After a long absense I’m getting back into MRRing and have a couple of basic questions.
First–foam. Reading a the Basic Benchwork book JeffWilson talks about pink and blue foam boards. No building supply here seems to know about these choises and a very few–one so far–carry wall insulation foam-white in various sizes. Is this a product available at lumber yards orwhere? I may have finally found a sourse for Homasote and with luck will get the shipping cost down to less than double or triple the cost of the sheet.
Second I 've read some thoughts about humidifiers. Since we have constant humidity probably unnecessary here? And it is not servere–just constant.
The white stuff is not all that suitable for scenery construction (other than maybe filler under pink or blue - but it is not that much less expensive). The pink (Corning) and blue (Dow) foam insulation is usually available at Home Depot or Lowes (or a large local lumber yard). Pink/blue foam has structural capabilities, the white doesn’t. It’s also cuts more precisely.
The humidity could be a problem (no experience with constant on a major layout) but it’s change from dry to wet to dry that leads to expansion/contraction thus cracking or misalignments or buckling.
In mild-winter areas, pink and blue foam is not typically found at Lowes and Home Depot, so it’s often a waste of time to look there. On a Hawaiian island, it may be a bit tricky, but you could try these pink and blue foam dealer finders.
Before you spend a ton of money on shipping sheet(s) of homasote check out California Roadbed
he mills all his Homasote into equal thickness sheets and then cuts them into roadbed and sub-roadbed in lengths of I believe 36" which is UPS shippable. He not only saves you form all the dust and choking involved with working with Homasote but it may even save you a ton on shipping. For those of us who can run down to the local Home Depot and grab as many sheets as we like we have options that do not involve high shipping costs so one can agrue I’ll do it myself and save. You unfortunately don’t seem to have that option.
I was recently given a Kalmbach book on doing a simple 4x8 layout by a friend whose son, when young, showed a brief interest in trains. The book is a compilation of a series in MRR mag back in the late 1990’s on making a complete layout. The book talks about using foamcore as the baseboard. Easy to cut and strong enough. I use the Dow board but might have considered this if I had seen the book sooner. Don’t know if humidity would make foamcore impractical for Hawaii.
FYI: Lowes in Martinsburg, WV, no longer carries the blue extruded foam board. In the last month or two they have started carrying Green Guard Extruded Polystyrene Insulation Board made by Pactiv in 1" and 2" thick 4’ x 8’ sheets. As far as I can tell, it’s composition is the same as the blue or pink board. I don’t know if this applies to all Lowes stores or just ours.
Re: Humidity. I have read that the optimal humidity is between 40% and 50%. If you get up into the 60% or 70% or above range you run the risk of mold, etc. as well as having problems with the wooden components of your bench work. If the humidity remains constant all year, then you’ll probably not have a problem with the bench work as was pointed out in one of the other posts above.
The foam we should use is “expanded polstyrene foam” Dow originally made it as now do others. I do not think the color matters, other than to marketers. The “white” foam is multitudes of preform polystyrene spheres that are melded together under pressure and heat. They do not form a continuous piece of foam and is not as rigid as the pink/blue stuff. I found my material at non-big box building supply companies. Some blue foam has removable vapor barriers on each side, useful for homes, but should be removed for modeling purposes. The pink foam does not necessarily come with the vapor barrier. I have had no problems attributable to humidity and foam layout construction. I have used this in Texas and Georgia, above and below ground. FWIW, Andy Chandler
Many forum members from California have reported that foam is almost impossible to find there. It is, after all, a material typically used to keep the cold outside air outside. It’s not particularly necessary in such mild climate.
Foam is basically immune to humidity problems. That’s one thing that makes it a great layout base material. It’s also stiff and rigid, and can easily span 18-24 inches between supports in HO scale. (For O-gauge, the trains weigh more, so you might want to use tighter supports.)
This continues to amaze me: if you’re running air conditioning to any appreciable degree, insulation will work equally well keeping keeping the hot air out as it does in keeping the warm air inside in colder climes.
Spans will vary with thickness, obviously, but it is pretty-well immune to moisture. In Ontario it’s a recognised vapour barrier for home construction, in addition to being an excellent insulator.
I used homasote on a previous layout, I didn’t really care for it. It can be affected by heat and humidity, so it won’t lay perfectly flat, and it’s very messy to cut. If you’re using pink or blue foam you really don’t need homasote under the track. Since humidity can be an issue where you are, I’d look into something like Kato Unitrack where you have the plastic roadbed attached, so it’s more resilient. You can use Woodland Scenic risers and grades on top of the pink or blue foam, or just use WS products right on top of a plywood base.