White Oak Floor on Heated Slab

[jlmccuan]

We are building a new earth sheltered home.  Dyed, stained and etched concrete slab cut 30" on bias, except in the kitchen, where my wife wants to use some very nice 36" x 18' logs cut for the flooring.  We would like to use radiant heat in the floors throughout, but could zone the kitchen area differently.  At this point, we can still do whatever as far as installation, quartersawn, straightsawn, thick, thin, long, short, t&g, bias ends, narrow and wide, whatever. Logs can be processed however needed.  Can we get it all?  Heat under the wood, minimum floor height differential from the rest of the great room?  The kitchen can be placed as a separate slab.  Home should be a fairly even environment in terms of temp and humidity.  No direct sun on the wood.  Would prefer no exposed fasteners or pegs at worst.  The wood part of the floor would amount to 200 sq ft or less with counters holding down the edges except for the 42" entryway.  Any and all help greatfully accepted.  I'd love to find we can use a rough finish on the concrete, glue the wood and leave the temp on that zone set on XX degrees year round.

Thanks much
Jim McCuan

[Den Socling]

You have a lot of questions that I am not qualified to answer but I'll see if I can get a discussion started. I would talk to somebody with a lot of experience with radiant heat. The wood should be 3/4" thick T&G. Some people want wide "planks" but widths around 3-1/4 are easier to work with. You may need a layer of wood between the concrete and the hardwood as a buffer and something to nail to. 

[red oaks lumber]

putting wood over cement is tricky any way let alone with infloor heat.there are ways to make it work. nail and glue 3/4 thick 1x2 g.treat every 16" , fill the 3/4  space with gypcrete, by doing this the heat from your tubes will still radiant upward thru the floor, with an air space the infloor might not work very well.
 having said all that, how long will the concrete need to cure so the moisture content is low enough so your floor wont swell ? i dont know. but, that answer is going to be very important.

[Magicman]

The only time that I have seen that done, the slab was lower in the kitchen area so that the finished Oak floor was level with the other "Scored" floor.  I saw the finished kitchen floor, but really don't remember exactly how it was done.  (maybe treated 2X4 joist which would mean that the slab was 4" lower)  It had a "hollow" sound when you walked on it.

And, welcome to The Forestry Forum.   

[jdtuttle]

Flooring contractors around here won't install directly on concrete especially with radiant heat. You need an engineered flooring specifically designed for your application.
jim

[coyotencuttin]

+1 on not on concrete with radiant heat. the better way would be to use raupanel system http://na.rehau.com/construction/heating...plumbing/radiant.heating/raupanel.shtml that the piping stays in a channel in the subfloor. very little chance of an accidential nail strike. it would be a mess in concrete that had finished flooring down and found later.

[Magicman]

OK, I got the answer on the application that I saw.  First, it was NOT a radiant heated floor.

The slab was recessed 1½".  Plyform was anchored to the concrete slab.  (Plyform is ¾" treated T&G plywood)  The ¾" Oak flooring was then nailed to the Plyform.

I guess that the radiant heat could be excluded from the Oak flooring portion if it was thought to be a problem?  Anyway, I just wanted to clarify the application that I was familiar with.

[Larry]

We were thinking about hardwood on radiant floors for a while.  I did a lot of investigation and it is doable if certain rules are followed.  The first is the heat has to come on slowly...seemed like over 3 days, than leave it alone for the winter.  The second if I remember correctly, is never to exceed 85 degrees in the slab.  I didn’t think we could live with those rules.  Our climate in the winter has wide temperature swings.  I’m gone at times and Kathy along with some of the family can be quite impatient when there cold.  They would crank up the thermostat without a thought.  Some of the better systems do have built in safeguards.

We are still planing hardwood on a slab...just without the radiant heat.

