particle board over 2x6 tongue + grv [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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09-05-2001, 11:39 AM
I have an area about 175sq ft that I'll be putting Saltillo tiles on. I plan on using 1/4 hardibacker. I'll be putting this on a particle board floor that is on top of 2x6 tongue and groove. There is no vapor barrier underneath the house, and I can't get to this section to put one in. However, it is very dry here. I have read several nightmarish posts about particle board. Could this be another if I move forward? Is there another solution to ripping it out?

Any comments would be appreciated.


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John Bridge
09-05-2001, 04:08 PM
Hi Kevin,

I'm going to vote for removing the partical board and replacing it with some kind of backer board.

Let's see if we can get some more votes. We rule by consensus here.

09-05-2001, 04:31 PM
Hmmm...does this matter?

I looked again to be sure and my hunch was right. It's not particle board. It's either OSB or wafer board. I can't tell because there's so much of that yucky foam and glue from the foam backed carpet that was unfortunately glued down.

Does this make a difference?

For those interested, and as promised (from an earlier post) about Ultimate Frisbee is going in the "Mud".


Bud Cline
09-05-2001, 06:44 PM
Waferboard, strandboard, chipboard, particleboard, barnboard,'s all the same useless stuff when it comes to flooring, moisture or the potential for moisture.

09-05-2001, 07:20 PM

Hardibacker says you can install their 1/4" board over "exterior grade OSB" over joist no more than 16" centers. To be honest with you, I'm not exactly sure what qualifies OSB as "exterior". Again, to be honest, I have installed over OSB at customer request. (did not want the additional expense of removal/replacement) Don't know of any problems to-date (oldest about 3 years) however, if it was my house, the OSB would probably have to go.

For what its worth.

Bud Cline
09-05-2001, 07:39 PM
I've done the same many times. Usually that isn't my decision.

Rob Z
09-05-2001, 08:27 PM

I would put backer board over SOB only with the insistence of the customer after all the disclaimers and caveats I could give.

I have no experience with Saltillo, but i know from John that it is a weak tile and needs a very firm substrate.

John, does this sound beefy enough for Saltillo?


09-06-2001, 11:25 AM
OK, I ripped out the board last night. It was much easier than I thought, kind of fun, too. But now we have a new and improved problem.

My floor is a post and beam thing. Don't know the technical name, but here goes. I have a ranch house with no basement. The crawl space is about 3.5 feet. The floor is support by cement footers with 4x6 posts supporting 4x6 beams. I didn't get an exact measurement, but it seems they are about 3 maybe even 4 feet apart. On top of this is the 2x6 tongue and groove.

How can I convert this into a stable enough floor? What should I do underneath, and what should I do on top?

SIDE NOTE (may not be important):The particle board (SOB) was 3/4 of an inch. The hardwood floor in the next room is about 7/8 of an inch higher than my current 2x6 tongue and groove. So we have that to work with to make it flush (which isn't a huge prioritiy.) I got Cs in grammar in junior high.

Rob Z
09-06-2001, 02:35 PM

Congrats on the SOB tear out. You are now on your way to being part of Anti-Particle Board Club. It's a prestigious group, I tell ya.

Did you mean to say that the 4 x 6 posts (vertical) are spaced 3-4 feet apart under the 4 x 6 beam (horizontal)? If so, what is the size, span, and spacing of the joists (sit on top of the beam, horizontal, and taller than they are wide).

We have a gen-u-ine expert around here to deal with post and beam Q's. His name is CX, and he'll be along later tonight.


09-06-2001, 03:09 PM
Rob, your post makes me think I'z in trouble.

There are no joists! The beams are horizontal and the posts vertical, I got that. But the 2x6 t&g lays directly on top of the beams at a 45 degree angle. The span of the beams that the 2x6 rests on are about 3 or 4 feet.
Something like this: (x -- post, === -- beam)

"a" is 3-4feet away from both "b" and "c".

