Watertight roof around downpipe

[Jupiter01]

I am planning a small lean to shed at the side of my house. It will be half a metre wide and around 3 metres long, running alongside the external wall of the house.
It will have a flat rubber roof with led flashing folded into the bricks of the house. Since the roof will be at an angle, I may have to step the led flashing but need to give that some more thought…

In one corner, I have a square downpipe from the guttering at the top of the house. It’s difficult to explain but I don’t want to leave this outside the shed as it will be impossible to get to and I will need to build the shed side and another side for the outside fence. Complicated…

How do I have this square downpipe going through the rubber roof and osb board without it leaking water into this shed and under the rubber roof layer?

I am fine with having the pipe visible within the shed (or May box it if it’s an issue) but want to make sure it’s water proof at the top.

Thanks in advance.

 

[DAZB]

You will need to install something such as this...

FlatSeal Flashing - Black EPDM 25mm to 175mm Ext. Pipe Dimensions | Roofing Superstore®

This FlatSeal flashing is made from EPDM (Ethylene Propylene Diene Terpolymer, a highly durable synthetic rubber roofing membrane), ideal for flat and low-p...

www.roofingsuperstore.co.uk

You could change the square downpipe to round just above the sleeve to achieve a tighter fit and square to round downpipe adapters are an easy fit....

FloPlast Square to Round Rainwater Downpipe Connector Black 65mm - Screwfix

Order online at Screwfix.com. Converts square line downpipe to 68mm round downpipe. Cost-effective solution for both new build and refurbishment applications. Compatible with most major manufacturers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[Jupiter01]

You will need to install something such as this...

FlatSeal Flashing - Black EPDM 25mm to 175mm Ext. Pipe Dimensions | Roofing Superstore®

This FlatSeal flashing is made from EPDM (Ethylene Propylene Diene Terpolymer, a highly durable synthetic rubber roofing membrane), ideal for flat and low-p...

www.roofingsuperstore.co.uk

You could change the square downpipe to round just above the sleeve to achieve a tighter fit and square to round downpipe adapters are an easy fit....

FloPlast Square to Round Rainwater Downpipe Connector Black 65mm - Screwfix

Order online at Screwfix.com. Converts square line downpipe to 68mm round downpipe. Cost-effective solution for both new build and refurbishment applications. Compatible with most major manufacturers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Are these type of fittings available for square pipes do you know? If not, I can use the adapter and switch to round pipe within the shed.
Have you used these and are they effective?

Would a tiled roof (instead of rubber) make matters any easier?

Thanks for your help.

 

[Harry Bloomfield]

In one corner, I have a square downpipe from the guttering at the top of the house. It’s difficult to explain but I don’t want to leave this outside the shed as it will be impossible to get to and I will need to build the shed side and another side for the outside fence. Complicated…

Would it not just be simpler, to shorten the lean to, so it doesn't cross over the down pipe?

 

[Jupiter01]

Would it not just be simpler, to shorten the lean to, so it doesn't cross over the down pipe?

The downpipe will then be sandwiched between the side of the shed and section of fencing on the other side. It will be impossible to get to and a cranny for leave and dust to gather. I am unable to leave a bigger gap as I have a constraint on the other end of the shed too and it wont let me achieve the size of shed that I am after.

 

[DAZB]

They do square ones too and although this is specifically for a metal roof it would still work in your case.....

Dektite® Combo Square EPDM Pipe Flashing For Metal Roofs - Black (20 -

Dektite® Diverter for High / Low Roof Pitches. No ponding or damming. The large base of the Dektite® Diverter dramatically reduces and diverts rainwater back up that can occur on very low or high pitched roofs and deep ribbed roofing profiles. No need to cut around pipes, just quick straight...

www.roofingoutlet.co.uk

 

[Jupiter01]

I thought this picture would help explain my situation and where this shed will be situated.

The shed will go within the grey soil pipes to maximize this space and past the white gutter on the furthest end. The current shed (top right) will be removed and the gate will move to that side. That end of the shed will effectively be the fence panel next to the gate when looking from the other side.

 

[Harry Bloomfield]

The shed will go within the grey soil pipes to maximize this space and past the white gutter on the furthest end. The current shed (top right) will be removed and the gate will move to that side. That end of the shed will effectively be the fence panel next to the gate when looking from the other side.

That's a soil pipe, from a toilet, rather than a fall pipe from a gutter.

 

[Jupiter01]

That's a soil pipe, from a toilet, rather than a fall pipe from a gutter.

The grey pipes are soil pipes. The square white pipe at the furthest end is a downpipe from the guttering.

 

[catlad]

oofingsuperstore.co.uk/product/dektite-seldek-aluminium-base-epdm-pipe-flashing-for-pitched-roofs.html
That might be better.

 

[Jupiter01]

oofingsuperstore.co.uk/product/dektite-seldek-aluminium-base-epdm-pipe-flashing-for-pitched-roofs.html
That might be better.

I've seen versions of these where you can wrap them around without having to remove the pipe. That would make a lot easier of they are effective. Any experience of them?

 

[catlad]

Yes" But in your case I would just move the down pipe!

 

[Jupiter01]

Yes" But in your case I would just move the down pipe!

Where to?