Polycarbonate overhang and guttering

[tell80]

As I mentioned above: keep the overhang to 30mm - 40mm.
Ignore the 60mm nonsense.
A 60mm overhang depending on the fixing height of the gutter on the fascia, and the pitch of the roof then the 60mm overhang is more likely to interfere with any flow of debris swollen water in the gutter than a smaller overhang.

 

[noseall]

With regards to the position of the gutter and the poly, would it make sense to trim the ends of the rafters flush with the rim joist, something like this?

Looks ok. 60mm overhang will put the roof discharge smack in the centre of standard 110mm guttering. Gutter clips add an additional 8mm or so to the distance. Ignore tell80 he is a clueless troll. 30mm is a joke.

 

[Nige F]

debris swollen water .

like a tsunami ?

 

[Nige F]

Without using falls try setting a gutter on three sides of a semi-detached house with one outlet available, & see what water damage, & expense might result for a householder?

Without setting a fall to outlet how will "rain know where the outlet is" when the OP's gutter is filling with debris & leaves?

What if your idea of "level" sags a few mm's and creates a pond beyond a debris dam?

What if your nonsense is contrary to the Bldg. Regs?

What builder has but one outlet on 3 sides of a semi ? do tell. A pond beyond - poetic but pathetic hyperbole

 

[mrrusty]

Personally I'd use the alukap XR system and flat poly multiwall. Use their aluminium poly edgeing along the front and back edge. It will be much nicer than corrugated. https://www.clearamber.com/browse/sc-ALUKAP_XR45mmBARS-220/

 

[OldKettle]

Thanks for all the further advice.

I am still in the process of putting the purlins up and have a couple of 2500mm x 950mm sheets ordered, which will allow me to mock up a full length (4.7 metres in places) and also overlapping horizontally.

I have also mocked up a section of gutter with some flat sheets of multiwall that I have left over from a greenhouse. 60mm overhang is working fine, but will check with the corrugated. The gutter spec has 1.90 litre/sec when installed level, which I may eventually do, but have currently mocked it up with a fall.

https://cdn.aws.toolstation.com/items/manual/manual-aquaflow-rainwater-compatibility-chart.pdf

While I have been up, installing the purlins, it become apparent that reaching the full width is going to be a challenge in some places as @big-all suggested, so that is going to take some thought. Even if I could get a higher platform, I still think that the placement of the sheets will require me to get on the roof at some points. I wanted to avoid that, but looks like I will have to, at least in some places.

I agonised over the look of multiwall vs corrugated for a while, but I actually don't think I mind the corrugated, and it seems to have the best clarity and strength, and also feels like it could be less maintenance than the multiwall (which seems to have more potential failure points).

 

[big-all]

the funny thing is after around 19 years off the lean to shed having corrugated plastic i am now converting to polycarbonate as it needs replacing every 8-10 years so at 68 i am using homemade wooden "T" sections at the joints with 45mm strips off pvc screwed on top to make a "H" section so from now on its a simple slide out and spot replace as next doors cat jump the perhaps 4ft from my flat bathroom roof onto the plastic making it fail half life around 5 years

 

[OldKettle]

The purlins are now up and I have bought a couple of sheets to have a look at.

They are not fixed down yet, but they fit well and a recent shower drained into the gutter well.

I am just waiting for a further order to arrive before I start fixing.

I was going to skip putting foam fillers on the purlins, as the manufacturer ones were going to cost me an extra £60 for each pair of sheets, but I have found some that are about a quarter of the price, and so am starting to wonder whether they might be worth it to cut down on roof chatter when raining, although I think it would look nicer without them.

These are the ones I was looking at (unfortunately only currently available in black). Any thoughts on whether they would make a big difference to the structure, or the chatter?

https://www.amazon.co.uk/Black-Corrugated-Filler-Purlin-Closure/dp/B08X2R8Z9G

 

[Burnerman]

Looks like a neat job!
Personally I would always use the filler - it keeps insects as well as draughts at bay. I didn't, and instead used expanding foam which is a right mess, but that was years ago when the foams weren't readily available.
John

 

[Nige F]

The purlins are now up and I have bought a couple of sheets to have a look at.

They are not fixed down yet, but they fit well and a recent shower drained into the gutter well.

I am just waiting for a further order to arrive before I start fixing.

I was going to skip putting foam fillers on the purlins, as the manufacturer ones were going to cost me an extra £60 for each pair of sheets, but I have found some that are about a quarter of the price, and so am starting to wonder whether they might be worth it to cut down on roof chatter when raining, although I think it would look nicer without them.

These are the ones I was looking at (unfortunately only currently available in black). Any thoughts on whether they would make a big difference to the structure, or the chatter?

https://www.amazon.co.uk/Black-Corrugated-Filler-Purlin-Closure/dp/B08X2R8Z9G

 

[Nige F]

Out of interest how much overhang into the gutter. I can't tell from the pics.

 

[big-all]

general comments
your overhang into the gutter may work better perhaps 20mm more your gradient looks fine but suspect with the right wind you may frequently get drips blowing back onto the timber
now it wont harm the timber, but it may start discolouring the timber something you may want to avoid ??
i have planed mines as 68mm yours looks about 45mm

 

[OldKettle]

Looks like a neat job!
Personally I would always use the filler - it keeps insects as well as draughts at bay. I didn't, and instead used expanding foam which is a right mess, but that was years ago when the foams weren't readily available.
John

Thanks. Do you reckon I should put them on all of the purlins to reduce noise also? I'm not really sure how noisy it might be, or how much difference they will really make

Out of interest how much overhang into the gutter. I can't tell from the pics.

general comments
your overhang into the gutter may work better perhaps 20mm more your gradient looks fine but suspect with the right wind you may frequently get drips blowing back onto the timber
now it wont harm the timber, but it may start discolouring the timber something you may want to avoid ??
i have planed mines as 68mm yours looks about 45mm

The sheet is only very roughly placed in the photo as I have been moving them about a bit today.

I'm aiming for an overhang of 60mm. I tried testing that by pouring water from a bottle, but the flow was too high to be realistic and it just overshot the gutter.

I haven't tried with a hosepipe, but before I could get round to setting it up it started raining reasonably heavily and with that, the gutter worked fine at 60mm. The only proviso was that the roof sheet is not fixed down yet, and so it is sitting a bit higher than it eventually will.

 

[big-all]

Thanks. Do you reckon I should put them on all of the purlins to reduce noise also? I'm not really sure how noisy it might be, or how much difference they will really make





The sheet is only very roughly placed in the photo as I have been moving them about a bit today.

I'm aiming for an overhang of 60mm. I tried testing that by pouring water from a bottle, but the flow was too high to be realistic and it just overshot the gutter.

I haven't tried with a hosepipe, but before I could get round to setting it up it started raining reasonably heavily and with that, the gutter worked fine at 60mm. The only proviso was that the roof sheet is not fixed down yet, and so it is sitting a bit higher than it eventually will.

yes indeed i thought it was approximate and you had it in hand
it was just one off those situations where its so obvious it doesn't need mentioning unless its not so

 

[Nige F]

As I mentioned above: .
Ignore the 60mm nonsense.
A 60mm overhang then the 60mm overhang .