Hello,
I looking for some guidance on subflooring (osb vs ply). I am building an ICF home on the Bruce Peninsula (we get lots of rain/snow from Great Lakes). I will be waiting on a timberframe roof structure until late Dec. The floors will definitely get their share of weather before being closed in.
I am concerned about the weather exposure…the Norboard osb is alot less expensive, but will it hold up?
The subfloor are spec’d at 3/4″, and will get 1 1/2″ thinset ontop for hydronic heating.
Any suggestions?
Thanks in advance,
Mike,
Lions Head, ON
Replies
3/4 advantech or equal. This is an osb type product but much better than the standard fare. This will hold up for months without failing. Nothing else made of wood will.
and drill drain holes.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Another vote for advantech
I used LP High Performance OSB and it made it has been amazing. It went through an entire winter and now an entire spring and summer (plenty of rain) and hasn't swelled a bit. I did put a coat of Thompson's on it... not sure if that helped. I did my garage attic floor with standard 3/4" OSB... coated with Thompson's and after one heavy rain it swelled up some.... especially at the seams. I strongly recommend the LP High Performance... I am guessing it is similar to Advantech, although I have never used Advantech.
hi Doobz26 we did the exact same thing with the LP high Performance OSB, with the Thompsons, with the winter and the spring and the summer with all its rain and yeah - it is still hanging in there. we are happy about that. however just now i am seeing a few spots where it is "popping up" so to speak. do you think this is going to be okay in the long run? the spots are few and non no bigger that 2-3".
i also have a questions for you about the LP - after we put the thompsons on, with the next rain, a fair amount of black streaking was noticeable - more so in the areas that received the most exposure to sun. did you have a similar experience and if so, any guesses as to weather or not this is a concern or what this could be?
I used LP High Performance OSB and it made it has been amazing. It went through an entire winter and now an entire spring and summer (plenty of rain) and hasn't swelled a bit. I did put a coat of Thompson's on it... not sure if that helped. I did my garage attic floor with standard 3/4" OSB... coated with Thompson's and after one heavy rain it swelled up some.... especially at the seams. I strongly recommend the LP High Performance... I am guessing it is similar to Advantech, although I have never used Advantech.
I am not a big fan of LP as a general rule. They have had way too many product failures in my life. I lived right next door to one of their plants and have no respect for their corporate philosophy.That aside, maybe this is a decent product.but the reason for my response to this one is to let you know that Thompson's water seal is mostly a thinned wax solution. It is typically good for only six months before sunshine oxidizes it away and it needs recoating. Foot traffic probably reduces that to a third as long. Might be time to sweep up and recoat.
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3/4" Advantech is your best bet. Not only is it flatter, easier to get tongues in grooves, more weather resistant, it's cheaper than 3/4" T&G plywood. I recently priced it here and paid about $23/sheet for the Advantech, ply was about $28/sheet.
In the olden days, we used to install 1/2'' cdx ply under all floors that received mud bases. Typically the mudbases were 3/4" under ceramic tile.
There really isn't any need to install a t&g system under a 1.5" mudbase. The T&G system was designed as a one layer system for carpeting and replaced the earlier systems of 1x6 diagonal boards, covered with 5/8" particleboard underlayment.
If your budget is real tight, you might consider using only 1/2" osb, square edged. Personally, I wouldn't hesitate in using it, especially if I am using 1.5" of concrete above it.
I'm sure there will be a few people that would freak out thinking about this suggestion...but they've probably never laid an entire subfloor of 1/2" cdx. It works.
jim
fka (formerly known as) blue
I won't freak out - just laugh.Half the OSB I have known would not have enough strength left to pour the gypcrete on top of it after half a winter worth of weather on it laying flat like that with no roof protecting it.
