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Unread 02-17-2016, 03:16 PM   #1
ktl5005
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2nd floor bathroom remodel. joists acceptable to handle weight?

Hi guys. New around here from the great state of PA.
My wife and I are doing a bathroom remodel on our 2nd story of our home. Built in the 1930s with block foundation, but has had updates since.

Bathroom measures 7'x6.333'
2nd floor bathroom joists are 2"x8"x10' with 16" on center (old wood, unknown species, and roughly measure 1.75"x7.5"). One end of the joists sit on load bearing double beam, other end (which is by the wall to the staircase) sits on 2x4, with a direct 2x4 stud below it (mix of plaster and drywall walls).

Bathroom as 2 load bearing walls.
We plan on doing a 3 wall alcove deep soaker tub(60x32 acrylic, weighs 80lbs), with tile surround.
Also plan on tiling the floor. Tiles are 12x24 (same tile for tub surround, weight roughly 8-9 lb a piece)


Joists run parrallel to tub. Bathroom sits perpendicular on roughly 6 joists, and bathroom is on the load bearing side.

Flooring is vinyl, which is over glued lineuloeum, over thin subfloor on top of tongue and grove. We plan on tearing up the first level of vinyl flooring, leveling the floor, the adding OSB and either cement board and tile membrane or DITRA before tile.

Question is can the joists support all the load of tile floor, tile tub surround, deep soaker tub?

I ran the deflecto and it estimates I am at L/367, but am wondering if I am correct, and if it can handle the live load of a fully loaded soaker tub with everything else( tile, tub tile surround, double vanity etc) and correct dead load

Thanks in advance!
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Unread 02-17-2016, 08:36 PM   #2
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For sure. You should not have a problem with wight. I'm more then confident that there will be know problems. If the house was built in the 30's it is real 2x4 walls and real 2x8 joist! As for you floor your right on lifting the old stuff up the bare 3/4 tough and grove. Start fresh. Depending on what flooring out side the bathroom in would lay 3/8 plywood with plenty of screw spaced nicely every 3" along seems and 6 " throughout field Once that's done find your low spots and use a self leveller to bring up to hight of high spot. Or use a 1/4" plywood osb with lots of staples. Every2" along seems and every 4within field. ( or screw). Then lay your ditra with thin set and then self level fro low to high and let dry. Good luck
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Unread 02-17-2016, 08:39 PM   #3
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Ps. Be sure to water proof your walls.
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Unread 02-17-2016, 09:41 PM   #4
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Welcome, Keith.
Quote:
Originally Posted by Keith
other end (which is by the wall to the staircase) sits on 2x4, with a direct 2x4 stud below it (mix of plaster and drywall walls).
I need a little help with that. Do you mean the joists sit on a stud wall perhaps? If not, could you clarify a bit?
Quote:
Originally Posted by Keith
Bathroom as 2 load bearing walls.
Again there, I'm afraid. I trust that's has two load bearing walls, but are these walls in that room supporting what's above, or are these walls under the bathroom, supporting your bathroom floor?
Quote:
Originally Posted by Kevin
...over thin subfloor on top of tongue and grove.
Is that T&G plywood or OSB or is it T&G sawn boards? If sawn boards, the minimum you can install on top of it is nominal half-inch exterior glue plywood with no face of grade lower than C. On top of that you can install whatever tiling substrate suits your fancy and your tiles. Keep in mind that for your large format tiles the industry requirement for flatness of the substrate is no deviation from intended plane of more than 1/8th" in ten feet nor 1/16th" in two feet. That's a very flat floor and you'll be glad to have it when you start setting those tiles.

I've got some serious disagreement with the advice of our new friend, Ty, above.

1. Again, the minimum requirement over sawn boards is nominal 1/2", not 3/8ths".

2. There is no commonly available 1/4" plywood or OSB that is suitable for any part of a subfloor for ceramic tile.

3. Stapling is not an acceptable fastening method for subflooring for a ceramic tile installation.

4. If you elect to use Schluter's Ditra, or similar, as your tiling substrate, you must, per the manufacturer's recommendations, do all your leveling or flattening before installing the membrane, not on top of it.

As for your floor supporting your tub, you could probably fill your tub with water and invite as many neighbors as will fit in the room without doing any structure damage to your house. Would you exceed the allowable joist deflection for your new tiled bathroom floor? Yeah, probably so. But without seeing your layout and knowing more about the support questions I had above, it's difficult to say whether normal use would be a problem. Consider that your joist deflection is based upon every square foot of that floor being loaded with 40 pounds. Get out your calculator and see if you'll be planning to exceed that.

My opinion; worth price charged.

Welcome also, Ty. If you're in the tile trades in some capacity, drop by the Professionals' Hangout and start a thread of introduction and tell the folks what you do and where you do it and how long you been doing it and such. Putting some of that information into your User Profile is also helpful in letting the folks you're helping see where you're coming form.
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Unread 02-18-2016, 09:12 AM   #5
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Hey CX and Grizzly Gibbs:

Joists measure 1.75x7.5, which is alot closer than the new stuff to true 2x8.
I know to waterproof the walls.

1. Yes, the one end of the joists sits on a 2x4 studded wall, with each joist supported by a 2x4 stud directly underneath it.

2. The 2 bathroom walls that are load bearing are outside exterior walls and only supporting the roof line above. What is supporting the bathroom is what i described above 2x8x10 16" on center, one end resting on a double beam exterior load bearing joist, other ends sitting on 2x4 with 2x4 studs directly underneath b/c there is a staircase on the other side.

