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-   -   What size screws for underlayment (https://www.johnbridge.com/vbulletin/showthread.php?t=115593)

Kman 02-22-2015 03:19 PM

Unless it's pushed up very high, there's no reason you can't shave off a little to get it in line with the others. Of course, that will require removal of a good part of the subfloor to get it to it.

Motordoctor 02-24-2015 07:48 PM

The never ending kitchen floor saga.
I thought I would try getting the subfloor a little closer to being flat so it didn't "telegraph" through the plywood. Dug out the belt sander and had at the high area on the one joist. After 4 hours and 4 belts I got about halfway in a 2ftx4ft area. That's going to be way too slow.

Decided I need more power, at that rate it would take a month of sanding to get the job done. So drove to Home Depot and rented the big bad drum sander. Truthfully I was underwhelmed by the stock removal rate of it even with 24 grit sanding belts. Sanded the entire floor but it's still not as flat as I would have liked. Spent about 5 hours on it, probably took about 1/4" off the high area around the one joist. I guess it's as good as it's going to get, can't make love to it forever. There are low areas, little more than 1/8" in a lot of spots but I've wasted entirely too much time on this now. At least the plywood won't have a big hump in it right over the joist anymore :)

Weird place to be high, it's on the third joist over from the door about 3/4 span near the resting point for the joists. So it's not like I could jack the other low ones up since I would think that spot would be in the middle and not near one of the ends. It is what it is. Can't rebuild the whole house just so I can put in $130 worth of tile.

I hope setting the tile goes easier than this ;)

cpad007 02-25-2015 11:59 AM

Wood moves. When that joist started drying out, it released some tension and caused a hump. I betcha there's a decent knot in the area where you found this hump...or there may be nothing visual at all. Gotta love wood!! :D

Motordoctor 02-27-2015 11:00 PM


Originally Posted by HardiBacker Installation guide
• Install smooth side up.

Install HardieBacker boards perpendicular to subfloor panels.

•Stagger all HardieBacker board joints. Do not align HardieBacker board joints with subfloor joints

• Never allow all four corners of boards to meet at one point.

•Lightly butt the board joints. Do not leave a gap or force edges together.

•Join factory-cut edges together in the body of the floor.

•Keep board edges 1/8” back from walls and cabinet bases.

Dumb question here, does this mean I should put down the CBU parallel to the floor joists? Since the plywood underlayment is perpendicular to them.

cx 02-27-2015 11:39 PM

Dan, structurally it matters not a whit which direction any of the CBU panels fall with reference to the joists. I noticed that part in the Hardibacker installation instructions about orienting the panels opposite the plywood panels very recently and don't recall ever having seen it before. But if that's the way James Hardie wants you should install them, then that's the way we'll recommend you install them.

I think the part about not gapping the panels is relatively new as well. Seems to me they usta call for a 1/8th" gap. But, again, if that's now the way they want'em installed, I recommend you install'em that way.

My opinion; worth price charged.

Motordoctor 02-28-2015 09:02 AM


Originally Posted by Hardibacker cement board installation guide
determine layout of HardieBacker cement board

•Stagger all HardieBacker ® cement board joints. Do not align with subfloor joints.

•Never allow all four corners of boards to meet at one point.

•We recommend an 1/8” gap between board edges.

•Keep sheet edges 1/8” back from walls and cabinet bases

Sorry about that, the first quote was from their guide, but wrong section. It was the vinyl flooring section. I hate trying to read online PDFs, being an old geezer I prefer books. I watched their instructional videos and they showed laying down the CBU perpendicular to the plywood. Too bad, putting it perpendicular to the joists would have been easier since the room is 10ft wide.

cx 02-28-2015 09:08 AM

Gotta admit I don't read the installation instructions for the other flooring types when I'm on those manufacturers' websites. Hell, I have plenty trouble keeping the tile information straight in my little pea brain.

Glad you got it sorted out, though, and that it's just like we thought it should be. :)

Motordoctor 03-02-2015 11:22 PM

Another odd ball question here. Since I've never worked with mortar before I'm not familiar with its characteristics. When I put down the CBU, I'm going to use a 3/8" trowel to help even out the subfloor deviation. So I set the CBU on the mortar, move it around to seat it and check the X-Y axis for level/flatness. Assuming it comes out level and most importantly flat, will putting the screws to it at this point change that? Meaning does the mortar squish out when you apply a clamping force or does the stuff stay put? Sorry for the dopey questions but I'm sitting around twiddling my thumbs waiting for the Mortar I ordered to show up.

cx 03-03-2015 09:37 AM

Dan, you do not want to try to level or flatten your subfloor while installing your CBU. You must install the CBU according to the manufacturer's instructions, which will usually include a trowel size and material type.

You can flatten a subfloor at the joist tops or you can flatten the floor on top of the CBU, but you don't try to flatten between subfloor and CBU. You'll get a little flattening just by installing the CBU, just as you might when installing a second layer of subflooring, but you must attach the CBU directly onto the subfloor as instructed.