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I wouldn't think about leaving 1/2" osb outside all winter either. If that is what the poster intends to do, I'd opt for the board floor if money is an issue. Otherwise, I'd just use 3/4 t&G osb, which I have left exposed for many months, including a winter. If the entire floor will get 1.5" of crete, that standard t&g OSB could easily survive two hard winters. I would drill the holes as Jeff suggested. Back in Micigan, I used to cut the heat and cold air returns if I knew the deck was going to take a few weeks of rain. Snow really never bothered the deck much....especially if there were drains for the meltoff.
I don't want to get into an osb discussion because it's obvious that some regions are selling a vastly inferior osb product.
I would consider running two layers of SE 7/16" osb though, if I didn't want to feel the sponginess of the one ply as we did the mechanicals. I'm actually liking Frenchy's suggestion of dimensional lumber best if his cost figures are accurate. I don't see any reason for spending extra money on a rough subfloor that will get 2" of crete as the finished surface.
fka (formerly known as) blue
There are some good points for the boarded floors per frenchy on this one
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I agree Piffin. Its hard to give that wacky guy credit but what's right is right. I'm probably one of the few in here that actually like the old Canuck (can I say that without getting booted) but I tend to like old geezers that are eccentric old characters. I'd probably enjoy a tour of his place.
Frenchy, if you aren't selling lifts anymore....what are you selling?
jimfka (formerly known as) blue
Shellac
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ba dum bum!
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
and a bow!
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Jim Allen,
Myself.. I spend my day trying to find a suitable position that will yield the sort of income someone my age needs.. The Market for Telehandlers here in Minnesota is badly saturated and it will likely be more than a decade before someone can once again make a decent living selling those.. Home builders telehandlers last 25 years easily so even the first ones I've sold 17 years ago are still out there cheaper to fix than to replace.
I've had plenty of offers to be a manager because of my experiance but frankly I'd make a miserable manager.. I do know how to sell and I really enjoy doing it so I think I'll hold out for a bit longer.. I do however think that my days of selling construction equipment is over..
The only jobs I'm offered doing that involve selling skid steers (bobcats) and if you knew just how butt ugly and hard work that was you'd feel like I do, leave those jobs for the new kids just starting out.. Selling heavy equipment is really about long term relations. I have 10 or 12 years at most left in my working career and that's not really enough time to develope relations with customers sufficent so that you can make a decent living..
The only heavy equipment customers who buy from new salesmen are those who make price the only decision. To be successful doing that you must sell your equipment at a price that ensures you are the cheapest. Doing that means your income is marginal at best..
I'm out here in northwestern Washington State and we know a little about rain out here. We always use OSB sub floor in any weather. In the winter when we know it will be wetter, we might pay a little more and get Weyerhsuser Gold Edge but in the summer we might save and get something cheaper. Either way I stay away from plywood. We have had problems with de-laminating.... much more so than with OSB. Worst case with OSB for us has been that we might need to run a belt sander over some of the joints before carpet. If you're pouring 1-1/2" of thinset, no need for the sanding.
Mike,
Another option? How about solid wood?
Wait,, I can go to local sawmills and buy softwoods like pine etc. for less than 15 cents a bd.ft. that's the price they sell it to pallet mills for.. here's the economics. a sheet of plywood, OSB is 32 sq.ft. so 32 bd.ft of solid wood will cost you around $4.80 cheaper than you can buy 3/4 inch OSB. let alone plywood..
You might also be able to buy some overun hardwoods for the same price.. once it turns a little grey even the nicest hardwood doesn't have much of a market.. Wood sold to pallet mills is what they call mill run it will have some knots etc.. but they have to be solid.
Here's a real trick. If you have the wood sawn at 6/4 (inch and a half) then you can put it down and install the pex from underneath.. what you do is buy aluminum flashing and run it over a bead roller. the bead roller leaves a groove for the pex used. then use a roofing nailer to nail the aluminum up (roofing nails are an inch and a 1/4 the wood is an inch and a half.. )
as long as the finish floor has nails that are less than an inch and a half you can put the finish floor down safely..
the potential savings is massive.
Oh, and it's what I've done..
Frenchy, I was also thinking that if he was opposed to 1/2" osb, he might lay 1x6 boards diagonally, just like the good old days. Your idea of using heavier framing lumber merits some discussion.
