Lean-to roof: solid polycarbonate

Fine Cheers · 22-10-2020 12:04am #1

Just completed a car port type structure on side of house with a EPDM roof. Now plan to add on another 3m length but with a clear poly roof in 5mm or 6mm clear solid. Not keen on the multiwall and want the end result to look as much like glass as possible. Just wondering has anyone else used the flat solid poly on a roof ? Support structure is all timber - joists at 6oomm ctrs. Roof slope 10 degrees. Length 3m x 4m across slope. Will probably use 2 sheets of 3050mm x 2050mm. Will need to notch around SVP, flue and wall pier. I believe it is relatively easy to cut and drill ? Will fix directly to timber below with cladding / rubber washer screws.

listermint · 22-10-2020 9:03am

It will look. Like glass for the time it's in the tape wrapping and for five minutes after its installed.

Weather and the sun will take care of the rest. It makes a poor glass replacement for those reasons. It makes an ok roofing structure to allow decent light through but likes wise it is what it is.

Lumen · 22-10-2020 9:20am

Have you considered using ordinary toughened glass panels?

It's probably similar or cheaper than 5 or 6mm polycarbonate. You can presumably just give exact dimensions with cutouts to the supplier, or supply cardboard templates.

Then bond it to the timbers using an appropriately flexible product (Tek7?). If you keep the widths down and maybe use 400mm centres they shouldn't be too heavy to handle.

GreeBo · 22-10-2020 9:36am

I would go multiwall, your use case is what it's designed for.

Rover365 · 22-10-2020 11:46am

DIY KING wrote: »

Just completed a car port type structure on side of house with a EPDM roof. Now plan to add on another 3m length but with a clear poly roof in 5mm or 6mm clear solid. Not keen on the multiwall and want the end result to look as much like glass as possible. Just wondering has anyone else used the flat solid poly on a roof ? Support structure is all timber - joists at 6oomm ctrs. Roof slope 10 degrees. Length 3m x 4m across slope. Will probably use 2 sheets of 3050mm x 2050mm. Will need to notch around SVP, flue and wall pier. I believe it is relatively easy to cut and drill ? Will fix directly to timber below with cladding / rubber washer screws.

Im about to put up solid poly in the next couple of weeks. Im using a 6mm clear poly fixed with alum glazing bars. Ive sourced the materials from clear amber in the uk. Worth checking out. There are suppliers of clear poly in ireland but limited in size of sheets. Im sure they do 3x2m though i needed 5m lengths.

How are planning to fix the sheets to the timber? If its in an exposed spot id be worried just using screws

popa smurf · 22-10-2020 12:00pm

DIY KING wrote: »

Just completed a car port type structure on side of house with a EPDM roof. Now plan to add on another 3m length but with a clear poly roof in 5mm or 6mm clear solid. Not keen on the multiwall and want the end result to look as much like glass as possible. Just wondering has anyone else used the flat solid poly on a roof ? Support structure is all timber - joists at 6oomm ctrs. Roof slope 10 degrees. Length 3m x 4m across slope. Will probably use 2 sheets of 3050mm x 2050mm. Will need to notch around SVP, flue and wall pier. I believe it is relatively easy to cut and drill ? Will fix directly to timber below with cladding / rubber washer screws.

Any pics hoping to build a seating and barbecue area in back of house a fairly open spot so would need to be fairly sturdy.

Calahonda52 · 22-10-2020 1:00pm

Rover365 wrote: »

Im about to put up solid poly in the next couple of weeks. Im using a 6mm clear poly fixed with alum glazing bars. Ive sourced the materials from clear amber in the uk. Worth checking out. There are suppliers of clear poly in ireland but limited in size of sheets. Im sure they do 3x2m though i needed 5m lengths.

How are planning to fix the sheets to the timber? If its in an exposed spot id be worried just using screws

Are yiou a distributor for clear amber, or did they just sell it to you anyway.
What did the shipping cost as a % of the total?

Rover365 · 22-10-2020 1:39pm

Calahonda52 wrote: »

Are yiou a distributor for clear amber, or did they just sell it to you anyway.
What did the shipping cost as a % of the total?

I ordered through roofingmegastore. Buildforless.co.uk also deliver to ireland. Delivery was around 80 in an order of about 4k but think that is a fixed cost with roofingmegastore. I think it comes direct from clear amber. When ordering they said it would be about 6 weeks wait but came in 2.

Lumen · 22-10-2020 1:46pm

Ooh, this "patterned" polycarbonate looks interesting. No issue with scratching if it comes pre-scratched. :pac:

https://www.roofingmegastore.co.uk/axgard-pattern-flat-glaze-polycarbonate.html

Lumen · 22-10-2020 1:47pm

btw, I reckon it works out cheaper in materials to go with 400mm centres and thinner polycarbonate. That stuff is really expensive compared to treated timber and nails.