My opinion; worth price charged.

Motordoctor 03-08-2015 09:28 PM

I finally got my mortar today so putting down the CBU starts tomorrow. After I put down the mortar and put the screws to it I'm assuming that walking on it is a bad thing? The reason I ask is this: don't want to put myself into a corner so if walking on it before the mortar sets is bad, I will have to do it in a couple of steps so I have an escape route. Thanks

cx 03-08-2015 09:32 PM

I know of no CBU manufacturer who prohibits walking or tiling on newly (and correctly) installed panels on floors.

Motordoctor 03-09-2015 07:45 AM

Ok. Couple of actual tile questions now ;)
  • Are the 18x18 tiles prone to "lippage"? Meaning do I need a leveling system? When the mortar sets will that move the tile's plane?
  • To keep the mortar out of the plywood joints and out of the wall spacing what works? I've heard of just using tape, and also caulking.

Houston Remodeler 03-09-2015 09:38 AM

Lippage has a few factors;

1- How flat are the tiles to themselves ? Lay one upside down on the other facing upwards. Try to give it a spin or to rock the upper tile. Look at the gap between the edges.

2- How flat is the substrate?

3- Troweling / setting skill level

4- Mising the thinset too loose will cause sinking tiles

5- Too little thinset will cause sinking problems

Motordoctor 03-09-2015 04:52 PM

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Well, I got half the CBU down, used one bag so far. Have to say, that's hard work. Mixed it a little on the stiff side and that really gives your forearms a workout. I didn't know how fast the bucket would set up so I was going flat out for about 2 1/2 hours. Gave me a couple of nice trowel blisters, didn't have time to stop and put a piece of padding in there. Putting down the mortar didn't take long, it was putting all those screws in that burned up the time. The pot life was outstanding, I had to pick the wife up at work, then come back and the mix was still good so I put down one last sheet and used up all the mortar.
You tile guys are studs, that's all I can say. Probably give my back a day to rest and back at it again on Wednesday. Hopefully by the weekend I might actually put a tile down :clap1:

cx 03-09-2015 06:11 PM

That's why you'll find a lot of pros switching to roll-up sheet membranes for their tile underlayment, Dan.

Motordoctor 03-09-2015 06:31 PM

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I can see why, it's one hell of a lot lighter than the CBU and no screws. I just couldn't bring myself to spend that much money. When somebody else is paying though, I can see it. Bottom line, on a job, time=money. I had a few tiles in the garage from the previous owner so I put them down on a piece of CBU. Now I'm not a tile virgin anymore, I set two tiles :dunce:

cx 03-09-2015 06:37 PM

Good time to pry them up and check your coverage, Dan. Very important step, 'specially when you're too new at the game to have developed your technique to get consistant coverage at the level required for the application.

Motordoctor 03-10-2015 06:39 AM

That's what I figured. How long should I let it dry? Although it's been about 15 hours now.

davem 03-10-2015 06:46 AM

The easiest time to check coverage is right after you set it. I'm sure you could still pop them off now and have a look though. :)

cx 03-10-2015 08:11 AM

Do it now, Dan.

Motordoctor 03-10-2015 08:43 PM

Here's a dopey rookie question. After mixing a 50lb bag of mortar and having to work like a rented plow mule, I decided I need to mix smaller batches. So I'm thinking I put 1/2 the water specified in the bucket, pour in about 1/2 bag and mix, adjusting for consistency as required. After I use up the mortar, I'm assuming that all the old stuff has to go before I can mix new stuff. I can take a hose and rinse it out but where do I pour it? What do you do with it? Either that or I have to toss the bucket and grab a fresh one each batch. Thanks.

cpad007 03-10-2015 09:19 PM

Put the slurry into a spot where you can spread it out so it'll evaporate and when sufficiently dried out, toss 'er in the trash. I think that is the most 'green' thing to do.

Kman 03-10-2015 09:58 PM

I keep a "trash" bucket around, usually one that I've accidentally left grout or thinset and and has set up. That one becomes the receptacle for leftover thinset.

Bruce D 03-11-2015 07:43 AM

Used a large empty plastic pot I had on the side yard and lined with a black lawn and leaf trash bag. Added leftovers to bag as I went along trashed when dry. Got this idea from watching a construction site where cement truck tailing were dumped in a plastic lined trench and allowed to dry.

cx 03-11-2015 09:09 AM

I believe the tile industry standards call for dumping that bucket cleaning residue in the neighbor's hedge row or potted plants, Dan. :D

cpad007 03-11-2015 10:46 AM

Care to site the paragraph and page number for that, CX? ;)

Motordoctor 03-11-2015 12:40 PM

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Originally Posted by CX
I believe the tile industry standards call for dumping that bucket cleaning residue in the neighbor's hedge row or potted plants, Dan.

I know Nothing!