2x6 tongue and groove run at a 45, like 2 to 2 to 2.

I'm at work now, so I can't go measure, unfortunately. We'll get the exact measurement tonight. But I don't think it makes a difference.


Right, it doesn't make a difference, because since I'm dealing with Saltillo, I'm probably going to have to crawl under there with the spiders and monsters and put in bracing every 16 inches perpendicular to the carrying beams. Like this: ( ``| - bracing 2x6 with deck hanger)
| | | | | | | | | | | | | | | | | | | | and so on..
| | | | | | | | | | | | | | | | | | | | and so on..
Right? Will 2x6 work here if I use the metal hangers, or do I have to bulk up and go for the 2x8? By the way, the spacing is not accurate in the diagram, I would use far fewer, or whatever would bring me to 16".

Maybe CX can help me there. I don't think I want to put any more posts with cement footers, but he might tell me to that, too. Might as well put a vapor barrier down while, I'm there, right?

You guys rock. If you're ever in Bend, OR, beers are on me!

Rob Z
09-06-2001, 05:04 PM

Wow! Your computer drawing skills are excellant. I can't even draw a big "Z" to respond to Jim Buckley. Oh well...

How old is your house? We are definately gonna have to let CX scratch his head over this one. It's outta my league. You are going to have to do some serious framing work to get things beefy enough for tile.

Christina and I travelled through Oregon on our honeymoon. We really liked it.

Careful what you say about that free beer thing. There are a lot of beer drinking tile setters on this board that wouldn't mind an excuse to make a trip out west.


John Bridge
09-06-2001, 05:06 PM
Okay, guys, I think I'm sort of, kind of getting the picture.


Seems to me in Bend you would have a lot of rock and your footings ought to hold. The post and beam thing has been around a long time in different parts of the country. I think you've got a pretty substantial subfloor, even though there are no joists.

I think maybe Rob and the other backer board guys might want something besides backer over the tongue and groove, although I've heard "da Man" Dave Gobis mention that he used to go over floor boards with backer and had success doing so. What do I know? I'm just a worn out mud man.

Bud Cline
09-06-2001, 05:15 PM
3/8" ply and then 1/2" CBU. This will bring the finished tile in proud of the finished hardwood in the next room by about 5/16", typical. Schluter edging maybe or 1/4" wood transition.

Rob Z
09-06-2001, 05:26 PM

the only thing that I can remember i worked on that was somewhat similar to this was an old building in Wash DC that had T&G heart pine flooring laid directly over 16"oc joists. That flooring was perpendicular to the joists, not at a diagonal, and thus wasn't as strong. But the 3- 4 foot centers you have I really think are gonna be a problem that an extra layer of 3/8" ply won't solve.

That job in DC...that floor deflected quite a bit, and that was over just 16"oc!


09-06-2001, 05:27 PM
Hey, Rob, while I sincerely appreciate the compliment, let us set the record straight: Only thing CX is an expert at is being CX, which he does about as well as it can be done. There are other catagories where I qualify as pertty good and a whole lot of catagories where I know enough to stay out of trouble most of the time.

That said, I don't think the existing situation is all that bad. I was hoping John would weigh in here with what he was going to require as the correct way for the Saltillo to be set in this situation, but I see he was kinda non-committal (over to the deep end I woulda said wishy-washy). I see the first problem being the available vertical space Kevin has to work with.

As you know, those of us who do Saltillo (me incorrectly, the others correctly) want an inch and a half below finished floor to work with. Keith indicates he has 7/8ths of an inch. I don't know about setting Saltillo over anything other than mud, and for mud we gotta have depth.

I'm not a guy with any tables for allowable flex for something like Saltillo. What is required? If it's L/360, I wouldn't doubt he already has it, depending upon what that T&G 2x6 material is. If the 4x6 beams are set on 36 inch centers, and the posts the same, I wouldn't doubt it. If more stiffness is required, he can get that with additional bracing under the floor, but still is left with only 7/8ths inch to work with.

