I went to Home Depot to find some 1/2" plywood to use for a sub roadbed. I looked mostly at 2'x4' sheets as opposed to 4'x8'. Unfortunately most of the sheets I came across were not flat, i.e. quite warped. I ended up getting a 2'x4' birch plywood sheet which seems much more solid than others and much flatter.
Question: Is there a "type" or "grade" of 1/2" plywood to use to make sure you have a good FLAT sheet? Or is this the nature of the beast? How do you ensure a good flat surface for laying down the cork roadbed and track?
Thanks in advance!
Hey Chris-
Most 'grade' designations, particularly at the big box stores, are only concerned with appearance. Fewer knots, cracks, footballs, etc.
Plywood warps, that's the nature of the beast. Getting a higher number-of-ply plywood helps (more plies to stress against each other and cancel out the differences), but lateral reinforcing and cross bracing is the only reliable way to control warpage.
Plus, lower 'grade' plywood is more likely to have deadly splinters. Ouch!!
Good luck.
Robert
LINK to SNSR Blog
Birch plywood is nice stuff and if that is what it takes to get flat plywood, spend the money. I myself bought 2x4' "handi-panels" from big box stores, all of which were stored and sold flat and on the floor, and had no warp. When I needed a few more and the store was sold out, I bought a 4x8' sheet of normal grade plywood and had it ripped into four 2x4' panels (my car can't handle a 4x8) thinking it would be ok but that 4x8 sheet was stored and sold suspended by two supports at the far ends, and had a built in warp both lengthwise and widthwise. And while both sides of the handi-panel were smooth and usable, one side of the full 4x8 was obviously rougher in texture with lots of "football" shaped plugs. I used what I bought but there clearly was a big difference, and the warped plywood had to be bulled into submission and used lots more screws.
Similarly a big box store had slightly damaged handi panels that they stored and sold on edge in a bargain area away from the main display (in a roofed but outdoor unheated part of the store) and by storing on edge those too gained a permanent warp. So it isn't just the quality of the plywood per se, but also how the store elects to display and sell them: flat on the floor is best (and in the heated part of the store).
Once you added in the slight charge for ripping the 4x8 at the store, the cost advantage to the "cheaper" plywood disappeared.
Dave Nelson
When I built my helix (32” R) I needed thin plywood and ran in to the warping problem also. That was back in the late 80s and even though everyone’s advice was not to use OSB that was the only ¼” thick I could find that wasn’t warped. Well 30 years later it is as good as new, I had to drill holes for everything because of the hardness but it really came out perfect.I glued Midwest cork to the ¼” OSB making the total thickness of the helix ½” + code 100 flex track.Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
ChrisVA I went to Home Depot to find some 1/2" plywood to use for a sub roadbed. I looked mostly at 2'x4' sheets as opposed to 4'x8'. Unfortunately most of the sheets I came across were not flat, i.e. quite warped. I ended up getting a 2'x4' birch plywood sheet which seems much more solid than others and much flatter. Question: Is there a "type" or "grade" of 1/2" plywood to use to make sure you have a good FLAT sheet? Or is this the nature of the beast? How do you ensure a good flat surface for laying down the cork roadbed and track? Thanks in advance!
Welcome to my world! I live in northern Virginia and have looked at plywood at Home Depot and Lowes with dismay. Most of what I've seen was very bowed or warped too. And since the pandemic, the prices have risen dramatically to add insult to injury.
I don't use plywood at all, but instead use OSB. I've been using 19/32 thickness OSB for my sub road bed and 13/32 (7/16?) for sheet areas where I've mounted Homasote on the open grid benchwork.
The OSB I've been using seems to be pretty flat and work well for my benchwork.
My wife and I bought some birch for our bathroom tub frame. If what you got is like that, it's way too nice for benchwork, and probably quite expensive.
Here are some photo's of my OSB benchwork. Before the pandemic the 7/16 OSB was about $9 at Lowes - cheap and cheerful. I see the 19/32" OSB is $36 presently! Dang! Fortunately I've gotten 95% of the wood I need for my layout before the prices shot up. Pandemic evidently to blame for lumber price hikes.
This is a sandwich of OSB and Homasote for the staging yard:
Here is 19/32 thickness OSB I'm using for subroadbed. It's a bit thicker than half-inch but needed because it's stiffer when in narrower cuts.
Here is my previous layout using sheets of OSB.
Here is a deck using OSB over staging on my previous layout.
Here I'm using OBS for the subroadbed on risers on my previous layout.
Rio Grande. The Action Road - Focus 1977-1983
The 3/4 ply I got from Lowes isn;t warped, at least not in any way that won;t be flat if attached to a flat support structure. So there's a bow across the sheet - you aren't going to just ley it on the frame and hold by its own weight, are you? Any slight hump is going to be pulled out as soon as you screw it down.
Using it for the side panels of a cabinet or something - that's a different story.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
ChrisVA...Question: Is there a "type" or "grade" of 1/2" plywood to use to make sure you have a good FLAT sheet?...
I'm uncertain as to the need of a flat sheet: if you're using it in sheet-form, the usual practice is to secure it to a framework of some sort, using nails, screws, or construction adhesive.The majority of my original layout used 3/4" firply, good-one-side, but all of it was used mostly as cut-out curves, supported on risers above the open grid framework (select pine 1"x4") which provided the base. In some areas, I used remnants of plywood (mostly 3/4" or 1/2" leftover from building my house) to support structures, and most of that was on risers, too. Areas where straight-ish track was needed was mostly atop either strips cut from the 3/4" sheets or 1"x4" boards, also on risers. When I added a partial second level to the layout, I used 11/16" T&G sheathing plywood, also good-one-side, but it was attached to the open grid framework (1"x2" and 1"x4" select pine) as sheets, using screws. The T&G allowed me to use leftover parts of the cut-up sheets, whereas, without that feature, I would have needed a couple more sheets. The original portion of the layout (still not "finished") has been in place for over 30 years, with no sagging, warpage or any other anomalies, and the partial upper level for 5 or 6 years (I think), also with no issues with warping - it's screwed to the wall studs, and supported by custom-welded brackets which are lag-bolted to the studs. I have, at least once, lain atop the upper level in order to paint rails which were otherwise out-of-reach... no sagging, no warping, no problems.
