My (painfully slow) carport rebuild now has all the joists in place and I am wondering whether to roof it with corrugated plastic - as before - or something different.

The original structure collapsed under the weight of snow two years ago which caused the joists to sag sufficiently for their ends for slip off the supporting posts. That design flaw has been remedied in the rebuild but I am wondering if it would be prudent to build a roof that can be walked on for the purposes of snow clearance.

What do the team think?

Richard


PS a side window in the kitchen does look into the carport but it is not an 'in front of sink so that one can look at the view window'.

R

well that plastic goes brittle and the wind cracks it off on anything I've
used it on.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"RJS" wrote in message
...
My (painfully slow) carport rebuild now has all the joists in place and I am
wondering whether to roof it with corrugated plastic - as before - or
something different.

The original structure collapsed under the weight of snow two years ago
which caused the joists to sag sufficiently for their ends for slip off the
supporting posts. That design flaw has been remedied in the rebuild but I
am wondering if it would be prudent to build a roof that can be walked on
for the purposes of snow clearance.

What do the team think?

Richard


PS a side window in the kitchen does look into the carport but it is not an
'in front of sink so that one can look at the view window'.

R

On 10/08/2012 09:20, RJS wrote:
My (painfully slow) carport rebuild now has all the joists in place and I am wondering whether to roof it with corrugated plastic - as before - or something different.

The original structure collapsed under the weight of snow two years ago which caused the joists to sag sufficiently for their ends for slip off the supporting posts. That design flaw has been remedied in the rebuild but I am wondering if it would be prudent to build a roof that can be walked on for the purposes of snow clearance.

What do the team think?

Richard


PS a side window in the kitchen does look into the carport but it is not an 'in front of sink so that one can look at the view window'.

R


Perhaps not quite enough information. I assume you are talking about
clear plastic rather than the bitumen fibre stuff. Can't you clear snow
with a long-handled broom, or is it very wide or obstructed? How much
slope have you got? In my experience plastic clears itself OK if there
is a reasonable slope (but I don't get two feet of snow in a night). But
if you are talking about walking on it presumably the slope is less than
15 degrees. How much benefit would you get from the light? If it is a
big window this may make more difference than you would think.

On Friday, August 10, 2012 9:38:23 AM UTC+1, newshound wrote:




Perhaps not quite enough information. I assume you are talking about

clear plastic rather than the bitumen fibre stuff. Can't you clear snow

with a long-handled broom, or is it very wide or obstructed? How much

slope have you got? In my experience plastic clears itself OK if there

is a reasonable slope (but I don't get two feet of snow in a night). But

if you are talking about walking on it presumably the slope is less than

15 degrees. How much benefit would you get from the light? If it is a

big window this may make more difference than you would think.

Yep, I'm deliberately sparse with info to prevent overload with irrelevancies and would rather provoke questions.

Carport is approx. 7.6m x 3.5m and has a slope of 5 degrees. Not much I know but they are all the same round here - which I know is no excuse for me not to have increased the slope. It collapsed under 0.6m of snow in 2010. Kitchen window is 0.8m x 0.8m

https://picasaweb.google.com/OldGit0...eat=directlink

Richard

On Friday, August 10, 2012 9:38:23 AM UTC+1, newshound wrote:



Perhaps not quite enough information. I assume you are talking about

clear plastic rather than the bitumen fibre stuff. Can't you clear snow

with a long-handled broom, or is it very wide or obstructed? How much

slope have you got? In my experience plastic clears itself OK if there

is a reasonable slope (but I don't get two feet of snow in a night). But

if you are talking about walking on it presumably the slope is less than

15 degrees. How much benefit would you get from the light? If it is a

big window this may make more difference than you would think.

Hi,


The original material was corrugated plastic. I have a specialist supplier of plastic sheeting in various weights so wouldn't be using the rubbish from the DIY sheds.


Carport is approx. 7.6m x 3.5m and has a slope of 5 degrees. Not much I know but there all the same round here - which I know is no excuse for me not to have increased the slope. It collapsed under 0.6m of snow in 2010.

Kitchen window is 0.8m x 0.8m Lights are almost always required in the kitchen.

Pictures he

https://picasaweb.google.com/OldGit0...eat=directlink



Richard

"RJS" wrote in message
...
My (painfully slow) carport rebuild now has all the joists in place and I am
wondering whether to roof it with corrugated plastic - as before - or
something different.