I gotta go talk with a customer. Be back later. I say we kick around how he is going to deal with the tile, then we can decide what to do with his sub-floor.

My opinion; worth price charged.

09-06-2001, 05:35 PM
I'm looking forward to you guys kicking around my problems. Kick away. Haha-aha-ha.

As far as the height issue, I'm willing to have an oak transition. With

09-06-2001, 05:43 PM
In addition to post and beam, now we can talk about Post and "Oops!"

Anyway, to continue above....WITH the 3/8 plywood and 1/2 CBU (what is that?) and then thinset and saltillo, I am estimating we'll be about 3/4" above the hardwood, maybe 7/8"?

Can't I just run an oak strip 1x4 and taper down to within 1/4" of the hardwood. Grandma doesn't live with me. This is not something I'm too concerned about. Though the implications could be more severe in the kitchen, I guess. I'm pretty sure it work out there, too.

I'm most concerned about the floor being strong enough. But, you guys are the ones kicking around my problems, so I'll let you sock that one up a bit.


Rob Z
09-06-2001, 07:00 PM
Hi Kevin

OKAY... I missed the 2 x T&G....I was thinking 1 x T&G!!

Still, I am having a hard time visualizing this floor.

Here's what I would do, if it was my job and tile absolutely had to go on it and it wasn't gonna happen to have someone crawl down with the snakes and the spiders to do framing work.

I would add 5/8" or 3/4" T&G plywood over the existing floor, screwed and glued. I would then use DITRA (read about DITRA at for added insurance against deflection. The use of DITRA will not be a budget buster for the size floor you have.

I would then set the tile with the best thinset I could buy.

I would skip the use of backer board, going with the argument that backer boards do not add any structural value to the floor (the subject of another debate, Kevin).

This may be overkill.
Some of my friends here on the Forum have accused me of this before, and I'm sure it will happen again.

Contact Peter Nielsen at Schluter (he is th technical director) and ask his advice about the use of DITRA in your house.

That is what he is there for. He is a straight shooter, and was a fine tile setter before leaving the dirty work to wear a suit.

Now I'll await the arguments that will follow....

Rob Z

09-06-2001, 07:03 PM

CBU - cement backer unit, generically refers to all brands of this type product. Technically, hardibacker is a cement fiber unit, homogenous throughout. Most of the others are cement sandwiched between layers of reinforcing fiberglass mess. They are all designed to accomplish basically the same thing.

I've never set Saltillo over a pier and beam floor, but with the layers Bud recomends in combination with the existing support structure, I would be tempted to "go for it." However, you might want to let the "gang" kick it around abit more!

John Bridge
09-06-2001, 08:32 PM
Well, I never thought mud was an option here.

2x6 T&G is pretty substantial stuff. It suffers from the lack of integrity that all boards do. The plywood will hold things together and provide a good base for the CBU. Saltillo tiles don't require anything different than any other tile.

If the floor springs (bounces), the installation won't make it over the long haul. If it's stiff, it ought to be okay.

And again, the cost of my opinion is even cheaper than Kelly's, which is free.

09-06-2001, 09:28 PM

I am NOT entering into a discussion of how to set tile here, not with this group.

That said, I am going to make some assumptions. I am assuming that it is acceptable to set Saltillo on a base other than "mud". I am assuming that CBUs add nothing to the structure of the sub-floor, but only provide a suitable surface for adherence of thinset. I am assuming that a product like Ditra serves the same purpose but is thinner in verticle profile.

If all that is true, the optimum situation for you would be to be able to put the thinnest suitable covering over the existing 2x6 subfloor and set your tile on that, giving you a nearly flush match with your adjacent floorings.

I wanna know for sure what is the spacing between the floor joists/beams, the general dimensions of the floor to be tiled, the direction the beams run below that floor, and whether or not you are willing to add structure under the existing sub-floor. Three and a half feet of crawl space is quite adequate working space. Is the floor insulated between the existing beams? Does the 2x6 floor feel solid as it is now? Are the 2x6s screwed to the beams (if not, you'll wanna correct that no matter what else we do).