I don't know enough about radiant heat, but I thought the 1.5" of concrete acted as a storage medium and was an important component of the heating system. Your suggestion seems to eliminate that. Maybe I'm misunderstanding something.
I'm also curious about how you would treat the joints if you didn't lay a mud base. What is the finished floor covering.
jimfka (formerly known as) blue
Hi Blue, er, Jim,Welcome back to Breaktime! I'm reasonably certain Frenchy used hardwood for his finish floor, with shellac on it. Just ask him to tell you about it ;-)Bill
Jim Allen
This is a subfloor right? Well if he buys sawmill lumber it will be green and it will shrink. not in length, not much in thickness but in width a fair amount.. if he butts each board tight to the next one he will wind up when the wood fully dries out with small air gaps between boards.. (ever tear up the finish floor over an old plank subfloor?) In my case it's about 3/8ths to 1/2 inch Now if I were to put carpet over that floor I'd use 1/4 osb or luan plywood to keep from telegraphing the gaps to the carpet.. if I use hardwood floor that's not an issue.. same if I tile over it..
Those gaps are what helps this system work effectively.. Don't lay the boards diagonally.. three reasons. first you are increasing the span of the wood roughly 1.5 times. so if he spans say 12 inches and you put the wood at a 45 degree angle from the longest point to the longest point you are spanning 18 inches.. second your labor to install will go up dramatically, and third you'll have a lot more waste wood..
The only reason to install wood diagonally was to provide a better brace for the old balloon framed houses built that way.. since they did it on the walls they also did it on the floor..
The concrete helps and hurts infloor radiant heat..
Yes it's a storage medium but that means that the system is extremely slow to react to changes.. it would be normal for a temp rises to not be felt until breakfast if raised at dinner time.. Since he's using ICF's he has plenty of heat storage available to him already. In addition should a leak or blockage occur it's far simpler to pull down the bottom side of the floor and access the tubing than to attempt to break up concrete and go looking for it..
There are a couple of other things I do to make my system work for me. I put reflective Icsoanurate foam under the whole system.. that does two things.. first it sends the heat upwards more efficiently warming your feet rather than the heads of the people below. Second it makes the floor/ceiling really quiet!
That all makes sense to me Frenchy. I like the idea of having acess to the tubing for repairs but I also like a mudbase. I've done several 3/4" mudbases for tile and I've always loved the solid feeling after the mud cures.
In this case, the gaps that would occur from green wood would be meaningless if he pours a 1.5" mudbase. I've always laid 15#felt prior to the mesh which acts as a break between the subfloor and mudbase. I suppose the shrinkage would occur in the green wood without affecting the mudbase.
Bill, thanks for the welcome.
jimfka (formerly known as) blue
It is better to not use particle boards for flooring that will get thinset. Exterior grade plywood is usually recommended. That goes for all types of particle board to my knowledge.
You are the first one to mention particle board here.You know how often plywood delaminates, right?
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I considered particle board in the general sense here. To me that means MDF, OSB, and various forms of chipboard(larger particles), such as sturdi-floor.
In my experience, none of these get recommended as a good substrate for thinset and eventually tile.
I believe lauan falls into this category too.
I have no experience with advantek. Perhaps I have something to learn here?
In any case, I have consistently found exterior-grade plywood to be recommended as a subfloor that is appropriate for thinset and tile.
Actually, I don't know what you mean about the frequency of plywood delamination. I'm all ears.
Also, I am getting more hesitant to use any specific term when discussing construction materials. It seems that every day someone invents a new angle that obscures comparisons. Therefore I used the term particle board, which covers a whole spectrum of wood chips and epoxies (glues) formed under pressure. I believe all of the particle board choices have been used as bases for tile.