Also, 400mm goes into 2050mm wheras 600mm doesn't.

listermint · 22-10-2020 1:48pm

Glass for me, I hate poly stuff. Hate it with a passion. Reminds me of all the cheap sheds ive ever been in.

Lumen · 22-10-2020 1:50pm

listermint wrote: »

Glass for me, I hate poly stuff. Hate it with a passion. Reminds me of all the cheap sheds ive ever been in.

Bus shelter!

Rover365 · 22-10-2020 6:46pm

listermint wrote: »

Glass for me, I hate poly stuff. Hate it with a passion. Reminds me of all the cheap sheds ive ever been in.

I was originally looking at glass but getting 5m lengths was an issue. Also safety. I dont like the look of the normal poly so hopefully this clear stuff looks better and will last a decent amount of time. Its got uv protection so hoping to get 10 years of it looking good and can easily replace

Rover365 · 22-10-2020 7:00pm

Lumen wrote: »

btw, I reckon it works out cheaper in materials to go with 400mm centres and thinner polycarbonate. That stuff is really expensive compared to treated timber and nails.

Also, 400mm goes into 2050mm wheras 600mm doesn't.

Im going with 1m centres (6m x 1m sheets) as i think it will look better and let in more light. 400mm centres u'll have alot more timber.

Will hopefully have it all up in the next 2 weeks so will let everyone know how it goes

Lumen · 22-10-2020 7:06pm

Isn't 1m too wide for 6mm poly? Will it not sag?

Oh, I guess you'll have noggins to support it, right?

Calahonda52 · 22-10-2020 7:09pm

Lumen wrote: »

Isn't 1m too wide for 6mm poly? Will it not sag?

Oh, I guess you'll have noggins to support it, right?

My guess is it will, I have seen triple poly sag at 1m

Fine Cheers · 23-10-2020 12:12am

Thanks everyone and apologies, I must have had my email notifications switched off.
All feedback appreciated. Budget is key here too. The area is for bins, bikes, veg table etc.
I have set out the roof at 3050mm long to suit sheet. Sheets will be UV treated.
Sourcing from either 365 plastics or plastic solutions both in Ireland circa €280 per sheet for 6mm.
Just have to re-route a balanced flue before I can finalise roof.
I plan to use the proper cladding screws with washer seals every 600mm ctrs.
I also need to consider joints in the poly and keep them to a min.
Thinking of just overlapping the sheets as you would with standard metal cladding.
This will result in only one joint across the midpoint of the roof ie perpendicular to the slope.
An overlap detail would surely be more weather tight than a glazing bar that could also hold water.

blackbox · 23-10-2020 10:06am

People seem to be confusing polycarbonate with perspex (also known as methacrylate, Crylux, Plexiglas acrylic, Acrylite, Astariglas, Lucite).

Perspex is very easily scratched, but polycarbonate is quite scratch and weather resistant, but much more expensive.

Still not as scratch resistant as glass, but has other benefits.

Lumen · 23-10-2020 10:30am

Well it really depends on how the light falls on it.

This is a piece of polycarbonate (5mm maybe) I've had lying around the kitchen the last few weeks. It was perfect, now it is scratched.

Mango Joe · 23-10-2020 10:39am

I'd love to see photos/plans people.

Would love to have a bit of outside shelter for patio etc.

Also to stick a clotheshorse!

listermint · 23-10-2020 10:45am

blackbox wrote: »

People seem to be confusing polycarbonate with perspex (also known as methacrylate, Crylux, Plexiglas acrylic, Acrylite, Astariglas, Lucite).

Perspex is very easily scratched, but polycarbonate is quite scratch and weather resistant, but much more expensive.

Still not as scratch resistant as glass, but has other benefits.

no confusion here, it wont be looking well after a year outside. Glass is cheaper actually. you could even source second hand units off adverts strip them and use them. For a project like this id probably spend the money on the wood and get second hand glazing. Especially if im using the area for growing veg. far easier to keep glass clean looking as good as install day.

SouthWesterly · 23-10-2020 10:49am

listermint wrote: »

no confusion here, it wont be looking well after a year outside. Glass is cheaper actually. you could even source second hand units off adverts strip them and use them. For a project like this id probably spend the money on the wood and get second hand glazing. Especially if im using the area for growing veg. far easier to keep glass clean looking as good as install day.

I'm planning on building a greenhouse. I'm currently looking for disused windows. Much cheaper than buying one of the glass is free.

NIMAN · 23-10-2020 10:50am

Another person who would like to see some photos of ongoing builds or finished ones.

Thinking of sticking a lean-to on to the side of my garage so both cars can be sheltered in the winter nights.

