Scaffold boards for a table top - joining?

[Dan_1981]

Got a few spare scaffold boards which once sanded up a little and stained will make a nice desk top.

Bought a couple of box steel frames for legs at either end.

Obviously I can screw the boards onto the frames at either end but is it necessary to bond the individual boards together maybe some dowels and wood glue or screw them into each other or should attaching to the elgs be enough to hold it all together?

[Big Al.]

Join using a biscuit joiner.

You can machine as many slots to hold as many biscuits as you need to do a sturdy job.

Here for a demo, loads of other to watch.

[Slagathore]

Lots of people just use glue, but you could add dowels to try and help align the boards if they are a bit wavey.

[2Btoo]

I'd be looking at either biscuit jointing them or dowel jointing them.

Neither is hard. Either will give you a much more regular top. Lay them out on sash cramps and glue them nice and solidly as well before putting them on the frame.

Sounds like a good project.

[chappj]

Definitely biscuit join every 30cms or so.

I built a table using scaffold boards a few years go and didn’t leave the wood to acclimate properly and it still moved around even with the joining.

[130iTrack]

Make sure to alternate the direction of the end grain for each board to limit how much each one cups. If you are putting a cap or breadboard on each end of the boards, don't screw/fix in through the end as it will tear itself apart. A domino cutter would work well for this.

[Chrisbis]

Use PU 5 min or 30 min or 45 minute glue for best results, as long as you have some sash clamps.
It's the best glue ever.

PU glue comes in a pourable tub (like pva) or in a cartridge sleeve for a silicon gun application

Alternative to dowels or biscuits or dogs is using kitchen worktop bolts.
Need a router tho and some sort of jig.

Edited by Chrisbis on Saturday 16th February 14:02

[DonkeyApple]

If you don’t have a router etc then drill and peg is going to be pretty much good enough. I would hazard that the most important step is to keep the wood for some time in the room where the table is to be. Unsightly but it lets the wood aclimatise and should stop any big movements once you’ve pegged and glued it all together.

[Chrisbis]

And of course there's KREG jig


Great for jointing/ joining anything together.

Edited by Chrisbis on Saturday 16th February 14:08

[chappj]

Definitely biscuit join every 30cms or so.

I built a table using scaffold boards a few years go and didn’t leave the wood to acclimate properly and it still moved around even with the joining.

[Richie C]

Needed a second one?

[rival38]

@chappj

May i ask: where did you get the metalwork (legg and board holders) from?
Looks like a really good arrangement and one I would like to copy.

I could get some made up, but the angle of leg splay would be useful if you happen
To recall?

Many thanks.

[2Btoo]

Chrisbis said:

Use PU 5 min or 30 min or 45 minute glue for best results, as long as you have some sash clamps.
It's the best glue ever.

PU glue comes in a pourable tub (like pva) or in a cartridge sleeve for a silicon gun application

Interesting. I've never ever got on with PU glue and hate the stuff. Why do you rate it so highly?

[Dan_1981]

Thanks all. The boards are used but only need a bit of a tidy up.

Don't have access to a biscuit so will opt for copious amounts of glue and a couple of dowels per length.

[chappj]

Apologies, I’ve no idea why my list was duplicated.

I had a local engineering firm make up the metal brackets for me. It cost circa £100.

I managed to dig out the measurements.

[uncinqsix]

2Btoo said:

Chrisbis said:

Use PU 5 min or 30 min or 45 minute glue for best results, as long as you have some sash clamps.
It's the best glue ever.

PU glue comes in a pourable tub (like pva) or in a cartridge sleeve for a silicon gun application

Interesting. I've never ever got on with PU glue and hate the stuff. Why do you rate it so highly?

I don't like it either. Other than some possible gap-filling properties if the joint surfaces themselves are a bit dodgy, I can't see what it does better than a half decent cross-linking PVA.

[DonkeyApple]

Dan_1981 said:

Thanks all. The boards are used but only need a bit of a tidy up.

Don't have access to a biscuit so will opt for copious amounts of glue and a couple of dowels per length.

If it were me, I’d be considering half inch dowels at pretty regular intervals, even with good bracing underneath. My general school of thought is that it is better to be thinking ‘ I don’t really need this’ while applying the glue over ‘I hope I’m using enough’.

[RSVR101]

Both PU and PVA form a good bond but PU will expand and create a better joint if the edges aren’t perfectly planed and flush.

Dowels or biscuits or better still a domino joint will help but as scoffold boards have a higher moisture content than a kiln dried softwood intended for furniture if it wants to move as it dries out it will, irrespective of what method has been used.

If it’s a rustic table top finish the OP is after then this all adds to the effect. It can always be sanded flat and filled after the worst of the movement has happened. If a slightly higher end finish is desired it may be worth getting a local joiner to plane up some kiln dried softwood boards, it won’t cost much and they will have more knots and features than scoffold board which tend to have few/no knots.

[uncinqsix]

RSVR101 said:

Both PU and PVA form a good bond but PU will expand and create a better joint if the edges aren’t perfectly planed and flush.

Better get the edges perfectly planed and flush then

If it's a more rustic look with uneven joints/gaps expected, I'd use epoxy, which leaves the finished joint looking tidier than PU.

Another thing to bear in mind with edge joining is that it's a good idea to plane the edges so they are very slightly concave along the length of the boards. They'll come together in the middle under clamping and glueing, but it means the ends of the joints are under compression and less likely to open up as the wood expands and contracts.

[Flibble]

Some dude did a lot of glue testing for wood joints:
https://woodgears.ca/joint_strength/glue.html
PVA comes out ahead of PU, the main determinant of strength is surface area, so the expanding PU glues are worse because the foam reduces effective surface area.