Wall Cladding Build-up Query - Flat Roof Detail

[jamesmonk83]

Hi All,

I'm currently bulding a home office using a SIPs kit, the structure is up and wrapped in a breathable membrane but I'm strugglng to get my head around how the cladding and EPDM roof are to be finsihed.

There's no overhang so just straight walls, my plan is to batten vertically, then horizontally and then attach some metal roof cladding sheets vertically. My query concerns where the wall build-up of battnes/cladding sheets meets the roof/roof trim.

I've attached a crude diagram of how I would expect it to finsh but I can't seem to find anything online actually stating the correct way of finishing it.

Am I on the right track?

Thanks in advance!

James

[Iceverge]

I'd be keen to run the Edpm roof out over the walls. 

[jamesmonk83]

41 minutes ago, Iceverge said:

I'd be keen to run the Edpm roof out over the walls. 

 

Thanks for the reply, I wasn't sure whether that was an option. Wouldn't the Epdm need to be fixed to the metal cladding or would the room trim hold it all together?

[saveasteading]

Agreed with Iceverge. OR you need a decent slope and also an utterly watertight seal of metal to roof, using mastic and lots of screws (which you should anyway.

 

I would lap the roofing over the edge so that any stray dribbles go outside your wall cladding.

Even better would be to dress the roof covering up a batten that forms an edge.

 

the metal trim is best not being 2 flats faces like that, as that will distort when screwed.

better to have it shaped like my dodgy sketch attached. the 180 returns are 'welts' and stiffen considerably, as do the other bends. That will look much stsraighter and allow much tighter (and more watertight) fixing, with a bead of special mastic underneath.

 

That will cost twice what a 90 deg one will, so is up to you.

[Iceverge]

I would prefer to see the EDPM run  continuously over the eave like here. That way water will have a lot of trouble making its way into you wall and roof. 

 

[Gordo]

Haven’t seen that trim before. Big improvement on what I saw in past. Not a fan of EPDM flat roofing due to the weakness sealing joints. You will need a ballast also to hold it down if I recall correctly. Haven’t seen this used much nowadays. Best go for PVC or GRP in my humble opinion. Particularly PVC where I have experience of giving 40 years leak free service

Edited October 28, 2021 by Gordo

[jamesmonk83]

Thanks for all the replies, that all makes sense.

[SimonD]

20 hours ago, jamesmonk83 said:

My query concerns where the wall build-up of battnes/cladding sheets meets the roof/roof trim.

 

What metal cladding are you using? Basic corrogated sheets or standing seam? If it's standing seam you need a board directly behind the cladding, ideally with a membrane behind it. You also need to make sure you have a continuous 25mm ventilation gap at the top and bottom of the cladding.

 

Check curb looks good but you can also rip some chamfered timber and take the epm over that. That would be my preference as you then don't need the rubber water seal or mastic sealant.

[saveasteading]

Corrugated sheets provide you with the challenge of the corrugations.

With a sinusoidal panel the junction to a parapet flashing is rather random.

With a basically flat panel you get the upstands at usually 300 or 333, sometimes more,  centres. Therefore  draw a sketch first dealing with perhaps a flat at one cut end,  and a  crown at the other. Then imagine a raindrop trying to run in, remembering that water is magically drawn towards any weakness.

[jamesmonk83]

1 hour ago, SimonD said:

 

What metal cladding are you using? Basic corrogated sheets or standing seam? If it's standing seam you need a board directly behind the cladding, ideally with a membrane behind it. You also need to make sure you have a continuous 25mm ventilation gap at the top and bottom of the cladding.

 

Check curb looks good but you can also rip some chamfered timber and take the epm over that. That would be my preference as you then don't need the rubber water seal or mastic sealant.

 

I was planning on using a box profile style sheet like the attached pic (standing seam I guess?).

 

So are you saying that I should be replacing the battens with a board or including a board as well as the battens? I'm very new to the concept of metal sheet cladding, I was just going for a timber cladding look originally then changed my mind and assumed the same principles of using battens applied but from what you're saying I guess this isn't the case or I have I misunderstood?!

[SimonD]

9 minutes ago, jamesmonk83 said:

I was planning on using a box profile style sheet like the attached pic (standing seam I guess?).

 

So are you saying that I should be replacing the battens with a board or including a board as well as the battens?

 

No, don't worry. Box profile has the structure strength not to need a board behind it. Just remember to ventilate the cavity though.

[jamesmonk83]

12 minutes ago, SimonD said:

 

No, don't worry. Box profile has the structure strength not to need a board behind it. Just remember to ventilate the cavity though.

 

Okay great, yes I was planning on having a gap top and bottom to help with air flow. Thanks for the help.