[jlmccuan]

OK, thanks for the input thus far.  If we exclude the radiant heat from the kitchen portion of the slab, and recess the slab to accomodate the wood ( both of which I'm willing to do ) could I run a small forced air system in the toekick of the cabinets to get that portion of the room to not add to "my feet are cold" syndrome?  Similar to the effect of the fridge, or are we back to the same problem?.  Kitchen/bar is part of a great room with cabinets all around the kitchen/bar except for a 48" walkway to get into the kitchen workspace.  I really like the idea of the wood being flush with the rest of the room's polished and scored concrete.  Wood is requested in the work area for ease of knees. 

  While working out the rest of the floor/heat question, I have some really nice white oak for the floors.  What would be good dimensions for sawing these for the intention of use in this floor?  Slab saw and rip, or slab, dry, then rip.  Any advantage to quartersawing for this use?  I have plenty, so the waste isn't as big an issue.

[PC-Urban-Sawyer]

Yes, you want to quartersaw the oak if at all possible. The truly quatersawn oak will expand and contract less across the width of the board than either flat sawn or rift sawn.

Additionally, quartersawn white oak is likely to have a good bit of the "fleck" pattern showing which is considered beautiful aqnd desireable by many people.

Another factor to consider is the width of the flooring planks. The narrower the individual plank the less change in width due to seasonal changes in humidity levels. Also, wider boards tend to cup more.

You should get the wood kiln dried to minimize problems as well.

Good luck.

Herb

[John Mc]

I know of a bunch of houses with radiant heat under a hardwood floor in my area of Vermont, but I don't know of anyone using Oak. We used White Ash at the recommendation of our builder. This was on our first floor, with a basement underneath. We wanted a slab for thermal mass, so laid foam board on top of the subfloor for insulation, then had sleepers nailed perpendicular from how the flooring would run (so we'd have something to nail the flooring to. Laid the tubing in between the sleepers, then poured lightweight concrete over the tubing up to the level of the top of the sleepers (I'm thinking this was about 1.5" thick??)

It has worked well for us. We do have to run the radiant heat fluid in the zones under the hardwood at a lower temp than where we have a bare slab in the basement or where we have tile over the lightweight slab. There is a thermocouple in the slab that keeps it from dropping below a preset temperature. This is tied into the thermostat on the wall which regulates room temp.

I don't see why the same thing won't work on your concrete slab, if you can figure out how to get something to nail into (glue would not be my choice, but I know some people install the "prefab hardwood floors with glue).

One of the keys is to pick the right species of wood for the flooring. That's why we used white ash... we were told this is one of the better hardwoods to go over radiant heat floors.

I'd bet a good radiant heat company would have a solution for you... but maybe Oak is a species that doesn't work too well? I don't know enough about it to comment.

John Mc

[jlmccuan]

Thinking out loud again, and please chime in with any thoughts.  If the section of concrete under the kitchen is a separate slab and heat zone to bring it up slowly and keep it there (if you're hot, move your feet) during the heating season.  And if recessed 1.5". Could we glue in one .75" layer of floor perpendicular to the finish grade level floor, then nail the finish grade as usual? Or would this make the whole thing worse?  Really, the floor could perhaps be treated as a rather large work mat and maybe even not run it under cabinets in this case.  Maybe I should think of this in terms of a large butcher block ?

[John Mc]

Wood is an insulator. You don't want two layers of wood. You need to find a way to get your wood flooring to lie directly on the slab. Little or no airspace, and no other layers between the floor and the slab.

There are people who are experts at this who have no doubt already solved this problem (and who could tell you whether Oak is a species you should even be considering over radiant heat in the first place). Our builder did not design the radiant heat. He went to a company that specializes in it, and they told him "this many loops of tubing in this area (different when under tile vs wood, I think) - they even told him what temperatures to set the heating water at in the various zones.

We do not leave our heat on all the time. We set it for what we want, and let the thermostat and in-floor thermocouple handle the rest. We've had no problems. I don't recall that we were even told to do anything special the first time we fired it up... we just set the temp and that was it. (Our builder was rather particular about who he bought the hardwood flooring from. He wanted to make sure it was dried properly and stored properly until we were ready to use it.)

