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Unread 10-05-2014, 08:38 PM   #1
HDmstng
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HD's 4th Bathroom Remodel

Well I'm back at it again, and in the planning stages at the moment. This bathroom is 5' wide x 11.5' long. It is over a vented crawlspace and the floor joists run perpendicular to the 11.5' length. There is a steel beam the joists rest on, and it basically dissects the length of the bathroom nearly in half. The floor joists span 13.75' in both directions.

They are 2 x 10's the 1.5x9.25 variety, in good condition, but I'm not sure what species of wood. According to the Deflecto calculator, if they are douglas fir, I'm good even at a 14' span with a deflection of L/380. But if I go with unknown variety in good condition, I fail at L/290. Don't plan on using natural stone, but am worried about cracking since I am on the edge.

The house was built in 1972 ish, and I'm in SW Ohio. I can get a good look at the joists, but there is nothing stamped on them as to their make up. Any way to tell if they are douglas fir or not?

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Unread 10-05-2014, 08:57 PM   #2
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Welcome back, HD.

If you'll add that geographic location to your User Profile it'll remain permanently on display to help with answering some types of questions. If you don't, the information will be lost before we leave this page.

About the only sure way to determine the species, if you're not equipped, is to get a knowledgeable person under there to have a look. You could post some photos and we could take a guess, but with the distortions usually associated with online photos, that's pretty much what it will be. Sometimes the species is fairly clear, most times not.

Even more important than the deflection to my thinking is gonna be the treatment of the ends at the support beam under your tile installation. A photo or two of that area would be very helpful, or at least a very good description of what's there.

My opinion; worth price charged.
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Unread 10-06-2014, 10:44 AM   #3
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Howdy CX!

I'll try and get some pics this evening, but I'll do some splain' now. The crawlspace is roughly 30'x20' (outside to outside). There is a 20' steel I-beam that splits the crawlspace into two halves of 14-15' each. The I-beam has one center support and the ends are supported by one exterior and one interior concrete foundation walls. There is also a basement that shares the interior concrete wall and crawlspace. I'll need to pull down some insulation to see specifically how the crawlspace joists rest on the beam. Since the basement is roughly the same size as the crawlspace, I'm assuming they did it the same way. In the basement, the 2x10's sit on the sill plate on one end, and I beam on the other and are staggered. One goes to the back of the house, the other to the front of the house. One is next to the other, and they only overlap by the width of the I beam (6-8").

What concerns do you have in regards to the beam?
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Unread 10-06-2014, 09:09 PM   #4
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Attached are a few pictures inside the crawlspace. You can see the elbow coming down and the drain in the first picture. That is towards the front of the house and the tub/shower, toilet, and sink are all on that side. They would be parallel to the main steel I-beam. The the second to last one is from the basement showing how I assume the joists sit on the I-beam in the crawlspace. Plus a shot of the joists if on the off chance wood species can be determined.
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Unread 10-06-2014, 09:17 PM   #5
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A quick sketch of the bathroom, the floor joists are in blue, the I beam in red. The room is 5' wide x 11.5' and there is an exterior wall (orange arrow) where the tub is that runs parallel to the floor joists. I'll need to determine where exactly the beam runs in relation to the bathroom.
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Unread 10-06-2014, 10:00 PM   #6
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The problem you encounter in those situations, HD, result from loads in the center of the two joist spans in areas other than where you're tiling. The loads there that deflect the joists have a tremendous leverage over the end of the joist that's sitting on the support beam. While that movement maybe be very slight, it's vertical and very forceful. Vertical movement is not something ceramic tile installations care much for.

I certainly can't tell you from over here just how much of a problem you might have, but it's a consideration.

I would guess those joists to be Yellow Pine or something similar and not of very good grade at all from the little we see in the photos.

But that's what you've got and if you wanna tile over it it's entirely up to you. I'd want some really good subflooring in that room before I installed my tiling substrate and tile.

My opinion; worth price charged.
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Unread 10-07-2014, 07:31 AM   #7
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Can you tell that to the Mrs' CX? What you are saying makes perfect sense, give me a lever big enough, and I can move the world. Or in this case, give me a joist sitting on a beam with just enough deflection, and I can crack your tile.

That makes sense explaining also why we have some cracking where we do. I chalked it up to how it was installed. Based on other rooms in the house, the subfloor is 3/8" (not a typo, 3/8's) plywood, followed by 3/4" particle board (and no, not OSB, but saw dust glued together), mastic/glue, and tile. There is one area about 0.5' x 1' and is currently taped down because the tiles are loose, and that is right over the beam.

One bit of good news, I can put a substantial subfloor down. The adjoining hallway has 3/4" hardwood, followed by 1/2 (maybe 5/8") plywood, and then the good old 3/8" original subfloor for a minimum thickness of 1 5/8"! Ripping out the 3/8" subfloor in the bathroom would allow for two 3/4" pieces of plywood (or other suitable subfloor material TBD), plus 1/8 ditra. Would that do it for the subfloor?

If I can get the joist deflection under control then I should be able to limit any vertical movement at the beam. The question is, how much stiffening does the floor joists require?

Currently I'm at L/290 based on my spans.

1) Sistering the joists would get me up to L/581. But there could still be issues with the vertical movement as the sisters would be resting on the beam.

2) Plainrider's T-Beam technique with 2x6's would get me to L/725.

