Hi,

I wish I'd found this forum a couple of weeks ago, as there seems to be a considerable body of knowledge here. I've already made some decisions on this project which may not be optimal. Unfortunately, our finances are such that some of them were required, so even if I were able to undo them, I'm probably going to need to soldier ahead with this and make the best of it.

What I have is a manufactured home, about 1500sqft, to which I'm in the process of building a moderate sized addition (24x26, basement under the addition only). I am retrofitting the existing house with a hydronic radiant floor heat system which I'm planning to install in an overlay over the existing subfloor (the mfg home's engineered floor joist system and limited crawl space working area would make installing this under the subfloor very difficult). The water for the heating system will flow through 1/2" PEX set on 12in centers, with sleepers around it, then hardwood flooring will be installed over the sleepers. (3/4" #2 red oak, 2 1/4" wide)

I have some questions about this installation. Probably more will come up over time.

1) I'm planning on using 3/4" plywood for the sleepers so that the floor height isn't raised more then it absolutely has to be. Is this the best material for this? How should this be affixed to the subfloor. I was originally thinking it would be nailed, but I've also considered staples.

2) Since I'm cutting these myself, I can make them any size, how wide should they be, and what spacing? There will be a radiant barrier (reinforced foil) under the tubing (and the sleepers), and it requires an airspace to be effective, so I don't want to block off any more of it then I have to.

3) For this specific installation, would staples or cleats be preferred for holding the flooring down? I've read that staples hold more firmly, but going over the radiant heat, I wondered if perhaps allowing more flex might be preferable.

4) What do I do about the paper/felt that's usually installed under the hardwood? Can I skip it? Should I just put it on the sleepers? I'd really like to be able to see the tubes while I'm nailing the floor down so I don't get any stray nails in them!

5) The kitchen and bathrooms will be getting tile flooring instead of wood, but the height issue is similar. I'm wondering if I can get away with not removing the cabinets. What do you think?

6) After reading about a lot of finishes, I'm very seriously considering Osmo Polyx Oil. I like the look of oil finishes I've done on furniture projects in the past, and it looks like the application is easier, requires less specialty tools, and most of all the finish is easily repaired if it gets damaged. I have four children, a dog, a cat, and probably more pets to come (the new place is out in the country) and the ability to do spot repairs is a giant plus to me. Does anyone know how this finish will behave over the radiant heat? Are there any recommendations for other finishes that might be preferable if this isn't a good idea?

Having read a bunch of posts here over the last couple of days since I found the forum, and I now understand that solid wood really isn't the best material to use over the radiant heat. Unfortunately, it's already ordered, it's really about the only thing that we could afford, and it's what my wife wants. The up side is that we both love rustic looking wood floors, so things like gaps between the boards, knots, cracks, etc won't bother us much. Even squeeky wood floors aren't that big of a deal. We lived with those for the last 11 years in the 1920s house we had previously and it was never a problem. Not that squeeky floors full of gaps are my objective or anything, but...if it happens it's not a total disaster.

Sorry about the novel-length post, I really appreciate any advice you can offer!

Greg

1) You could use 3/4" pine or fir boards instead of plywood but any of those will work for your screeds (sleepers). If it were me, I'd use 3/4" x 2" solid fir boards, glued and screwed into the floor joists when ever possible and into the subfloor.
2) The sleepers need to be 12" oc and they should be a minimum of 1.5" wide but wider is better if you can.
3) I usually prefer staples but in your case, cleats may be the wiser choice.
4) You need to see the sleepers as that is what you are nailing to so don't cover with felt. You could consider 6 mil clear polyethylene but that could cause problems as well. So I'd skip that and just lay directly to the sleepers.

Most importantly when installing solid over radiant, the radiant system should be up and running before the install and the wood flooring well acclimated. Never allow your radiant system to exceed 85 degrees wood floor surface temperature.