[mooses]

I used White Oak on my Radient floor and on the ceiling/floor for the second floor, which also is Radient. But my floor was on joists. Stapled to the 3\4 ply with foil over the tubing , 10 " of ins. over the foil and 1\2" ply over the ins. I have the thermostat set at 68 and my floor moved about 1\8" to 3\16" during the winter and back to being tight during the summer. Talk to people who have instalded it, that's were I got all my questions answered and it turned out great with no problems.

[John Mc]

My white ash floor over a lightweight slab nailed to the sleepers I mentioned above stays tight year round.

[Holmes]

Radiant heating your entire slab will work. For the kitchen area if you want to make the floors the same height drop that floor 1.5"  put 3/4 sleepers down every foot and nail your floor to the sleepers. The air space under the floor will have little effect on temperature. PC- Urban-Sawyer is right on about the wood.
The concrete heat will need to be on for a few weeks to dry out the slab. You must have a good vapor barrier under the concrete slab not to mention at least 2" of solid blue or pink foam board insulation.Do not use the foil backed foam board insulation . Foil bubble bubble foil insulation can be used also, I would use it with the white vapor barrier up first,  then the foam board, 2  1" layers perpendicular to each other , wire mesh then wire tie the tubing to the wire mesh. The 5'x9' flat wire mesh panels go down easier a make for a neat pipe installation usually 12" on center.   
    1" of wood has a r value of.8 . That is not a problem for radiant heat. It is best to keep the thermostat tinkering to within 3 degrees, but you can set different zones to different temps.
   Radiant heat does not shrink floors. Lack of humidity shrinks wood.    Narrow quarter sawn wood is the best to use.
 You could put sleepers into the concrete as it is poured,that might be the easiest way to do it. I think what you want to do will be the most comfortable way to heat your house.  Holmes

[Hilltop366]

  Wood is requested in the work area for ease of knees. 

I don't think you will find wood over concrete will be any better on the knees than concrete unless there is something else in there to let the wood floor move.

Did a apartment renovation of a building a few years ago that had unheated concrete floors where the biggest problem was dampness caused by condensation from warm outside air condensating on the cooler floor even though the floor was covered with vapour barrier and carpet, we ended up using 1" blue foam with 1 x strapping over it and a layer of 3/4" t&g ply then carpet or vinyl flooring. This cured the condensation and cold floor problem with the added bonus of a very forgiving floor on the joints.

[jdtuttle]

Have you thought about staining the concrete?
http://www.concretenetwork.com/staining-concrete/
jim

[jlmccuan]

The rest of the great room will be stained and scored.  Lot's of good input folks, thanks.

Jim

[Handy Andy]

  Gymnasium floors are laid over concrete.  They use rubber pads to give the floor some "give".  I saw one laid one time, they put down the pads about every 3 feet, then 2 layers of plywood, offset, then nailed the hardwood down which held the flooring to the 2 layers of plywood,as the plywood wasn't nailed beforehand.

[ljmathias]

Hey, Handy Andy who's name is "Jim," question on the pads: were they laid edge to edge or was there space in between to let the subfloor breath a little?  Thanks.

Lj

[DR_Buck]

My floor originally had parquet glued to concrete when we bought the place.   After we scraped it off there was lots of tar/glue residue in the concrete that could not be remover.   I put 6 mil plastic sheet over the concrete, then screwed 3/4 T&G plywood down with tapcon screws.  Cover the whole thing with carpet 13 years ago.  Haven't had a problem.   

The next remodel which is starting real soon I'm taking up ceramic tile in the kitchen and screwing down plywood again this time covered with bamboo flooring.    The wife does not want ceramic in the kitchen anymore.

BTW - My slab does not have underfloor heat. 

[Don_Papenburg]

Radiant heat will  radiate through an air space and wood.  As i started to build my house I just heated the basement with radiant infloor .  My basement temp was 70  the first floor was about 65  from the basement heat radiating through the 3/4 ply subfloor.     Air gaps have little effect on radiant heat   Wood has slightly more effect than air.