Lumen · 23-10-2020 11:01am

In greenhouse applications the problem with traditional horticultural glass is that it's usually not toughened, and is very thin to keep costs and weight down. I did a tour of a restored walled garden a few years ago and they said their glasshouses needed substantial repair after every winter due to storm debris. If you put that stuff on something humans walk under you'd be tempting serious injury. A kid in my school died when he fell through a plate glass window and cut his jugular.

However, toughened glass should be perfectly safe provided it can't fall down, as it smashes instantly into tiny cubes which are completely safe even raining down on people's heads.

Anyway, polycarbonate is amazing stuff provided that you can tolerate scratches.

I'm planning a covered pergola/pavillion thing next year and still haven't decided.

GreeBo · 23-10-2020 3:38pm

For those using perspex/acrylic/polycarbonate and fixing with screws, make sure you make the holes wider than the screws as otherwise, come next summer, you are going to have cracks from every hole...

Fine Cheers · 23-10-2020 7:22pm

I will take a few snaps over the weekend, still a bit of a building site.
I am calling it a car port but there will not be any vehicles in it.
Pool table and gym at one end for teenagers, (and occasional clothes horse), bins, bikes etc at other end.
3/4 of it has solid timber roof (T&G boards on rafters) with EPDM, the remaining quarter to be polycarbonate clear roof, just to keep bright as I have solid composite cladding gates to the front. This is all built to the side, between house and boundary wall. 12m long x 3.6m wide.
Currently open at back end but getting side covers made to close in during the winter.

rje66 · 23-10-2020 10:16pm

This is something I did recently. Works for me. BTW its glass.

listermint · 23-10-2020 11:25pm

Lovely job

whizbang · 24-10-2020 12:12am

I overlapped multiwall ploycarbonate once.

Never again.
It just wicks the water through, turns the whole lot green and manky in about a month.

Fine Cheers · 24-10-2020 12:17am

Nice job with the glazing. Are they painted timber joists with glazing gaskets and cappings ? What glass spec did you go with ?
On the overlapping of the multiwall, you hardly have any photos ?

Lumen · 24-10-2020 2:39am

whizbang wrote: »

I overlapped multiwall ploycarbonate once.

Never again.
It just wicks the water through, turns the whole lot green and manky in about a month.

I think the ends are supposed to be sealed to prevent this.

rje66 · 24-10-2020 8:04am

DIY KING wrote: »

Nice job with the glazing. Are they painted timber joists with glazing gaskets and cappings ? What glass spec did you go with ?
On the overlapping of the multiwall, you hardly have any photos ?

Yes painted and used the glazing bars, they ain't cheap.
Think glass is 10mm toughened. They are very heavy so was conscious of weight.

Calahonda52 · 24-10-2020 10:08am

Lumen wrote: »

I think the ends are supposed to be sealed to prevent this.

yep there is a breathable tape

Fine Cheers · 24-10-2020 8:19pm

Here's some of photos. The area to the front where you can see the timber rafters is the area to be glazed with solid polycarbonate hopefully.

20201024_140245.jpg

20201024_135542.jpg

20201024_161049.jpg

rje66 · 24-10-2020 9:01pm

DIY KING wrote: »

Here's some of photos. The area to the front where you can see the timber rafters is the area to be glazed with solid polycarbonate hopefully.

20201024_140245.jpg

20201024_135542.jpg

20201024_161049.jpg

Nothing spared on the the joisting!!!

Fine Cheers · 24-10-2020 9:24pm

:rolleyes: Indeed but that was really to match the depth of other roof and and to allow poly or glass run over the little parapet. 225 x 50 x @ 600mm ctrs well over sized without doubt but main roof rafters are 175 x 50. Span = 3.7m .
Also wanted it fairly sturdy to brace the front wall of cladding / gate.

NIMAN · 25-10-2020 9:20am

How is the rain draining off the existing roof?

Fine Cheers · 25-10-2020 10:37am

I have a continuous concealed gutter just below the concrete wall capping with the epdm dressed into it. For the poly element though, as the wall steps down I plan just to run the sheets out over capping and water will run off into adjoining grassed open space (we are end house). This will also allow some ventilation to bins etc.

listermint · 25-10-2020 12:29pm

Would have to come out significantly far so as not to come back and drench the wall and the gap. Probably as much as 300mm

Calahonda52 · 25-10-2020 5:53pm

or he could fix a drop down in a bit from the edge

Fine Cheers · 28-10-2020 3:21pm

6mm toughened glass is working out a hell of a lot more expensive than 6mm solid poly. That's just for the material and then need to add in gaskets, cappings etc (which are not cheap) whereas with the poly I will be just drilling through and fix. Also need to notch around a flue and column. I know that can be done with the glass too but when I think of the glass weight and getting it up into place etc, I think I will stick with the 5mm or 6mm clear solid poly for this project, whichever I can source.
Also going to go with straight forward overlap joint across the roof of about 150mm and see how it goes. I will shim up the upper sheet the 6mm. I'll keep ye posted.

