Spot the difference

[Mr Blobby]

Another day another issue on site.

So on our garage flat roof drawings WBP ply is specifed.

I checked with the builder and, sure enough, the invoice lists "MALAYSIAN 8 x 4 x 18mm Complies with EN13986 EN636-3 Structural use"  Which I think is ok and meets the WBP spec, right?

 

So far so good.  However....

 

 

 

 

 

 

 

Not all sheets are the same colour.  Some are lighter in colour and are affected by mould, where the darker sheets appear mould resistant.

 

Some questions:

 

1.  Am I right to suspect that the mopuldy sheets are not the same as the other sheets and not to the required specification?

2.  If the answer to (1) is yes, then apart from being really annoying, how bad is this? 

3. If this is a problem, then what should I do about it?

 

Edited November 15 by Mr Blobby

[Jilly]

Can you measure the thicknesses? Call the supplier or better still, go and look in their yard to determine if they have mixed up either batches of the same stuff, which is just a colour issue, or mislabelled part of the delivery, which you’d need to know, to decide if it’s an acceptable substitution. 
What a pita

[Mr Blobby]

40 minutes ago, Jilly said:

What a pita

 

Yes it is.

 

I should add some context here.  The builder ordered the ply and subbied the roofers. My guess is that the builder, as usual, ordered the absolute minimum amount of ply to try and maximise profit.  I suspect he didn't order enough so the roofers ran out of material and, to get the job finished on the same day, got a couple of extra sheets from the local builders merchant. Which is less than a mile away.

 

The pictures show just a small section. Only about 10-15% of the sheets look different.

 

Oops, I just noticed the two pictures in my original post are actually the same affected area, so here is the other affected area on the other side of the garage.  The mouldy sheets are much lighter in colour (where they are not mouldy!)

 

 

 

Is this a big deal? 

The roof is watertight and so replacing the ply is not easy.

 

 

Edited November 15 by Mr Blobby

[Iceverge]

Any Ply is a mould magnet. 

 

Can you get up on a ladder and prod at it with the pointy end of a screwdriver or a penknife. 

 

If it's not showing any signs of rot I wouldn't be overly concerned. 

 

You could get them to clean off the mould I suppose. 

 

 

 

 

[Mr Blobby]

I've just done some basic maths from the builder's invoice for the ply and there is no way that he ordered enough Grade-3 ply to cover the whole roof. 

I am quite certain that there has been, for whatever reason, a bit of substition here.   🙄

Edited November 15 by Mr Blobby

[Galileo]

As far as I know (which is not a lot) EN13986 EN636-2 is what class 2 structural grade plywood for use in a humid area is, WBP has long gone as a term. If I recall correctly, the Chinese hardwoods are the better types as they are naturally mould resistant. I suspect that the lighter stuff fitted is EN13986 EN636-1 which is for internal structural use where there is no humidity.

I'd bleach wash it, let it dry out and then seal it with whatever you have to hand, stain, varnish etc.

[Mr Blobby]

33 minutes ago, Iceverge said:

Any Ply is a mould magnet. 

 

 

.. but there is no mould on the treated grade 3 ply.  Only the cheap substitute sheets.  Which are not to the listed spec.

 

I just find it intensely frustrating when trades substitute specified materials for cheaper alternatives to make a few quid at my expense.