WBP or OSB?

[David WE Roberts]

I asked about fascia boards a short while ago, and got plenty of good advice. I have decided to cut from 18mm * 2440mm * 1220mm sheets of WBP or OSB.

However I didn't get anything about the relative merits of WBP plywood vs. OSB.

Looking at the Travis Perkins web site and the OSB looks cheaper than the WBP (as expected) - strangely the OSB 3 looks cheaper than the OSB 2.

Looked at the DIY Wiki and the links gave two views (both from the US, I think). One said OSB will replace WBP. The other said that you could expect expansion problems with OSB on the cut edge.

So - front fascia across the front of the roof and side boarding under the side overhangs to be cut from WBP or OSB and then painted. There will have to be 4 joins in the visible run across the front. I am assuming that I will make diagonal joins, glue them, then smooth and fill to try and hide them.

So am I O.K. to go with the cheaper OSB or do I need to go for WBP?

Cheers

Dave R

[sm_jamieson]

I just got a load of OSB3 for a shed. Half the price of WBP ply. I believe the OSB is less likely to twist etc. But I'm sure not quite as water resistant as ply. I'm going to paint it or clad it eventually, and I sealed the cut edges with bitumen paint.

However, if you are going to paint it, it will not look good. You can see the strands on the surface to some extent.

What size are the boards ? You can get 25mm x 150mm treated planed softwood. I actually used this on my extension but covered it with PVCu fascia. Is that an option too. You can get it with a nice ogee profile on the bottom edge.

Simon.

[David WE Roberts]

Thanks. Front board is probably 400mm deep by 7.8m long. I have rejected softwood and plastic (discussed in an earlier thread).

We are debating if the visible strands will be a problem or opportunity :-) With certain treatments e.g. varnish or stain they could become a 'feature'.

[Tim Watts]

I was looking at soffits and fascias last night. Just one thing occurs as a result: do you need an eaves protection strip (for if the edges of your felt are dodgey?

must admit - I'm in a similar quandry. I quite like the idea of plastic (in mahogany) but I also like sticking random eye hooks in the gutterboard for hanging things like tarpauline work area covers off (no workshop or garage). Holes in wood don't matter. Holes in plastic do. Perhaps I should just put a black eyebolt in every rafter end and make it a feature!

[Tim Watts]

I applaud your open mindedness - but I think OSB looks as appealing as Keith Richards after a night on the lash...

Ply will stain/varnish up quite well, especially if you take a sander to it first.

[Dave Liquorice]

I don't think OSB will take to any damp at all well. The bits of OSB that I've had about outside have effectively fallen apart, similar bits of WBP ply have just gone green and black but haven't delaminated.

As for making the OSB strands a "feature", hum well each to their own but to me it would look shoddy and scream "couldn't afford to do it properly". Same painted, the rough surface would also tend to make nice places for algae/lichen to grow.

[sm_jamieson]

I've got some OSB3. I'll do a similar experiment and let you know how it takes to the weather. Its supposed to be glued with resin which is waterproof. Like the diff between normal ply and WBP I guess.

I agree. 'Twould not look good.

Simon.

[David WE Roberts]

Can't be that much rougher than my painted concrete blocks :-)

[Tim Watts]

Is this the shed?

[David WE Roberts]

TMOAS!

[Tim Watts]

Just seen the new picture. That's not a shed, it's a bomb shelter! ;-#)

Looking solid. What are those roofing panels? Aluminium?

[js.b1]

What board do they use for sarking board?

With low pitch roof (circa 22 degree & below) it is common to tile, felt & sarking board - plus scotland and coastal areas tend to do same. Interlocked tiles at very low pitch (ie, people start reaching for second onduline roof underneath) do not seal as well as you would think (or hope!).

I always thought it was OSB4, but suspect most "generic" board out there is OSB3 unless stated otherwise. Marine Ply to BS1088 is good, but I doubt someone wants to pay for that stuff in 18mm... I want the cruise liner that's attached to it for that price.

[David WE Roberts]

Come the next hurricane it will be a hard decision between the house and shed for the more robust shelter. ;-)

The roof is plastic coated metal sheeting - Google 'plastisol'. It is actually green, but the low angle of the sun makes it look white for some reason. I may post another coupkle of pictures to show the roof from on top and underneath.