Lumen · 28-10-2020 4:53pm

DIY KING wrote: »

6mm toughened glass is working out a hell of a lot more expensive than 6mm solid poly.

That's interesting.

The triple glazing I bought was €132/sqm + VAT for 3x6mm layers, which works out at €44/sqm and includes argon filling, low e coatings and sealing into a unit.

6mm poly is about €46.50/sqm + VAT on the 365plastics.ie website, and that's before cutting.

listermint · 28-10-2020 8:26pm

Lumen wrote: »

That's interesting.

The triple glazing I bought was €132/sqm + VAT for 3x6mm layers, which works out at €44/sqm and includes argon filling, low e coatings and sealing into a unit.

6mm poly is about €46.50/sqm + VAT on the 365plastics.ie website, and that's before cutting.

ya glass is quite cheap, i get quite surprised how cheap tbh.

Fine Cheers · 28-10-2020 9:43pm

Is that price for toughened glass ? I have more prices coming for 6mm toughened which is what has been recommended. I've been told that you can't get toughened longer than 3.1m ? Ideally I'd use 6 panes 3.8m long x .6m wide to match rafters.

Lumen · 28-10-2020 10:22pm

DIY KING wrote: »

Is that price for toughened glass ? I have more prices coming for 6mm toughened which is what has been recommended. I've been told that you can't get toughened longer than 3.1m ? Ideally I'd use 6 panes 3.8m long x .6m wide to match rafters.

Yes, toughened. Now in fairness I'm taking the cost of the individual panes making up the unit, it's possible that individual panes are more expensive for some reason, but maybe shop around.

Whereabouts in the country are you? I got quotes from First Glass and Diamond Glass in Dublin for delivery to Wicklow.

Honestly, I think polycarbonate is fine, it's incredibly strong and light but I couldn't justify spending more or even the same for it given how easily scratched it is.

Mango Joe · 29-10-2020 11:46am

I'm not an expert in these builds in any sense, believe me....But this thread seems to be arriving at a point where a good polycarbonate V glass debate makes a lot of sense and could be very helpful when people are decision making in the future.

I'm open to correction - But to my mind a build using glass is going to top a polycarbonate build any day.

There's just so much that can go wrong with polycarbonate cracking, scratching, going cloudy from UV light, sagging, splitting, mildew growth within....

With glass you've safety considerations overhead, extra weight, and extra cost/labour with more specialised fittings.

I think it would have to be glass for me, interested to hear people's thoughts.

Lumen · 29-10-2020 12:01pm

Mango Joe wrote: »

There's just so much that can go wrong with Polycarbonate cracking, scratching, going cloudy from UV light, sagging, splitting, mildew growth within.....

Solid polycarbonate doesn't have problems with mildew within, that's only an issue with the multiwall and only then if the edges aren't properly sealed.

UV also shouldn't be an issue provided that you buy the polycarbonate with the UV protection on it.

The ultimate solution is scratch-resistant polycarbonate, which is used where you need safety, light weight and similar optical/scratch resistance to glass. Unfortunately

(a) it's horrifically expensive
(b) all the coatings are different, and trying to figure out which ones gives what level of scratch resistance is a total head melter.

Calahonda52 · 29-10-2020 2:18pm

L,
The OP may have mildew in the overlap if driving rain gets up under it.

The key with the UV is to know what side should be up.

I had a job done years ago where the sheets came, pre-cut, covered in a green film on one side and orange on the other.

The lads doing the job duly stripped both films off while the sheets were on the ground, so nobody knew which side was up, the orange film was the uv resistant side.

It all got replaced, they kept the old sheets for their next job

Fine Cheers · 29-10-2020 3:26pm

Good discussion and thanks for the input, much appreciated. I'll keep ye posted.
I need to balance budget with ease of installation and the end use which is bin / bike storage etc as opposed to a patio, decking etc.
Calahonda, have you any photos of your project, how did it weather over time ?
The overlap detail I need to have a close look at to avoid mildew etc.
I either fix one sheet tight over the other or have say a 10mm gap between the sheets to allow for cleaning.
Overlap length will be circa 150mm at 8 degrees pitch. I can use a packer or spacer and seal to prevent blowback.

Calahonda52 · 29-10-2020 6:06pm

No pics. don't live there anymore, it weathered pretty good over the 25 odd years I was there after it went up.
Should have said it was not clear, it was twin wall polycarbonate.
I did gently power wash it once or twice for moss only

Fine Cheers · 02-11-2020 6:38pm

So think I have flue sorted so need to get going on finishing roof. Managed to source 2 large sheets of 6mm clear polycarbonate so going with that. I have single sided glazing tape to use at perimeter to give a good seal. Do I need to place anything between the poly and top of Intermediate timber rafters ?

Lean-to roof: solid polycarbonate

Comments