EPDM Kerb Edge Trim

[Mulberry View]

We're in the process of detailing our whole house roof with a Sika single-ply membrane. We'd like a nice kerb-edge trim (ideally Zinc/Alu), but how would this be detailed if fitted after the membrane? Is this a normal thing to do? I've not approached an installer yet, maybe they'll know the answer, but asking you good chaps!

 

 

If anyone has done similar, pics would be welcome.

[gaz_moose]

those fillet strip details look fiddly. 

the plastic kurb edge trim just gets nailed on with poly top nails and looks kind of naff. I guess you could nail it along the top edge so you dont see the fixings.

[Mulberry View]

13 minutes ago, gaz_moose said:

those fillet strip details look fiddly. 

the plastic kurb edge trim just gets nailed on with poly top nails and looks kind of naff. I guess you could nail it along the top edge so you dont see the fixings.

 

I'm not experienced at all with this type of roof, so any/all feedback is appreciated.

 

I guess the drip edge could be turned back up on the inside and fixed to the underneath of the 40x70 timber, they're used to that detail with Zinc roofing if I was to get trims done by a Zinc installer. But how to seal it to the Single-Ply on top? Architect seems to show another membrane.

[gaz_moose]

ive only done 2 epdm roofs so am far from an expert. it looks like your epdm is set to somehow go over the top of the edge trim. with the plastic stuff the edge trim goes on last then you pull the epdm downwards and trim it with a stanley knife.

 

theres loads of videos on it by a youtube guy called oakwood garden rooms, thats how i learned it.

[Gone West]

We had a Sika single-ply membrane installed on a small extension a couple of months ago. The edge trim upstand is a steel profile covered with a membrane. The profiles were fitted first, then the underlay and then the roof membrane was welded to the profile. The edge of the roof was just a double layer of 18mm OSB.

[Mulberry View]

14 hours ago, Gone West said:

We had a Sika single-ply membrane installed on a small extension a couple of months ago. The edge trim upstand is a steel profile covered with a membrane. The profiles were fitted first, then the underlay and then the roof membrane was welded to the profile. The edge of the roof was just a double layer of 18mm OSB.

 

Thanks for this. Helpful. So the steel profile is seen from the ground I assume? Don't suppose you took any pics of it in progress?

[Gone West]

1 hour ago, Mulberry View said:

Don't suppose you took any pics of it in progress?

I'll have a look, probably not from close to.

[Gone West]

These are the best I've got, sorry.

 

 

 

 

 

[Andehh]

Ours look very similar to the above, if your desperate I can nip up and take some pictures. 

[makie]

10 hours ago, Gone West said:

These are the best I've got, sorry.

 

 

 

 

 

Shouldn't be an issue if they have welded it correctly but that up-stand should be on top of the base layer.

[Gone West]

9 hours ago, makie said:

Shouldn't be an issue if they have welded it correctly but that up-stand should be on top of the base layer.

IIRC the upstand is on top of the underlay.

[makie]

15 hours ago, Gone West said:

IIRC the upstand is on top of the underlay.

The bottom picture, it is not.

[Gone West]

8 hours ago, makie said:

The bottom picture, it is not.

I don't understand. The underlay used is a material that looks like a dark green nylon pot scourer and isn't visible in the last picture 😕.

[Nick Laslett]

@Mulberry View, not the exact same finish requirements, but here are some pictures of how they did our flat roof. Aluminium trims are fitted at the same time as the Sika membrane. 
 

 

The bespoke Aluminium Trim appears to be riveted to the Sika membrane. 
 

Then another strip of membrane is glued over the top. Hard to tell, but from left to right it goes: slate tile, lead, aluminium, membrane strip, membrane. 
 

 

 

For your detail, you would have a bespoke piece of aluminium to cover the curb. 

Edited Monday at 09:05 by Nick Laslett

[Nick Laslett]

“Sika Sarnafil Single Ply Trims” appears to be the magic words. 
 

https://cwgsheetmetal.co.uk/roof-flashings-edging-trims/#3

 

 

USA website here with lots of detail pictures, which give an idea. 
 

https://www.hickmanedgesystems.com/brands/sika-roofing

 

Good video showing how membrane and trims are fitted. 
 

https://youtu.be/V7zutZU_Jwc?si=SPFDU7ByOXvNTPGI

 

Edited Monday at 09:05 by Nick Laslett

[Gone West]

7 hours ago, Nick Laslett said:

Aluminium trims are fitted at the same time as the Sika membrane. 

That's interesting, our trims were steel and were screwed down and the membrane was welded to the trim.

[Nick Laslett]

44 minutes ago, Gone West said:

That's interesting, our trims were steel and were screwed down and the membrane was welded to the trim.

I actually think the ones in my picture and link are galvanised steel. 
 

Looking at our flashing schedule they called it “Trocal Metal”

 

https://grc.sika.com/dam/dms/gr01/3/010945011000000001_Sika_Trocal_Metal_Sheet_Type_S_eng.pdf

 

I’m not sure why I thought they were aluminium. So ours are galvanised steel too. 

[jack]

I don't like the idea of welding a membrane onto a trim where the slope is away from the trim towards the membrane.  

 

We have a Resitrix membrane and I've been really unhappy with how it was done. The detail over the outside edge of our parapet wall looks like this:

 

 

It's theoretically fine as long as the welds (they're modified bitumen based) hold.

 

The problem is that the trims are aluminium, so there are joins at least every 3 metres. As the trims expand and contract with temperature, the welds near the joints are put under quite a bit of lateral stress. In our case, many of them have failed for a couple of inches either side of the joins. I don't doubt that water getting into the space and freezing makes it worse over time.

 

Also, water tends to pool along the welded edge due to the direction of the slope, making it very easy for water to get into the failed joins. It would've mattered a lot less of the weld had failed but the slope were in the other direction.

 

In summary, if I'd known then what I know now, there's no way I would have accepted this design. Assume that welds, joins, glue, etc. will always fail over time. The design needs to be such that, if that happens, water is still largely shed in the correct direction without having a route into the structure through the failed join.

 

 

[mjc55]

On 18/11/2025 at 09:44, jack said:

I don't like the idea of welding a membrane onto a trim where the slope is away from the trim towards the membrane.  

 

We have a Resitrix membrane and I've been really unhappy with how it was done. The detail over the outside edge of our parapet wall looks like this:

 

 

It's theoretically fine as long as the welds (they're modified bitumen based) hold.

 

The problem is that the trims are aluminium, so there are joins at least every 3 metres. As the trims expand and contract with temperature, the welds near the joints are put under quite a bit of lateral stress. In our case, many of them have failed for a couple of inches either side of the joins. I don't doubt that water getting into the space and freezing makes it worse over time.

 

Also, water tends to pool along the welded edge due to the direction of the slope, making it very easy for water to get into the failed joins. It would've mattered a lot less of the weld had failed but the slope were in the other direction.

 

In summary, if I'd known then what I know now, there's no way I would have accepted this design. Assume that welds, joins, glue, etc. will always fail over time. The design needs to be such that, if that happens, water is still largely shed in the correct direction without having a route into the structure through the failed join.

 

 

Why was the trim not put on top of the membrane?