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I have a fairly simple project I'm considering which will require slabs of approximately 3-4 inches thick.

Because of its light weight and price I thought I might use 2x4 dimensional lumber to make the slabs, the largest of which will be approximately 60x18x3.5 inches, but I'm concerned because of the poor quality of dimensional lumber.

Is laminating the planks enough to counter the tendency to warp that plainsawn lumber is prone to if I alternate the grain patterns, or should I just get higher quality pine?

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Is laminating the planks enough to counter the tendency to warp that plainsawn lumber

Basically yes although there are no guarantees.

'Jointed' slabs are inherently stable, even when one or more of the individual boards are less than ideal, because of the construction.

The long-grain glued faces are immensely strong and individually and together will work to keep the glue-up flat. And a rough rule of thumb is that the more glue joints there are the stronger the piece ends up. But for wide projects the more joints the more difficult the glue-up becomes, so it can be advisable to do it in sub-assemblies and then glueing these together to make up your final width.

For maximum stability be aware of the radial and tangential direction of the grain and try to orient this uniformly for every piece. This is not always possible but it's a good thing to aim for as the more uniform you can make the seasonal expansion and contraction the better.

Grain direction and movement

The ideal is to orient the tangential grain such that the greatest expected movement is up and down, not side to side. Side note: this is one reason for the traditional preference for quarter-sawn wood, which tends to expand less across its width than plain-sawn or flat-sawn boards.

I'm concerned because of the poor quality of dimensional lumber.

Stock selection is often overlooked today but it's perhaps more important now than ever, especially with dimensional lumber which can be of poor uniformity, and is outright poor quality at times.

The best course would be to select your two-bys for straight grain and being free from knots and defects over a number of visits but again this is not always possible, given individual circumstances and sources of supply.

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  • I've got a thicknessing sander with a 3 foot belt, plenty of room for this project, but I could see it being necessary to do in sections if I were making a table to match. – Daniel B. May 12 '15 at 21:55
  • @DanielB. A thickness sander is ideal for this, certainly beats belt-sanding it! And hand planing can be a problematical, the more boards present the greater the chance of switching grain leading to problems with tearout. – Graphus May 13 '15 at 7:32
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In a word "yes" the slab will be stable.

Depending on how you are using the platforms you can either run the wood over a jointer and glue the boards together, or just glue the boards together, or nail the boards together with 16 penny nails.

If you pay attention to the grain as you mentioned and avoid clumping knots at the same location along adjacent boards, you should wind up with stable and surprisingly strong platforms.

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