Baseboard bracing

[rreckless]

I'm building a 3m x 1m baseboard and thinking about the bracing under 12mm ply (I have access to a very good deal on decent quality ply, hence 12mm) and I'm wondering if having 4 bracing struts, 1 on each edge and 2 evenly spaced between along the 3m length would offer enough support, without needing additional bracing across the 1m width. My gut feel is it would be fine as the 1m width essentially has some bracing every 33cm or so.

Any thoughts? Am i wrong?

[aleopardstail]

I'm building a 3m x 1m baseboard and thinking about the bracing under 12mm ply (I have access to a very good deal on decent quality ply, hence 12mm) and I'm wondering if having 4 bracing struts, 1 on each edge and 2 evenly spaced between along the 3m length would offer enough support, without needing additional bracing across the 1m width. My gut feel is it would be fine as the 1m width essentially has some bracing every 33cm or so.

Any thoughts? Am i wrong?

while I tend to work in old money I find making sure a board is supported at least every 24" is a decent idea (9mm ply). If I read you right you mean having a frame thats two long bits on the sides and then four short bits - two on the ends then two more evenly spaced.

so roughly three 1m squares of bracing with the 12mm ply on top?

will the top be one solid sheet or will there be joins? if there are joins you want a wider brace under the joins, single sheet and should be fine.

be aware the framing needs to be a decent depth to manage torsion/twisting (and a decent depth makes fitting legs more secure), something like softwood framing with further ply on the sides going down ~6" can be good for this, keep in mind though a single board that size is going to be heavy and awkward to move, check you can get it where its going and can get the wood lengths you need in

[rreckless]

In old money, the board will be 9' 10" long and 3'6" wide. I was thinking of having a frame with 4 long bits and 2 short bits (one either end), so the whole 9'10" length is supported, while also offering support every 13" across the width. Based on the idea of support every 24", it sounds like it will work nicely

The board will be split in to 3 sections, 3'3" x 3'6" each I think, purely for transporting the wood when I collect it.

Something like this will be the wood used for the frame https://www.diy.com/departments/smooth- ... 302_BQ.prd

[aleopardstail]

38mm square framing should be ok, though 38mm deep and narrower could be just as good

going for long sections will work, could benefit from some staggered sections going across though between them.

three sections brings its own issues, even if this will be bolted/glued into one thing so designed not to come apart again I would plan for some additional 6' or 8' lengths bracing, perhaps the inner to or outer two beams, then screw & glue these to the underside. stops all the weight being carried by the joins otherwise you are building in weak points.

if you want it to come apart you will need deeper framing to carry the bolts etc but if the idea is "assemble and it only leaves by being cut up in situ" and just a bit of deeper framing is fine.

how are you attaching legs?

[rreckless]

Yeah, it's just set up and leave, so I'm hoping it should be fine.

For legs I'm planning on using the same wood as the bracing, glued and screwed in to corners and then another pair of legs at 3' and 6', so 8 legs total.

If I notice any sagging, I may well end up adding 3 more legs in the middle of each 3'x3' section.

[rreckless]

This is a very crude plan of the frame and legs. Thick lines are bracing, circles are legs, thin lines are joins

Looking at it, for the difference in cost, I might put some cross bracing where the joins are, just to stop flex and give a bit more strength

[aleopardstail]

you shouldn't need more legs than a 3' spacing, even with only 38mm deep timber, however to be honest I'd be looking closer to 4"x1" for the framing, or 2.5"x3/4" at the very least. I would also either have braces as you have shown by the thin lines to support the deck joins directly

some diagonal bracing of the legs will also be beneficial (or something like a 12" high 3' wide ply panel fixed between the lateral pairs of legs then some diagonals at least 18" from the leg to board join at 45 degrees.

the "gold standard" is "I can sit on this and its fine", though not always needed. you will also find with a deeper framing the legs can be fitted more securely.

maybe 4"x1" outer framing, which could be two bits of 2"x1" stacked one atop the other with suitable screw & glue and the joins overlapping to get the full length as a single strong beam.

12mm ply is strong but it will sag, even if only slightly, especially one it has some weight, this is worth doing right and not spending more time on the framing is something I serious regret with my current layout. Dingleberry (ok 4'x2'6" so a lot smaller) is rock solid bending either way and against torsional twisting with an outer frame and a "X" cross brace (the X stops the twisting dead)

other one thats a lot easier to do, make the legs a bit thicker, at least 44mm square, a full 2" square if you can - specifically because you can get some nice adjustable feet that will bolt to the sides which will make levelling it all a lot easier (or even lockable castors)