Gary, how critical is it for all of his head joints to land on the sleepers. Can he fudge a little here and there with the 2-1/4" endmatched? Do you think there might be more of a waste factor needing to be considerred due to a possible need to cut more pieces to have butt joints land directly on sleepers?

With strip flooring, end butts do not need to end on top of the screeds (sleepers). The flooring is simply racked out as normal and nailed to the screeds.

Thanks Gary, I honestly did not know for sure. I see one of these jobs on the horizon for a B & B that is being retroed currently with Hydro heat and the builder is a frequent customer .... I know he'll be calling soon and we'll be able suggest a decent solution for their flooring needs.
Thanks again

Thank you for your response. I appreciate you opinions on this very much.

The reason I was thinking 3/4" plywood for the sleepers is that it's closer to an actual 3/4" dimensionally, and it's somewhat more stable (and the cost is probably a bit lower, but I can deal with that). Why would you pick solid fir over plywood?



Thanks, I'll keep an eye on the surface temperature when we start using it. I am curious about running the system before the floor is installed. I've read that recommendation before and I understand why you'd want to do it if you were installing your flooring in the wintertime, when the extra heat would make a big difference in the expansion of the wood, but how would it help in the middle of July when I'm running the AC? I'm planning to pressure test the loops (both before and after the wood flooring is installed, don't want any nail holes), but I'm hoping to get away with not having to actually run hot water through the system until later. The water heater for the radiant system will be installled in the basement of an addition which isn't built yet. It won't be finished enoiugh to install the water heater until next fall, but I'm trying to get the floor done in the existing house so that we can move into that as soon as possible, while work proceeds on the addition.

If you think it's that valuable to circulate hot water before then, I can hook up a temporary manifold to the hot water system in the existing house, but it's not going to work very well with the electric hot water heater that's in there. Do you think this is really necessary, given the climate here in south-central Kansas in July? (hot, moderately humid)





I am SURE glad you asked that, 'cause I'd been thinking I'd need to make all those joints fall on the sleepers. Knowing I don't need to do that will save me a ton of work!!

What do you think about the choice of finish? Is there something else I should be considering for this particular installation?

Thanks,
Greg[/quote]

Solid lumber will hold fasteners better. However, you are correct that plywood is more dimensionally stable.

It is recommended by many manufacturers of radiant systems. However, since you are not using any concrete, in this instance, it may not be needed. It is important to acclimate the flooring well.

You can use any floor finish you wish. With a floor that may be subject to more movement, I think I'd prefer a finish that would not side bond as many waterbased finishes do. So I'd stick to a solvent based finishing system. I have no experience with the OSMO wax finish

My personal prefrence is waterox tung oil for beauty and elasticity plus ease of application. I'm also starting to do my homework on the OSMO oil hardwax ... just looks so good on the floors I've seen and seems to be great for spot repairs and ease of application as well.
just my$.02
Good luck!

I am doing almost the exact same thing as you did. What worked about your plan and what didn't work? I will probably use 3/4 by 2" furring placed 8"OC. And I am planning on using recycled planks to go with the rest of the house. House did the cleats work for you? How about spacing between planks? Did you place them tight or did you leave some spece for movement? Did you hit the PEX? Tell me how it went.

Thanks,

Rich

Hi Rich,

I've taken longer getting started on this then I expected, so I can't give you any results yet. At this point, I've collected all the parts I need, and the old flooring has been removed, but I had to put things on hold to go do some work on another house and that's prevented me from getting going on this one. I'm hoping to get back to it in the next couple of weeks.

I'm using 1x3 pine furring strips (actual dimension is about 5/8 x 2 1/4), which will be glued and screwed to the joists. The flooring is 3/4" red oak, 2 1/4" strips. There will be radiant barrier (reinforced foil) under the PEX, over the subfloor, between the furring strips. I'll be securing the PEX using short pieces of nylon strapping material, stapled to the subfloor.

