[Anthony MPC]

My first O-gauge table is quarter inch 4x8 plywood with homasote on top. Wanting to expand for with a U or L, layout is a little pricey for me with the same materials with inflation being what it is currently. Are there alternatives to consider that are a little more thrifty?

 

[Lehigh74]

Oriented Strand Board (OSB) in nominal 1/2" thickness is probably quite a bit less than 1/4" plywood or 5mm underlayment.

 

[CTValleyRR]

OSB is one of the few things I usually recommend against. Each of those little chunks can expand and contract individually, giving you a very unstable surface. Probably less of an issue in larger scales, but stil, something to consider.

Personally, I am a big fan of extruded foam insulating panels. They're more expensive now, like everything else, but still not as sky high as lumber.

 

[Lehigh74]

Yep. OSB will expand big time if it gets wet. But I used it (nominal 3/4") for some of my attic layout when I was building it back in the 80s when I didn't have the bucks for plywood. Even thought the attic does get humid sometimes, 30 some years later, the OSB has not given me any problems. And if it's covered with homasote, there is less likely to be an issue.

 

[Dennis461]

Consider using wooden pallets. If you can source enough good free ones, take boards from one and fill the gaps in another. A bit heavy, but cheap and the wood gets covered in foam or those plastic signs from the side of the road (or homasote).

 

[mesenteria]

All good ideas. I have just accepted it as a fact of life that where all four of my layouts have existed, in basements, but one was in a loft above an out-building garage, one is wisest to have some rudimentary climate control. With milled lumber, plywood (which is quite stable and doesn't respond as much to humidity variation), and water-activated scenery materials, I have kept a dehumidifier on 24/7 so that it cycles when the humidity goes outside the 48 and 66% extremes. This has worked well. For a $170 investment, you would be able to use pretty much anything you can find cheaply that would be engineering-wise rational and durable to use. Including OSB, particle-board, Masonite, hardboard, door-skin, lath, strapping, pallet scraps, and MDF....oh, and Homasote.