The bench work for the New SIW is about to be installed and it will be Homosote over Plywood. I would like to begin the trackwork by painting the Homosote a light tan.
Do I need to prime the Homosote first?
I recall homasote being very porous so I would say no.
No…It is not necessary…It has already been treated with moisture barriers. Contrary to popular belief, it is not very porous…after all, it was designed as a moisture barrier. Been using it as sub road/road bed for many yrs:
http://www.pakline.com/homasoteboard/homasoteboard.html
Take Care! [:D]
Frank
Frank, thanks for the correction, I must be remembering the dust from cutting it.
Henry
It is not a moisture barrier although somewhat moisture-resistant. I recommend either a separate primer or one of the newer paints that have an integral primer. I used the latter by Behr on my Homasote.
Dante
Not all Homasote is the same, just because it is called that…there is also Homasote made with wood, which is less moisture resistant.
I have been getting mine at a family owned business for many yrs. and they being in the lumber business for 105 yrs. selling mainly to independant contractors, I truely trust their advice on the subject. I also used to pick-up and deliver their building materials right from the Mfger in MT, OR, when I owned My own semi’s…including Homasote registered trademark brand.
Take Care! [:D]
Frank
‘‘Homasote® board consists entirely of paper fibers converted from recycled wastepapers. Added to this are ingredients that give it the superior weather-resistant features for which Homasote® board has become so famous. The small amount of newsprint ink remaining through the processing gives the board its grayish tint.’’
Homasote as a company makes several products. What we use generally is 440 sound board. That is made from recycled paper products that is bound together with a wax product. It is water resistant on its’ own without a sealer. It expands and contracts with changes in humdity like any cellulose product. If your layout is in a location with less than 40-50% change in humidity there really is no need to seal it. Over that there is a benefit to seal the Homasote to reduce the moisture transfer. It will take paint just fine without a primer but using a PVA primer will make the color coat go further and be less expensive in the long run if you have a lot to cover.
Steve Cox
Cascade Rail Supply
If you paint Homasote as I suggest, you will minimize the dimensional changes due to changes in humidity. As Steve noted, your location environment makes a big difference. If you have any doubts about Homasote’s resistance to humidity changes in your location then do the painting on all surfaces and edges; also, on the plywood substructure. If you don’t do it before assembly, you will never be able to do it thoroughly after assembly.
Although my train room is environmentally controlled, those controls are changed when I am away for extended periods. Therefore, to be safe rather than sorry, I paintef all my wood, plywood and Homasote before assembly (the Homabed roadbed after installation). It took time and some money (little compared to the cost and time of the layput), but the results have been worth it. I have had no noticeable dimensional changes in the benchwork or the trackwork. I’ll admit that I will never know if the same would be true if I had not painted everything, but if it weren’t true, there would be little I could do now to correct the problem.
Dante
P.S. “Moisture-resistant” is not quite the same as “moisture barrier.” The latter refers to the ability of a material to resist the passage through it of moisture vapor. Homasote claims to be moisture-resistant, not a moisture barrier.
I paint my Homosote road bed with latex paint with no primer and it seems to work fine. My layout is in my basement which frequently has water on the floor after heavy rains. Priced out proper water proofing of basement and it was going to cost more than the house will bring on the open market. So I live with the occasional clean up with the shop vac and run a dehumidier year around. Have not noticed any swelling to the painted homosote road bed which is installed over 1/2 polystyrene insulating board on 1/2 plywood.
Ditto was James Moon does - I use latex paint in some earthtone color and paint both sides to give it a base color and a bit of of a moisture barrier.