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talktoterrence 01-29-2012 09:45 AM

Shower stall rot remodel...
Hey All,

New to the forum - but picking up a lot of advice since purchasing my first house. Thanks in advance for any help.

Quick question, long explanation. I've replaced some rotted subfloor in a bathroom under the previous owners shower stall, pretty hacked in and def a remodel at some point. Knucklehead had carpet on top of MDF in a bathroom - crumbled and rotted right down to and including subfloor! Anyway it was a ~30x40 fiberglass pan with 12x12 tiles up ~7ft walls.

Since replacing the subfloor and rotted sections of plates/studs, I've begun framing in the new stall approximate same dimensions. Did however widen the opening, 2x8 header, with jacks (went beefier). Walls are also taller now to be 80 inches when complete.

Anyway, question is weight. I plan to mortar the pan, and mosaic tile. The bathroom sits in a outside corner, and the stall about 6 feet from joists entering foundation, perpendicular to joists. 12"OC 2x8's @ 14'5 span with bridging - zero deflection noticed. Hard time deciphering span tables and would love a some expertise before deciding to put the shower back on whether it would be wise to do so.

I can't quite tell if this was part of the original house - despite finding it on some basic architectural plans we were lucky enough to find in a closet...thinking maybe later remodel plans. Custom architected/built house in 1970.

Thanks a ton all.


ddawg16 01-29-2012 11:22 AM

Welcome Talk.....very good explination of your situation....above par for most 1st posts.

We have one guy here who is an expert on this hopefully he will chime in.

Your setup sounds almost exactly like my sub-floor....2x8's 12" OC. I had some droop in my bathroom...real serious uder the shower due to a leak and rot. I ended up replacing a 10x14' section of was actually easier to put in the floor joist than take out the old ones.

Since you want to beef it up a bit, there is nothing wrong with doubling up a few floor joists. I did that in a couple of places, especially where a wall landed....I also poured a couple of pads and installed a girder under the bathtub.

As for spans.....I'm starting to think that was was ok in 1970 doesn't fly now. I'm in the middle of a 2-story addition and my upstairs is 2x12 12"OC...and the longest free span is 14'. Significantly stronger than the existing house.

talktoterrence 01-29-2012 12:09 PM

Thanks ddawg - appreciate the advice.

Good news is that none of the joists were rotted/affected by the water damage, so I won't be replacing any of those.

I like the peace of mind a girder however. I think I'll make that my plan for the day. However pouring pads pretty much isn't going to be an option. I live in the mountains, and while I have crawl space, the house is built almost exclusively on boulder. Digging into that is a non-option :)

Any suggestions how to go about this, or options. How many 2xn? I'm thinking I'll run a girder perpendicular under the four joists the shower will sit on top of. Don't know if I'll be able to get it dead center due to drain etc - but close.

Thanks again!

ddawg16 01-29-2012 12:22 PM

You don't have to be dead center....

For my girders, I used 4x6's. Here is a pic of one of them.

But without something pushing up against the's not going to really do much for you. I would think you would be better off sistering a couple of 2x8's up against your existing joists

talktoterrence 01-29-2012 07:29 PM

Thanks again for the advice and pic. Took the day off - first weekend day off since I moved in over two months ago. Trying to decide best approach.

Did you run your girder exterior wall to exterior wall, or a short support section under the tub? Not sure the best approach here. I'm guessing if I do so (wall to wall) it would be best placed mid span. My cross bridging runs the width of the house directly under where the stall is going.

Just trying to decide if I'm over-thinking things and making an engineering project out of a bathroom remodel :whistling2:

Anyway your advice has been invaluable. Reflection is a good thing. I'm having a engineer out to look at a spot of rotted girder (3 2x10's) at the foundation that I'm not in the mood to attempt... I get this all figured out than I can just have fun with putting on the 'makeup' as my wife calls it. Having a blast with this stuff, structural elements just cause me to pause...


gregzoll 01-29-2012 07:47 PM

Back in the 70's, carpet was what you saw in bath's, up to the early to mid 90's. Underlayment for carpet was pressed sawdust, now they are back to using exterior grade plywood as the sub. So stating that the contractor is a hack is beyond what you realize how homes were built at that time. The 70's saw a boom and change in how homes were built on the cheap in Tract's.

aureliconstruct 01-31-2012 07:16 AM

You should be all set with your 2x8 12oc for a mud job on the floor if none of the joists are rotted. If you want to feel a little more secure, you can do what ddawg16 suggested.

oh'mike 01-31-2012 07:41 AM

I ran a deflection rating----Bad news---over span for tile----2x8--12" on center---14.5 feet--

243------you need 360 for tile --720 for natural stone---

You need to beef that up----

talktoterrence 01-31-2012 10:15 AM

Thanks Mike. I'm just glad my gut served me right and I halted things when I did. The last remodel of that bath was definitely homeowner done - and had some shady framing to make a new fiberglass pan fit. I'm guessing it was at one time a full fiberglass frame when the house was built in 70.

