EPDM Overlap / Apex Roof

Beebopper · 2 Sep 2014

Hi guys - been reading / getting tips from the forums for a while, but got a question I'm struggling to answer...

Currently building an outdoor shed / office which is a bit of an odd shape due to the area it is sited in. The roof will be covered in epdm, but due to the shape will lay two pieces to cut waste.

The roof is apex and I am thinking the best way to do this is to join the sheets on one of the down slopes and bond with the epdm bonding adhesive. But logically I don't think it's wise to apply a joining strip, as it'll hold water on the top side of the slope, and having just two bonded pieces will allow the water to flow down the roof (lower epdm laid under the higher piece and overlapped by approx 15").

Is this the best approach to take, not laid this before.

Thanks...

Mw Roofline · 2 Sep 2014

It will be fine, even better if there is a pitch on the roof the water will just run over it. That's if I think I know what you mean.

Can you join the two on the ridge line and formflash along the join?

Beebopper · 2 Sep 2014

Mw Roofline said:
It will be fine, even better if there is a pitch on the roof the water will just run over it. That's if I think I know what you mean.

Can you join the two on the ridge line and formflash along the join?

Hi - thanks for the reply, yes it's possible to join along the ridge line as that is straight...

however, to me it would make more sense overlapping over the ridge and joining on one of the down slopes, this would give the ridge extra thickness of epdm (2 layers) and a join on the down slope (highest layer on top of lower) so that water will just run down and not collect behind a bonding strip. I'd look at using the bonding adhesive on the overlap just on the joining sections of epdm sheet.

But I'm no roofing expert!

Hopefully this makes sense, I think you understand what I'm trying to achieve

Mw Roofline · 2 Sep 2014

Yes I see your point. Just go with that then mate

Beebopper · 2 Sep 2014

Great thanks, just wanted to check I'm doing this bit right! Should be laying the epdm this thurs, fingers crossed all goes well!

Beebopper · 3 Sep 2014

Got another query guys re roof prep before laying the epdm...

The roof is constructed of tongue & groove boards, and there are some missing knots and ever so slight gaps and dips in the screw holes...

Should I fill these before laying the epdm to ensure all is smooth? And if so, any particular type of filler? I don't fancy a bad reaction with the firestone adhesive.

I've got some external filler, but it states cannot be overprinted with solvent based epoxy and polyurethane paints. But polymer based and waterproof based coatings ok.

Can anyone help please?
Thanks in advance...

cotswoldbuilders · 3 Sep 2014

For the neatest join use 75mm splice tape.

Any holes etc will show, use a 2 part filler.

Beebopper · 7 Sep 2014

Hi guys, thanks for all your replies. Got the epdm installed all ok, but we've hit a bit of an issue with the gutter trims. In the instructions it says to trim the epdm to 50mm on the edges, however we didn't realise that the gutter edges needed the back plate installing before the 50mm is measured, and we don't actually have quite enough epdm to pull in and fix with the trim

So, is anyone aware of a gutter edge system for epdm that doesn't need much or any epsm overlap from the roof deck that we can use instead? Or a way of overcoming this?

Thanks...

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EPDM Overlap / Apex Roof

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