Here's a portion of the original construction (it forms the grade to the partial upper level) showing some of both the open-grid framework and the risers used to support the 3/4" cut-out roadbed...
...and a view of the underside of part of the upper level, with a compound welded bracket supporting things...
...the open grid framework uses 1"x4" lumber for the front and rear members, and also at the ends of each segment, while the intermediate crosspieces are all 1"x2"
Wayne
I have used plywood of various grades and types, and I have also used OSB for benchwork.
Being a carpenter by trade, I choose based on the situation, but as others have said, all sheet goods need to be properly braced and suported.
Sheldon
When I started my layout about 12 years ago, both Home Depot and Lowe's carried a grade of 1/2" plywood they called "Hardwood Plywood." This was really nice 7-ply plywood, finished both sides, no voids in the inner layers, and significantly cheaper (around $26 per sheet) than high grade birch plywood. I used this Hardwood Plywood to build all of my open grid benchwork and it hasn't warped even a fraction of an inch since. When I added a new yard to one end of my layout a few years ago, I found that the Hardwood Plywood product was long gone. The plywood available at big box stores today is abysmal, sometimes not even having the same number of plys at both ends! As I wanted the same benchwork quality as the rest of my layout, I was forced to go to a real lumber yard and buy a sheet of 1/2" birch plywood for $60!!!
Another option might be "cabinet grade" plywood as it is meant to be dimensionally stable, clean and smooth, but not visible without crawling into a cabinet. This stuff should be high quality and possibly cheaper than true birch plywood.
Hornblower
The disadvantages to MDF are that it is HEAVY, difficult to drive fasteners into without first drilling pilot holes, fasteners often tear out over time, and while it doesn't warp, it will sag significantly if not well supported (more MDF and more weight).
OSB is used here in Southern California as shear panel (earthquake resistance) and is NEVER meant to be seen.
ChrisVA I went to Home Depot to find some 1/2" plywood to use for a sub roadbed. I looked mostly at 2'x4' sheets as opposed to 4'x8'. Unfortunately most of the sheets I came across were not flat, i.e. quite warped.
I went to Home Depot to find some 1/2" plywood to use for a sub roadbed. I looked mostly at 2'x4' sheets as opposed to 4'x8'. Unfortunately most of the sheets I came across were not flat, i.e. quite warped.
Rich
Alton Junction
I went to a lumber yard and bought 1/2" AC plywood when I started to build my layout. The big boxes don't sell that grade of plywood, and it did cost more. I went for the quality. Since I was not using a cookie cutter design, I did the following:
I had the lumber yard cat my sheets to the lengths and widths I needed. Next, I let the wood acclimate in the train room for about a week. Then I painted the underside with a ceiling white paint and the top and side with a gray color paint since I couldn't find a good 'earth' color to use.
The plywood did not warp and since I have built my cross supports on 12" centers, I've basically eliminated any type of warping. The most important things I learned was to let the wood acclimate and then seal it before putting down any type of cork or ground cover..
Neal
hornblowerThe disadvantages to MDF are that it is HEAVY, difficult to drive fasteners into without first drilling pilot holes, fasteners often tear out over time, and while it doesn't warp, it will sag significantly if not well supported (more MDF and more weight).
I have experienced all of this, plus MDF swells & blisters if it gets wet. Consider this as you glue down your scenery.
I built my spray booth from MDF, and it is perfect. I would never use it for track support.
-Kevin
Living the dream.
ChrisVAQuestion: Is there a "type" or "grade" of 1/2" plywood to use to make sure you have a good FLAT sheet? Or is this the nature of the beast? How do you ensure a good flat surface for laying down the cork roadbed and track?
There has been some good suggestions so far. All I can find down here in 1/2" or 15/32" plywood is cheap garbage.
I do have a marine lumberyard nearby. They have 3/4" plywood that is perfectly smooth on both sides, and has seven plies. This is very strong, and all sheets I have bought have been perfectly flat.
It also has very tight grain and does not splinter as it is cut, routered, or sanded. I do not know what it is exactly called.
Sorry I cannot help with the 1/2" specifications.
This riverbed shows the kind of 1/2" stuff I can get from a big box store down here.
In my experience with plywood, once warped, forever warped.
Menards has shelves that are 2' wide and range from 4' long up to I think 10'. I usually use the white ones, they have ones with the natural wood grain but I figure no one's going to see it under the layout scenery. They're very strong and so far have all been very flat.
Lastspikemike If your benchwork is strong enough to support the plywood then screwing down 1/2" plywood will flatten out any bowing.
If your benchwork is strong enough to support the plywood then screwing down 1/2" plywood will flatten out any bowing.
I'm going to use 1x6 Poplar and 1/2" furniture grade Birch plywood for the new layout. And put 1/2 homasote over that for yard areas, as well as homasote roadbed under other trackage.
It will be "open grid" or "cookie cutter" in most places, so that you can get up under the scenery to some hidden trackage.
Rolling terrain scenery, typical here in the piedmont of the Appalachians, will be plaster on wire screen.
But what would I know, this is only the 6th layout in 50 years, not counting the three I helped others build.
And I already have a large supply of Phillips screws....