Pitch for EPDM + Green Roof + Skylights

[Tetrarch]

Looking at an East-facing 8m x 3.5m extension with 3 2m x 1m rooflights.

 

Is it possible to slope the whole roof to simultaneously satisfy the drainage requirements for the single-storey flat roof itself (EPDM),the roof lights and a green roof as a single pitch. The plan is for the rear elevation to have a parapet with no drainage and for the runoff to exit in the direction of the red arrow below.

 

My thought process was that an appropriately pitched roof would make construction of the upstand simpler (and therefore cheaper) as it would need no slope to be created. I've been looking at the sealed units from Roofmaker, ID Systems and EOS Systems so far as, even though higher priced, they are modular and therefore quicker (= cheaper) to install with fewer things to go wrong

 

Notes and requirements:
 

Non-opening rooflights

Triple-glazed 

70/30 solar-control glass or equivalent

 

Regards

 

Tet

[saveasteading]

I don't understand the question. Are you asking if there is a particular pitch suitable for these different products.?

Nor do I understand how there is a parapet but no drainage.

 

I should point out that I am not a fan of green roofs. What is your reasoning for having one?

 

I think water should be got off a roof as efficiently as possible.

To delay it going to increase flooding would be admirable but there are other ways.

To sequester carbon and clean the air, I'm not convinced yours would end up on the right side of the +/- considerations, but will be glad to hear.

[BotusBuild]

Something like this?

The part of the roof that has the rooflights has a 9-10 degree pitch, and will later have a gree roof installed, as will the flatter part to the left of the rooflights, where I will be fitting my PV

[Tetrarch]

On 25/09/2023 at 12:38, saveasteading said:

I don't understand the question. Are you asking if there is a particular pitch suitable for these different products.?

 

 

Exactly that.

 

On 25/09/2023 at 12:38, saveasteading said:

Nor do I understand how there is a parapet but no drainage.

 

 

Apologies for not being clear. I am proposing that there is a gap in the parapet wall (at the point of the red arrow) to allow drainage

 

On 25/09/2023 at 12:38, saveasteading said:

I should point out that I am not a fan of green roofs. What is your reasoning for having one?

 

I think water should be got off a roof as efficiently as possible.

To delay it going to increase flooding would be admirable but there are other ways.

To sequester carbon and clean the air, I'm not convinced yours would end up on the right side of the +/- considerations, but will be glad to hear.

 

The reason for a green roof is mostly aesthetic. The Master Bedroom is directly above the extension and has lovely views of the back garden and beyond. To be frank it is the reason that we bought the house. Though I am a huge fan of EPDM it is a little disappointing as a major part of your view - hence the green roof. the only practical benefit is the reduction in noise when it rains

 

Sequestering carbon and cleaning the air fall somewhere between "zero" and "bugger all" on my "Scale of care"

 

Agree with drainage requirement. I was really enquiring what would be an optimal fall to cope with the green roof and how much water would I be designing for.

 

Regards

 

Tet

Edited September 26, 2023 by Tetrarch