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Unread 03-26-2008, 08:42 AM   #1
songbirdfeeder
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Need deflection figure on solid oak floor joists

We recently purchased a 1959 home built with all solid oak. The floor joists measure a full 2 1/2" X 8" and are laid 16" OC. We want to put ceramic tile in our kitchen where the floor joists are 14' long. My dad believes the floor is plenty strong to support tile, but the deflecto only comes up with L / 332. Can we lay tile?

Thanks, Mary
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Unread 03-26-2008, 09:06 AM   #2
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Welcome, Mary.

While Oak is a very strong wood, it's not particularly rigid. With a full 2 1/2" thickness (pretty unusual dimension, that ) and 8" height, you may meet the L/360 requirement for ceramic tile, but I don't have any span table to prove that.

Tell Dad we're not concerned with strength, but with deflection, here. But if he want's to tile over what you have, well, it's your project and your dinero, eh? Customer isn't likely to sue in the event of tile failure.

Do be sure he's willing to install sufficient subflooring, which is frequently more critical than the joist deflection.

My opinion; worth price charged.
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Unread 03-26-2008, 09:30 AM   #3
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Hey CX, Thanks for the quick response! I understand what you mean about strength not equaling deflection. I just hate to get the tile in and have it all start cracking. What would you recommend to make a substantial subfloor?

Yes, I know the dimensions are unusual. The previous owner was also the builder (he passed away a few years ago). I was told by a neighbor that the previous owner picked out the trees and had a friend (who ran a sawmill) cut the lumber to his specifications. He was an engineer and the house really is amazing. We just had replacement windows put in and everyone who gave quotes was surprised at how almost perfectly square the windows are.

Mary
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Unread 03-26-2008, 09:47 AM   #4
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Oak stiffness depends on the species and where the tree grew. The Modulus of Elasticity (a measure of stiffness) for different species varies from about 7.9 to 18.1 ksi (1000 lbs per square inch). Compare this to Douglas Fir, 11.9 to 13.1 ksi. Not knowing your wood species, I would use the second choice in the deflectolator, unknown wood in good condition. Since the deflectolator also includes a 20% fudge factor, your joists should be fine for ceramic tile if you used the second wood option.

For a good subfloor, 3/4" tongue and groove plywood is good. If the builder used 1" planks, add a layer of 1/2" plywood and your choice of underlayment.
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Unread 03-26-2008, 01:09 PM   #5
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Laying tile in laundry room and kitchen

We are ordering new kitchen cabinets this week and will be demolishing the old kitchen in about 3 weeks. Our plan is to use the adjacent laundry room as a temporary kitchen when we tear out the old one. However, during the next week I will be laying tile in the laundry room. The two rooms are connected and we wanted to continue with the same tile in both rooms. My questions:

1. Can I lay the tile in the laundry room and just stop near the threshold to the kitchen, and then lay the tile in the kitchen a month or so later?
2. Is the threshold the best place to stop?
3. Is there anything special/different I need to do regarding stopping the grout at the threshold?

Please be detailed in your answers as I'm a newbie!
Thanks, Mary
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Unread 03-26-2008, 01:17 PM   #6
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Quote:
18.1 ksi
Them must be "special" oak trees, Injineer Bob.

I never knew that. And I thought Doug Fir could get up to the 16.0 range.
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Unread 03-26-2008, 01:21 PM   #7
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This the same project as in your floor joist thread, Mary?

1. Yes.

2. Popbably.

3. Depending upon the structure, it may be a good place for a soft joint. We'd need to know more about the structure and size of the tile installations.

My opinion; worth price charged.
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Unread 03-26-2008, 01:46 PM   #8
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I just did this exact sceanrio, well only a week or so between the kitchen and laundry room install. I used mapei grout and the matching Keracaulk (sanded) matches the grout perfectly. My pattern is a pinwheel pattern on the diagonal so the "threshold" in the doorway is a jagged line. If the caulk didn't match perfectly this would look really silly, but it all worked out great.
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Unread 03-26-2008, 01:53 PM   #9
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Yes, CX, this is the same room (kitchen) as floor joist thread. I didn't continue with the floor joist thread because I thought the question about where I stop laying tile didn't have anything to do with the floor joists. Maybe I was wrong since I don't know what a soft joint is. Sorry! The laundry room is about 8x11 and the kitchen is 13x15. I'm using 12" tile; nothing fancy.

Mary
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Unread 03-26-2008, 02:19 PM   #10
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Long as it's the same general project, Mary, keep all the questions on this same thread so folks who want to help can see the history and what's been previously axed and answered.

Soft joint is a movement joint and it sure wouldn't hurt for you to have one in that doorway between those rooms. Depending upon your tiling substrate, you may want to have a joint in that, too. All it does is provide for some movement in the tile installation without cracking tiles or grout.

You must provide an empty joint all around the perimeter of the installation, too.

My opinion; worth price charged.
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Unread 03-27-2008, 06:49 AM   #11
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Thanks for the advice, CX, bbcamp and Ricks2047!

One question about the soft joint--should the soft joint in the substrate be in the same location as the soft joint in the tile? Or is it better that they're NOT in the same location?

Thanks again,
Mary
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Unread 03-27-2008, 06:58 AM   #12
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Joints wanna be stacked vertically, Mary.

My opinion; worth price charged.
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Unread 03-28-2008, 09:37 PM   #13
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What's the best way to cut the hole for the toilet in the hardiback?

Also, is it okay to go around heat vents and door casings?
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Unread 03-29-2008, 09:39 AM   #14
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Carbide blade for your jigsaw, angle grinder, short-radius Hardiboard shears, scribe and break, whatever tool/method is available to you.
Quote:
Originally Posted by Songbird
Also, is it okay to go around heat vents and door casings?
Not sure I understand. As opposed to covering the vents? Door casings you'll want your tile to go under, doesn't matter on the CBU.

Would you please go to the UserCP, find Edit Signature and enter a first name so it will appear in each post for us to use?
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Unread 03-30-2008, 08:06 AM   #15
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Tile to hardwood flooring is one of the easiest transitions to make, Mary, at least from my perspective. In your case I would complete the tile installation and then make wood reducers to fit each transition.

The Schluter profiles are made to be set directly under the tile while installing. And yes, I would certainly recommend you have them on hand before you start if that's to be your transition of choice.

The pull saw is my weapon of choice for undercutting jambs and casings, too.

My opinion; worth price charged.
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