Think about moisture barrier and pt lumber and insulation and the unevenness of the existing concrete floor.

 

4x4 pressure treated beams 5' o.c. or so, sitting on the concrete, leveled w/ plastic shims (3 1/2")
Definitely add vapor barrier and insulation
2x6 d. fir or syp 16" or 24" o.c. for your floor joists (5 1/2")
3/4" plywood subfloor brings you up to 9 3/4"
Floor covering (tile, carpet) brings you to just over 10"

Mac

 

I would def. try something along the lines of what mac said. I would lay 2x4 PT w/ 24" between them and glue and nail them inplace. Then install 24" x 1 1/2" foam between the 2x4's. Then lay 6 Mil poly over it and staple it down. Lay another 2x4 plate around the perimeter and like make said again at 4-5' O.C. going the opposite direction of the PT on the concrete. Then your F.J. over them going the direction of the PT on the concrete @ 16 O.C. 3/4" subfloor over them. The hights of everything need to be determined on sight. Just the way i would do it

spencer

 

Here, PT is required for direct contact with concrete.

 

Yup, I think it's that way pretty much nationwide. That's why all three suggestions included the use of PT lumber where wood touches concrete.

Mac

 

That would not be allowed in my area and they use the minimum height in crawlspace to enforce it with the local requirement being 36 inches. I've done joist on concrete and seen it done in other parts of the country but I never liked it.

What if you get critters in those joist spaces or you get some drainage water down there you would never even know it until it was too late even with pt. yuk. I'd get some roadbase fill and pour a slab.

 

Here the wood to concrete rule pertains to bottom plates,sill plates, and studs shot to the walls. Not to joist systems.

 

The only part of the joist system that would need pt for this idea would be the house side rim joist and the two outermost joists (the only wood in the joist system that would be near/touching concrete). This is assuming the garage has stemwalls on three sides.

Mac

 

If you want the floor to be level, I would suggest that you use treated sleepers. Find your level along 2 parallel sides, run a 2x4 upright between those sides. Using a pencil laying flat on the floor, scribe a line on the 2x4. Cut along the scribe. Now, place the sleeper on the floor at the location that you scribed it, and snap a string line from one side to the other(along the level lines). Cut that, and then attach it with screws, hard nails, or pins. You don't need too many sleepers, it depends mostly on what you are using for joists, how far apart the joists are, and how much area you have to span. As far as the level lines go, assuming you use 2x8's with 3/4" sub-floor, you would want the level line to be 8" below your existing sub-floor. That would mean that your sleepers would be approximately 2" tall.

 

I'm in Fl now but I lived in Co most of my life. I believe the 18" rule has something to do with moisture. But on the front Range the soil is the problem. (Expansion) I saw a garage pad in Ken Cayl that heave 2 ft.

 

Can you not eliminate "touching" the garage floor at all and simple secure a 2x8 to perimeter walls and use joist hangers to build a deck sitting approx. 1.5 to 2 inches above garage floor. This will eliminate the need to worry about shimming an uneven floor, vapor barriers, ect. I would apply a dry-lock type "paint" to the floor, install the floor, insulate it with polystyrene, cover it with 23/32" T&G flooring (glued and screwed) and apply desired fininsing (tile, carpet, ect).

I am assuming your exterior walls in you garage are dimensional lumber, altough a similar system would work with CBS type construction using PT lumber and "tapconning" it to exterior walls.

I would be hesitant to rely working off a poured concrete floor as they are rarely level, and inherently not designed to allow for a floor to be built on top of them. If the floor happens to selttle, crack, ect, what happens to your new floor? (imagining floor tiles cracking of poppoing up) At least when using the exterior walls to support the weight, you have the added assurance you are transferring the load to exterior walls, which theoretically are spported by a footing and designed to carry a load and resist settling.

 

Can you not eliminate "touching" the garage floor at all and simple secure a 2x8 to perimeter walls and use joist hangers to build a deck sitting approx. 1.5 to 2 inches above garage floor. This will eliminate the need to worry about shimming an uneven floor, vapor barriers, ect. I would apply a dry-lock type "paint" to the floor, install the floor, insulate it with polystyrene, cover it with 23/32" T&G flooring (glued and screwed) and apply desired fininsing (tile, carpet, ect).

I am assuming your exterior walls in you garage are dimensional lumber, altough a similar system would work with CBS type construction using PT lumber and "tapconning" it to exterior walls.