The original structure collapsed under the weight of snow two years ago
which caused the joists to sag sufficiently for their ends for slip off the
supporting posts. That design flaw has been remedied in the rebuild but I
am wondering if it would be prudent to build a roof that can be walked on
for the purposes of snow clearance.

What do the team think?

Richard


PS a side window in the kitchen does look into the carport but it is not an
'in front of sink so that one can look at the view window'.

---------------------------

Ours uses that corrugated stuff, its been there ~ 10 years, fine. It rattles
a bit in high wind but I've never lost any. I do worry about the snow but
it'll only collapse about 3" onto the camper

On Friday, August 10, 2012 9:51:18 AM UTC+1, brass monkey wrote:



Ours uses that corrugated stuff, its been there ~ 10 years, fine. It rattles

a bit in high wind but I've never lost any. I do worry about the snow but

it'll only collapse about 3" onto the camper

Mine collapsed onto the MIL's car! Pictures he https://picasaweb.google.com/OldGit0...eat=directlink

"RJS" wrote in message
...
On Friday, August 10, 2012 9:51:18 AM UTC+1, brass monkey wrote:



Ours uses that corrugated stuff, its been there ~ 10 years, fine. It
rattles

a bit in high wind but I've never lost any. I do worry about the snow but

it'll only collapse about 3" onto the camper

Mine collapsed onto the MIL's car! Pictures he
https://picasaweb.google.com/OldGit0...eat=directlink

Ouch

On Fri, 10 Aug 2012 04:19:48 -0700 (PDT), RJS
wrote:

Mine collapsed onto the MIL's car! Pictures he https://picasaweb.google.com/OldGit0...eat=directlink

Not surprised; it didn't look as if it was adequately supported at
all. Otoh, when done properly, corrugated plastic sheeting is pretty
strong stuff.

On Friday, August 10, 2012 2:53:46 PM UTC+1, Grimly Curmudgeon wrote:


Not surprised; it didn't look as if it was adequately supported at

all. Otoh, when done properly, corrugated plastic sheeting is pretty

strong stuff.

Correct. The joists were skew nailed to the 4"x2" wall plate and to the 4"x2" plate siting on top of the four posts. Where the joist reached the posts there was a steel lip of about 1/3" supporting the end of the joist. The weight of snow made the joists sag and pushed the posts away from the house, resulting in the ends of the joists falling off the steel 'lip' putting the whole weight of snow plus roof onto the skew nails. Add to this wood that turned out to be pretty poor and you have a recipe for the inevitable. Remarkably there was no damage to the car.

The replacement structure is slightly different insofar as I have supports for each new pressure treated 4" x 2" joist made from 70mm RSA bolted to the wall and the far end of each joist is supported across the whole of the top of the post - about 100mm in all. There are coach screws up through the posts and wall supports into each joist. What were single plates fixed to the wall and across the tops of the posts are now sections between each joist, fixed to wall and steel supports or to the 50mm RSA linking the tops of the posts. Hopefully that will take the weight of more snow than the end wall of the house can bear!

Jokes aside, is the consensus of opinion to go for corrugated plastic? It would mean no access to the roof. Bear in mind that it is 7.6m x 3.5m.

"RJS" wrote in message
...
My (painfully slow) carport rebuild now has all the joists in place and I am
wondering whether to roof it with corrugated plastic - as before - or
something different.

The original structure collapsed under the weight of snow two years ago
which caused the joists to sag sufficiently for their ends for slip off the
supporting posts. That design flaw has been remedied in the rebuild but I
am wondering if it would be prudent to build a roof that can be walked on
for the purposes of snow clearance.

What do the team think?

Richard


PS a side window in the kitchen does look into the carport but it is not an
'in front of sink so that one can look at the view window'.

R

The only other clear plastic I can think of is multiwall polycarbonate, very
expensive and requires a completely different structure. Won't break though.
http://www.flickr.com/photos/ara-chl...in/photostream
See conservstory above. (Aluminium rails)
There are kits for fixing it both on to timber and metal.

On 10/08/2012 09:20, RJS wrote:
My (painfully slow) carport rebuild now has all the joists in place and I am wondering whether to roof it with corrugated plastic - as before - or something different.

The original structure collapsed under the weight of snow two years ago which caused the joists to sag sufficiently for their ends for slip off the supporting posts. That design flaw has been remedied in the rebuild but I am wondering if it would be prudent to build a roof that can be walked on for the purposes of snow clearance.


I think that, given the proximity of the neighbour's house, it would
feel very gloomy in the kitchen if the roof were entirely opaque. What
about a compromise - a mixture of solid and translucent? You could then
bridge the translucent sheets off the solid for access for maintenance.