Rob, John, Bud, Latney (I miss anybody?):

If the existing 2x6 sub-floor can be made suitably rigid, is there any reason Kevin could not install something like Ditra directly over it and tile over that?

Inquiring minds want to know.

09-06-2001, 09:54 PM
Hi cx,

No you shouldn't bond Ditra to the 2x6 planks.Anti-fracture or not,the boards can warp and push up the Ditra and tile.I wouldn't even want to get it in contact with thin-set,afraid of the warping.Me?I would,of course,opt for a mud bed over tar paper after screwing down the floor.That's because I'm partial to mud floors and suggest them whenever possible to do so.

I don't like the fact that there's such a large span under these planks.This is one of these floors that we'd have to personally see and walk on(and drink beer on)to assess it and decide how to prep it for tile.

09-06-2001, 11:05 PM
OK, here's my address:
1260 NE Dempsey, Bend OR.
Busch Light Draft OK? Miller?

CX here's the info you requested:

The beams are 4 feet apart. The general area is two rooms:
ROOM #1) 9+ feet by 15+ feet shown below. (view from above)
|============= == are the beams

The second room is about 5 feet (varies to 8) by 20 feet.
Try to follow this:

___ = a five foot section.

... = an eight foot section.


The two rooms connect where the ====1====1 would meet if you put the rooms side by side. Got it?

The other information you requested:
1) Insulated? No.
2) I don't think it's that solid. It doesn't bounce, but when I jump the dust jumps too. You CANNOT actually feel it under your feet though. It may or may not skip the cd player...
3) The 2x6 t&g are not screwed in, so I will do that. 3.5" deck screws ok?

I am willing and able to go under the house and brace the beams. I don't know how to do it. Would I just hang a 2x10 perpendicular to the beams on either side of the room, and then hang another 2x10 or 2x6 parralell to the beams and then screw the 2x6 into those? What is the best way to do this?

NEW NEWS: Listed in a previous post, the 2x6s run at an angle. In the big room (9x15), the boards run perpendicular to the beams. Just so you know. I found that out tonight when I pulled the particle board in that room. Wacky.

I hope this isn't one of those jobs that the more you read the less you understand what the hell's going on. Beers are still on me...

Thanks gentleman.

09-07-2001, 12:03 AM

We can get beer anywhere. Will trade information for fly fishing. Guess you're a little far from the Umpqua, but I know you got plenty water close about.

Brain's a little fuzzy just now. I'll ponder some more and comment manana. Not looking as good as it first did, though. Also looks like you need to order a whole lot more than 175 feet of tile, unless I'm fuzzier than I think.

Further opinion tonight would be worth even less than price usually charged.

09-07-2001, 12:41 AM
my brain fuzzy 2.

Yes, I think when I wrote the 175sq ft I was talking about one room. But, now I want to do both rooms, so I'm looking at more like 175-185 or so.

Doesn't look good, huh? Well, I'm up for anything, under the house, spiders, or even dropping the idea of tiling. Yikes!

This 2x6 t&g doesn't look so bad. Maybe I'll throw some Behr's stain on it and call it good. Thanks for all of your thoughts everybody. I really appreciate it.


Rob Z
09-07-2001, 06:57 AM

In all the MFR's specs and the TCA specs that I am familiar with, no one allows for the use of tile over any joist spacing greater than 16" oc (except for DITRA, with 2 layers of plywood on 24" oc).

None allow for the use of any products or tile over dimension lumber.

A three to four foot span, even with 2 x T&G, seems a lot to me.

I would definately try P. Nielsen at Schluter. See if can come up with something for you. You're not anything but the phone call to give it a shot.

Off to work now. Will check in later.