Anyway - in a bit of a predicament now. What I thought was a simple job, replacing some rot, reframing, and throwing the drywall back up, turned into a little bit more than expected. I'd like to move ahead with putting in girder. Doubling joists would involve tremendous work in moving pipes and wires etc. which is outside of my skill/comfort level. If that's required - I think I'll have to go with a lighter shower stall than originally planned.

Can a girder be installed just under the midspan of the bathroom, say in an 8ft length? Or is this something that would have to go outside wall to outside wall? Also any ideas for concrete pad workarounds? The ground under my subfloor is largely rock/boulder. Would precast concrete blocks work?

Regardless, I'm having some structural people out to look at an unrelated issue in the crawlspace. I figure it best to get everything checked out, and settle my paranoia.

Appreciate the help guys.

ddawg16 01-31-2012 01:53 PM


Originally Posted by talktoterrence (Post 840222)
Can a girder be installed just under the midspan of the bathroom, say in an 8ft length? Or is this something that would have to go outside wall to outside wall? Also any ideas for concrete pad workarounds? The ground under my subfloor is largely rock/boulder. Would precast concrete blocks work?

Talk....2 of my girders are like in the pic....stuck out there and not attached to any beams or walls....then two of them are hung off a footing....

I don't see any issues putting a girder at say the 8' point. What you are basically doing is reducing the 14' span down to 8'.

As for precast concrete blocks....are you talking about the ones that look like a piramid? That might work...but I would think that you need to anchor them to your ground somehow. You might need to drill into your rock....embed some rebar...then pour a small pad to sit the blocks on. Once the blocks are in place...shim the girder as necessary.

oh'mike 01-31-2012 05:28 PM

If you add a girder like D-Dawg suggested you are solid as a rock---

2x8--12" center--8 foot span is 1090---360 is good for tile--720 is safe for natural stone--

talktoterrence 02-01-2012 10:56 AM

Sounds good. Thanks guys. I feel sufficiently prepared to get to work on this now this weekend.

I'm hoping to get down at least a little bit in a 3 places before hitting rock for the support beam to pour some pads. It's looking more like 5ft out from the exterior wall, perhaps I'll shoot for centering under bathroom wall directly above. The crawl space entry prevents me from going out too far which sits on the other side of that bathroom wall shared with my boiler, etc. Entry is sistered all around with 2x8's (which I would expect) - two running the full length - so should get even more stiffness there being so close to stall.

18x18x6 suffice enough for this - rebar grid - being not a main support? Or is that overkill? Will do some 4x4 posts for girder at about 8ft in length under the area.

Thanks all the help - hopefully not too many more questions!

oh'mike 02-01-2012 11:15 AM

Your plan sounds good----I like to see a thicker pad than 6 inch---depends on the soil under there ---

ddawg16 02-01-2012 11:34 AM


Originally Posted by oh'mike (Post 841302)
Your plan sounds good----I like to see a thicker pad than 6 inch---depends on the soil under there ---

I agree with Mike....even with rebar...6" is kind of thin with that kind of point loading....

The spec for my pads was 12x12x12...sitting on adobe soil....they ended up being more like 16x16x12 with the 6x6 concrete post you see....

A couple of things I learned from doing mine....

Make it makes it a lot eaiser when it comes time to set the girder....I actually took a long board and screwed my post forms to that board...I then anchored the board to my floor joists so that the concrete posts where properly aligned.

I put my forms together with screws....made it easier to remove....not a lot of room under my existing house.

Let it dry....give the pads at least a few days to dry before you install the girder and start jacking it up and installing shims.

The following 2 pics are what my bathroom looked like 6 years ago....we had a shower that leaked....the floor was actually sagging almost 2" in this area.

In this pic you can see one of the pads I 'was' using to support the floor.
We ended up not putting the shower back in....I used one of those pads to support the area under the bath tub.

Here is a pic of one of the new girders that is supported by the footings....
The reason for all this....this area is where we installed the stairs....those 2 footings your looking at were poured last summer 'under' the house....that wall on the right is the same wall in the above pics in the seperates the bath from the now supports the stairs....

talktoterrence 02-01-2012 01:39 PM

Another awesome post. Thanks DDawg/Mike.

I'll go thicker on the pad for sure. You had quite the job there - I'm thankful my joists were fine! Thanks for tip re pad placement. As for jacking - wasn't planning on it due to the fact there is no more than 1/8th to 1/4th inch of settle I'm seeing. Floor is solid and level. Was going to mallet in the posts for a tight fit, and secure accordingly to give the support I was looking for. Please let me know if I am incorrect in my thinking - otherwise thank you again.

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