Replies

1. 
   calvin | Apr 28, 2010 03:40pm | #1

   Man

   That's a lot of questions.

   Rotary hammer for the amount of holes you want to drill-unless you have a lot of youth and time.

   Impact driver for running the screws in.

   Use 1/4'' screws that are hex headed (easier to drive, less chance of stripping out the head-you'll have to predrill a bit of depressing to countersink the screw heads-use a 5/8's spade bit,  Run your masonry bit through that pilot.  Drill down beyond the proper depth for the screw-pull up, drill down, pull up-you need to clear the hole of the concrete dust.

   (or use a PAD-powder actuated device-Shoot concrete nails into the slab-way quicker/easier and to only some-not as good as tapcons.)

   I would use 3'' screws (if not shooting nails).  2-1/4 are too short.

   Using PL Prem will cushion the low spot and help adhere your sleepers between the tapcons.  I'd go 2' oc on the tapcons.  No glue, you'd have to tighten it up.

    For 3x4 ply I'd use the diamond on your tape if you're using 2x4's for sleepers  The diamond is at 19-3/16's and on from there.  That means the breaks for Plywood will be 8', you'll lose the ability to start with a half sheet-but the drop of a 38-3/8ths will become another starter that'll fit your layout.  With 3-1/2'' wide sleepers the distance between them will be just a bit wider than a conventional 16'' layout.  If the 500 pound machine feet are placed near your sleeper location, you'll have no problem.   If you're real concerned-use a 16'' layout and your space between will be about a foot.  Certainly enough for more extreme point loads.

   Vapor barrier?  Certainly can't hurt-you've already got one beneath your slab.  If the sides are isolated from moisture and it's dry now-you should get no more added moisture to the slab..  I certainly would do it now, rather than pulling up the sub and doing it later, if you want to install a barrier at all.

   Tapcons are rated for use with pressure treated wood, make sure McFeeley's are as I imagine they would be.

   Is there insulation under the slab?  or are you planning on it below the subfloor?

   I'm sure there were more questions, but that's all the wind I have.

1. 
   Lyptus | Apr 28, 2010 05:05pm | #2

   PAD alternative?

   Thanks for your advice.  Given the number of holes I'll be drilling the care required to clear the dust from each hole, I'm really starting to think more about using Powder Actuated Nails.  The cost will be about the same as renting a rotary hammer drill, buying the screws, etc.  However, I worry that some nails may crack the slab or misfire and have to be sawed off.  I hate to open up a Screw vs. PAD debate but if it were you- and your dream workshop- what would you do?

   - Lyptus 

1. 
   calvin | Apr 28, 2010 08:50pm | #4

   What would I do?

   Well, in my shop I have concrete.  If I were to do it again, I would have heated it underslab hydronic.  As it is, I didn't. 

   The previous shop was wood over concrete-sleepers and foamboard.  Salvaged wood board flooring from a barn.  Warm and comfortable.

   I'd nail them, having tapcons of necessary-I've already got all the tools to do whatever necessary whenever necessary.

   My shop is mainly mobile.  On occasion -shop work in the garage combo.

   I like the above idea if you find it working while you do it. I I felt it necessary to use two layers of ply (I probably wouldn't)  I would however, stagger all the joints but run the ply the same directioin.

   I'd insulate too.

   If it wasn't working-screw it down.

2. 
   [email protected] | Apr 28, 2010 07:45pm | #3

   Do you have a sketch of this?

   I am wondering how this is going together that you need to drill anything into the new floor.

   The loading from you machines is typically 4 point loads, and not a distributed load.  Also, the spacing of sleepers will be only to limit the sag in the plywood. 

   In my mind you are kind of working against yourself.  The purpose of the wood floor is to give some flex so it is easier on your feet, and building it stiff enough to really support heavy tools well, means that it is stiff enough to be hard on your feet and legs.  I'd just buy a really good pair of work boots, with cushioned soles, and stay on the concrete floor.

   Back to your question:  If I were doing this: 

   I would put down a layer of heavy 10-mil poly now directly on the concrete.  Concrete gains strength the longer it is kept damp.  The Bureau of Reclamation is still occasionally breaking concrete cylinders they have had in storage since Hoover Dam was built.  Those cylinders are still gaining strength.  And, while the concrete is "cured", it is still gaining strength. 

   I would install pressure treated 2X4 sleepers at 16-inches on center.  14-inches on center does not match up to plywood, or other sheet goods.  I would not secure the sleepers to the concrete.  They are not going to move around much, particularly once the floor is in place.  The only possible complication I can foresee from not screwing them down, is the floor might rise from the sleepers warping if the gain / loose moisture.  But I would be surprised if it became an issue.  And, if it you could then drill through the whole floor, and screw it down. 

   I would do two layers of 5/8-inch plywood, or OSB, laid in opposite directions, and be sure that the joints are overlapped between the layers.  Depending on the cost differential between pressure treated 2X4s, and T&G subflooring and regular sheet goods, I might forgo the T&G, and just put  short pieces of 2X4 under the joints, as "blocking".  Glue and screw everything.  Odds are you will have to cut the sleepers to length, so you might be able to get the blocking mostly from scraps.

   You didn't say what the finish floor is going to be, but if you use good plywood for the top layer, you could possibly forgo the cost of the flooring, and get away with painted plywood for years.