09-07-2001, 03:17 PM
Hello everyone,

Thanks for checking in. Rob, I phoned Peter Nielson, and emailed the tech email address. No one has gotten back to me unfortunately.

If no one has anymore ideas because you have to feel the floor yourself, perhaps I should get an installer in here to check it out. Problem is, I don't know enough TO KNOW if they know what the hell they're talking about. Ya' know? Any suggestions on what I should ask to measure them up? Is there an objective/measurable standard that I should ask for when bracing the floor? Is it different for Saltillo?

If anyone has any bracing techniques, know that I am more than willing to go down there and do it. I just don't know what's the best way.

Thanks much...
It's friday.


Bud Cline
09-07-2001, 03:31 PM
Is there any noticeable flex (bounce) or deflection in the floor?

I kept seeing this structural configuration in the back of my mind and it seemed very familiar to me. Today it came to me. In years past I have built many pavillions (group shelters) in parks and this is the configuration used for the roofs. 4" X 6" on 4' centers decked with 2" X 6" T&G pine. They were hell for stout but I'm sure there was no live load figured into the assembly. This was in Texas so there also was no snow load either.

This doesn't help much I realize but I do remember how strong those roofs were. Still an iffy situation but I'm kinda leaning toward the possibility of it working fine.

I wouldn't know where to find specs that report loadability of structures with floor members 4' on center.

09-07-2001, 03:32 PM
Haven't forgotten ya, Kevin. Gotta use up this here daylight while it's not full of falling water.

Be back later. What about that fly fishing?

Rob Z
09-07-2001, 03:38 PM

Peter N. has always returned my calls and emails, so I'm sure you'll hear from him.

Careful promising fly fishing to CX. He'll be there "in no time".


09-07-2001, 03:41 PM
I like the positive attitude. Keep it coming.

I can't talk the talk, but I know the fishing's good. I'm in sight of the Deschutes River right now. We also have a number mountain lakes, a few resevoirs, and two or three other good rivers. I'm from Ohio, and I really need to step it up and get into this fishing thing. I've gone a few times, but got skunked. I did some bass fishing on the John Day with a fly rod, and caught a few. That was really fun, and it's a beautiful river. You can't lose out here. Steelhead will be running soon, so if you hurry you could do some real fishing.

I'm not saying anything about Texas fishing; it should be pretty clear by now I SHOULDN'T say anything about fishing. I don't know shin from shitola...err something.

Thanks for keeping me in mind.

Rob Z
09-07-2001, 03:43 PM

The dilemna of who to call is a big 'un.

I am willing to be flown to Oregon to look at this, particularly during any hunting season.

On a serious note, there are ways to determine how much flex is in the floor. We need CX back to explain that machinist dial indicator he has. That can be rigged up to measure how much the floorboards flex between the joists while under a load.

CX? what's that thing again?

there was a picture of the set up in a Fine Homebuilding about a year and a half ago.


09-07-2001, 03:44 PM
Sorry Bud, I forgot to answer your question.

The flex is minor, I think. If I jump up a foot in the air and come down, yes 4 feet away, a book will bounce too. I weigh 400 pounds, though.

OK, just kidding, I weigh 190. Not kidding about the book. But when I bend my knees and bounce up down without actually leaving the floor, it feels very solid, and no it doesn't seem to bounce at all.


John Bridge
09-07-2001, 04:39 PM

A tile substrate can't stand a lot of bounce, and it won't handle much over zero flex. Oh, it will for a while, but not over the long haul.

I believe in the power of positive thinking, too, but we've got to be pragmatic here. I hope the brains around here can engineer something for you. Hell, some of these guys graduated from high school, and some even went to college. Hell, some even graduated from college.

09-07-2001, 08:26 PM
I will have any and all to know that I have personally drove by soma the biggest universities in this here newnitedstates, of which I have been to all 50whatever of'em! And I got me one a them High School paper thingees a long, long time ago. So much for credentials.