The particle boards are not ever considered structural AFAIK,
The strand boards are, and given nearly equal billing with plywood in that capacity.Plywood has been seen delaminating more and more often over the past 10-15 years, making it far less trustworthy in a challenging use such as this regular and extended wetting before ever seeing the covering gypcrete.Advantec is a nigh quality OSB using higher pressures and better waterproof resins to glue it up so it is widely recognized for withstanding extended soakings.
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I believe particle board is frequently used under tile,although nobody recommends it. Here I mean the MDF-type particle board. My comments were addressed with that in mind. In spite of the good advice given here, I believe particle board is very attractive to homeowners, hobbyists, and hacks. Thirty years ago, I built a kitchen countertop, with the best materials I could find. I used 3/4" MDF under the tiles, which were high quality, as well as the cast iron sink. I did not spare expense. I sometimes wonder whether that counter top held up, although I have learned that MDF is not the right product in this application.
This is a learning process. Think about all the lawsuits concerning OSB in the last 20 years. Everybody thought they were doing the right thing.
I recently also thought that a higher-priced, higher-quality OSB product (Sturdi-floor) available in big boxes was a great choice for a second layer of floor in bathrooms under tile. After installing it, I read the labels on the sheets, which were not very legible. They said that the product should not be used under a tile floor. I ended up adding a third layer, which was exterior grade 3/4" plywood.
I assume that advantek is a better product for this application. Time will tell. Often, today's better product is tomorrow's failure.
Finally, my gut feeling is that delaminating plywood is a problem associated with cost-cutting and a drop in standards. There is a long history of plywood being a fine product, even though I now regularly see inferior plywood products delaminating, especially in hardwood plywood veneers. A couple of years ago, I was installing sublfloors and realized that I could no longer rely on the sheets to be either square or dimensionally accurate. I thought it was a sad sign of decline.
I'm not sure where the talk of tile crept in here. This job in question is a subfloor for a thin gypcrete tho he starts out using the term thinset.But no wood base is appropriate for under tile directly. I you are adding an underlayment to the subfloor, it should be a CMU board product, or a mud base."This is a learning process. Think about all the lawsuits concerning OSB in the last 20 years. Everybody thought they were doing the right thing."I know more guys who have refused to use OSB or Waferboard all those years than I do guys who have used it thinking they were doing the right thing. So I would not agree with using the term, "Everybody" except in a generic sense here.
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But no wood base is appropriate for under tile directly. I you are adding an underlayment to the subfloor, it should be a CMU board product, or a mud base.
In the scenario I was describing, I was going to add hardibacker over sturdi-floor.
I found the hardibacker to be not totally flat to the sturdifloor once screwed down, although the sturdi-floor was solid and flat. In other words, even after screwing down the hardibacker, I could push down with my hand in some spots and see movement. I decided that this would cause problems with tile over time. So I pulled up the hardi, added a layer of plywood, and proceeded. Hardi recommends thinset under their product, and the thinset I used recommended exterior grade ply, and said not to use particle board-type bases or lauan.
So here is my floor: Original 3/4" ply over 2X10 joists @ 16" OC, 3/4" Sturdi-floor over that, 3/4" CDX ply over that, LM thinset, Hardi, thinset, and finally the tile. It makes for a thick floor, but I have the ceiling height to handle the extra inch or so.
Concerning your other comment, I was referring to huge lawsuits concerning the use of OSB, especially in the northwest, where the OSB delaminated. This was a problem that affected tens of thousands of homes.
Just for curiosity and to clarify - Did you not have adhesive or thinset under that hardi? And how often did you have it screwed? Hard to imagine it flexing between screws when itis glued too.
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I had a very flat and stable floor. After strengthening and adding support to the floor joists in the basement, I put a second floor in the bedroom, closet, and bathroom areas.
The house was mostly well-framed, except for one problem. The beam that holds the main floor up was not properly located under the columns (short walls) that hold up everything above. Bottom line, after about 20 years, the house was going through some contortions. I spent six months slowly raising the sagging areas, using about 16 jacks in the basement. I then added significant supporting walls and corrected the results, symptoms, and causes. This left me with some squeaky floors. I did the usual screw and glue and the result was fine.
