shifting large amounts of heavy rubber roof around, and allowing huge excess for the change of angles due to the deep end of the box gutter.

Can add pics if helpful.....

 

[omph]

I've done exactly this. I created the box gutter, and applied a couple of coats of fibreglass resin. I then used offcuts of EDPM, contact adhesived to the box gutter on the sides and bottom. Held a piece of 2x2 in the box gutter and cut the roof EDPM against it. Then held it down, and drew with chalk the line of the EDPM into the gutter. Then contact adhesive on the gutter and the roof EDPM, and rollered together.

Seems absolutely fine, and the joins are all in the right direction to shed water. Had no issues to date.

Trying to use a single piece will be a nightmare, and possibly involve shifting large amounts of heavy rubber roof around, and allowing huge excess for the change of angles due to the deep end of the box gutter.

Can add pics if helpful.....

Pics would be nice. I will be working on it next week, will see how I can manage.

I was thinking of reducing the slope of the box gutter to diminish the creases, or perhaps make the gutter a V-shape. The V-shape is an interesting concept as no slope is required and and there won't be much stale water sitting in the gutter.

 

[phatboy]

Sorry, I thought I had in progress photos, not just a before and after!

Hopefully this is of some help. When it’s dry at the weekend I can pop up there and get some better pics if helpful.

 

[omph]

Sorry, I thought I had in progress photos, not just a before and after!

Hopefully this is of some help. When it’s dry at the weekend I can pop up there and get some better pics if helpful.
View attachment 312679

Very well done. What was the slope on the box gutter ? did you use firrings ?

 

[phatboy]

Very well done. What was the slope on the box gutter ? did you use firrings ?

Thanks!

The slope was about 70mm over 9metres. I built the box gutter out of ply, and laid the base at an angle into the box, then carried it up in 4 sections to the roof. The roof of course has firrings on both sides leading to the gutter.

The first pic shows the hopper I build out of ply as well. Everything got 2 coats of fibreglass resin over it, and 4 coats in the hopper as I was never going to get good rubber cover in it.