Flashing a polycarbonate roof against a brick wall

[Russ42]

I have just completed roofing the pergola with polycarbonate and now need to flash the high side against a brick wall. Do I need to cut a channel into a mortar line and sit the polycarbonate flashing into this channel and water proof with silicon?

1. is there an alternative to channeling the wall

2. is silicon the best sealant for this job? Which silicon/product for this external application?

3. what should I do if the poly flashing doesn't line up with a mortar line?

[MMF155]

Hi

 I have been following this very helpful very helpful thread - thank you team!  Now I would appreciate some further assistance.

My project is to install a clear polycarbonate sheet awning over a potting bench that I’ve made on the side of my brick house.  The bench is 2400mm and fits in around existing pipe work and windows.  My plumber installed a laundry sink I  recycled so I even have the luxury of hot & cold water  because the bench is on same side as hot water service. 

The awning will be 2500mm wide to give 50mm overhang each end.  The length will be around 1700 onto a base plate on posts I’ve set in concrete.  The awning will discharge water directly onto the garden bed along the fence line .. so no gutter.   I am going to follow MitchellMc suggestion above to use angle iron /foam and silicon cf Suntuf prefab apron flashing.

I have bought 4 sheets of Suntuf polycarbonate corrugated profile. 860mm  x 17mm x1.8m.  I will have a wall plate of 70/35 mm and same size for the rafters.  I think …..I will have 5 rafters rebated based on 2500mm divided into 4 - giving 625mm centres.  I will have a single purlin -recycled fence palings.

So finally my questions…. First -The sheets are 860mm  and the rafters are 625mm. What’s best practice to install given the difference?? 

Do I cut each sheet to match the rafters spacing (625mm spacing) and attach at rafters with a min 1.5 Ridge/trough overlap. 

Or do I just overlap them until the end and trim off excess and gave overlaps in midair?? The latter seems unlikely. 

thanks

[EricL]

Hello @MMF155

It's great to hear that the discussion has both helped and inspired you to install your own polycarbonate roofing. I suggest adding more purlins to prevent the polycarbonate from sagging due to lack of support. The maximum overlap for each sheet is at least 2 corrugations. If you have enough purlins the only sheet you'll be cutting is the very last one.

With a rafter depth of 1700mm I suggest putting a purlin every 500mm. I recommend putting one at the very start of the rafter with a spacing of 500mm in between and the final one will be placed at the very end of the rafter regardless of the remaining distance. You can have a larger space in between them, but this reduces the support for the polycarbonate sheet.   

Here is a link to the Suntuf Installation guide: Suntuff Installation 

If you need further assistance, please let us know.

Eric

[MMF155]

Thanks Eric!  When the rain erasers in Melbourne tomorrow l be out and on the tools 🙂

[MitchellMc]

Keep us updated @MMF155, and please reach out if you need further assistance. We're here to help.

Mitchell

[GMR]

This has been a really helpful discussion & has also helped me as I also need to put flashing between an existing pergola/awning (perspex) & brick wall. I think you've answered how I need to do it but my really dumb question is - How do you even get up there to do the work without getting on top of the perspex & breaking it?

[MitchellMc]

Welcome to the Bunnings Workshop community @GMR. It's wonderful to have you join us, and many thanks for your question about installing flashing.
 

That's not a dumb question at all. It would be silly to climb up on the roof without any thought. Ideally, it's best to install the flashing first and then slot the sheets underneath it as you're installing them. That way, you can be on a ladder next to the sheets as you move along the roof. 

If the sheets are already installed, you might be able to work off ladders on either side of the roof. It would be best to stay off the roofing sheets entirely. Hiring scaffolding is an option worth thinking about. If that won't work, I'd recommend you employ the services of an experienced professional that will have suitable safety gear to complete the work. 

There are potentially other methods involving getting onto the roof, but none that I can recommend due to the high risk of falls from height. Your safety is my greatest concern, and depending on how the roof was constructed, it may or may not support your weight.

On one of our supplier's installation pages, this question was asked, and they recommended that "Walking directly on polycarbonate sheeting is not recommended. In situations where you need to get across the polycarbonate it is recommended that you use a "crawl board" or in other words a plank! It should span across a few of the supports underneath the roofing to spread the load. Be sure to take care not to scratch the sheets too – you can use a blanket underneath."

Please let me know if you have any questions.

Mitchell
 

[GMR]

Thanks a lot for that MitchellMc... yep that makes sense. Yeah the sheets are already installed... & it's a total length of about 8m or so, so bit hard to reach the middle parts from the sides. Thought there may be some trick I wasn't aware of, but good to have the options confirmed by you. Just thought my other option could be to reach the area from the windows above so might check that out... Thanks again!

[DIGDIG]

Really helpful blog. I've got a similar flashing to install but mine is longitudinal to the roofing so I won't have the foam infills (and I'm using metal corrugated panels). Do I need silicon/adhesive between the flashing and roofing or just mechanical connections? And what length screws would you recommend as a minimum to connect flashing to roofing?

[MitchellMc]

Welcome to the Bunnings Workshop community @DIGDIG. It's terrific to have you join us, and many thanks for your question about installing flashing.

Typically, it would be best to lay your roof sheeting, add a layer of foam infill along the length and then screw down the flashing through the sheeting and into the support structure. Use the same screws that will be fixing the edging of the sheet to the roof structure, so the standard roofing screws which are 50mm in length. Alternatively, you could run a thick bead of silicone between the roofing and flashing, and when the flashing is secured in place, it should compress the silicone. 

If you can't screw through the flashing, roof sheet, and then in the roof structure and can only screw through the flashing into the roof sheets, I'd recommend pop-rivets of short Zenith 12G x 20mm Galvanised Hex Head Metal Screws.

Please let me know if you have any questions.

Mitchell
 

[DIGDIG]

Thanks Mitchell,

I am going to use corrugated sheets (something similar to this https://www.bunnings.com.au/fielders-s-rib-corrugated-steel-cladding-2400mm-0-42mm-bmt-zincalume-ste...) and was having a look at the various angled flashing you had - do you have a suggestion on width required for flashing? (I see you have 50x50 and 75x75) - I need for both 'roof to brick wall' along the side of the structure and 'roof to corrugated wall' at the higher end of the structure