3) Adding additional support beams would get me to L/1386. Cutting the spans down from just under 14' to 7'. Would need to add two since the bathroom is split down the middle.

May need to find someone locally to better diagnose the situation also, any recommendations for someone in the SW Ohio area?

Thanks,
HD
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Unread 10-07-2014, 07:52 AM   #8
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Yep, and ol' Archimedes weren't even no tile man, far as I know.

You can try the T-beam approach if you want. Nothing wrong with the principle there, but the actual execution is the problem in real life.

The mid-span support wall or beam is generally the most effective when practicable.

Regardless what else you elect to do, you do recognize that the particle board needs to go, right? And with it the 3/8ths" plywood, which is acting as an unwanted spacer and nothing more. Removing it all might make the access to the crawl space easier for any stiffening operations you have in mind, too.

Starting over with a first layer of nominal 3/4" plywood would certainly be helpful and another layer of 1/2" plywood would make me feel a lot better.

My opinion; worth price charged.
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Unread 10-07-2014, 09:26 AM   #9
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The particle board and 3/8's subfloor were definitely going to go. Same with the vanity, toilet, soffitt over the tub. Will get in some basement/crawlspace guys in regards to an estimate for installing the beams. Logistically getting the beams in could be difficult. There is a vent opening, somewhere along the lines of 8" x 12", that a beam maybe able to fit through.

T-beams I could do, but I'm 6'5'' and would like to spend as little time in the crawlspace as possible!


The overall plan for the bathroom is to turn the tub/shower into a 60" x 32" walk in shower with the remainder of the layout staying the same. With the extra room for building up the subfloor, was even thinking of going curbless. Probably not with that beam in place though.
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Unread 10-29-2014, 10:26 AM   #10
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Had a structural engineer in to take a look since I had some questions about the bathroom walls being load bearing and not sitting directly over the main beam but the front wall being about 20 inches off and the back wall 40 inches off. No issues with that, but he was worried about the deflection on the back wall.

His recommendation was to use a 4x4 header (that maybe a typo so will double check) at mid span along the effected joists using 4x4's as columns set on deck piers. The deck piers would sit directly on the crawlspace floor. I believe this is the type of pier he is thinking about in the pic.

Only issue is there is a lot of gravel underneath the vapor/radon plastic barrier plus I'll have to deal with making sure the radon barrier stays intact once the piers are on top of them.

He had also mentioned during the inspection using an LVL beam supported by brackets or angle iron attached to the foundation walls as a midspan support beam. He hadn't spec'd out the beam, but did ask for that and the specs on the angle iron.

I like the idea of the lvl beam since they arne't supported on the crawlspace floor as the piers would be. Am worried there might be settling with those piers, not to mention cutting up the radon barrier.

Thoughts on the best approach?
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Unread 10-29-2014, 12:46 PM   #11
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I'm surprised your engineer was not concerned with the settling of those supports, too, HD.

And if you use a 4x4 as your support beam, you'd need your posts pretty close together. I agree that might be a typo.

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Unread 12-08-2014, 02:03 PM   #12
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Uggh, this is becoming a nightmare. Got a quote for installing two midspan beams. OUCH! Need 2 since the bathroom straddles the main beam.

I mentioned the strongback/T-beam idea Plainrider has talked about and the structural engineer actually believed it would be sufficient. He recommended using 2x6's and screwing it in every 8 inches.

It's not a bad idea, but the floor joists are stuffed with insulation and the insulation is held in by chicken wire. Obviously that all has to go and same beam guy quoted $2/sq ft for that job. They have to wear respirators, in a crawlspace, etc... not a fun job. But we do/did have mouse issues so I can't blame them.

Third idea is back to the deck blocks like the structural engineer suggested. Use two 2x6's as the beam, and put a deck block under each joist. I would need to support 8 floor joists on each side.
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Unread 12-08-2014, 08:18 PM   #13
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You give up on the LVL beam?
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Unread 12-10-2014, 04:49 PM   #14
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Not yet CX. The LVL's spec'd by the structural engineer are massive, 5.25" wide x 16" tall to span 16'4". Could get them down a lot if we do a midspan support, but I'm trying to avoid that. Mainly because the crawlspace is 4' tall and we have a passive radon system installed. Putting in a footer (two actually) was going to be a pain.

Interestingly, the company I spoke with about installing the beams said they used precast footers that they set on the ground. He didn't get into much details, but I assume they do some leveling, etc...

Makes me wonder though, can you just form and pour the footer on the top (right on the plastic barrier)? Or do you have to dig down. There are no frost issues inside the crawlspace.

To top it all off, SWMBO said she wasn't interested in converting the tub into a walk in shower but would much rather have a whirlpool tub...not that that makes much of a difference in terms of the flooring deflection.
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Unread 08-03-2021, 07:44 PM   #15
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It's been a while but revisiting this project. Ended up going with a wood laminate flooring in the bathroom since tile was out of the question due to deflection. The mid span beam was just going to be too costly.

The current bathtub has a bath fitter liner that is going on 18 years. The last few days, it appears to be extra squishy between the liner and the old tub. SWMBO has decided it is time to remodel the bathroom and convert the tub to a shower.

With the deflection issues, I know we can't do tile on the floor. But if I go with say a standard size kerdi shower pan 32"/36" x 60", can it be tiled? Or will I need to go with a shower pan instead?

Thanks all,
HD
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