Hi,

It became apparant when the tiles where stripped that the 1970s monkey who
made my dormers (large dormers, half a room each) was a complete moron.

In short, the roofers strongly recommended sheetsing the inside of the 3x3"
timber frame with glued and screwed 18mm sheet to add stiffness and to brace
the odd bits of timber that are not particularly well jointed.

So the question is:

Ply or OSB for structural sheeting work?

And if ply - what does "structural ply" actually have over "regular" ply,
apart from the price? Is "shuttering" (the cheapest) "structural" by default
or the opposite.

When I was a lad, ply was ply, except for marine ply - we didn't have much
of a choice to my memory


Cheers!

Tim

--
Tim Watts Personal Blog: http://www.dionic.net/tim/

If you are reading this from a web interface eg DIY Banter,
DIY Forum or Google Groups, please be aware this is NOT a forum, and
you are merely using a web portal to a USENET group. Many people block
posters coming from web portals due to perceived SPAM or inaneness.
For a better method of access, please see:

http://wiki.diyfaq.org.uk/index.php?title=Usenet

"She got her looks from her father. He's a plastic surgeon."

On Tuesday, January 15, 2013 9:27:15 AM UTC, Tim Watts wrote:
Hi,



It became apparant when the tiles where stripped that the 1970s monkey who

made my dormers (large dormers, half a room each) was a complete moron.



In short, the roofers strongly recommended sheetsing the inside of the 3x3"

timber frame with glued and screwed 18mm sheet to add stiffness and to brace

the odd bits of timber that are not particularly well jointed.



So the question is:



Ply or OSB for structural sheeting work?



And if ply - what does "structural ply" actually have over "regular" ply,

apart from the price? Is "shuttering" (the cheapest) "structural" by default

or the opposite.



When I was a lad, ply was ply, except for marine ply - we didn't have much

of a choice to my memory





Cheers!



Tim

I've certainly seen OSB being used in lots of Grand Designs style projects and in US stick-built homes and I guess it is performing a structural role, though the frame is important too. 18mm osb is pretty strong and OSB type 3 is waterproof to an extent. I would have thought OSB 3 would be fine for the job.

Off some website or other:

Sterling Board - OSB Type 3
OSB (Sterling Board) Type 3

Type 3 is a strong, versatile board suitable for structural use in humid conditions, ideal for applications as diverse as roofing, flooring, hoarding and wall sheathing etc.

Simon.

On Tuesday 15 January 2013 09:39 sm_jamieson wrote in uk.d-i-y:

I've certainly seen OSB being used in lots of Grand Designs style projects
and in US stick-built homes and I guess it is performing a structural
role, though the frame is important too. 18mm osb is pretty strong and OSB
type 3 is waterproof to an extent. I would have thought OSB 3 would be
fine for the job.

Off some website or other:

Sterling Board - OSB Type 3
OSB (Sterling Board) Type 3

Type 3 is a strong, versatile board suitable for structural use in humid
conditions, ideal for applications as diverse as roofing, flooring,
hoarding and wall sheathing etc.

Simon.

Thank you Simon.

The frame is not crooked - so it should sheet up nicely. And it's not
falling down - it's just not as good as it should be.

OSB visually is not a problem - this would be further covered by extra
celotex then plasterboard.

If anyone can explain "structural ply" I'm still interested though - for
other reasons

--
Tim Watts Personal Blog: http://www.dionic.net/tim/

If you are reading this from a web interface eg DIY Banter,
DIY Forum or Google Groups, please be aware this is NOT a forum, and
you are merely using a web portal to a USENET group. Many people block
posters coming from web portals due to perceived SPAM or inaneness.
For a better method of access, please see:

http://wiki.diyfaq.org.uk/index.php?title=Usenet

"It would be better to live under robber barons than under omnipotent
moral busybodies."

In message , Tim Watts
writes

The frame is not crooked - so it should sheet up nicely. And it's not
falling down - it's just not as good as it should be.

OSB visually is not a problem - this would be further covered by extra
celotex then plasterboard.

If anyone can explain "structural ply" I'm still interested though - for
other reasons

Bit here....

http://www.plywooduk.com/ceMarking.pdf
--
Tim Lamb

On 15/01/13 09:27, Tim Watts wrote:

Ply or OSB for structural sheeting work?

And if ply - what does "structural ply" actually have over "regular" ply,

For your application the incremental cost of using a better quality
product is likely to be small, so I would suggest buying exterior ply.

AIUI "structural" means "tested as conforming to a standard".

With timber joists that means each individual joist rolls through a
deflection test machine and is automatically labelled (e.g. C16, C24).
Don't know how they test sheet products.

On 15/01/2013 11:46, Dom Ostrowski wrote:
On 15/01/13 09:27, Tim Watts wrote:

Ply or OSB for structural sheeting work?

And if ply - what does "structural ply" actually have over "regular" ply,

For your application the incremental cost of using a better quality
product is likely to be small, so I would suggest buying exterior ply.

AIUI "structural" means "tested as conforming to a standard".

With timber joists that means each individual joist rolls through a
deflection test machine and is automatically labelled (e.g. C16, C24).
Don't know how they test sheet products.

But just what is better about ply than OSB?

--
Rod

On Tuesday 15 January 2013 11:13 Tim Lamb wrote in uk.d-i-y:

In message , Tim Watts
writes

The frame is not crooked - so it should sheet up nicely. And it's not
falling down - it's just not as good as it should be.

OSB visually is not a problem - this would be further covered by extra
celotex then plasterboard.