When I finished the master suite, except for the bathroom, I had to stop procrastinating on what to do about the sturdi-floor. Since it was screwed and glued, replacement was not an option as long as there was a reasonable alternative. I also did not want to risk tile popping up. I tried putting hardi on the sturdi-floor, to which I would be able to add the thinset and tile. I figured if any moisture got through, by the time it got to the sturdi-floor, it would not result in damage to the tile.
This was an experiment to see how the hardi would work to solve my problem. I was not satisfied with the result. As I said, it was spongy even after being screwed down to a solid two-layer subfloor with screws on a six-inch grid. I previously used hardi only on walls and that worked out fine. I did not want to take the chance of having a spongy floor that would eventually cause cracks in the tile. I did not want to put a thick mud base over the hardi since I had already raised the floor as much as practicable. I did not want to ignore the warning signs on the sturdi-floor or on the thinset product that said not to use the thinset over OSB-type products.
So I removed the hardi, installed a third subfloor layer, and used thinset on the hardi as their instructions require. This was topped off with suntouch mat embedded in thinset beneath the tile and turned out solid. When I do this again, I will use ext ply as the second layer of subfloor in the bathroom for sure, maybe on the entire floor.
If I didn't get my point across, I am saying that I did not trust the hardi enough to fasten it permanently to the sturdi-floor, which proved to be a good decision. Although it seems counterintuitive, the hardi does flex a bit in some places even when screwed on a 6" grid. That is unacceptable for a tile floor that would sometimes get wet as people walk out of the shower.
So you did not use thinset under the Hardie, which is the reason it felt spongy. You can't blame the product for not feeliong solid when you didn't install it in that way.Now then - a lot of your comments had to do with making the substrate strong and deflection-free. But there is another reason for using a mud base or other CMU board under tile. That is because the wood bases move differently than the masonry products with changes in temperature and humidity. That can create shear stresses that break bonds.
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I didn't use the thinset because a: The information printed on the sublfloor said not to use it and b: the thinset instructions said not to use it over OSB-type material. I was attempting to experiment to see if I could get the hardi to hold tight enough to avoid putting on another layer of floor. I found out that it was too spongy for my instinct. I don't blame the material. The deficiency was mine in not reading the instructions on the flooring.
Now, with thinset on plywood, the hardi has formed a very strong and stable floor. It feels almost as strong as a concrete slab the way I have built it. Next time though, I think I will try to float a mud base.
Sasquatch, I'm shocked! I cannot believe anyone would go to that much trouble to use hardibacker. Hardi has really put one over y'all. I find it ironic that you'll double your material bill, double your labor bill and then still have to add the hardi panel, with thinset, rather than to put a simple mudbase down.
That is marketing power if I've ever saw it. Hardi has really snowed the buying public over. They claim that their product makes it easier to install a substrate for tile, when in fact their warranty requirements make it significantly more costly both in every way possible.
The biggest irony is that the finished product (the substrate) is significantly weaker than the system that they are trying to replace. Installing a "drypack" mudbase is actually a very easy thing to do. You yourself commented about the Hardi product being wavy after installation. That would never happen with a mudbase.
After 30 years in Michigan, I've yet to see a professional tilesetter using Hardi (or the other company ) panels.
I guess mudbases are just another one of those "lost arts" heading toward extinction. Good grief....I sound just like the old farts I used to make fun of LOL!
Happy tiling.
jimfka (formerly known as) blue
Actually, Jim, I have installed several mud bases in custom showers and they turned out very well. Even the bathroom mentioned has a custom shower, completely sealed with chloraloy and noble ts. I just never considered a mud base for an entire bathroom floor. I will consider it for the next house I build. Although I am getting to be quite an expert on sloping shower floors, I actually hate to try getting large areas acceptably flat with mud. It is a mental strain for a perfectionist who does not do it every day.
In any case, I will stick to using hardi on walls, along with durock, depending on the situation. Both have their uses. I like how I can make precise cuts in hardi, but like the stiffness of durock.