I would be hesitant to rely working off a poured concrete floor as they are rarely level, and inherently not designed to allow for a floor to be built on top of them. If the floor happens to selttle, crack, ect, what happens to your new floor? (imagining floor tiles cracking of poppoing up) At least when using the exterior walls to support the weight, you have the added assurance you are transferring the load to exterior walls, which theoretically are spported by a footing and designed to carry a load and resist settling.

this would be the way to go, vapor barrier on concrete, insulate between joists.

 

Appraiser, home inspectors, fireman, and buyers have problems with inaccessable spaces under floors. And how would you vent these closed spaces?

Even if you did pt, vapor barriers, and found a way to vent it, what do you tell the next buyer/ home inspector/ appraiser?? You can show him pic of what you did but what about the 3rd buyer 12 years from now? There would be no way to know what mold, bugs, and dead critters are down there. I'd go slab. It'd probably be cheaper anyway. In floor heat too.

 

Appraiser, home inspectors, fireman, and buyers have problems with inaccessable spaces under floors. And how would you vent these closed spaces?
Even if you did pt, vapor barriers, and found a way to vent it, what do you tell the next buyer/ home inspector/ appraiser?? You can show him pic of what you did but what about the 3rd buyer 12 years from now? There would be no way to know what mold, bugs, and dead critters are down there. I'd go slab. It'd probably be cheaper anyway. In floor heat too.

Have done quite a few floor systems
over slab, never had a complaint from
HO, inspector, or mechanicals.
How does slab on slab solve
any of the problems you raise?
Well except for "critters".
I usually wouldn't allow for
"**** access" anyway.
What I've found in regular crawl spaces
would be a pretty long list.
Many folks prefer wood floor systems
to slabs, especially if half the room
is already wood.

 

Simple answer is Yes, it's just a sleeper floor, I would suggest you glue the floor joists to the floor, also be sure to use a good vapor barrier. As the code is written a crawl space foundation must have a minimum of 18 inches although there is an exception that states "the use of pressure treated lumber is acceptable if the clearance is less than the minimum requirement" .

Suggestion is to have the entire floor treated with a generous Boracare treatment to prevent the infestation of termites.

 

Ok, does it need to be vented and how do you vent it??

 

Dunno 'bout the front range,
I couldn't figure out your footing
on a bet.
I've done it, plans approved, built,
inspected, accepted, and occupied.
Several times over. Would do it again.
Apparently you wouldn't, and maybe can't.
I wouldn't even audition to play a
Colorado code expert on TV! :laughing:

 

Yeah, we have some weird stuff including but not limited to our floating walls. Makes it easier for ghosts to move from room to room. :laughing:

 

Ok, does it need to be vented and how do you vent it??

"Need" as in "code" - don't know. Or as in "really should", ya. Moisture will come up through the concrete slab and get trapped there.

Traditional sleeper floor, they used to just lay 2x4's out on the concrete floor. Then everyone would be surprised when the floor rotted out ten years later.

But you can make it work with a few updates. First, sit the sleepers on sill plate gasket for thermal break and moisture barrier.

Next, think about DriCore sub-flooring. It's just OSB on a million little plastic sleepers - and here's what they recommend:

...We recommend that the panels have a 1/4" space away from all perimeter walls and room obstacles, such as support posts or stairs, to allow for airflow ...

...Vent cover installation for increased airflow Increasing air flow under DRIcore panels can be accomplished easily by installing vent cover openings into the finished flooring and DRIcore panels every 10’ around exterior perimeter walls. De-humidification and proper mechanical air handling systems will help ensure continued air flow for moisture and humidity reduction. To finish off, install a low profile vent cover and inspect periodically....

In other words, treat the space under the floor as a space to actively keep ventilated.

I once worked on a place where all the wall cavities had been treated like this - very interesting construction.

 

.....
Next, think about DriCore sub-flooring. It's just OSB on a million little plastic sleepers - and here's what they recommend:.....
I once worked on a place where all the wall cavities had been treated like this - very interesting construction.

DriCore is installed directly on the slab....
it has no bearing on the OP's situation.
As to the floor system that
"rotted out ten years later.."
Obviously, you need to look up vapor barrier
when you purchase your next do it yourself manual.
I can't imagine what you think would be accomplished
by using sill seal gaskets under treated sleepers
laying on 6 mil vapor barrier.
Actually I can't imagine what you're thinking...period.
(Same advice as before, Find someone who has a clue.)

