Plywood or Not

[gazza_lean]

Having had a contractor recover a flat concrete roof on an outbuilding with a felt covered timber frame I am now convinced that they have used different timer to that specified
I am told that the timber panels on one section -which looks like crushed bark chippings (sorry no expert ) -is in fact Marine grade Ply
Other panels are 6mm ply but with no markings (its very pale and looks exactly like the stuff they sell in B&Q) again I am told this is marine grade ply.

The edgings on which the panels sit which are supposed to be tanalised timber boards are equally pale and I can push a screw into it with only marginally more effort than a drawing pin.

I have had the contract manager on site but I suspect huge porkies at play because I can't prove otherwise.,

I now need to track down an expert to come and ID this stuff and be prepared to put it in writing ,
So Should I go to a timber merchant , a carpenter or an engineer/surveyor?

Thankfully no money has changed hands yet so I hold the whip hand but they'll be back Monday so I need to get something sorted quickly.

All help suggestions gratefully received

Gazza

PS I have photos of the wood if these would help

 

[noseall]

it sounds as if they have used o.s.b. (oriented sterling board).
this is in no way marine grade ply, and a heck of a lot cheaper.
its only good for an under deck, beneath felt roofs etc, and is also used as a building site hoarding.

 

[Scrit]

I'd agree with noseall. You're being spun a yarn

The edgings on which the panels sit which are supposed to be tanalised timber boards are equally pale and I can push a screw into it with only marginally more effort than a drawing pin.

It might be tanalised. Tan. generally comes in green or brown in the UK. The brown is quite dark, the green can vary from a pale green to just a greenish cast and tanalised softwood is soft until the solvent carrier evaporates off (anywhere from a couple of days to a over a month, depending on weather), but one thing that tan has is a very distinctive smell - the older CCA stuff left you with a "pizza dough" sort of smell/taste, whilst the current stuff has a distinctive smell which I can't really describe but is very different from the resiny smell of sawn pine.

I am loathe to say it, but a surveyor's word would probably carry more weight in a court of law if you have to go that way. Why not publish the photos and let ius all see?

Scrit

 

[gazza_lean]

Thanks very much for this, it is indeed OSB (judging by picis on the web) but I am not sure how to post the photos to here.

I should have mentioned in my original post that these panels are being laid over battons nailed to the old concrete roof and this creates a 1/2 - 3/4" sealed air gap underneath the panels once the felt has been laid, does this delay or accelarate any potential deterioration in the panels?

Once complete they will be overlaid with felt but the OSB is abutting a vertical wall and one wonders how they will seal the ends which I suspect are the vulnerable parts of this type of board.

By coincidence the 'chippie' has just returned and asked if he could come tomorrow to finish off (Sunday?) so I challenged him on the OSB board he was using and despite telling me just 2 days ago that he was using ply he has now changed his story to 'This is the board that is made for flat roofs" (but he couldn't name what it was)
Oh! and it was his mate who said it was marine ply , when he should have said exterior grade!

Needless to say, he has been invited to stay away until I have spoken to his firm.

Anyone for a stetson?
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[breezer]

I am not sure how to post the photos to here.

see forum information (and note my signature)

 

[masona]

This is the board that is made for flat roofs" (but he couldn't name what it was)
Oh! and it was his mate who said it was marine ply , when he should have said exterior grade!

Oh dear, OBS boards are really mainly for shed roof/floor etc