Put the radiant heat in the slab  fasten 3/4 ply over  CIS membrane  This will keep water from migrating .   Put your slab over extruded poly  insulation board put the pex on top of the foam concrete over that so the pex is at the bottom of the concrete  ( no danger of nail or screw holes)   
Then you can use the oak .  Quarter sawn no wider than 3 inch before it is T&Ged     Set you floor temp for no more than 85 and keep it there for the heating season.   Put the thermal couple in the floor and the thermastat  hidden  Then put in a placebo  thermastat  on the wall.   In a differant circuit you can have a baseboard heat  to make up room heat if needed,  I don't think you will though.

[sbishop]

 Don_Papenburg

I'm on the same boat as jlmccuan wanting hardwood over concrete radiant heat.

I've got a garage that is attached to the house that will be converted into a family/tv room. it has radiant heat in the concreate. In the house now, we have lots of tile...i'm starting not to like tile. So i have thinking maybe it would be possible to put down some hardwood.

 Don_Papenburg, how do you suggest attaching the wood to concrete? subfloor or glue direct to concrete.

Thanks
SBishop

[Tug Hill Walt]

Another possible solution:Recessed slab, use foil-bubble-foil insulation, Snap in tubing holders and 2x sleepers. 5/8 subfloor and your finish floor. This is basically the same system as in a conventional home over a cellar or crawlspace. Just think of it as just having a really, really low cellar.

[StephenRice]

Wow, Jim.  You have a LOT of opinions and suggestions here, so I am hesitant to even throw another one in the pot.  As a building contractor, I have put down a wood floor or two over the years.  Most of those were glue down or nail / staple down applications.  However, in your case, I would suggest neither.

First of all, congratulations on your decision to build an earth sheltered house!  That alone should greatly reduce your heating and cooling costs. 

I would NOT pour the kitchen slab separately from the rest of the house slab if you can pour it at once and still have the recess that your floor requires.  That would only promote cracks around the edge and a place for moisture and termites to come up.  Keep the slab continuous and also the plastic vapor barrier under the slab.  That is especially important around wood floors.  You need a dry slab under there.

I question the amount of benefit that in-floor radiant heating system would have under at least 3/4" of oak flooring in an already underground or earth protected home.  Is it really needed in the kitchen area?  How large is your kitchen and how open of a floor plan do you have?  Perhaps something as simple as a ceiling fan might help air flow and distribute heat from the other rooms where there is in-floor heating?  The cold feet syndrome would definitely be more pronounced over concrete or tile than over wood.  Perhaps it may not even be necessary if the kitchen is not too large?  Also, would you normally have small rugs in areas where you would stand for a while, such as in front of the kitchen sink or countertop where food prep would occur?  That would not only pad the floor for extended standing, but also keep the feet warm with or without radiant heating.

Regardless of whether or not you use radiant heat in the kitchen area, you still have to remember that kitchens and bathrooms share one trait... they are high moisture areas where water inevitably gets on the floor from time to time.  So, expansion and contraction is a situation that you will have to face no matter what.

Those things taken into consideration, whether you use the radiant heat in the floor or not, my recommendation is the same.  First, when pouring the concrete, make sure that you have a good continuous vapor barrier extending under the whole slab and pour the slab as a monolithic structure... in one piece.  Recess the slab for the depth of your flooring (usually 3/4") plus about another 1/8" to 1/4" for one or two layers of rolled foam flooring underlayment.

Install your cabinets on top of plywood or shims.  The flooring should NOT extend under them.  Instead of nailing or glueing your flooring, I would suggest that you get router or shaper bits (depends on whether you are using a full shaper or just a router table to mold your flooring edges) that provide a snap-lock joint rather than a standard flat tongue and groove joint.  That way, you can install your flooring as a floating floor instead of a glue down or nail down application.  This will allow your flooring to expand and contract with the temperature and humidity / moisture fluctuations (like when water is splashed on the floor or you want to mop it) without binding and warping and such.