If anyone can explain "structural ply" I'm still interested though - for
other reasons

Bit here....

http://www.plywooduk.com/ceMarking.pdf

Thank you; that is very useful
--
Tim Watts Personal Blog: http://www.dionic.net/tim/

If you are reading this from a web interface eg DIY Banter,
DIY Forum or Google Groups, please be aware this is NOT a forum, and
you are merely using a web portal to a USENET group. Many people block
posters coming from web portals due to perceived SPAM or inaneness.
For a better method of access, please see:

http://wiki.diyfaq.org.uk/index.php?title=Usenet

"It would be better to live under robber barons than under omnipotent
moral busybodies."

On 15/01/2013 10:38, Tim Watts wrote:
.....
If anyone can explain "structural ply" I'm still interested though - for
other reasons

It complies to BS5268: Part 2 and, as such, is deemed to satisfy
Building Regulation 7, which requires that any building work shall be
carried out with proper materials.

Colin Bignell

On Tuesday, January 15, 2013 11:48:51 AM UTC, polygonum wrote:
On 15/01/2013 11:46, Dom Ostrowski wrote:

On 15/01/13 09:27, Tim Watts wrote:



Ply or OSB for structural sheeting work?



And if ply - what does "structural ply" actually have over "regular" ply,



For your application the incremental cost of using a better quality

product is likely to be small, so I would suggest buying exterior ply.



AIUI "structural" means "tested as conforming to a standard".



With timber joists that means each individual joist rolls through a

deflection test machine and is automatically labelled (e.g. C16, C24).

Don't know how they test sheet products.



But just what is better about ply than OSB?



--

Rod

Quote from sterling board product details:

Sterling Roofdek is designed specifically for flat roof decking and
pitched roof applications. The board combines all the features and benefits
of SterlingOSB T&G and measures 2440x1200mm; perfect for roofing
The sanded surface is designed to offer excellent adhesion for glues,
self-adhesive felts and bitumen. The board is completely free from
voids and knots and provides the ideal solution for roofing.
In other words, it's as hard working as you are. Sterling
Roofdek is BBA approved, and permitted for structural
applications under BS 5268:Part 2.1996 and Eurocode.

That also implies that the other Sterling OSB boards do not comply with BS 5268.

Simon.

On 15/01/2013 13:15, sm_jamieson wrote:
On Tuesday, January 15, 2013 11:48:51 AM UTC, polygonum wrote:
On 15/01/2013 11:46, Dom Ostrowski wrote:

On 15/01/13 09:27, Tim Watts wrote:

Ply or OSB for structural sheeting work?

And if ply - what does "structural ply" actually have over
"regular" ply,

For your application the incremental cost of using a better
quality product is likely to be small, so I would suggest buying
exterior ply.

AIUI "structural" means "tested as conforming to a standard".

With timber joists that means each individual joist rolls
through a deflection test machine and is automatically labelled
(e.g. C16, C24). Don't know how they test sheet products.

But just what is better about ply than OSB? --

Rod

Quote from sterling board product details:

Sterling Roofdek is designed specifically for flat roof decking and
pitched roof applications. The board combines all the features and
benefits of SterlingOSB T&G and measures 2440x1200mm; perfect for
roofing The sanded surface is designed to offer excellent adhesion
for glues, self-adhesive felts and bitumen. The board is completely
free from voids and knots and provides the ideal solution for
roofing. In other words, it's as hard working as you are. Sterling
Roofdek is BBA approved, and permitted for structural applications
under BS 5268:Part 2.1996 and Eurocode.

That also implies that the other Sterling OSB boards do not comply
with BS 5268.

Simon.

BS 5268 has disappeared so there would be no need to!

"Farewell to BS 5268. Welcome to Eurocodes.

31 March 2010 saw the withdrawal of all parts BS 5268. For timber and
wood-based products, BS 5268-2 is superseded by Eurocode 5 (EC5) or to
be more precise BS EN 1995 - Design of Timber Structures."

http://www.iom3.org/news/farewell-bs...come-eurocodes

But more info. he

http://www.norbord.co.uk/products

However interesting, that does not actually answer my question! If
anything, it makes it sound as if OSB is better than ply.

--
Rod

On Tuesday, January 15, 2013 1:29:20 PM UTC, polygonum wrote:
However interesting, that does not actually answer my question! If
anything, it makes it sound as if OSB is better than ply.

I think OSB4 is the highest OSB, and marine ply, and true marine ply BS1088 are the highest ply. You can sometimes get BS1088 on Ebay as job lots relatively cheaply - however I suspect not as cheap as OSB. OSB is routinely used as the web in engineered timber joists for both floors and roofs - and can be amazingly stiff.

Just avoid "ply" from sheds which can be really poor quality, full of voids, disintegrates if it sees a cloud.

On 15/01/13 11:48, polygonum wrote:

But just what is better about ply than OSB?


An equivalent thickness ply is quite a bit more rigid, and more
difficult to pull through nails/screws IME.

On Tuesday, January 15, 2013 2:54:27 PM UTC, Dom Ostrowski wrote:
On 15/01/13 11:48, polygonum wrote:



But just what is better about ply than OSB?





An equivalent thickness ply is quite a bit more rigid, and more

difficult to pull through nails/screws IME.

True, I put down some 18mm OSB3 on the loft floor (I had some left over) and certainly noticed it was more bendy underfoot than 18mm ply would (wood ?) be.
Simon.

On 15/01/2013 15:18, sm_jamieson wrote:
On Tuesday, January 15, 2013 2:54:27 PM UTC, Dom Ostrowski wrote:
On 15/01/13 11:48, polygonum wrote:



But just what is better about ply than OSB?





An equivalent thickness ply is quite a bit more rigid, and more

difficult to pull through nails/screws IME.

True, I put down some 18mm OSB3 on the loft floor (I had some left over) and certainly noticed it was more bendy underfoot than 18mm ply would (wood ?) be.
Simon.

Thanks.

--
Rod