Corrugated roofing - recommended fixing method seems "wrong"
DDS
The manufacturers of roofing materials such as Onduline show how to fix
their product:
http://www.ondulinebuildingproducts.net/Onduline%20Fixing%20Guide%20Grey.pdf
( http://bit.ly/eaI9Rb if mangled )
They show that you nail through the "crest" or top of the "wave" profile
rather than through the trough or valley. To my mind (I appreciate that
I must be wrong) that approach seems flimsy; trapping the Onduline
between the head of the nail and the structure you're fitting it to
would be much firmer if there wasn't a void inbetween, wouldn't it?
I presume the reason for the manufacturer's approach is because the peak
stands a smaller chance of any standing water, whereas the valley is
where the water will flow when it rains. Minimising the chances of water
ingress through the roof is a primary concern, fair enough.
Given that you are told to use "waterproof nails" (or screws) c/o
Onduline PP or Safetop fittings, is it really such a risk to screw/nail
down via the valleys rather than the peaks?
DDS
John Williamson
As I understand it, fastening through the peaks uses the elasticity of
the corrugated material to absorb movement, while allowing it to spring
back. Nailing through the bottom of the trough would mean you have a
rigid fixing between two rigid items, so when things move, the joint
would fail earlier.
--
Tciao for Now!
John.
Andy Dingley
> I presume the reason for the manufacturer's approach is because the peak
> stands a smaller chance of any standing water, whereas the valley is
> where the water will flow when it rains.
That's one reason. Thermal expansion is another. Nailing through the
crests with long nails allows a bit of lateral movement with
temperature changes.
Bill
<johnwil...@btinternet.com> writes
>As I understand it, fastening through the peaks uses the elasticity of
>the corrugated material to absorb movement, while allowing it to spring
>back. Nailing through the bottom of the trough would mean you have a
>rigid fixing between two rigid items, so when things move, the joint
>would fail earlier.
This seems eminently sensible to me and is what I did with the screws I
used.
I didn't want to use nails because the piles of junk and things hanging
from the roof inside would have fallen off when I nailed. I used screws
and washers, and think I achieved a sound, consistent fixing. When I
climb up there for the damsons, it sometimes gives a bit, but has been
fine.
It has also survived the recent gales, torrential rain, ice and snow and
last summer's sun as well as the previous years.
If I were re-roofing somewhere else, I'd definitely use this method
(screws through the peaks) again. The only slight difficulty was
sourcing the nails and washers rather than using the Onduline/Wickes
nail kits. I had to go to two different suppliers.
--
Bill
Matty F
> I presume the reason for the manufacturer's approach is because the peak
> stands a smaller chance of any standing water, whereas the valley is
> where the water will flow when it rains.
The peak will have a few square inches of rain catchment above the
screws, while the valley may have water from a lot of the roof area
coming down.
harry
> In message <8tdenmF9m...@mid.individual.net>, John Williamson
> <johnwilliam...@btinternet.com> writes
Corrugated roofing is traditionally fixed through the crest so that
water doesn't get in. There are lots of fixings,(nails, screws,
curved washers etc) most have a soft washer underneath but don't
press that hard onto the roofing material (depending on how rigid it
is.) If you fix in the valleys, it will definately leak.
On the other hand there now exists steel "box profile" plastic coated
sheeting that is flat in the valleys. The fixings for this have steel
washers and a neoprene seal that go in the valley. Because the valley
is flat, they are screwed up really tight. The whole roof/wall is
much stronger and more rigid. You see lots of this on agricultural and
commercial buildings, go to any industrial estate. It's all custom
made off the roll. They make all the other bits too (crests, valleys,
bargeboards etc.)
DDS
> The manufacturers of roofing materials such as Onduline show how to fix
> their product:
> They show that you nail through the "crest" or top of the "wave" profile
> rather than through the trough or valley.
>
> Onduline PP or Safetop fittings, is it really such a risk to screw/nail
> down via the valleys rather than the peaks?
>
> DDS
Thanks for all of the replies - there are several extra points which
hadn't occurred to me. I knew my thoughts were wrong and now I am
confident that when I fit Onduline, I'll do it properly.
DDS
Skipweasel
> Onduline PP or Safetop fittings, is it really such a risk to screw/nail
> down via the valleys rather than the peaks?
>
Yes - I've seen it done by a Doubting Thomas like you - and it leaked
like a sieve.
--
Skipweasel - never knowingly understood.
Kipper at sea
> hello
>
> The manufacturers of roofing materials such as Onduline show how to fix
> their product:
>
>
> (http://bit.ly/eaI9Rbif mangled )
>
> They show that you nail through the "crest" or top of the "wave" profile
> rather than through the trough or valley. To my mind (I appreciate that
> I must be wrong) that approach seems flimsy; trapping the Onduline
> between the head of the nail and the structure you're fitting it to
> would be much firmer if there wasn't a void inbetween, wouldn't it?
>
> I presume the reason for the manufacturer's approach is because the peak
> stands a smaller chance of any standing water, whereas the valley is
> where the water will flow when it rains. Minimising the chances of water
> ingress through the roof is a primary concern, fair enough.
>
> Given that you are told to use "waterproof nails" (or screws) c/o
> Onduline PP or Safetop fittings, is it really such a risk to screw/nail
> down via the valleys rather than the peaks?
>
> DDS
The fixing nails supplied by Onduline have a screwer thread on the
shank and the cap on the head is shaped on the underside to fit the
contour of the crown of the sheet. If theses are put in the down of
the roll the sides of the nail cap dig into the side of the roll and
will not form a seal at the bottom of the roll.
robgraham
> On Mar 4, 11:39 pm, DDS <D...@home.com> wrote:
>
>
>
>
>
>
>
>
>
> > hello
>
> > The manufacturers of roofing materials such as Onduline show how to fix
> > their product:
>
> >http://www.ondulinebuildingproducts.net/Onduline%20Fixing%20Guide%20G...
>
>
> > They show that you nail through the "crest" or top of the "wave" profile
> > rather than through the trough or valley. To my mind (I appreciate that
> > I must be wrong) that approach seems flimsy; trapping the Onduline
> > between the head of the nail and the structure you're fitting it to
> > would be much firmer if there wasn't a void inbetween, wouldn't it?
>
> > I presume the reason for the manufacturer's approach is because the peak
> > stands a smaller chance of any standing water, whereas the valley is
> > where the water will flow when it rains. Minimising the chances of water
> > ingress through the roof is a primary concern, fair enough.
>
> > Given that you are told to use "waterproof nails" (or screws) c/o
> > Onduline PP or Safetop fittings, is it really such a risk to screw/nail
> > down via the valleys rather than the peaks?
>
> > DDS
>
> The fixing nails supplied by Onduline have a screwer thread on the
> shank and the cap on the head is shaped on the underside to fit the
> contour of the crown of the sheet. If theses are put in the down of
> the roll the sides of the nail cap dig into the side of the roll and
> will not form a seal at the bottom of the roll.
Interestingly it's not rain - except for really disastrous rain, that
is the problem from my experience. I did a recycle of some of the
small corrugation clear plastic roofing - typical used on lean-to's.
One sheet went on upside down (silly me!) and it was the snow that was
the real finder of the holes; once it started to thaw, the water
collected at the bottom of the corrugations and really pee'd through
as the holes were the easiest route downwards.
Rob