How to seal gap between polycarbonate roof sheets and adjacent brick wall?

Hi workshop community,

I have a decked pergola area with polycarbonate roofing adjacent to a brick wall. There is a gap of approx 1 cm between the edge of the polycarbonate and the wall and during heavier rain, the deck ends up getting wet! The previous owner who had the pergola installed did not have any flashing or similar put in to prevent water leaking onto the deck.

As a temporary measure, I've inserted a 10 mm polyethylene foam in the gap which understandably fails to improve the situation - the water just ends up running behind the foam and down the wall.

Can anyone suggest a solution to seal the gap? I would be interested if anyone had a solution other than flashing that might be just as effective.

Cheers,

Daniel

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Comments

MitchellMc

Welcome to the Bunnings Workshop community Daniel @dyfuse. It's wonderful to have you join us, and many thanks for your question about sealing a pergola.

Typically that gap would be sealed with flashing. I'd suggest either a polycarbonate barge capping adhered to the wall with Sikaflex 11FC, or you could potentially could fix a steel barge capping. I think the clear barge capping would be relatively unintrusive.

What alternatives had you envisaged?

Please let me know if you have any questions.

Mitchell

dyfuse

https://www.workshop.bunnings.com.au/discussion/comment/24787#Comment_24787

Thanks for the quick reply @MitchellMc!

It is difficult for me to safely access the top side of the polycarbonate roof in order to place flashing and apply adhesive, so I was curious to alternatives that I would be able to install/implement with access via the underside of the roof.

Do you have any suggestions as to how to either install the barge capping solution you mention above or an alternative solution if I primarily have underside access only?

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/75038#Comment_75038

Hi @MitchellMc and @dyfuse

I found this purpose built Roof sheeting solution for myself and @dyfuse completly by accident instore and it fits the bill perfectly as it was designed to do and it can be done completely from under roof. @MitchellMc would know I recently extended polycarbonate roofing the house facia so no rain in outdoor room.

Oh more colours avaliable this is an example.

Suntuf 300 x 45 x 20mm Classic Cream Back Channel FrameI/N: 1010805 $24

https://www.bunnings.com.au/suntuf-300-x-45-x-20mm-classic-cream-back-channel-frame_p1010805

Suntuf 20 x 20mm x 3m Back Channel Foam I/N: 1010487 $25.60

https://www.bunnings.com.au/suntuf-20-x-20mm-x-3m-back-channel-foam_p1010487

Suntuf 300 x 45 x 20mm Windspray Back Channel Frame I/N: 1010803 $24
Predrill channel use sandwich foam (i like the concrete expansion foam to 10mm thick some time is has pull away strips or cut it to size) and pre silicone it on and let it set over night Easier to juggle up high when set. Then when you screw channel to wall the foam will seal it and allow movment OR optional silicone bead to timber and channel join all from underneath access for wall seal.

When installing channel roll it up and over roof edge Long side on top of sheeting there is a 20 mm gap in channel to put screw though your predrilled channel into the wood at nice even hight with the roof resting natuerally against top channel longer lip.

Now its a simple process from underneath to neatly push in custom sealing foam along bottom lip try to keep foam square shape if possible.

No roof access required .

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/75038#Comment_75038

You could install the flashing from underneath, but it will be quite fiddly to install it correctly, @dyfuse. Flashing needs to go above the roof and not under it. The idea is that water hits it and runs off, inhibiting it from accessing the joint between the sheet and the wall. If you install the flashing under the sheet, the water can make it to the joint between the sheet and the wall, and your flashing might fail.

We certainly wouldn't want you to get injured, so it might be best to consider employing the services of a professional to complete the flashing installation for you. If you did decide to complete the project, please read through this helpful guide: How to use ladders safely.

Mitchell

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/101214#Comment_101214

Hi @MitchellMc @dyfuse

Those two suntuf items are commercially designed and made you might need to address this issue with them and or advise Bunning not to sell them . They are dead easy to install .

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/117530#Comment_117530

Hi @Jewelleryrescue,

To clarify my above comment, the product you've suggested has a portion above the roof's surface and is suitable. I was simply stating that it wouldn't be advisable to, say, glue a right-angle length of flashing under the roof.

Mitchell

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/126997#Comment_126997

So your saying via your drawing which mirrors my original diagram100% and description and Suntuf products x2 and Bunning product description are right all along because it is a legitimate, underroof installation plan as per suntuf product designs. Well thanks for that at least.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/133272#Comment_133272

My apologies for the confusion, @Jewelleryrescue. My reply was to @dyfuse about being able to install flashing on the underside of the roof, not to you about your suggestion of using a back channel. Back channel is perfectly fine to use, and I agree with your recommendation.

