Need help leveling floor

[MortarHead]

I need help in determining the best way to level out the bowl that is my kitchen floor. The perimeter is all level but towards the center of the room (OSB at walk-through) the bowl deepens to about 1" and an 1/8". I was going to do SLC (primer over the OSB/plywood/TNG) and then install 1/2" backer board then my 20x20 tiles. Would that be an appropriate course of action?

Thanks,
Alex

[Houston Remodeler]

Alex,

Sounds like your joists have sagged a bit and thus your flooring wouldn't support tile all too well. Have you run the floor framing through the Deflecto-meter? The link is in the thick blue bar above, under Members List

[MortarHead]

I have sistered on to about about half of the joists previously (2x8's), so i feel pretty confident that the floor would support tile. I'll have to look into the Deflecto-meter.

I think what I am planning on doing is trying to take a little bit of the cupping out with thinset and then then hardibacker over the entire floor, then use SLC to try and get out any other low spots. Does this make sense to run it like this?

[MortarHead]

Ran the Deflecto and here is what I got. FYI, some of th joists are 16" OC and a few are 20", while a few more are like 12" OC.

For joists that are Unknown wood, but in good condition, 7.25 inches tall, 2 inches wide, 16 inches on center, and 10 feet long between supports, the deflection calculated is 0.245 inches.

This translates to a deflection of L / 489.

Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Ceramic tile, Congratulations!

[bbcamp]

Nominal 2x8s are 1 1/2 by 7 1/4 inches. Are yours actually 2 by 7 1/4 inches?

[MortarHead]

All of the old joists are turn of the century and in fact 2". The sistered joists would be 3.5"

[bbcamp]

OK. As for correcting the sag, don't try to do it with thinset under the backerboard. It's there only to fill any voids between the subfloor and backerboard. Use the SLC to get it all. Remember, SLC will make the entire floor level. If there is a doorway that's lower that the others, you'll have a step up at that location.

[MortarHead]

Got all the hardibacker installed today. Luckily had a hand in doing so.

I'll have to do some measurements but I'm curious as to how the SLC is going to work as the cup near the middle of the room is what I am trying to level, however, being an older home (early 1900s) the center of the house is the low point for the entire house. Will the SLC just migrate toward the center of the house and away from the cup in the center of the room?

What type of SLC would anyone recommend? I have one small 25lb bag from Lowes Laticrete with Primer, but I don;t think one bag is going to be enough.

[tileman2000]

Ardex K-15 is a good SLC,if you can find it easily.

[MortarHead]

How fast does the K-15 set-up? This is something you have to pour all at once, right? I mean, you could re-pout SLC over SLC if it wasn't right the first time?

[tileman2000]

It's walkable in 2 hours,your tile can be set 16 hours later in 70 F.

you'll need a mixing drum because 2 bags are mixed at a time.7 quarts per bag.Mixed for 2-3 mins with a mixing paddle.

Shouldn't need to repour,it self levels,but you do have to work fast,so if you can getting someone to mix for you while you pour would be a big help.

[MortarHead]

thanks, Ill see if I can find it locally. I would assume primer it a must? I read that if using SLC on top of hardiboard, it is best to use 2 applications?

Also...

I'll have to do some measurements but I'm curious as to how the SLC is going to work as the cup near the middle of the room is what I am trying to level, however, being an older home (early 1900s) the center of the house is the low point for the entire house. Will the SLC just migrate toward the center of the house and away from the cup in the center of the room?

[tileman2000]

Yes,primer,then SLC will go to any low spots in the floor.Might take more to fill the dip in the center of the room.

[MortarHead]

Ive read its good idea to use some sort of damn around the perimeter of the room, something like foam tape, and then once the SLC cures, leave the foam tape in place for expansion?

[tileman2000]

Yes foam tape..Sill Seal comes to mind.

http://www.acehardwareoutlet.com/pro...rce=GoogleBase