Replies

1. 
   rslatm | Dec 27, 2002 01:45am | #1

   Might be better posting it in Breaktime as that's their specialty.
2. 
   IanDG | Dec 27, 2002 06:06am | #2

   What you suggest is feasible providing the sub-base is solid but there could be a problem with condensation.
   The waterproof membrane (Visquene sheet or whatever) needs to be on top of the insulation to protect against condensation moisture affecting the plywood and underneath the 2" x 4"s to protect against moisture from the sub-base.
   I don't like unventilated voids under timber floors, especially if there's a possibility of moisture -- you're creating prime conditions for rot so could you reduce your bearers to 2" x 2" and fill the voids with insulation? After all, if the sub-base is flat and solid the bearers are only serving as a nailing base.

   IanDG

3. 
   Splintie | Dec 27, 2002 06:25am | #3

   Jeff, unless you use .6 treated timber and plywood in that application, you can likely kiss your floor goodbye in ten years or less. Using visqueen over rock will result in plenty of punctures that will obviate its use.

   Most folks would haul in some sand to make a level floor, sprinkle it to compact it, lay 2" of EPS over that, visqueen either over the sand or over the board (i like it under the board to keep it from being torn; others say the other way is better), and pour a min. 4" slab. I didn't use rebar in mine bec i wasn't using really heavy equipment, but i did have reinforcing fibers put into the mix. 

   You need to use EPS foam, not XPS, and it has to be rated for compression, not the less-dense stuff that is used in walls. Different brands of foam go by different names for this quality, so this needs to be verified. You can also insulate the perimeter to minimize losses through the thickened edge.

   Advantages are that it is permanent, warm, dry, and if you want to roll a big drill press across it, it won't give way. 

   
   

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   Edited 12/26/2002 10:33:26 PM ET by SPLINTIE

4. 
   Marcello | Dec 27, 2002 09:11am | #4

   Jeff,

   You can skip the concrete but you will need some ventilation so the wood does not rot.  It is pressure treated, but think of all those ends you cut to make the boards fit - they are exposed to the elements, in this case ground moisture.  Also where the fasteners penetrate the wood you are exposing it to potential rot.  Moisture will find a way.  You need to ventilate under the wood to keep the moisture in check.  A vapor barrier you will need regardless of weather it is wood or concrete, it is just a good a idea.  If you have insulation at the perimeter of your shop, (horizontally a min. of 24"into the shop space and vertically to below frost line), you won't really need any on top of the concrete slab.  To make the floor resilient, wood sleepers and plywood decking on top of that is sufficient.  If you want to avoid all that work, maybe looking at having 1/2" rubber matts were you will be doing most of your standing around.  Hope it helps.

   Marcello