One major advantage you have here is that it is a DIY project, which means you can waste as much of your own time as you are willing to get what you really want.

This floor can be made to take tile. Ain't no question about that.

I'm still too fuzzy to grasp your drawing but it doesn't matter that much. And I must still be real fuzzy because it still looks to me like you're laying more like 250 feet of tile, given the dimensions in the drawings. But that doesn't matter much either.

On the section that has the 2x6 subfloor laid at a 45 degree angle (which, by the way is already more floor than you get total on a lot of new construction), it will be no problem at all to add 2x6 joists perpendicular between the existing beams, preferably on 16 inch centers. This alone will give you enough floor for whatever floor covering you wanna put down. I know that is a large statement, but given your description of the existing situation, I'll stand by it. Now these joists have to be installed well to get the desired effect.

If I were doing the job for myownself I would first get some good 2x6 material. My choice would be #1 KDAT treated Southern Yellow Pine. I always use treated wood under buildings even when they are way above ground like yours is - just the way I do it. I caution you NOT to use regular treated wood, but ONLY KDAT (Kiln Dried After Treatment), which usually is only available in #1 grade which is just what you want anyway. Regular TW is always wet, wet, wet when you get it and shrinks, shrinks, shrinks after it is installed. KDAT will shrink a little, but not too much. Don't be bashful about making sure the stuff is dry - pick up a similar piece of TW and KDAT TW and you should immediately feel the difference. The KDAT should be noticably lighter.

Crawl under there and measure real close. Come out and cut real accurately. You want a tight fit - not a hard drive fit, but you want to have to encourage it in there. And you want that kind of fit for each board.

On your first trip under, you have measured along each beam and marked the position of each new joist on each end. You will draw a line from beam to beam on the bottom of the flooring in what will be the center of the new joist. You will get your handy cordless drill (if you don't own one this is the perfect time to buy one - NO household should be without one) and drill along this line, and staggered either side of the line maybe 3/16th inch, two 1/8th inch holes in each 2x6 floor board, spaced about an inch or so from each edge. These you will use to screw the floor down from the top.

You will take your joist under there, tap it in place, drill in each end three 1/8th inch holes - one in the center on one side and two on the other side - which will start about 1 1/2 inch from the beam and angle at just under forty five degrees toward the opposite side of the joist and slightly up toward the floor above you. With your other cordless drill (yes, perfect excuse here, Kevin), the big one, you will drive 3 1/2 inch deck screws into each drilled end of these joists.

You will go upstairs and screw the flooring to the new joist using the pre-drilled holes which are, of course, right where you want them. These would be 3 inch screws on my job.

Now if you are really serious (and especially if you have a helper) you will apply glue to the top of each new joist as you put it in. I would do this on my job, but it will be a big pain in the ass to have to run upstairs and screw down the floor with each new joist. I would also, especially if you have a helper, put a couple screws through the flooring into the new joist before I would screw the joist to the beams. And you will have screwed the floor to the existing beams before you have begun any of this, by the way. After you have done all this, you can go back under there and add joist hangers if it makes you feel better. I would not do this on my job, but that's your call.

When you have finished - and I don't think this is all that big a project, depending upon how well you are equipped - I would just get these tile geniuses off the dime and make one of them tell you the minimum thickness material you can apply over this floor that will let you set tile upon it, 'splaining to them that you already got a floor.

Now the other floor with the perpendicular flooring is a little different. There you gotta figure a way to run another suitably sized joist parallel to and centered between the existing beams. Can't do much for you there without knowing what is available where the ends of this new joist/beam would sit. No doubt in my mind this one can be done too, just not as simple. We can work on that one if you decide we're on the right page with the first one.

Questions, comments, disagreements, suggestions?

09-08-2001, 02:57 AM
cx, thank you so much.

It all makes perfect sense. I think I'll follow your advice to a T. Thanks for explaining "why" too. I know it takes extra time, but understanding why really makes a difference when you're going to do something "extra." All of a sudden it doesn't feel so extra because it's the right way.