 

ok there a millon ways to do this job but from the start i was thinking the same thing as pknyrayn before i read his. Build the floor as a normal floor only lay down a 6 mil vapor barrior first ,maybe glue it to concrete around edge. dont know what your span is but 2x8 or 2x10 joist with 2x10 rim and flush center girder. only shim the rim and center girder where needed. you'll need to use a transit or builders level to draw a line arround walls and reference that to the house floor or just measure down from ceiling but dont assume the concrete is level. The concrete was designed to hold a car with 1000 lbs per wheel point loads itil hold a floor.

 

I would like the floor to match the same height as my exisiting floor inside my house. This would require me to raise the floor off the cement garage floor. I have to raise it about 10 inches.

Next, think about DriCore sub-flooring. It's just OSB on a million little plastic sleepers - and here's what they recommend:

OP: "Can I just lay my floor joist directly on the concrete?"

Which OP did you read?

OSB with a million little sleepers placed directly on concrete would put garage subfloor 9" below the rest of the OP's house flooring - he specifically stated he wanted the floor at the same level. That's why it has no bearing in this thread... that, and you'd need a perfectly level garage floor. I've seen many that are and some that aren't.

Mac

 

OSB with a million little sleepers placed directly on concrete would put garage subfloor 9" below the rest of the OP's house flooring - he specifically stated he wanted the floor at the same level. That's why it has no bearing in this thread... that, and you'd need a perfectly level garage floor. I've seen many that are and some that aren't.

Mac

Next, think about DriCore sub-flooring. It's just OSB on a million little plastic sleepers - and here's what they recommend:

...We recommend that the panels have a 1/4" space away from all perimeter walls and room obstacles, such as support posts or stairs, to allow for airflow ...

...Vent cover installation for increased airflow Increasing air flow under DRIcore panels can be accomplished easily by installing vent cover openings into the finished flooring and DRIcore panels every 10’ around exterior perimeter walls. De-humidification and proper mechanical air handling systems will help ensure continued air flow for moisture and humidity reduction. To finish off, install a low profile vent cover and inspect periodically....

In other words, treat the space under the floor as a space to actively keep ventilated.

That is - when you enclose a space over a concrete floor with DriCore, the company recommends taking positive steps to ensure ventilation under the floor to avoid moisture problems. What did a number of posts inthis thread allude to? Problems in the enclosed space under this guy's theoretical sleeper floor. Soooooooo - take a lesson from DriCore - "treat the space under the floor as a space to actively keep ventilated"

Sheesh.

 

You're definitely going to want to protect the floor joists from moisture somehow. Even if you don't have actual pools of water on the concrete, it absorbs water from the ground below it like a sponge and releases the water vapor into the air. You probably won't see the moisture because it dries the second it hits the air, like water in a potted plant, but if you lay wood directly on it, it's going to collect on it, rot, grow mold and become a habitat for insects.

 

That is why everyone with any
experience has said to start
with a vapor barrier!

 

Sounds like the IRC needs to address this specific type of construction and set some standards..... or specifically disallow it , my choice being the latter.

 

How is it any worse than burying everything
in concrete?
If something happened to the mechanicals,
what is more accessible? Bust up concrete?
Pull up a sheet of plywood?
I'm having trouble seeing your objection here.
It's not my first choice, but it has proven
a good solution to a fairly common "I need more
living space." problem.

 

1) I would like to see an IRC standard.
2) Slabs and clean fill are inorganic i.e. can't grow mold.
3)A slight waste plumbing leak under a closed wood floor could go undetected for years. Under a slab a slight waste leak is likely to seal itself and would be unlikely to affect the living area.
4) I'm not that crazy about living space over pressure treat anyway. The lateset PT has not been around long enough to know of any chemical concerns in an enclosed area.

Not really arguing because I've done these wood over slabs myself. Just throwing out ideas.

As I already mentioned, in most areas with frost protection, digging a crawler for this type of construction would be very simple because a skidder can go through the garage door.

