Can I Tile this Floor?

enduringNovember 11, 2011

This has been posted on the Bath Forum as well, but I ain't get'n no responses :(

I would like to put down slate tile, over an electrical floor heating system in my bathroom that connects to my kitchen. I want to know what I need to look for, prep for, and consider alternatives for, with my situation.

I have confidence that I can do this with my DH's brawn & brains.

Here is the underside of my bath. The area is 10' x 6'8", the joists are 8x2 (but not quite). Unfortunately the joist are 21" on center. This add on space is somewhat different than the rest of the house which as 16" OC joist. The diagonal flooring boards are 6" or so in width, and I presume 3/4"-1" thick as I estimated the thickness looking at a knot hole. These boards have a slight gap between them:

Top side - It appears that there is 3/4" fir tongue & groove flooring over the diagonal boards but hard to tell without taking up the old linoleum - which is the next layer over the suspected T&G. I don't want to add more than 1-1/2" to the height of my floor above the T&G fir flooring, preferably 1".

1) Will this floor situation as is, (without the linoleum) be stiff enough for tile - with the subfloor and fir flooring?

2) Is it recommended that 4 more joist go in between the 5 that are there. Currently there is 1 at each edge and 3 filling the middle, at 21" on center.

3) Do I add plywood atop the T&G to add more rigidity?

4) I plan to replace the current cast iron tub with another cast iron tub. Is this added weight a concern with the added weight of stone tile?

5) I may tile the walls. Again, will that added weight be cause for concern?

6) What is the depth of a slate tile + prep + electric underfloor heating?

7) Is the tile flooring the last step to be done on a remodel? I will be relocating toilet, sink, putting in new tub, taking out plaster to insulate exterior walls, refinishing walls, adding new electrical, etc.

Thanks for your consideration.

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Without knowing for sure your subfloor and underlayment are probably adequate. 1/2" Hardi backer board should be all you need to add.
The joists need beefing up for sure. Add one between each original and crossbrace.
Why a cast iron tub? Acrylic is lighter and warmer.
1/2" hardi and another 1/2" for thin-set, wires and tile.
Install hardi then tub, tile, toilet and vanity.

    Bookmark   November 11, 2011 at 10:22PM
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Thanks Don92 for the info on the joist. I just posted a question on the remodeling forum about how to add joist. I told my DH about the cross bracing suggestion you made. The rest of our house is braced that way. Our basement is not finished so easy to see. This bath is over a crawl space unfortunately and difficult to work with. I think I mentioned that this bath was an add on to the original house. The rest of the house is joist properly.

The reason for the cast iron is tradition & durability. I agree that acrylic would be warmer. We have something like that in our other bathroom and I don't like how the finish has lasted. Though it actually might be fiberglass & is very old too. I know that American Standard has a product that sounds like a cross between cast iron and a synthetic product. Its called Americast. I might consider that tub but need to see it first. It has an enameled finish I think.

Background info: We live on a family farm in the midwest and use the tub for more than just the occasional bath. We may fill chore buckets, bath dogs, etc. I don't think acrylic will hold up to that level of use. We are the 3rd generation to live here. The old cast iron tub that was subjected to this use has lasted since 1950. It is actually in ok shape, no rust. I had considered taking out the tub altogether and putting in a utility sink but it is nice to have a tub in this location for kid baths. My kids have fond memories of bathing in this room just off of the kitchen. Being off of the kitchen I want it to look nice for company too.

We anticipate at least another 40 years of service with this remodel. While aesthetic design is in play here so is longevity of fixtures.

    Bookmark   November 12, 2011 at 2:01PM
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Old midwest country family here too so I understand the need for the cast iron tub; say no more. Just make sure you support that floor correctly. It wouldn't take much more than a little elbow grease to just remove all the floor so that your work area is all exposed. You would be more inclined to do all the work properly.

    Bookmark   November 12, 2011 at 3:51PM
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Don, you're making me faint with the removing the floor prospect! But my husband says you're probably right;(. Though he does think that we can get in there and do this job without the tear out. He has done a lot of stuff over the years being a farmer, jack of all trades, and in a past life an aerospace engineer (the math!). We have a 20 year old son who can crawl! So that space will be accessible. But I am listening to your caution of "You would be more inclined to do all the work properly" if the floor was taken out and area exposed. I added my link to the joist info request on the Remodeling Forum.

Here is a link that might be useful: Adding Joist to Existing & Intact Floor

    Bookmark   November 12, 2011 at 4:18PM
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I have been a remodeler for 35 years and time is money. If it was just doing a spot of plumbing in the crawl space I would deal with it but adding joists is the deal breaker. 4 hours of tearing out the floor and 2 hours of plunking down 2 layers of 3/4" plywood would be well worth the time spent. Also it would give me an opportunity to shim and level the floor and end up with a much better result.

    Bookmark   November 13, 2011 at 7:59AM
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Something to consider Don, thank you so much for your help in this problem.

One of my hold backs is my fondness of that old wood that is under there, even if I can't see it. It's all in good shape and the floor as is seems very strong. When I jump up and down I only hear a faint short tiny squeak.

I am glad to be getting the issues discussed now because there is time to consider issues without being rushed. This job may not start till next spring, or never, it depends on the corn & bean prices!

    Bookmark   November 13, 2011 at 8:47AM
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Hey Don, I told my DH what you said and my response to you. His reply was: "now he knows he's dealing with a nut case;)...welcome to my world!"


    Bookmark   November 13, 2011 at 9:57AM
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A "fondness" for subfloor? You must meet my wife. She has a "fondness" for an old tobacco barn on our property that you can see out the front window.I can't stand the thing! Your husband and I should be grateful our wives have a fondness for old beat-up things. Less chance we will be discarded for a newer model.

    Bookmark   November 13, 2011 at 11:52AM
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Lovely stuff and the kids are cute! But where's the barn?

I'm going to brag now, here is my first tile job, individually laid. I cut the soapstone too and with the help of DH installed it in our small kitchen remodel. Other aspects of the remodel where done by others:

    Bookmark   November 13, 2011 at 5:11PM
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The barn is there! Now that the leaves are gone it is glaring.
Great job on the kitchen! And good luck with the project.

    Bookmark   November 14, 2011 at 7:44AM
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Thanks Don!

    Bookmark   November 14, 2011 at 7:25PM
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looks good

    Bookmark   November 15, 2011 at 12:23AM
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