I'd look at box section steel for the solid , and either matching
profile grp or cheaper corrugated pvc between - making sure it's over
the windows, of course.

If you've had problems with condensation on the underside of the sheets
in the past, and are bothered by it, go for insulated box section steel
- not too expensive if you shop round for seconds or surplus sheets -
and either air-gap translucent sheets or multiwall polycarbonate.

--
Kevin

On Friday, August 10, 2012 8:07:08 PM UTC+1, Kevin wrote:


I think that, given the proximity of the neighbour's house, it would

feel very gloomy in the kitchen if the roof were entirely opaque. What

about a compromise - a mixture of solid and translucent? You could then

bridge the translucent sheets off the solid for access for maintenance.



I'd look at box section steel for the solid , and either matching

profile grp or cheaper corrugated pvc between - making sure it's over

the windows, of course.



If you've had problems with condensation on the underside of the sheets

in the past, and are bothered by it, go for insulated box section steel

- not too expensive if you shop round for seconds or surplus sheets -

and either air-gap translucent sheets or multiwall polycarbonate.



--

Kevin

Hmmm. Whatever goes up, it's not going to be expensive multiwall polycarbonate or similar. Until the snow incident I managed without being able to cross the corrugated plastic. Having said that, much to my surprise the cowboys who painted the house placed scaff boards on the corruagted plastic and then ladders on the boards to reach the top of the side wall. They didn't crack a single sheet!

And I'm not adding more joists to suit a fernickety panel spacing system :-) Hence wavy plastic or felted ply.

OTH there is this stuff: http://www.kingspanpanels.co.uk/Products/Roofs that a friend has used to good, but probably good, effect.

Rihard

On Aug 13, 2:51*pm, RJS wrote:
On Friday, August 10, 2012 8:07:08 PM UTC+1, Kevin wrote:

I think that, given the proximity of the neighbour's house, it would

feel very gloomy in the kitchen if the roof were entirely opaque. *What

about a compromise - a mixture of solid and translucent? *You could then

bridge the translucent sheets off the solid for access for maintenance.

I'd look at box section steel for the solid , and either matching

profile grp or cheaper corrugated pvc between - making sure it's over

the windows, of course.

If you've had problems with condensation on the underside of the sheets

in the past, and are bothered by it, go for insulated box section steel

- not too expensive if you shop round for seconds or surplus sheets -

and either air-gap translucent sheets or multiwall polycarbonate.

--

Kevin

Hmmm. * Whatever goes up, it's not going to be expensive multiwall polycarbonate or similar. *Until the snow incident I managed without being able to cross the corrugated plastic. *Having said that, much to my surprise the cowboys who painted the house placed scaff boards on the corruagted plastic and then ladders on the boards to reach the top of the side wall. *They didn't crack a single sheet!

And I'm not adding more joists to suit a fernickety panel spacing system *:-) * *Hence wavy plastic or felted ply.

OTH there is this stuff: *http://www.kingspanpanels.co.uk/Products/Roofsthat a friend has used to good, but probably good, effect.

Rihard

What's the point of insulating a car port roof?


NT

On Mon, 13 Aug 2012 07:02:39 -0700 (PDT), NT
wrote:

What's the point of insulating a car port roof?

I would suggest drips, but the insulation will all be at the same temp
top and bottom, so might not make any difference to condensation.
Otoh, uninsulated material can drip well in the right circumstances
and it's all at the same temp all the way through, so it might be
worth trying to see if it works.

On 14/08/2012 10:42, Grimly Curmudgeon wrote:
On Mon, 13 Aug 2012 07:02:39 -0700 (PDT), NT
wrote:

What's the point of insulating a car port roof?

I would suggest drips, but the insulation will all be at the same temp
top and bottom, so might not make any difference to condensation.

But it won't be at the same temperature in the circumstances that lead
to severe condensation under uninsulated roofs: a clear winter night
sky. The hoar frost phenomenon. If the roof is insulated, the underside
will probably not get a frost buildup.

The OP, having apparently dismissed my suggestions, then gives a link to
the stuff I'd suggested as the deluxe option. I don't understand the
reference to altering joist spacings: surely there are purlins that the
sheets themselves are fastened to? Especially corrugated plastic or
that awful Onduline stuff.

But I'm not a great fan of built-up felt roofing. You don't see it on
new warehouses. Lay it on Stramit for a real disaster.


--
Kevin