Floating a Floor Over Slab in California? READ THIS!

[sharward]

Courtesy City of San Diego Planning & Development Review...

• Clearance Under Wood Floors
  (Figures 2, 3, 4, and 5 would apply.)

Note a number of references to "hot mopping"!

I just confirmed with my builder that my garage floor does not have a waterproof membrane between concrete and earth. Therefore, in order to avoid ventillating the space (which would have meant cutting one or more ventillation holes in my outer leaf, which defeats the purpose of the outer leaf ), I may have to modify my design, probably to raise the floor another 10" or so.

(I'm adding the phrase "floated floor" here so that the search feature will pick up this thread when that search phrase is used.)

[Ballgame]

wow 10" is a lot

[knightfly]

Don't panic, grasshopper; at least, not til you run this past your "BRA's" (That's "Bureaucrats Run Amok")... Steve

[knightfly]

Doing that, your only vapor barrier would be the hot tar mop layer; everything should be able to breathe upward from that, and your dehumidifier will maintain all at 40%... Steve

[sharward]

Thanks, Steve. I did see that option, and I did note the "or," even before I posted. However, I didn't think I could apply it to my case initially.

So, you're thinking that I can go with pretty much my original plan in terms of the dimensions and such, and just substitute treated (or redwood) 2x6, and then maybe have to hot mop my legs? (That's the room's legs, not the ones attached to my body -- youch! ) And, yes, of course I'd make sure my "BRAs" are on the same page.

If so, that'll be a bit more of a pain in the butt, but a lot better than losing another foot of head room, especially with track lighting!

[knightfly]

Naa, just put your track lighting on bungee cords and wear a helmet...

And yeah, looks that way to me; I'd run it past your local BRA to be sure, and get him/it to actually SIGN OFF on that method...

BTW, instead of "better than porn", I've been considering "Don't call your doctor if your erection lasts longer than four hours, just THANK us..."

[Stick]

Hmmm... this probably applies to me...

What's "Hot Mop" mean?

[knightfly]

That's "trade lingo" for mopping an area with hot tar - done under bathtubs, shower pans, etc, also roofs in some cases (usually flat ones) ... Steve

Oh, best if you do this to HIRE it done; roofers normally do this, they have a special machine that heats the tar, and people who are USED to the job (I don't think ANYONE could actually LIKE that job) - and you should get lots of plastic to lay/tape on EVERYTHING you do NOT want tar stuck to. After that, be prepared to remove some tar off of a few things ANYWAY

[sharward]

Great point, Steve. Yes, I was having mini-nightmares of black goo gobs on my driveway and garage floor.

I also talked with a construction buddy of mine the other day about this... He said that contractors who do this (at least in my area) have wildly different pricing strategies... He said that in his experience, pricing ranges from $200 to $1,000 for the same amount of work. So, like anything else, get a number of bids.

[rod gervais]

and then maybe have to hot mop my legs?

Sharward,

just making sure nothing got missed in the translation here - you do not just hot mop your legs -

You hot mop the entire slab - and then your legs -

This creates an effective vapor barrier at the slab level.

I would expect that they would accept EPDM Rubber roofing as an acceptable substitute for the hot tar as long as the sleepers were placed over continuous traffic pads to assure the life of the rubber roofing.

EDPM would last longer than the hot tar - and should be found acceptable under the "alternative design" clause of the code.


Rod

[sharward]

Hi Rod,

Thanks for popping in.

Yes, I was aware that the hot mopping referred to the slab, and I don't dispute that the slab needs to be sealed somehow when there is no membrane where the slab meets the earth.

The reason I assumed that the legs would also need to be sealed is because figure 5 shows that San Diego's requirements are for sleepers also to be hot mopped, and figure 3 shows a 2" minimum clearance above the slab.

However, I have since learned a few things: (1) the 2" minimum clearance only applies to untreated wood, and (2) my municipality will accept another type of sealant.

I'm not freaking out as much about this item anymore. I now have other concerns to tend to, based on my recent visit to my friendly neighborhood permit center!

Also, I'm not sure what you meant by "continuous traffic pads." I'm not sure if that applies specifically to my design or not though, since I'm not using "sleepers" per se due to the slope in my garage floor.

Thanks again, Rod... Good stuff.