Of course, like the others said earlier, a quarter sawn profile that has a face width of about 2 1/4" to 2 1/2" (not counting the tongue) will be much more stable than a wide flat sawn board.  After milling the floor with the snap-lock tongue, simply install the floor directly over one layer of foam wood flooring underlayment.  You do not need to glue or nail anything, but leave a small gap of about 3/8" - 1/2" around the perimeter of your flooring to allow for expansion and contraction.  Of course, you must have your flooring very dry (6-8%, the dryer the better) before installation.  When you are finished, either buy or mill your own transition piece for covering the gap where the wood floor adjoins the stained concrete floor, and also install base and quarter round or shoe moulding around the edges of the room and under the edges of the cabinets to cover the edge gaps there as well.

Use a very good polyurethane sealer over the floor and that will help with the moisture as well. 

A guy that used to work for me years ago also was a professional skater and ran multiple skating rinks.  Once a year, they would refinish their floors with a product my friend called Roll-On.  Basically, it was a tough epoxy.  The beauty of the product was very little prep work other than a quick sanding and cleaning of the floors was necessary, it was super tough, very high gloss, and looked great.  It did not hurt that the product was simply and quickly rolled onto the floor with big paint rollers and then settled down into any cracks and self leveled.  He used the stuff to refinish his oak floors at home too.  Looked great.  Not overly expensive either.  You can use standard floor polyurethane, which will look great also, but it will not provide the water and moisture resistance and toughness that Roll-On will.  Their Ultra_Clear product will probably be your best bet.  It is a step up from the regular Roll-On that is used on most quality skating rinks.  The nice thing about using a Roll-On finish for your oak floors in a kitchen is that it is highly water resistant compared to other finishes and takes wear and abuse really well.

You can read a little bit about their products here:  http://www.roll-on.com/floor_coatings.htm

Here is a list of distributors across the U.S.:  http://www.roll-on.com/distribu.htm

For what it is worth, I hope this helps you some...

[jlmccuan]

Every time I check there is just more and better info.  I was a skater and wonder what product was used.  Are the snap together tooling bits available any where in particular?

Can anyone give a blow by blow description of quartersawing a log?
Thanks again.

[Hilltop366]

Put the radiant heat in the slab  fasten 3/4 ply over  CIS membrane  This will keep water from migrating .   Put your slab over extruded poly  insulation board put the pex on top of the foam concrete over that so the pex is at the bottom of the concrete  ( no danger of nail or screw holes)   

It is recommended to lift up the pipe and screen it is fastened to a few inches, then push back down when pouring the floor to make sure the concrete goes all the way around the in-floor heat tubing for the best heat transfer from the pipe to the concrete. From experience I can tell you that it does happen, I have seen as much as 3/8" of pipe exposed under the concrete even though the tubing was sitting on top of a steel mesh so it was not touching the foam insulation.

I am not sure if this has been mentioned yet or not, but another thought would be to put to the floor you want, the way you want it (lot of forgiveness for the joints) and put a generous toe kick (maybe 6") under your cabinets and put a hot air system in it ( using some hot water baseboard finned tubing and a small fan with duct work) to keep kitchen and floor/feet warm. I would still put the in-floor as well.

It will be interesting to hear what you do in the end.

[scsmith42]

Can anyone give a blow by blow description of quartersawing a log?
Thanks again.

The best thing would be to do a search in the archives - there are lots of posts on quartersawing.

Several years ago I read some information on another forum posted by someone that had been doing wide plank flooring over radiant heating for 15 plus years.  Their tact was to use very thin boards (around 3/8" thick or less), glued down to the slab with an excellent adhesive.  Obviously quartersawing would be preferred. 

They posted some pix of a 15 year old floor and it looked great.

This flys in the face of conventional wisdom though, and I have not yet personally tried this approach.  It made sense to me though.  Just sharing it as an idea.

[phuss]

I'll give my 2 cents worth....as a radiant floor designer, we have found that installing WarmBoard (or a generic knockoff) on top of ur slab, and then installing your wood flooring to the WarmBoard works really well. We do like to install 1" of foam between the slab and WarmBoard.

[John Mc]

What's "WarmBoard"?

[Magicman]

  What's "WarmBoard"?

Google it:   http://www.warmboard.com/