I belong to a modular HO club that uses 2 ft x 6 ft modules. We have three yard modules, two of which have a 3/8" plywood top covered with a glued on sheet of Homasote. The third was made later and is bare plywood. The rails end 4 1/2 inches before the edge of the module and we use standard 9" snap track to jump the joint in the modules.
The Homasote extends to the edge of the module. Over the last 25 years it has frayed and swollen something fierce. We now have a major bump in the jumper tracks where they cross over the gaps with the swollen Homasote. (Don’t ever use this stuff on modules, it is heavy and swells something fierce from humidity.)
I don’t want to rebuild the whole module with about 56 feet of track and multiple switches on it. I would much prefer to modify what I have.
What I want to do is make a clean cut in the Homasote near the end of the rails and replace it with something more stable like plywood up to the edge of the module. The new cut edge would get sealed with paint to control the swelling and delamination.
Alternately I could sand down the Homasote to make it level again and seal the new surface and edges with paint.
Has anyone ever done this or something like it? My main concern is getting a clean new edge on the Homasote and not gouging the plywood underneath.
Cut the homasote with a utility knife (I have done this many times). With a sharp knife you can get a clean cut.
Use a wood rasp and then sandpaper to whittle it back. I have done this too. The surface won’t be as smooth as the knife cuts but it might be easier to do it this way. Be prepared for lots of nasty dust from this process.
Set a circular saw to the depth of the homasote and cut lines in it about 2cm apart over the affected area. Using a mallet and chisel tap along under the strips. You will be surprised how the strips come up. Use a grinder to take off glue remnants. Insert new plywood, it should cover any gouges. If the gouges are a problem use a filler to level.
i agree with the circular saw idea. but, as for me, i don’t allow homasote on the property. i found it to be the most filthy, dimensionally unstable stuff i ever worked with. back when i could afford it, luan plywood did the trick for me.
I would cut the homosote back 4 1/2 inches and fill the cut out area with plywood or a good hardwood like white oak. Then seal everything with shellac. I’d use a 1 pound cut first to soak into the wood and follow it with a 3 pound cut to seal the surface. Shellac in the can (Zinsser’s Bullseye Sealcoat is a very easily found one) is normally 3 pound cut. You can dilute it with two parts of denatured alcohol to get the 1 pound cut. Shellac is very water and moisture resistant and should make the homosote much more stable.
Without seeing the actual degree of swelling, it is hard to give a definitive answer, but yes, you can sand down the Homasote. And yes, sanding does create dust but the amount is obviously dependent on the amount that has to be removed! You might try initial removal using a block plane and finishing up with sandpaper. For minor amounts of sanding, I have simply used sandpaper (120 grit? I am away from home and can’t check). For more extensive sanding, I have used a small powered finishing sander, but make sure you use one with a dust collector attachment!
I have 1/2" Homasote on top of plywood and have no swelling problems because 1) it is in a climate-controlled room and 2) I painted all surfaces of the board before I installed it. (That being said, I have some unsealed Homasote pieces in my attached garage (no climate control), and these have not swelled at all.)
Dante
P.S. I should note that I live in south-central PA. It does get cold in the winter and hot and humid in the summer. Of course, the humidity is not as high as in some parts of the South.
I am beginning to wonder if there are differing versions of Homosote as to the degree that they absorb moisture. As a carpenter, I have no use for the product but have ripped out tons of it. I have seen Homosote used as exterior sidewall (battoned @ seams) and only painted one side. This “stuff” must have exposed to New England weather for well over 30 years. It was beat and the edges slightly swelled, but otherwise still in decent shape. Now on the other hand, I’ve seen scrap pieces just left in a garage or basement that have swelled up to 1/8 to 3/16". Warped. bukled, bowed and otherwise distorted. Go figure, is there some sort of difference in the bonding glues of the product. Is the newer formed product less stable? Have no clue!!!
Just for the record, we did this this weekend. The extendable kind of utility knife worked best, with no sawdust. Took onlt a few minutes and one blade to cut across two feet of Homasote. Also, even though glued down it came right up when we started prying on it.