3. Looks like 1/4" saw board, which is on top of 3/4" tongue and groove. I have vinyl floor over glued linoleum. Plan is is take up vinyl, lay 1/2" plywood over linoleum (very well glued down and no way am I getting it up), level the floor with self leveling compound, then add DITRA with the tile on that. Right now I am quite level and over 7' span I am only off roughly 3/8" from flat.

I will post some pictures once I have enough posts and it allows me to!
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Unread 02-18-2016, 09:56 AM   #6
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Also, at 40lbs per square foot at a bathroom with 45sqft I have about 1800lbs.

Given 500lb tile (floor and wall), 60 for mortar, 80lb tub dry weight and up to 415lb loaded, 120lb cement board for tub walls, roughly at 1170lbs before vanity, toilet, linen cabinet and quartz top. Thinkin close to max but OK

Now dead load, I am over this just in tile. (45 square feet, 10lb square foot). Should I be concerned?

Again my deflecto is L/367
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Unread 02-18-2016, 10:34 AM   #7
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I'm having a little trouble with your math here, Keith.

The tile (if your tiles weight 9 pounds each (Post #1), that's 4.5 pounds per square foot, not 10), tub, mortar, wallboard, cabinet work (including tops), etc, are all part of your dead load. Yes, I'd recommend using at least a 20psf dead load for calculations when doing a remodel where tile is added, but our Deflectometer is a pretty conservative beast and uses a full 50psf for its calculations.

You'd need a structural engineer to come look at your layout to really determine your actual and anticipated loading to be really accurate, but I see nothing glaring in your descriptions. Filling the tub with water and people is certainly a consideration, and if you're seriously concerned you might actually wanna get someone in there to give you an evaluation or you might just wanna sister your joists (unless you can find out they're better material than you're guessing) and be done with it.

My opinion; worth price charged.
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Unread 02-18-2016, 10:53 AM   #8
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Tile is 12x24, or 2 sqft each and 9lb each. My math was never good...

Joists are set of pictured below.

I have thought about sistering a joist under the tub, or building a box under the tub to transmit the load to other joists.

So at a full 50psf I'm at 2250lb sqft total and in which case I am within that limit.
Attached Images
 
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Unread 02-19-2016, 02:01 PM   #9
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New here and hope someone still responds to this thread.

Re-doing our 2nd floor bathroom. Has 2"x8"x10' joists. 1930's home, wood in good condition.

My deflecto is L/367. Doing porcelain tile.
Drop down ceiling below bathroom so an access everything.
I like the idea of adding 2x4 along the bottom to increase stiffness, and also increase SPF of the load also.
Do the 2x4 need to rest on the exterior load bearing beam and interior studded wall, or do they butt up against each and get tide into each with glue and screws? No way I can jack up second floor to rest them on the joists.
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Unread 02-19-2016, 02:51 PM   #10
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Keith, it'll help if you'll keep all your project questions on this thread so folks can see what you're working on and what's been previously asked and answered.

That method of strengthening joists is good in theory, but not so simple in actual practice. And, personally, if I could not "un-weight" the joists, I would not even try it.
Quote:
Originally Posted by Keith
and also increase SPF of the load also.
can't tell what you might mean there.

My opinion; worth price charged.
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Unread 02-21-2016, 04:14 PM   #11
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Attached are pictures of the bathroom and plan for remodel

I plan on using 1/4" Hardie Backer on the floor screwed and mortared over the glued linoleum after it is leveled, and 1/2" Hardie Backer on the tub surround.

Multiple people have stated to me now after asking them that the 2x8x10 should carry load of the tile (43 sqft on the floor, the rest of the 60 or so sqft in the shower) without issue. They did recommend 2x8 supports perpendicular to the joists to prevent twist and create big boxes to distribute load.

Can't wait to get started.

And why the pictures are upside down I do not know. They are the correct orientation prior to upload.

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Last edited by Kman; 02-21-2016 at 05:56 PM.
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Unread 02-21-2016, 05:59 PM   #12
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Quote:
Originally Posted by Keith
I plan on using 1/4" Hardie Backer on the floor screwed and mortared over the glued linoleum after it is leveled,
I have only one suggestion for you: remove the vinyl.


Quote:
Originally Posted by Keith
And why the pictures are upside down I do not know. They are the correct orientation prior to upload.
Turn your computer upside down.
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Unread 02-21-2016, 06:36 PM   #13
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I'm kinda lost now. ... Your way overthinking the weight issue . your house will not cave in. Who told you about the weight thing anyways? Do you mean drop ceiling below to install tub. (. Waste over flow). If so. You should not have to. With proper measurement and dry fitting pipes pior to gluing fittings, you should be able to hook all plumbing from above. Just ask for more details. In better detail. I would really try to remove all flooring. If not possable determain how much sub floor you have. And we will go from there. But it possable with a bit more effort... And just for the record 3/8 plywood is plenty for subfloor. I'm from Canada and we have much higher standers for building codes.
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Unread 02-21-2016, 06:59 PM   #14
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Quote:
Originally Posted by Ty
And just for the record 3/8 plywood is plenty for subfloor. I'm from Canada and we have much higher standers for building codes.
I'm sorry, Ty, but that's simply incorrect. The absolute minimum, per building code in this country, subflooring over the joists spaced at no more than 16" on center is 5/8ths-inch material.
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Unread 02-21-2016, 07:52 PM   #15
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That nuts. Are joist span 16" on centre. And 3/8 is fine. So question. With 5/8 what do you use to fasten? And whats the spacing
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