Oddly arranged flat garage roof

[Vips]

Hi,

I've spent some time trawling through the numerous threads but haven't quite found a solution to my oddly arranged roof.

Although I am reasonably handy with the materials associated with the roofing, I am unsure on the best design for the roof and would very much appreciate some advice on possible solutions. I am leaning towards an epdm roof, although I do have experience working with GRP too.

I will attach pictures of the current state of the roof(s). The garage is in two sections. One side (smaller), has relatively new joists (although they look rotten now), and is covered with metal sheeting. This side drains into a gutter on one edge. The other half is very rudimental, consisting of what are rotten joists at incorrectly spaced intervals, covered by damaged plastic sheeting. The plastic section is much longer and is pitched towards the centre of the garage and drains into a gutter which runs through the middle. The entire roof section is surrounded by a parapet.

I am considering a warm roof well insulated as I often use the garage as a workshop for woodworking. In order for there to be adequate height along the parapet to allow for the various boards, insulation, covering and possible flashing, I will need to lower the install of the new joists at a slightly lower level. I am considering a wall plate (ledger?), and then joist hangers. 150x50mm joists @ 400 centres as the span is only 2.6m.

As for the design, I can either leave the current longer pitch draining into the middle, or perhaps change this with a box gutter along the parapet?
I would like to remove the coping stones altogether and attempt to, using the correct detail, lay epdm over the edges. The problem is that the neighbours wall is awfully close and so have limited access to fix onto the side of that wall. I was considering pre fabricating the detail, then hang over the edge and screw into the top of the parapet, with the epdm leading straight over this?

The approximate size of the roof 5m x 2.5 (metal sheeted side) and 8m x 2.6 (plastic sheeted side).

I would greatly appreciate the best design suited to this perhaps oddly arranged roof.

Kind regards,

Vips

 

[^woody^]

Fix a timber beam on the inside of the party wall to allow you to built a wall up past the neighbours gutter - brick or timber clad in plastic and flashed into the gutter.

Then form a mono pitch roof sloping towards your garden

 

[Vips]

Hi Woody,

Thanks for the reply and taking the time to illustrate your idea. It does seem like a good idea, but my concern is when the neighbours decided to do any repair work to their roof, which I am told may be at some point, would I end up cutting off access to their gutter. Their gutter does overhang the coping stones on my side, which I believe is not strictly allowed, but we get on relatively well, so I'm trying to work on a solution to avoid any future and current problems.

 

[^woody^]

The junction on the party wall is always going to be the issue whatever roof you do.

You have to deal with what is there now, and then again if the neighbour alters his roof. There are no other options.

 

[catlad]

You could consider following woody's design but using mono ridge which you
could set to drip into the gutter.

 

[Vips]

Here are a few more photos. If I pitch from the neighbours side, I'm going to have to have a box gutter running along where the roof meets the rest of the house? I was considering removing the coping stones, prefabricating the edge detail, and screwing that on top of the parapet. Finish up with laying the epdm up and over.

Do I have to have at least 150mm between the roof top and the metal flashing?

 

[Vips]

Thanks for the help so far guys.

Can somebody provide me with a little more detail how to do the build up of the wall and create a mono ridge please? Would a box gutter as it meets the house and the small section of parapet be ok?