Twisted scaffold boards

[efunc]

Hi all,

I bought all these materials in lockdown, stored mainly in my garage, and am only now getting around to completing the project. It's a set of floating benches in the corner of my garden. The 4 boards that will constitue the seats are 2.4m long and 225 x 38mm. Not genuine scaffold boards, but rough sawn timber. It's not intented to have a high end look so I don't need furniture grade boards.

The problem is that I've just got them out of the garage and they are all slightly cupped along the width and twisted along the length. If I lay one corner flat the opposite corner at the other end is around 2cm off the ground. As such these are unusable as they need to but together flush and then mitre where they meet at the corner.

I think they were straight when they arrived, but I can't be sure. They definitely got slight wet outside for a few days back when delivered, but were kept in the dry for about 4 years. I don't really want to buy new ones, but might have to. Planing and sanding them would be a huge task and I would loose half the thinkness anyway, so I don't want to go there. Is it possible to straighten them with my steam cleaner? Or are they too thick to respond. I also don't have great clamps but could try all sort of bricks and blocks.

If I buy new boards and buid the benches when they're still straight are they going to be prone to cupping, shrinking and twisting anyway too, or will the joins and screws prevent any moevement?

Any advice welcome. Thanks!

 

[Scally-Ho]

With a decent gauge frame beneath those boards and a decent gauge screw to affix them to your base frame, all or most distortion should be pulled out as you tighten. Can you borrow some strong clamps for the fixing period?

 

[efunc]

Thanks for that. The boards are intended to be screwed directly onto the 2x3 battons of my framework with an additional 4 heavy duty steel wall brackets too. I would be worried about trying to force them down as they're quite thick at 38mm, not great quality wise, and might potentially split along the grain? I'm not expereinced enough to know and this is my first project of this nature. Would soaking them first be ill advised?

 

[Scally-Ho]

Some of those boards are already displaying shakes, so some decent intermediate batons on the underside could help ease the situation. You will never know unless you try build your expected bench. As for soaking, you might find they conform, or they could twist even more, so it's all down to the timber really and how stressed it was after initial sawing and the point of sale.

 

[efunc]

Yes, that is a worry. It would need considerable force to screw it down so everything's true, and this would then transfer stress into my framework which could distort over time. Just speculating. Perhaps it's just better to buy new wood, but the danger then is that over time as it continues to dry that too would twist. But at least it would be cut into shape and screwed together

 

[Harry Bloomfield]

The problem is that I've just got them out of the garage and they are all slightly cupped along the width and twisted along the length. If I lay one corner flat the opposite corner at the other end is around 2cm off the ground.

Any boards that long will likely have a similar twist to it over 2.4m. I would just use them, but try to arrange the twists, so they pull against each other. Use bolts, rather than screws, to pull them flat.

 

[foxhole]

Soak in water for a couple of weeks , screw them down before they dry which should reduce any twist or warp.

 

[efunc]

Interesting, thanks. That will involve quite a redesign. I was planning to just screw the boards down to my battens using 5x75mm decking screws for medium duty work. And the heavy duty wall brakets I'm using only have a couple of 5mm holes on the top side to screw down to: https://hwt.media-optimizer.hubble-...8532822/mira-150kg-2_1920x1920.jpg?1737019716 I could try to use coach screws as you suggest, but the 5mm holes might be a limiting factor here. I will also try to add lots of cross battens to bolt into and double my amount of bolts.

Not cheap, but I may end up seeing if I can find 4 straight boards instead and try to finish the bench as planned. I imagine that it won't get too out of shape over time as everything will be braced together

Any boards that long will likely have a similar twist to it over 2.4m. I would just use them, but try to arrange the twists, so they pull against each other. Use bolts, rather than screws, to pull them flat.

 

[robinbanks]

I would be worried about trying to force them down

I wouldn't be. 2 inches over 4 metres isn't a lot of twist at all. The cupping is worse, and you could see if things change when you keep the cupped side damp for a bit ..

It would need considerable force to screw it down so everything's true

I disagree. Bet it pulls flat with just two diagonally opposed 6x80 screws

(but consider Screfix turbo coach screws instead)

what are your thoughts on sawing them up lengthways so they're thinner? Eg if they're 8x2 now, make four 2x2s out of them. It diminishes the visual effect of cupping

 

[efunc]

Soak in water for a couple of weeks , screw them down before they dry which should reduce any twist or warp.

That sounds promising, but terrifying too for the point Scally-Ho made that they might end up bowing, cupping and twisting far more wildly. It's also a challenge finding a way to submerge 2 2.4m boards. certainly not an easy task in my patio.

I do have a polti steam cleaner which has quite a strong jet. I wonder if that could be roped into action somehow?

 

[efunc]

I wouldn't be


I disagree. Bet it pulls flat with just two diagonally opposed 6x80 screws

(but consider Screfix turbo coach screws instead)

OK, thanks, will look into these. cheers

 

[efunc]

what are your thoughts on sawing them up lengthways so they're thinner? Eg if they're 8x2 now, make four 2x2s out of them. It diminishes the visual effect of cupping

OK, I hadn't thought of that. I considered cutting into two or three 1m pieces along the length, but that compromises the strength of the bench because the boards need to straddle the length and form an important part of the bracing and structural support. But cutting lengthways is not a bad idea really. The challenge is doing it accurately as I haven't mastered my circular saw for ripping long lengths. But with a decent jig anything's possible..

 

[foxhole]

That sounds promising, but terrifying too for the point Scally-Ho made that they might end up bowing, cupping and twisting far more wildly. It's also a challenge finding a way to submerge 2 2.4m boards. certainly not an easy task in my patio.

I do have a polti steam cleaner which has quite a strong jet. I wonder if that could be roped into action somehow?

Wet boards revert to their condition when cut .
I used taupaulin supported around edge to form shallow “pond” to soak boards in, will take a week or two .
Monitor and hose down to keep wet .

 

[robinbanks]

But cutting lengthways is not a bad idea really. The challenge is doing it accurately as I haven't mastered my circular saw for ripping long lengths. But with a decent jig anything's possible..

You can screw one board to the next, in such a position that when the cut is run with the saw rubbing along the edge of upper board as it saws through the lower board, it forms the cut line

For example if the distance between the edge of your circ saw's base plate and the edge of your blade tooth is 35mm, and you're going for a rip 38mm, and your blade is 1.5mm, place one plank atop another, so that the long edge is 74.5 mm (38+35+1.5) away from the other, you'll run the cut and end up with a 38mm rip

The other tip I'd say; if you're going to do this on a saw with a thin blade, cut max 10 mm at a time, and run 4 cuts. It'll stop the blade wandering so much

 

[chirpychippy]

I built this out of brand new uncupped straight scaffold boards 3 years ago. One winter one summer and it wouldn't look out of place in a Crooked House.