Joining the ends of two pieces of OSB

[David WE Roberts]

Ignoring a lot of good advice I've gone for OSB fascia boarding.

I will have '3 and a bit' pieces of 16" board 2.4m long as the front of the roof is 8.1m long.

I plan to join (glue) the boards together along an offset to provide a stronger joint and also to mask the join if possible. However I now have to work out the angle of the join.

45 degrees seems a bit extreme with a lot of wastage, although obviously I do have some scope as I have about 1.4m over on the run. [Just went out and checked with my trusty square and ruler and the wastage is about 40.5mm so I could do this for 3 joins and still have a small margin for error.]

Any advice?

Also, any alternatives to epoxy resin for doing the join?

Cheers

Dave R

P.S. Wood will not be going up today because there isn't enough time to fully treat the reverse then fix, glue, and seal. Thunderstorms predicted for tomorrow 06:00. Therefore I will be tacking up some black plastic sheeting as fascia, windows and doors tonight to make the front reasonably weather tight.

[Andrew Mawson]

obviously I

small margin

fascia,

tight.

Presumably you are using OSB3 or it won't be waterproof. I have a feeling one side (the ribbed side) will be rather oily and not glue friendly. If I were doing this I think I'd experiment routing a groove in the end for standard beech biscuit joints and use a waterproof pva as the adhesive.

AWEM

[Tim Watts]

Yes - PU (polyurethane) glue (eg Everbuild, Gorilla). Can you not get a batten behind to support the join and use screws?

[David WE Roberts]

I was planning to do that as well but wanted a glue joint to give added strength and hopefully keep the water out.

Still puzzling over the angle of the join.

[David WE Roberts]

Oh, and that was 405mm not 40.5 mm. Doh!

[Tim Watts]

Vertical. If you can support it from behind - you can use a (say) 4" wide bit of OSB overlapping the joint, glue with PU or epoxy (not PVA - OSB is too rough IMO). 6 small screws tp help while the glue is setting (PU expands a little) The joint is inherently string and waterproof. Run a line of silicon down the exposed cut outside if you wish, for a better paint finish.

As it is screwed to the rafters (I assume), there is no need for fancy joints here. Simple butt will be OK.

[David WE Roberts]

O.K. Tim, thanks. Sounds good and also saves some wood. I had this memory that it was best to join two runs of wood at an angle to get a better bond because there was more surface area in contact but 16" is probably good :-)

I was also thinking that water would penetrate more easily down a vertical joint but I think if it is glued properly this should be O.K.

Probably better to have the joints mid way between two joists to allow the wood to conform to the slight but elegant curve in the front wall. Ah! Penny has just dropped. You mean glue the faces of the 4" piece and the OSB in front to provide a fully glued overlap of the joint, and don't rely on the ends to hold it together (I think). A shame that I have just painted the backs of the boards with bitumastic paint to preserve them in the event of water ingress. That is likely to impede a clean woodwood bond, I think :-(

I may be O.K. if I make sure that each joint is on a rafter although 2" is not very wide. Alternatively, just screw wood to the back of the OSB at the joint and glue the ends - some of the OSB will be above roof level and some will be below the wall plate so I won't be able to support the whole of the back anyway. The front is going to be a mini version of the old 'Wild West' false fronts - the fascia board finishing slightly above the front of the roof line and a few inches below the bottom of the wall plate.

Cheers

Dave R

[dennis]

I would just do it vertically and I would route the edges to give either tongue and grove or a simple lap joint.

[Tim Watts]

That's true - but for an edge join it will have no effect.

Exactly. The stuff doesn't require a structural joint overall as both bits are nails to the rafters.

However if you want to join the ends for presentation purposes, you'll be wasting your time reying to glue the edge. Thermal expansion/contraction will break it. And overlapped joint will keep the faces in line though.

In that case, forget the glue and screw or bolt the support on. It will be perfectly strong enough for the purpose.

Yes - don't bother.

Then your rafter is exposed to any water ingress through the join. Better to have the joing mid span.

[NT]

Use bits of 2mm metal strap and screw them on to the back. I'd stay away from biscuits and profiled ends, they'll only make the most vulnerable bit of the osb even more vulnerable, both in terms of water ingress & expansion, and biscuiting will only result in very weak ends of OSB.

Unless youre in a bungalow, no-ones going to go anywhre close to this, making a furniture standard finish irrelevant.

NT

[David WE Roberts]

[Tim Watts]

I think that is a very sound idea.

No it isn't. It's the Mother of all sheds.

[David WE Roberts]

Any idea where to get the channel? I've drawn a blank at Screwfix, and the first on line place wanted a bulk order. It would be nice to find a supplier in the Ipswich area :-)

Cheers

Dave R

[The Medway Handyman]

After all this cutting, painting, working out how to join etc - wouldn't it have been easier in uPVC?

[Tim Watts]

Try for either aluminium H section (or 2 U sections glued back to back with epoxy - that will be strong being metal-metal.).

Or fascias.com - have a look for the same joining strip used for soffit board which is probably similar in thickness to your OSB - that will of course be plastic.

Or drive around until you spot a uPVC fascias job in operation and nick his offcuts :)