On a related note, how does this sound? I'm planning on back buttering the 18x18 tiles. Is it a good idea to butter about four first, put down the mortar and set them 4 @ a time? I'm assuming here you put a nice thin coat on the back of the tile, just worried that it might set up too fast when it's that thin? Also "beating in" the tiles, that necessary?

Motordoctor 03-11-2015 09:03 PM

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Here's the tile layout I'm thinking of. Suggested by my mentor Bryan. You can either put down 6 full tiles with 3.5~4.5" tiles on either side or just shift the tile field 9" and have 5 full tiles with the two outside tiles about 12.5".

cx 03-11-2015 09:07 PM

The ANSI standards really do recommend no cuts smaller than half a full tile, Dan, if that influences your choice.

cpad007 03-11-2015 10:53 PM

No skinny tiles unless you can hide them under a cabinet or put 'em behind the toilet or something. They just look bad is all.

Motordoctor 03-12-2015 10:33 PM

Yeah, I'm going to put the oddball ones under the kitchen cabinets and sink. Finally got all the CBU down and filled the seams/taped. Looks like I should actually put a tile down on Sunday, have to work the next couple of days, the weather has finally started to turn and business is picking up.
Once I determine where to start the tiles, what is the best plan of attack? It's going to be a straight checkerboard pattern so there's no offset tiles. Should I do a single column at a time the length of the room or do four tiles at a time in a square pattern (two columns two rows). Or it really doesn't make any difference, it all comes out the same anyway:)

Motordoctor 03-15-2015 09:32 AM

Here's another odd question. SWMBO aka "the wife" wants a wall between the kitchen and living room either removed totally or partially (with a pass through). Since it's a load bearing wall and has furnace vents/electrical in it, not going to be an easy project. I was hoping not to have to deal with this because the season is almost upon me and once the season is here, all else stops.
So the question: At this point the kitchen floor is CBU and all seams taped. Is that floor safe to leave as is until the demo/construction is done on the wall? That way the tile won't be damaged by somebody dropping a hammer on it/etc. I would put down some flooring paper/tarps/padding to protect it as much as possible. Thanks

cx 03-15-2015 09:45 AM

If you can keep it effectively covered I wouldn't worry about it, Dan. Effectively being the operative word there.

In situations where longer term protection of finished floors is required I generally lay down builder's paper and then 1/8th" Masonite with the seams taped. Has always worked well for me.

My opinion; worth price charged.

Motordoctor 03-15-2015 10:16 AM

Thanks. The tile job is going to be put on hold until it's decided what part of the wall is going. If the whole wall goes, then the tile field will be shifted about 8 inches so I will wait on that.

cx 03-15-2015 10:22 AM

Always remember the remodeler's moto, Dan: When it doubt, tear it out! :D

Motordoctor 03-15-2015 12:51 PM

A friend of the wife's said he had somebody to do it. He brought by a Hispanic gentleman probably standing out in front of Home Depot, who asked after looking at the wall, "why do you want to take that wall out?" Not what the wife wanted to hear and since the consequences of not properly supporting the upper building structure by taking out the wall could result in a headache or worse. So we decided to pass on the help. He means well but his participation in anything is the kiss of death.

The wife has a MB560SEL that needed transmission work. He brought over a couple of gentlemen from the Home Depot and they proceeded to tear out the transmission and put a junk yard replacement in. Took them three full days to do that and after it was all said and done, the car is now undriveable. Took a perfectly good car and made a driveway ornament out of it. I don't have anywhere to work on it other than my driveway and yanking a transmission out in my driveway isn't in my future plans. So now the car's going on Craigslist and hopefully I don't get beat to death by hustlers trying to give me scrap value.

Motordoctor 03-15-2015 06:45 PM

What is a good choice for a demo blade for 1950 Plaster walls? They're plaster over metal lath over what looks like drywall with holes in it. I've tried demo blades, wood with nails, metal cutting, carbide tipped, and they all just wear the teeth off. Tried a carbide demo blade on a Skil saw, after making a 2ft cut, it's so dull now it won't cut a 2x4. I was thinking maybe a metal cutoff blade fiber type blade? I even tried hitting it with my belt sander with 36 grit and it barely touches the stuff. It's like cut a foot, toss the blade, cut another foot, toss the blade, repeat until you run out of money or blades :crazy:

cx 03-15-2015 07:05 PM

I've had surprisingly good results with these Rigid blades from Homer's, used in a regular circular saw. I do use a dedicated saw I have for such applications on accounta that kinda work is pretty tough on'em.

Homer's website shows some much less expensive "turbo" blades, but I've never tried any of'em.

Caution: Gonna be dusty as hell.

If water-feed is an option, I'd try my little Felker FHS-4 or similar so long as you don't need more than about 1 1/4" depth (I think).

cpad007 03-16-2015 02:51 PM

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How about some

Attachment 174244


Motordoctor 03-16-2015 04:29 PM

The cops around here would probably shoot me just for having a picture of it. If I actually had some C4 they would call out the terrorist task force and drop a nuke on me:goodluck:

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