new subfloor question

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  #1  
Old 01-01-05, 09:22 AM
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new subfloor question

i've pulled up a portion of the original subfloor in a 2nd floor bathroom in preparation for new underlayment for ceramic tiling. the supporting members of the subfloor are 2" x 8"s, 16" oc. there is no supporting 2" x 8" joist under the wall of one side of the bathroom and the nearest joist is parallel to and runs about 9" from this wall. people traffic alongside this wall will be minimal since it's behind the door and there is 4' length of hot water heat baseboard unit that runs alongside it. the width of the heating unit is approximately
3 1/2". i hope i've understandably described this situation.

will i need to provide additional subloor support, perhaps braces, or am ok with screwing in new 3/4" exterior plywood about 9" away from the wall?

are there minimum "distance from the wall requirements" that need to be adhered to when installing a new subfloor?

there may be other locations in this bathroom where i will have a similar issue to contend with.

thanks

bob
 
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  #2  
Old 01-01-05, 09:38 AM
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can you see the joist that's hidden under the wall in question? If so you could run short lengths of 2x8 between the one that's 9" away and that one.

BUT

I'm guessing since it's 5 1/2" under the wall, that's not an option.

Hmmmmmm

I don't guess there's attic space adjacent to the bathroom your talking about? If that's the case you may be able to get in there and see the next joist in line, so you can nail the short 2x8's to it.

Either way, here's what I'm REALLY thinking(if it was mine): Although it may not be the best, 9", right against a wall, SHOULD be ok. Little or no traffic, and really only 5.5" left to walk on after the BB heat is in, or if you could leave it out a little further , even better. It's hard to come up with anything without being able to see what you have there in person, but I'll keep thinking about it, and you keep us posted, deal?
 
  #3  
Old 01-01-05, 10:01 AM
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thanks for the quick response.

your guess is a good one. the nearest joist is about 5 1/2" under the wall. the room adjacent to this wall is a bedroom.

it would be possible to install braces between the 2 joists, reaching under the floor with my screw gun and using steel attachment brackets. maybe that's what i should do, 6"-8" apart for the entire 8' length of the wall. about 2' of this wall is on the tub side of the room, but the tub is not directly adjacent to this wall. there will be about 14" of space between the end of the tub and the wall. there, i will be installing a tall cabinet.

another possibility might be to sister in a joist which would reduce the gap from 9" to about 7 1/2".

if i install braces or a sister, is it best that they be the same size as the joists, or could i use 2"x6"s instead?

bob
 
  #4  
Old 01-01-05, 10:58 AM
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Not really a guess, 16" centers leaves 14.5, and your 9" away .

But anyway, yeah if you can reach it with a screw gun, I would install the cross bracing before I would sister in another one, but anything is better than what you have now. 2x6's are fine for no more area than you have. If you put them 6 or 8 inches apart tho, you may have trouble getting the gun in for the last one, 16"OC should be good.

Keep us posted.
 
  #5  
Old 01-01-05, 01:18 PM
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got one in and that's the easy one. and i'll be having trouble getting the gun in on all the rest since i'll be wrestling in and around the base board heating unit to screw in the remaining braces. not too worried about the last one or two braces, since that portion of the bathroom is deadspace. perhaps one brace will do there. no tile there with a 12" wide, 6' high cabinet above it. the cabinet will be supported by about 5" worth of framing to raise the cabinet so that the baseboard heating unit doesn't interfere with the opening of the lower cabinet door. are you able to visualize this know.

i'm focusing on making sure that all underlayment upon which ceramic will be installed has sufficient. i always tend to go overboard with such work. where one screw would do, i'll install 3.

i'm a little concerned about the portion of 3/4" ply upon which the tub will rest. 300 lbs of cast iron. but i'll reserve this portion of my work for a new thread.

thanks so much.
 
  #6  
Old 01-01-05, 01:38 PM
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Totally missed the ceramic tile thing.

Tile will need concrete backerboard on top of the plywood, and even then with 9" hanging over....I dunno ...

If it's close to the tub, how bout framing up from the joist that's 9" away, tie into the wall framing, and making a little bench. Maybe cover with tile, something to sit on while getting dressed or...whatever...and it solves the framing issue.

Leave a little overhang in the seat (9" is a little small anyway) and put the BB heater under it. If your worried about burning yourself, make the bench, say 15" and cover half of the front of the bench with wood and tile (sorta hiding the heater, but leaving enough room for the heat to get out). Most BB heaters say it's safe to have anything you like within 3 or 4" in front of the heater.
 
  #7  
Old 01-01-05, 02:20 PM
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yes, 1/2" durock will be installed on top of my 3/4" exterior grade ply.

a bench??? that's no good for several reasons, the most important of which is wifee. besides, it will interfere with the 12"cabinet.

how about bracing the braces that will join the joists? do you understand what i'm suggesting here?

bob
 
  #8  
Old 01-02-05, 11:24 AM
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Hi Bob,

how about bracing the braces that will join the joists? do you understand what i'm suggesting here?
If you're talking about a metal connector that's attached to both the joists and the cross bracing, yes such products are available from Simpson & other makers at any lumber yard or home center. Here's a link to their products page, http://www.strongtie.com/products/Ca...?source=topnav

Now as to your tile underlayment, if you can stand the height issue, two layers of 5/8" plywood glue & screwed down would give you a much better subfloor base for tile than the single layer of 3/4", then set the cbu in thinset and screwed down. You could deal with some of the height issue by using ditra instead of 1/2" cbu. Let us know if you've got more questions.
 
  #9  
Old 01-02-05, 12:50 PM
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AHHHH...wifee...had one of those once ...if she don't like the bench idea, then scratch it, forget I mentioned it, and if YOU mention it, tell her it was YOUR idea....not mine .

Ok, all kidding aside, I meant next to the 12" cabinet, I guess I'm not picturing it the way it actually is. I was thinking, left to right, facing the wall we're talking about, was: The tub(against, and parallel to, the wall to our left, with one end against, or close to, "our wall")...then a space(where the bench would go)....then the 12" cabinet(against the wall to our right). But at any rate, cross bracing would solve the problem just as effectively.
 
  #10  
Old 01-02-05, 02:16 PM
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i think awesomedell's suggestion will give me to much height, tho i do understand that two 3/4" sheets of ply will supply more support than one.

here's what i've started to do. along the wall in question, i've begun installing 12" oc braces, that i'm pretty sure i can do the full 8' length of the wall. i've got four of them in place already. the problem installing them is that i have to reach under the wall, very tight space, and contort my body to get the screws in. cramps in my feet, legs, and hands, but i'm managing to get it done.

perhaps, every other brace, i'll run a cross brace. i may end up with a couple of 12" spans (2-3) between screws. if i decide to get real motivated and anal, i'll cross brace all the spans. that would allow me to have set my screws 6" apart along the full lenght of the wall. wouldn't this be adequate and eliminate the possible need for two 3/4" sheets of ply?

bob
 
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