I’ve ordered the turnouts for a 5-1/2’ x 10’ HO layout! The layout will be mostly cookie cutter plywood on 1" x 4" frame. Most of one lower loop will be a curved arc below a plywood yard & loop atop, but 90% will be cookie cutter big sheet plywood.
I’ve seen 1/2" and 5/8" plywood recommended, and I guess the thickness needed interacts with the underlying 1x4 joist spacing? The current MR articles on a 4’ x 8’ layout use 1/2" plywood with supporting 1x4’s at 18" spacing, for instance. Any strong opinions here on what is adequate or inadequate or has other advantages? I’ll be using Tortoise turnout machines and cork roadbed and presume they will be happy with either combined thickness. Home Depot has some pretty nice B/C sheets of both thinknesses. Might one argument for the thinner 1/2" might be the relative ease of the vertical transitions at the bottom and top of the ramp from the lower to upper level? Another is it’s lighter, easier. I can space 1x4’s however I want, I presume, as long as I use care regarding tunout locations and possible access holes I might need.
I plan to seal the plywood during construction to minimize moisture effects…what product to use…wood sealer? It will be in the climate controlled home…some but not extreme variation in temp / humidity.
Thanks for your help…including on various earlier posts that got me to decide to plow ahead.
I’m a 3/4" plywood guy, but that’s for a layout with relatively large areas that might need to support me…
My opinion is that it depends on the spacing of your support risers. Either 1/2" or 5/8" will work for you. I wouldn’t go over 18" between risers in any place with either. I’d stick closer to every 12" or a little more for 1/2".
If it’s going to be a long-lived layout, I’d go with 5/8", because plywood always sags a little, some just sags easier and more.
It depends on the quality of the layout and the materials. Generally, as a rule, exterior grade sheeting 1/2" should be more than adedquate for sub-roadbed with supporting structures no more than about 16-17" on centers. There reason is that 1/2" ply is quite flexible, and it will sag if allowed to span centers greater than about 18". For my current construction, I am trying to keep it near 15". It’s just one headache I want to spare myself.
Agree with Mike. My only input is, that if you do use the 1/2" ply, I would make sure that is is a quality grade. 1/2" BC, even “fir” 5 ply CDX works OK for solid decked areas, but if you want a sturdy 1/2" ply for “cookie cutter” strips of subroadbed, I would go w/ an sanded fir, 5 ply,underlayment grade or even 1/2" baltic birch.
I perfer 3/4" as Mike, however, many feel this is way overkill. Any quality grade of 5 ply fir will usually work for joist/ riser spans no more than 18-20max.
I feel ther is really no need to seal/ paint the plywood, especially for the location of your layout. Damp/ wet basement or areas of extreme humidity, yes sealer and dehumidifier should be used.
From my years in the paint industry I generally felt that if you were sealing wood a solvent based product worked better. Waterbased products generally dry porus and whatever you are trying to seal against could still get through. Waterbased products may cause the wood to expand as well.
I can see sealing if you live in a climate that has high humidity as it may prevent some expansion and contraction. To be effective one would have to seal the edges as well. A mineral spirits based product should be good enough but remember a solvent based product will stink and the fumes can be harmful. Do the sealing outside or in a well ventilated area. And let it dry there too. I probably would not use anything that contains a hot solvent. Especially if working indoors. By hot solvent I mean a product listed as flammable. Flammable fumes can be ignited as a flash fire.
I have not sealed my wood but there are times when I wished I had. Some paints and adhesives work better when applied to a sealed surface.
I just used Deft water based acrylic finish on my 1/2" Baltic Birch and other benchwork. Low fumes, easy water based cleanup, looks nice and very easy to apply. Requires at least 3 coats however.
I have had some experience with 1/2" birch cabinet grade plywood. It is very good for what we as MRRs require. Keep in mind that a rough grade of 3/8" plywood is used for roof sheeting for new homes and supports men walking around carrying loads.
That being said, I used the 1/2" birch with support at 16" on center just as I would in construction. Even on cookie cutter sections I don’'t hesitate to lean most of my weight on a section of track.
As for water proofing. I made a mistake by not painting the edge of a joint. When I spread the light weight Hydro Cal for ground effect the moister seeped into the seam swelling the end grain and caused a bump up to the track.
Lee, wow, how’d you end up fixing that! Usually 1/2" baltic birch will only swell if immersed in water. Maybe had a bad lamination @ the seam. did you screw down at each side of the roadbed, could have been track set between fasteners allowing some swell. I assume the deck was painted before plastering. I could see this happen to OSB or cheap pine CDX. Maybe a good reason to seal- “just in case”
BTY: I didn’t think that 3/8" CDX was ever allowed to be used anymore for roof sheathing. I have worked w/ 3/8" on 24" center but this is 60-70s construction in the “sun belt” CA, AZ) and did that deflect @ mid spans even w/ the clips. Of coarse 3/8" fir ply from 1960 is far stronger than even some of the plys found today ( even the cheapo pine 1/2"CDX).
Supporting weight without breaking is one thing. Sagging is another.
I may have contributed to blurring this line when I commented about having benchwork that can sustain my weight if I got up on it. Fact is that even 3/8" will support you.
But what I’m really doing with 3/4" is doing the best I can to minimize sagging. As I noted, everything sags, some just quicker and more extremely than others. That includes 3/4". But minimal sagging is bearable, so 3/4" works for me.
Which doesn’t mean that 1/2" or 5/8" is problematic. With properly spaced risers, you can still minimize sagging enough so it doesn’t become an issue. The problem is picking a thickness and then not worrying about riser spacing. Put the risers far enough apart and you’ll get unacceptable sagging with 3/4", too.
The real reason for staying away from 3/8" plywood? Because you’d have to have so many risers it would be a PITA. After all, 3/8" will support any model locomotive short of
As others had suggested I was trying to support the point of sealing the joint properly. I prefer to not tell people they have to do something, just suggest. [:-^]
The cause, was I did not fill the seam fully and you can’t get away with that on end grain. It doesn’t take much moister to swell end grain, it’s is like a sponge.
The fix. After it was completely dry I pulled up two feet of track and ground the surface flat. It was only about an inch or less that was swollen.
As for as building regs go. I suppose it depends on the local rules. I had my house built (subdivision) in 1990 and they used 3/8" to my dismay.
My room has a controlled environment-including humidity control-but I believe that sealing the 1/2" plywood deck and its 1/2" Homasote top was well worth the modest effort and cost. I sealed all 6 sides of each with Behr latex that “includes” the primer. It saves labor and approximates the cost of a separate primer plus finish coat. Also, that deck is on Sievers benchwork-also painted-with support joists at 12" o.c., typically, and occasionally 16" o.c… Although it has been up only a few months, so far, so good.