Homasote and panel spacing when installing

The manufacturer's recommendation for spacing is intended for construction applications where the material may be exposed to moisture fluctuations; the homasote will expand in moisture or high humidity environments, and the spacing is so that it will not buckle when it expands.

 

If you are using the homasote in an indoors, heated, climate controlled (at least in the sense of not being exposed to weather) environment, such as a train layout, you do not need to leave a gap between the panels.  If anything, you will have the opposite problem.  After a couple of years of being in a heated house, the panels will shrink enough to open the cracks between panels significantly.

 

I used 1/2" Homasote on top of plywood on my SG layout, and since it is a tinplate layout, I painted the Homasote and that is my layout.  As a result, the cracks are exposed, and as I say the cracks have widened as time goes by.  I have installed bushes and ground cover selectively to cover the worst cracks, but some of it is just the way it is.

 

I was greatly reassured when I found this picture of Richard Kughn's big Carrail layout (the owner of Lionel at one point); showing cracks in his Homasote as well.  Good enough for that tinplate layout, good enough for mine.  

 

Even if you are covering the Homasote with ground cover, the cracks will be worse if you space the panels.  Your worry using Homasote in this indoor, dry application is that the sheets will shrink, not expand.

 

 

 

 

 

Wow nice layout! That's good information. Thank you.

I see your using some sort of roadbed. I will be using flexbed.

 

 1.  Do you glue the panels to each other or to the plywood?

 

2.   With the roadbed and homosote is your layout Quiet? Are you Able to converse at a normal volume level? The room my layout will be in is finished with carpeting

Just so we're clear, you did get that the photo in my first post was not of my layout? (I have underlined the reference in my post.)

 

The Carrail layout didn't use roadbed, that's just painted gray on the homasote, and the track screwed down on it.

 

On my layout, I did not glue the Homasote panels.  I did use screws to attach the Homasote to the plywood underlayment.  The I used (short) screws to attach the track to the Homasote.  The track screws do not go through to the plywood, so the sound does not transmit.  The layout is in a big barn of a room, with hard plywood floors, and the sound of the SG trains running is very acceptable.  Easy to talk while the trains are running.

 

I also did not glue the Homasote panels to each other, although after a couple of years as the cracks opened up, I have used caulking to fill some of the cracks and then repainted.  Crack management is an ongoing process.  Lately, as I said, after having seen the picture of the Carrail layout, I have decided to just live with the cracks and not worry about them.

 

So, here's a picture of part of my layout:  if you trace the lines of some of the groups of shrubbery you can see where some of the widest cracks in the Homasote were.

 

All the green in the photo is painted Homasote.  I painted my vehicle roads gray with a 4" wide roller.  Was going to do something similar with the track bed, but it's all screwed down now!

 

 

 

 

We dont leave a gap. Butt it up tight and use masking tape over the joints to keep water out when you're doing the scenery/ballast.

I've been reading various topics related to homsote and layout building, as I get ready to construct my layout.

 

Repeatedly, I have seen people mention using masking tape as a gap filler. Please be aware that masking tape is not a permanent tape. As it ages and dries the adhesive fails, thus falling off. This may not be an issue for several years, and buried under scenery it may not be an issue at all... However, I suggest understanding the tape's properties before using it for such a chore.

 

And the "It's worked fine for me so it's OK" argument does not change the tape's actual properties, i.e it being an impermanent adhesive.

 

We dont use it as a gap filler, as there is no gap. The tape just goes over the seam, gets painted with a latex earth colored paint, and then covered with scenic materials. Its a cheap and simple process that does the job. I dont think knowing the properties of the tape is going to make a difference.

No, I didn't.  I pushed them pretty close together - may there was a half mm gap but no more.  No problems after eight years.

In 30 years I have never had a problem with homasote.  Installed it with no gaps and screwed it down.

One note on the Kughn layout. He used a grey paint for roadbed. It looks ok. I tried a spot with stone texture paint and feel it looks much better. One can not upgrade to this as the overspray is terrible. In the beginning very doable.

 

I have homasote on 2 layouts. I glued mine down with adhesive and painted it no problems. Shrinking would be more of a problem than expansion. 

Laidoffsick, it sounds like scenery covers the masking tape and so there is no issue.

 

I just wanted folks to keep in mind the impermanence of masking tape.

 

I'm planning a modular standard gauge layout and was considering the homosote on plywood method, but after this thread I am opting out of that technique. My concern is the gaps where the modules meet. Homosote being somewhat fragile is already a problem there, shrinking over time would increase the gap between modules... Not good as I am looking to construct a solid layout that could last decades.

And again I will offer a cost saving option:

Celotex soundstop or Quitebrace.

Similar properties to Homosote, less cost and more widely available.

these actually reduce sound better than homosote and to my knowledge do not shrink. (Ask your lumber yard / Home Depot / Lowes about that to be sure)

If you get damaged ones, ceiling tiles are also a valid alternative.

Make sure you allow the homasote to acclimate for several days in the same area it will be installed. Seal the edges before installation and use a good quality acrylic latex caulk to fill any gap between the sheets. Run a bead of caulk over the joint and smooth it out with your finger, keeping your finger wet by dipping in a cup of water with one drop of dish soap

Hojack, great looking layout.

Who would ever have time to notice cracks in the layout when looking at something that nice?

Great job. Greg