How to deal with varying thicknesses of Homasote

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#1
Hi Fellow Modelers,
I just finished building my benchwork and for my top, I used 1/2" plywood, with 1/2" Homasote glued on top of the plywood. I know there are "new and improved" methods, but I've been using Homasote for my top layer for over 25 years. Unfortunately, where various pieces of Homasote butt up against each other, I've discovered that one piece is higher than the other, sometimes as much as 1/8" or more. I believe that this will cause a problem when I go to apply my cork roadbed and track.....creating a bump.

Obviously, considering I used 8 pieces of 4'x8' Homasote and there are many places where there are differences in height, I cannot sand down all the higher sheets to get them to the level of the thinner sheets. My first inclination was to sand down the higher Homasote with a belt sander, trying to create a gentle slope away from the seama foot or so. This approach could get pretty messy and I think it will be difficult to determine when the slope should end. My next thought was to just shim the cork on the "thin" side of the seam, thus allowing for a gentle slope from the thinner Homasote up to the higher piece. I'm not sure whether a few inch slope, climbing 1/8" or more will cause a problem for my rolling stock.

I've read that many people have experienced the varying thicknesses of Homasote, even when they bought all their sheets in one lot at the same time like I did. What I haven't read about is how people solved the "bump" problem created by the varying thicknesses.

Any thoughts and suggestions would be greatly appreciated.

Thanks in advance,
Mondo
 
Last edited:

Sirfoldalot

Plucked Tailfeathers
Staff member
#2
If I Read this correctly - you are putting homasote on top of plywood and then cork roadbed on top of the homasote.
I'm not entirely sure why the need of the cork ... I just lay my track on the homasote, but this is not your problem. If it were me - I would try to place shims between the plywood and the homasote in order to avoid the differences in thickness using cut up cardboard from - like cereal boxes, or even different thickness balsa wood strips.
You should not have to raise more than 12-18 inches from a joint.
 

Iron Horseman

Well-Known Member
#3
I don't understand. Why not use all the strips that are the same height butted together then sand a transition to the other height and butt all them together? That way sanding or shimming is only required in a few places. I would sand or shim back, probably, up to 3 feet to make a 1/8" difference. 1/8" in a foot is just about a 1% grade.

I use an orbital sander rather than a belt as it gives me more control. Yes, it would be messy but just cutting homasote is messy to begin with. Just have a shop vac on and sucking while you are sanding. My sander also has a place I can attach the vacuum directly to it.

Then sort of off topic, why are you putting cork on the homasote? Seems redundant to have roadbed on roadbed. Are you tapering the edges of the homasote or leaving them square? Are you putting it on a solid plywood sheet, using cookie cutter, or open grid?
 
#4
If I Read this correctly - you are putting homasote on top of plywood and then cork roadbed on top of the homasote.
I'm not entirely sure why the need of the cork ... I just lay my track on the homasote, but this is not your problem. If it were me - I would try to place shims between the plywood and the homasote in order to avoid the differences in thickness using cut up cardboard from - like cereal boxes, or even different thickness balsa wood strips.
You should not have to raise more than 12-18 inches from a joint.
I like to elevate the mainline from the surface.....hence the cork roadbed. I hear you regarding shimming between the homasote and plywood but I have already glued down the homasote to the plywood. I kind of ignored the fact that there were different thicknesses as I was working diligently to get the Homasote glued down and really didn't think about the consequences until it was too late.

Thanks,
Mondo
 

migalyto

Well-Known Member
#6
You could also skim coat the approaches with drywall compound to give you a smooth transition. The problem will be that it will create as much of a mess as just sanding the homasote.
 
#7
You could also skim coat the approaches with drywall compound to give you a smooth transition. The problem will be that it will create as much of a mess as just sanding the homasote.
Hi Mike,
I like your idea because it will probably be easier than trying to shim with cardboard or some other material. Also, using a wide putty knife, I will be able to create a smooth transition for the lower Homasote to the higher/thicker Homasote. It won't be as messy as sanding the Homasote because I will only be applying the drywall compound to the exact area where my track is being laid, while sanding the Homasote would have required a much larger area.

Thanks for the suggestion,
Mondo
 

KB02

Well-Known Member
#8
If it were me - I would try to place shims between the plywood and the homasote in order to avoid the differences in thickness using cut up cardboard from - like cereal boxes, or even different thickness balsa wood strips.
You should not have to raise more than 12-18 inches from a joint.
Since your homasote is already glued down, use the above technique beneath your road bed?

I've got a section of track where the base was rather crudely cobbled together. I would say closer to a 1/4" height gap. I pulled some cork road bed as taunt as I could and then set a 3' section of flex track on top of that. A little shimming under the cork, some decent scenery and ballasting and you'd very know there was a gap.
 

Sirfoldalot

Plucked Tailfeathers
Staff member
#9
I like Kevin's (KB02) idea the best. I would not use drywall compound as it shrinks on drying and will make it harder to place a spike into - if need be. A length of balsa would be easy to sand and work with.
 

montanan

Whiskey Merchant
#10
I used Homabed for my layout. It has the same contours as cork road bed. All of my yards and siding were brought down to the level of the plywood. In this photo, the tracks into the yard coming from the left met the level of the plywood by raising the ply a quarter of an inch so there was a smooth transition to "ground level".

IMAG0662.jpg


In this image, yu can see the siding dropping in elevation to "ground level". What I did here was to use a router and gradually dropped the roadbed a quarter of an inch over probably a 12 inch distance with the roadbed meeting the edge of the plywood for a smooth transition. You can see the trrack dropping in elevation behind the switcher. It is a but messy, but this did work for me.

20180211_132140.jpg


I really like using homasote. I started the layout using hand laid track and turnouts and the homasote really holds the spikes well and holds ballast well.
 

Sirfoldalot

Plucked Tailfeathers
Staff member
#11
I used Homabed for my layout. It has the same contours as cork road bed.

I really like using homasote. I started the layout using hand laid track and turnouts and the homasote really holds the spikes well and holds ballast well.
In my opinion - there is nothing better!
 

Selector

Well-Known Member
#12
My bet is that the thickness variation, such and as much as it may be in the homasote, is not as much of a contributor to your abutment mismatches as are torsions and bends in the benchwork and in the homasote itself. Even so, I would use portions of door frame shims, the foot long ones, to shore up the nether surfaces of the homasote that needs to meet another surface more evenly.
 
#13
I'm a big Homasote fan. Holds spike well, yet they're removable. Dead silent.

I mounted mine on OSB board which has worked out very well. I'm a fan of leaving all options open at all times for changes. Rather than screw the OSB board to the layout framework, I used small L brackets underneath the layout to hold it firmly in place.

I too ran into a little variance in the Homasote, so all I had to do was loosen an L bracket, pry the OSB up a bit, and slip an extra thick large washer in place between the OSB and the layout framework and tighten the L bracket. For me, this was a much easier method of matching up the levels than any other way.

Seems to work out well.
 

Iron Horseman

Well-Known Member
#14
I like to elevate the mainline from the surface.....hence the cork roadbed. I hear you regarding shimming between the homasote and plywood but I have already glued down the homasote to the plywood. I kind of ignored the fact that there were different thicknesses as I was working diligently to get the Homasote glued down and really didn't think about the consequences until it was too late.
So you are using entire sheets of Homasote laid over the entire area of the plywood rather than just cutting ribbons of it to be roadbed under the track?
 



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