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Unread 07-25-2007, 06:53 AM   #1
milner351
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Location: Belleville, MI USA
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Deflecto-meter advice needed

This is a great site - thank you for making such an excellent forum available.

We've finally started the project of removing the worlds worst rust colored carpeting from our den, and some of the hardest to maintain nearly white linoleum from the eat in area of our kitchen which joins the den.

Beneath the den is a crawl space, with 2x10 fir joists on about a 13ft clear span on 16" centers.
according to the deflecto here - that's a thumbs up for ceramic tile, thumbs down for natural stone.

Here's the rest of the story:

over the 2x10 joists is 3/4" plank subfloor
over that subfloor is 5/8" plywood
over that is linoleum glued down tight which I roughed up with a rotary sander and 36 grit (per mortar bag directions)
then mortared down 1/4" hardibacker
we've gone through 24 sheets of hardi, over 1000 screws, and nearly 3 bags of mortar (hardi screws counter sunk and filled, seames taped and filled)

The plan now is to lay 18x18 porcelain daltile over the hardi (~3/16" thick tile)

I realize this is a lot of weight - and when finished the floor will be nearly 1-3/4" thick over the top of the joists....

Do I need to go into the crawl space and put in a beam in the center of the 13ft span supported by short steel jack posts on say 12"x12"x2" concrete pads?
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Unread 07-25-2007, 07:43 AM   #2
cx
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Welcome, Milner351. Please give us a first name to use.

The weight of a tile installation is seldom a cause for concern. It's the design deflection of the subfloor structure that most affects the installation, primarily the live load deflection.

Our Deflectometer is a pretty conservative tool and uses the full live and dead load total of 50psf in its calculations. So, generally, if your floor meets the Deflecto specs, you shouldn't need any more structural work to facilitate your tile installation.

More structure is always better, of course, but you meet the requirements with your existing structure if it is all in very good condition, of the correct wood type, has no excessive notching or boring, etc. And the subflooring, where most of the deflection problems occur, if properly installed, is also good. I'd be comfortable with it.

The only part of the whole installation that I wouldn't like in there is the "linoleum", but if it is not a cushioned vinyl type flooring, you'll likely get by with that, too.

My opinion; worth price charged.
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Unread 07-25-2007, 07:54 AM   #3
milner351
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That's what I was hoping I'd get in a reply. I will re confirm the wood species of the 2x10 floor joists if it's marked, and, will reconfirm the span as well.

I too was not a big fan of the mortar over linoleum idea - but the linoleum was down tenaciously, and it's the old stuff - no cushion to it whatsoever.
SO - as the mortar bag said it was OK to put over "sheet vinyl flooring" I went with it- but not before sanding the shine off with a body grinder and 36 grit. And - we mortared over the vinyl, then put down the hardibacker with a million screws, and we'll use porcelain specific mortar (Home Depot) to put down the tiles.

The floor feels very solid, but I know feel is not generally an accepted engineering metric!



This is my first time putting down tiles larger than 12x12.... and this will be in an area where a kitchen table and chairs will be.

Any tips and tricks to get these big tiles flat?

Any tips and tricks as to "feet" to put on the legs of tables and chairs going over tile floors to prevent scratching / marking the tiles?

Thanks for your reply!

- you can refer to me as milner (nickname) or John whichever you prefer!
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Unread 07-25-2007, 08:01 AM   #4
cx
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We're happy to call you whatever you wanna be called. Just go to the UserCP above, find Edit Signature, and enter Milner there so it will appear at the bottom of each post and we'll remember.

Big tiles want a flat subfloor. That will make more difference than anything in the installation.
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Unread 07-25-2007, 08:33 AM   #5
milner351
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Let's see how this works... the signature I mean.

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