 

[Q digging a crawler for this type of construction would be very simple because a skidder can go through the garage door.[/QUOTE]

and you end up with a shallow indoor swimming pool ( probably lower than grade. dont know havent seen the site) under the floor. Major work to water proof that or keep it drained if the yard is not graded right. Not worth it. Just lay the vapor barrior and not treated joist on treated shims! If it needs to be vented ( my opp. it dont) just some screened crawl space vents cut in to the out side will work.:thumbsup:

 

Use of PT wood indoors

Found this on another webite but i cant post the link cause im new

Indoor Use of Treated Wood
Pentachlorophenol treated wood should not be used in residential, industrial or commercial building interiors, except in laminated beams or building components that contact the ground and are subject to decay or insect infestation. When used for such purposes, pentachlorophenol treated wood must be covered with two coats of an appropriate sealer such as urethane, shellac, latex epoxy enamel or varnish.
The EPA has advised that creosote treated wood should not be used in residential building interiors. Creosote treated wood in interiors of industrial buildings should be used only for wood block flooring and for industrial building components that contact the soil and are subject ot decay or insect infestation. Such industrial application is acceptable, provided that two coats of an appropriate sealer are applied. For creosote treated wood block floaring, coal tar pitch and coal tar pitch emulsion are effective sealers. Urethane, epoxy and shellac are appropriate sealers for creosote treated wood when used other than as wood block flooring It is believed that limited interior uses of appropriately sealed pentachlorophenol and creosote treated wood will not cause unreasonable adverse effects to humans or the environment.
EPA has not advised against the interior use of arsenical treated wood because the arsenic air levels measured in homes constructed with this type of treated wood are not significantly different from background arsenic air levels when dust has been vacuumed from the wood surface. Therefore, wood that is pressure-treated with water-borned arsenical preservations may be used inside residences wtihout a sealer, providing that all machined sawdust is vacuumed from the wood surface.

Just thought this info might interest some of you.

 

Found this on another webite but i cant post the link cause im new

Indoor Use of Treated Wood
Pentachlorophenol treated wood should not be used in residential, industrial or commercial building interiors, except in laminated beams or building components that contact the ground and are subject to decay or insect infestation. When used for such purposes, pentachlorophenol treated wood must be covered with two coats of an appropriate sealer such as urethane, shellac, latex epoxy enamel or varnish.
The EPA has advised that creosote treated wood should not be used in residential building interiors. Creosote treated wood in interiors of industrial buildings should be used only for wood block flooring and for industrial building components that contact the soil and are subject ot decay or insect infestation. Such industrial application is acceptable, provided that two coats of an appropriate sealer are applied. For creosote treated wood block floaring, coal tar pitch and coal tar pitch emulsion are effective sealers. Urethane, epoxy and shellac are appropriate sealers for creosote treated wood when used other than as wood block flooring It is believed that limited interior uses of appropriately sealed pentachlorophenol and creosote treated wood will not cause unreasonable adverse effects to humans or the environment.
EPA has not advised against the interior use of arsenical treated wood because the arsenic air levels measured in homes constructed with this type of treated wood are not significantly different from background arsenic air levels when dust has been vacuumed from the wood surface. Therefore, wood that is pressure-treated with water-borned arsenical preservations may be used inside residences wtihout a sealer, providing that all machined sawdust is vacuumed from the wood surface.

Just thought this info might interest some of you.

That was pretty useful information
25 years ago.
The only place you will commonly see
penta treated wood is power poles.
Creosote is pretty much confined to
railroad ties.
The stuff at your lumberyard or
B Box is safe to use indoors.

 

This post is a bit old ,wonder if it ever finished. He's probably in a retirement home by now.:wheelchair:

 

New living space

K2, I'm still around. I was planning on digging out my garage floor for access to the mechanicals but it doesn't seem to be a very popular idea. I was concerned about screwing in a ledger on the existing garage 2x4 walls for the floor joist to sit on. It doesn't seem sturdy enough to me. I thought I might build a wall inside the existing garage wall or build up the floor on posts on top of footers and beams like I would build a deck. I want to run heat runs out to the new additional living space and water/drains as well. I have also been told that I need a 36'' crawl space by code in my area. Any advice? Thanks from Columbus Ohio.

 

K2, I'm still around. I was planning on digging out my garage floor for access to the mechanicals but it doesn't seem to be a very popular idea. I was concerned about screwing in a ledger on the existing garage 2x4 walls for the floor joist to sit on. It doesn't seem sturdy enough to me. I thought I might build a wall inside the existing garage wall or build up the floor on posts on top of footers and beams like I would build a deck. I want to run heat runs out to the new additional living space and water/drains as well. I have also been told that I need a 36'' crawl space by code in my area. Any advice? Thanks from Columbus Ohio.

I would lag a rim joist/ledger to the 2x4 wall and hanger off that rim. . 3 (3/8 x 5) 16 " on center should do it but someone should really do a little math on that. I have a calculator around here somewhere but there may be one on line. You could throw a few flat kickers under the rim down to the foundation but that really should not be necessary. That part of it might be the same even if you were doing an inaccsssable crawler.