Mitchell

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/137147#Comment_137147

All good

@MitchellMc

I am a tiny bit sorry for wanting to be right this time as that is absolutly not why I post. Your idea works too so we both have solutions

I try to only to add share solid ideas brain storm if you will then we can pick best combination of ideas.

I never see this back channel before at Bunnings as it not in the metal area so I was pleased to share especially as I just installed it too and had first hand knowlegde.

I was just using the back channel a super simple solution purpose made.

I flipped the back channel as water was not an issue here but if it was we could just add pre cut foam siloette lengths to seal back channel to roofing from underneath.

No wind rattle either.

There is a tip for colour bond wind noisy fence owner s use clear silicon with a fine nozzle and put a dab of silicon between rail and fence peaks touch point every 4th touch point and same at top . Use plastic nozzle to force small gap between rail and peak and insert nozzle 10mm so silicone dosnt show. No more noisy fence. I should do a post on that.

simple egde fixing for polycarbonate sheeting

dyfuse

https://www.workshop.bunnings.com.au/discussion/comment/139813#Comment_139813

Thanks for your replies @Jewelleryrescue and @MitchellMc! These are very helpful and also gives me an idea of some of the different solutions available.

@MitchellMc, if I choose the clear barge capping solution you first suggested, once I place the barge cap so it sits against the wall in the orientation as per your diagram, how would you suggest I best glue it to the brick wall? And how to do so without rain water getting in and running down behind the barge cap (in the gap indicated by the orange arrow in the diagram below)?

Also should I be concerned with any water dripping down the wall via the mortar 'channels'?

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/141652#Comment_141652

Oh @dyfuse @MitchellMc

I See that brown strip on the wall is foam running along the polycarbonate edge, I hoped was timber but you where already thinking on the right track as to a seal.

Well @dyfuse try use that as your wall to angle seal or what ever you choose against as the foam looks like cement expansion foam at 10mm thick that should depress into most mortar joints by screwing it flat and tight enough to form a seal but to do this you will will need to screw angle in multiple short gaps every 30mm or every 50mm or a vertical mortar joints if you use thicker wall 3mm 5mm aluminum it wont counter flex away from foam compression.

Well @MitchellMc has that solution for that design so follow his suggestion s it will work too, Both our ideas will work 🙂

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/141652#Comment_141652

You'd glue the flashing to the wall with Sikaflex 11FC, @dyfuse. The bead of Sikaflex will fill the mortar lines and prevent water from travelling down the rear side of the flashing.

Looking at your image again, that polycarbonate flashing will touch the roof timbers when you place it into position. So, you'll need to cut it to fit around them or go with the other option of back-channel flashing or steel barge capping.

Mitchell

dyfuse

https://www.workshop.bunnings.com.au/discussion/comment/143039#Comment_143039

Thanks for clarifying @MitchellMc. I agree the polycarbonate flashing will be issue to fit in the gap between the roof timbers and the brick wall, and I'd prefer not to cut it.

I'll try the back-channel flashing option with the Sikaflex 11FC and see how I go.

Thanks for all your help @MitchellMc and @Jewelleryrescue!

umarali1990

https://www.workshop.bunnings.com.au/discussion/comment/143039#Comment_143039

Hi Mitchell

I am having same issue as water run from back of sheet, where it is touching fascia under the gutter.. May I drill back channel flashing with fascia under the gutter?

and also some water leakage from screws. is there any option to seal it without changing roof screws? as it is very hard to go on polycarbonate sheets. it can break?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/144452#Comment_144452

Welcome to the Bunnings Workshop community @umarali1990. It's splendid to have you join us, and many thanks for your question about roofing.

To create a seal between the polycarbonate sheets and your gutter so water doesn’t blow back toward the fascia and drip underneath, you would typically install a foam infill strip. These strips are shaped to match the corrugations of your roofing and are sandwiched between the roof sheet and the gutter edge. This prevents water from flowing back up under the sheet and keeps the fascia dry.

Regarding the screws, could you confirm whether they’ve been installed on the peaks or in the valleys of the corrugations? In Australia, they’re generally fixed through the peaks, which helps keep water from sitting around them. Each roofing screw should also have a rubber washer that seals the hole. If these washers have perished or cracked over time, that’s likely the cause of your leaks. In that case, replacing the screws with new roofing screws and washers is the most reliable solution.

While you could try applying a bitumen or silicone sealant around the screw heads, it’s really only a short-term fix. Since the sealing has to be done from the top side, and accessing the roof can risk cracking the polycarbonate (especially if it’s older and more brittle), it’s best to tread carefully. If you need to get up there, spread your weight using a wide board across multiple corrugations. If you’re not comfortable doing that, it would be worth engaging a roofing specialist or handyman to handle the repair safely.

Please let me know if you have any questions.

Mitchell

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