Polycarb sheets

[Phil Pascoe]

I've a small roof to do on a new man cave I'm using polycarb sheets - is it ok to drill the holes or (as instinct tells me) should I burn them?

 

[JakeS]

I'm using polycarb sheets - is it ok to drill the holes or (as instinct tells me) should I burn them?

I don't know what the intent of the question is, but if you're asking whether it's physically possible without damage - I've drilled polycarbonate many times without issue. It machines pretty well and it's very unlikely to shatter in my experience.

 

[Phil Pascoe]

It's just that virtually every hard plastic I ever drilled has had cracks run from the holes outward - I've found it doesn't happen if the holes are burned rather than drilled. I've no actual experience of these particular sheets.

 

[Beau]

Should be fine.

Made lots with Polycarbonate and Hi-cast acrylic and never had problems with cracking. Be careful to clamp it well when drilling though as bits tend to snatch as they exit the hole.

 

[Lons]

Hi Phil

Definitely don't burn polycarbonate, you'll just bu**er it up! Actually, you shouldn't burn holes in any thermoformable plastic as it stresses the material and increases the possibility of failure.

Is it solid or multiwal sheet and what thickness?
If you're cracking it then you're not drilling it properly or too close to the edge. My background is in semi-finished plastics and I've drilled thousands of holes over the years without incident.
Clamp if possible, drill slowly and be careful as it breaks through or that's where it will crack. Don't drill nearer the edge than 12mm if possible though sometimes you have to risk it and when fixing use some rubber / plastic washers if poss and don't overtighten as polycarb expands, drill the holes oversize also for the same reason.

There's fixing and application information provided by Ge for Lexan and aslo Makrolon as well as others on the internet and the distributors usually have it as well, try Amari Plastics.
Make sure it's supported correctly with rafters at the correct centres dependant on thickness of the poly. Flexibility is it's major strength and why it's difficult to break but you have to fix it properly.

cheers
Bob

 

[MMUK]

Drill away that man. However, do it slowly and start with a pilot hole to prevent a larger bit screwing through and making a mess of it. Your finished hole should be about 2mm larger than your fixing to allow for movement

 

[Phil Pascoe]

Thanks everyone. Mind made up .

 

[Lons]

Thanks everyone. Mind made up .

Post some pics of the finished roof Phil.

I forgot to say when you mentioned burning that if solid sheet, you'd have a bit of a job to do it anyway as polycarb has a higher melting point than say acrylic or pvc.

We used to supply replacement 6mm sheet for bus shelters 'cos the little "darlings" carved their names into it but I was called out to see one out of interest where they had tried to burn though it with a blowlamp. Got through the plastic but then the blowlamp stuck in the hole and they had to leave it there as not possible to get it back out. #-o

As an aside, the older shelters were made for glass so had only 1/2" rebates in the metal frames, not enough for polycarb so 3M developed an amazingly strong d/s tape which was very secure indeed. Long time ago so can't remember what it was.

Bob

 

[Phil Pascoe]

It's nothing special, it's 27' x 5' - I'm roofing over the passage up the side of the bungalow. It's not for woodworking or indeed everyday use, but it'll give me an 8' metalworking bench and loads of shelf space. It'll free up loads of space in the single garage that houses my workbench and lathe.

 

[Lons]

It's nothing special, it's 27' x 5' - I'm roofing over the passage up the side of the bungalow. It's not for woodworking or indeed everyday use, but it'll give me an 8' metalworking bench and loads of shelf space. It'll free up loads of space in the single garage that houses my workbench and lathe.

How are you going to seal the joins Phil?

 

[Phil Pascoe]

It's east facing so takes next to no weather. I've allowed a 6" overlap (3"corrugation, and 9" on the ends) and I'm open to suggestions as to what to seal it to the wall with. We're spending money we haven't got atm, so I'm reluctant to spend nearly as much on the flashing as the sheets.

 

[Lons]

It's east facing so takes next to no weather. I've allowed a 6" overlap (3"corrugation, and 9" on the ends) and I'm open to suggestions as to what to seal it to the wall with. We're spending money we haven't got atm, so I'm reluctant to spend nearly as much on the flashing as the sheets.

Ah ok Phil, didn't realise it was corrugated you were talking about, from memory it's only about 1 mm thick so dead easy to drill and you'll be using proprietory fixings anyway as they fix at the highest point of the corrugations. You could burn holes in that but I still wouldnt recommend it as polycarb is UV treated on the top side and burning will affect that causing early failure.
I'd run a bead of silicone along each joint before overlapping, belt and braces as not essential and you can buy preformed sections for flashing against a wall otherwise use flashband but it's fiddly to dress along this kind of profile.

 

[Phil Pascoe]

The sheets were £16.13 to cover 1150mm and the flashing £7.56 for 700mm. I was trying to avoid the flashing. :shock:
There may be a change of plan as I can't get the sheets I was going to use in time.

 

[Lons]

Best laid plans and all that!
PVC might be worth looking at. Don't have as long a life but probably half the price and you can use flashband if you're careful just use a heatgun or hairdryer to soften a little when moulding into the channels.

 

[MMUK]

Bungalow? Can't you fit the roof sheets back to the wall and under the soffit? You won't need flashing then it the pitch is sufficient, just a decent silicone seal on the back edge before you push it up into place.

 

[Phil Pascoe]

Yes, I was waiting for someone to come up with that. It had occurred to me but I'm against the gable end, not under the soffit. A small leak although not welcome wouldn't be the end of the world - it would just run down the wall, and would be quite easy to repair.

 

[Benchwayze]

Phil,
I don't think I will carry forward my half-plan to downsize after all. I might find myself having to provide further rooms! :wink:

Best of luck.

John