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Hossenfeffer 07-14-2010 06:54 PM

Stability of Durock vs plywood?
A bit offbeat, this question.

I am looking into the possibility of using 1/2" Durock, cut to 2' wide strips as a base for model train layout. "Why?" you completely avoid dimensional changes due to humidity and temperature.

Is Durock completely stable regardless of humidity?

I know is it heavy, but it will be used in short 2' wide modules and it's weight may be ideal for sound-deadening.....a real problem with many materials used for this hobby.

Just a thought. Grateful of any tips. I see there are a few Durock products/formats to look into. This Next Generation version seems ideal.....less weight, score and snap etc.

Oh, oh, one fellow says it can be flexed and it retains the bent shape......not good.

Ron6519 07-14-2010 08:47 PM

Since this layout is in the basement, get a dehumidifier and paint the plywood.

Just Bill 07-15-2010 06:03 AM

While duroc is dimensionally more stable than plywood, it is not structural, as is plywood. Seal plywood, and as suggested, run a dehumidifier. Don't open basement windows, that only lets in warm moist air.

Hossenfeffer 07-15-2010 09:54 AM

Thanks for the painting tip.

This is a project going in the crawl space. I determined that the crawl space is quite comfortable gernerally. It has poly under the cement floor and is quite dust free from above. I have spent months monitoring the space for dust, temp. and humidity.

The monitoring reveals I should give the project the go so I have installed a dehumidifier, baseboard heaters, and I opened vents to the outside with powered baffles and fans to bring air in and blow it out as needed, or completely close it off as needed. I sealed the spaces between the exposed edge of the underlying poly and the bases of the interior and exterior foundation walls with expanding foam.

Humidity is highest in the summer and climbed to about 80% before the changes. Now it seems I can easily maintain it at the level of the main floor which remains around 65% to 68% at this time of year.

Would painted plywood remain dimensionally stable in 40% to 68% humidity swings?

Ron6519 07-15-2010 11:07 AM

Using a good quality exterior paint should give you the results you need.

racebum 07-15-2010 02:29 PM

since you aren't using a lot, marine grade plywood may be the choice wood. another thought if you need 2" wide is using 2x4s cedar would be ideal, smells great and is used in saunas. pine 1x3 could be another thought if you can ever find any that's dry and straight, just use the table saw to get what you want size wise

poly clearcoat on your wood of choice also improves humidity resistance. i have used clearcoated solid pine in very humid environments with great success. not sure if you would even need to on cedar since it's proven itself in sauna use so well.

Gary in WA 07-15-2010 03:25 PM

Backer board has a high permeability rating = 2.8 perm. Plywood, 3/8" = 0.75 B.b will absorb the humidity moisture like a sponge and store it as concrete is a water reservoir material. If you seal either product, the tracks will stay rust free. Plywood of choice for the loads. Use the correct plywood for the load, remember to use the reduction for single support vs. multiple supports. (Walking on, etc.) Use a vapor barrier primer- or three coats of exterior oil house paint, as Ron and others said:
Try some sound board sheathing under the ply to help deaden the noise echo if the layout is elevated. Curtains on the walls help too. Keep some large Rubbermaid containers (with lids) nearby if your location is subject to frequent power outages of any duration. Pop the engines into a box along with a dryzair packet or bowl to keep them dry if needed. Larger zip-lock bags work also, suck the air out with a straw before complete closing.

Be safe, Gary

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