Sasquatch, it's actually a lot easier to get large areas flat and level using the dry pack system. Its ten times easier than trying to flatten it out and make it perfect with hardi cement boards.
The technique is to set up screed rails and use screeds to pull the material level after doing a quick rough troweling. If you use a 6' screed, you have to set rails up every 6'. That seems to be my limit for workability. It's quite easy to set up rails. The last time I did it, I just used 6' strips of 1x1. I've used small sections of copper pipe. The possibilities are endless.
If you are laying cement board, you have to lay down a bed of thinset to "shim" out the low points. The problem with that is that you don't really know where the low points are, so you end up putting a uniform layer of thinset on over everything. That leaves the peaks and valleys intact.
The mudbase eliminates that quirk in the system by leveling everything out from the top, which is exactly the place where you want a flat perfect surface. Some areas of the base are 5/8", some are 7/8" but you don't know and you don't care. All you know is that the top is flat, level and ready for an easy tile installation.
I've also done the sloping shower base. I didn't do anything more than float it down to the drain by eye. It worked fine. I doubt that I spent more than ten minutes fussing with it. Just dump and form....there really isn't much science to it.
jimfka (formerly known as) blue
I look forward to doing the mud base next time. I assume shooting for one inch will not be too thin for a stable installation.
I've only done 3/4". That's whats been done for decades in MI. We put a layer of 15# felt, metal lathe, then lay in the mud, which is only damp enough to get a snowball to stick together. It's easy. I know that because I've done it and I'm not that good at mud.fka (formerly known as) blue
Thanks for the info, Jim.
I had previously assumed that 1-1/2" would be required. I guess I could have saved myself some hardi. There's always next time!
Whoa...wait Sasquatch.
I was never running any radiant heat through my mudbase...I was only laying a 3/4 mudbase as a substrate for the tile.
I hope I haven't confused the two different installations in our discussion.
jimfka (formerly known as) blue
No problem. I haven't decided how to do the radiant yet. It will be a couple of years, assuming I live that long. My plan was to do a lot more research on that subject in about a year. It seems the technology moves along so fast that what's best today may not be best tomorrow.
The house I am designing is a passive solar. The walls will be similar to a Mooney wall. I am planning to use 2 X 6 plates with alternating 2 X 4 studs, inside and outside so there will be minimal wood touching wood between the exterior and the interior. It will have some type of blown insulation. Over half of the house will be on a slab. The other portion will have a small basement for utilities. The plan is to have the radiant tubing in the slab portion. If the technology improves, I may use a full basement. I have been designing this house for about ten years, and still can't make my mind up about the foundation. I have even considered a regular basement with a 6" concrete ceiling/floor, although that would be expensive to build.
The latest idea ricocheting around the inside of my skull is to have I-Joists with a standard subfloor and then a thick mud bed in the zones where I want the heating coils, such as the kitchen, bathrooms, and other living areas. This could get complex as far as framing goes, so it will probably not happen.
I don't like the idea of having the radiant tubing under the subfloor, although I can see that that is one of the simplest choices.
Sasquatch, don't underestimate the ease at which a good framer could frame for varying level floor systems.For many, many years, we were forced to drop large sections of floors for the 3/4" mudbeds. It got to be second nature. It takes a few minutes of forethought but in most cases it doesn't involve much more than five hours extra work on 300 hour house. That equates to about $300 labor. I dont think that is "too much difficulty" for a custom frame.In MI, we build over basements and if you wanted half the house dropped for 1.5" of mud, we would build up one half with an extra sill plate. The joists would break over the beam and one set would get a second block to raise them up. Do it right, then happily live in it without regrets.fka (formerly known as) blue
That is an "elegant" solution, as it would be called in the world of mathematics - straightforward, simple, effective.
nothing less that Advantec by Huber will do that for me.
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ADVANTECH!!
I have framed through many New ENGLAND winters. Some decks left somewhat covered (uncovered) until spring, nothing beats advantech. Forget the price you won't regret it.