I noticed you mentioned running tubes 8" OC. One thing you may find is that radiant information sources seem to differ on the recommended tubing spacing. My local plumbing supply place has several people certified to design radiant heat systems (and uses one in thier office and warehouse), and they recommended the tubing be 12" OC rather then 8-10" like I had planned (based on info from a couple of prominant online vendors). Anyway, the local place said their info was based on the most current research and testing. So, I'm going with 12" OC for my tubing.

The one thing I'm a little uncertain about is how far to place the ends of the loops from the wall (where they run through the furring strips). I'm thinking they need to be about 5.5" in from the wall to avoid any problems with the face nails on the first couple of rows of wood flooring. That gives me 1/2" for expansion, and 2 rows of 2.25" flooring before I cross a heating tube. Anyone have any thoughts on that?

Greg

My question...

Who is the mill/manufacturer of the ¾" solid wood your planning on using over radient heat subfloor?


Have you contacted the mill and ask their recommended requirements to install their solid over a heated floor, and maintain a warranty on the flooring?

Mine is generic unfinished from Lumber Liquidators. I doubt it has a warranty.

Greg

Ghouse, Let me get this clear. So you are placing the foil/insulation in the valleys between the 1 x 3's? I am actually using 2 x 3's but the same idea. I was talked out of using the foil (somewhat) and told to use foam insulation, run the pex, and then fill (and cover the PEX)in the void with sand or self leveling concrete. I am also worried about the U turns at the walls. I have no solid idea on what to do there. I do have about 5/8" space in a little space under the sheetrock, but I was hoping to use this to place the return of the PEX. Bottomw line, I have no idea how to place the first row. I got a sample of 1/2" antique oak flooring but the tounge is so small that it will interferer with my paln to use 1/16" plastic spacers used for ceramic tile between rows (to allow room for expansion).

That's right, I am placing the foil over the subfloor between the 1x3s.



Mine is a retrofit to an existing (manufactured) house. There is already reasonable insulation under the subfloor, between the joists. I'm not sure why you'd want insulation on top of the subfloor. You'd only get about R5 from an inch of EPS, if you could get that much in there, and it keeps you from using your subfloor as thermal mass. I can understand adding mass with sand or concrete, but I don't want to do that for my project because of the added weight. I figured that given the 5/8" airspace in there, the radiant barrier should help reflect the heat the direction I want it to go. I presume I'll get some limited conduction at the point the PEX touches it, but I still think it'll be helpful.

One reason I wouldn't want to add insulation (or other stuff) on top of the subfloor is that one of my goals is to raise the floor as little as possible.



My thought is that I should be able to plan the U-turns and return line on the tubing runs so that they fall around the middle of a piece of flooring, that way the nails will miss them.

Anyone that's done these before? Is that how it's normally laid out?



How wide are the planks you're planning to use for flooring? Do you really need a gap that big between them?

Greg

From what I can tell, there is no insulation down there at all. Just a concrete slab, and then 2 x 6's creating a deadman floor. There is then a layer of foil and then the 5/8 plywood subfloor. No insulation at all. At first I was going to cover the subfloor with the double bubble foil insulation, and then contruct the 2 x 3' on top of that. But the Radiantec guy thinks that is a bad idea. He thinks I should glue/nail the 2 x 3's and fill the valleys with pink foam insulation and lay the PEX on that. And then put the flooring down. I would like to use 2 1/2 and 6" flooring to match a really rustic looking floor in my living room. That floor looks really old and my be older than the house (90 years) since there is wood in this house that was likely milled on the site. Since I don't have the heat going through the PEX yet, and since the living room has voids as big as 1/4 inch (and bark), I figured I can give it some space so no need to worry about expansion/contraction.

I just got a call that my insulation that I ordered from Lowes is in. It is that foil one side, bubble on the other. Is this what you are using? I saw you mention that this stuff works best when there is an airspace. The Radiantec guy seemed to say that air is a bad conductor of heat and than I want to solidify around the tubing.