I like your philosophy. Let's get it right the first time. In the other room, the perpendicular 2x6s, I think I've got that figured out. I'm going to hang some 2x8s, maybe 2x6s parralell to the beams (perpendicular to the 2x6). I am going to use hangers and butt them to another 2x8 that I'll hang off of the posts. If I can't hang them high enough to butt the joist, then I'll hang it lower and let it carry the joist on top.

With a span of 9 feet, I don't think I'll have to put another post underneath my "joist". I think the 4x6 posts down there can support it. I'll glue these too. That makes sense. The pre-drill was a great idea, duh!

Yes, I am doing about 275 sq feet. I added a room since the original post. But, that's not important.

John Bridge
09-08-2001, 11:21 AM
Sounds like super engineering to me, except that in Oregon you might not be able to get yellow pine. You might have to use Douglass Fir, which grows up around that neck of the woods. Doug fir is just as sound as yellow pine.

09-08-2001, 11:43 AM
John say sooth, of course, Keith. Doug Fir is actually the very best choice, but all the treated wood in our neck of the woods is SYP and I just always use it. Habit.

In your situation, untreated Doug Fir will outlast your grandkids by a wide margin.

10-21-2004, 02:39 PM
I see that this thread is old but...

I have the same type of floor (post&beam with 2x6 t&G all perpendicular to the beams) and have been trying to think of ways to sturdy it up for tile.

I like the idea of hanging a 2x8 off the post, perpendicular to the beam in order to have something to nail the new joists to. My question is, will this place too much stress on the post?


ps - you can fit everything I know about construction into a thimble.

10-22-2004, 05:56 AM
No, George, you won't overload the post by adding another joist. The load is already there, you are just distributing it better. Besides, it takes a lot of load overload a post. Like a couple of new stories, or a parking deck, or a helipad...

10-22-2004, 10:34 AM
Thanks Bob. I was just worried that hanging off the side of the post may somehow pull the post over(?). It's been interesting learning about how to go about this project. Apparently, this type of floor is not too common around here (WA).


10-22-2004, 11:48 AM
George gonna build hisownself a helipad?!! :eek:

Recon he's fixin' to tile it? :D

10-25-2004, 12:17 PM
Upon further review, I've decided to go with Rob's suggestion earlier in the thread and add some 5/8 plywood over the car decking. The floor area is small, a little less than 5ft by 6ft. Of course I have a couple questions.
With that small of area, does the plywood need to be T&G?
Is it correct to leave a gap of 1/8 between sheets and 1/4 around walls and tub?

I tried to use the search function but apparently I don't know the right terminology to find what I'm looking for. If this sort of thing has been covered a million times (I'm guessing it has), point me to it!


10-25-2004, 05:47 PM
No, you don't need T&G plywood over your car decking. Wouldn't hurt, but you don't really need it. But I'd do it, 'cause it wouldn't hurt, and it helps keep your sheets aligned vertically.

Yes, leave 1/8" gap between sheets and 1/4" gap around anything else.

10-25-2004, 07:35 PM
Please step away from the particleboard. Best thing to do is remove it from the house. Replace it with exterior grade plywood or Advantech. It was a common method in our area 20 years or so ago for builders to use particleboard over plywood. The only thing is they used 1/2" plywood with 5/8" particleboard on the top. Duh. We replace the particleboard entirely with 3/4" Advantech, then Ditra underlayment.

10-27-2004, 09:50 AM
Ok, I put the plywood in with screws and adhesive. The floor is now solid. It's time to tile. My last little problem is that I am now even with the ajoining floor. DITRA plus tile with about about 1/2 inch or a little more, I think. Is that anything to worry about?


10-27-2004, 01:13 PM
You can make or buy a tapered wooden transition strip for that. In a few days, you won't notice it.

10-28-2004, 10:30 AM
Thanks for all the help and the resources on the board. It's made things a lot easier.