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How can I tell if floor joists under bath tub are rotten?

How can I tell if floor joists under bath tub are rotten?


Old 04-23-14, 01:39 PM
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Question How can I tell if floor joists under bath tub are rotten?

Hello DIY Forum!

Question. How can I tell if 2" x 10" floor joists under bath tub are rotten?

I have got a condo under contract for sale. I am the buyer.

The condo was built in the year 1969. My unit is a second (top) level unit.

The finish floor in the bathroom has a pressed [i.e. chipped] wood board finish floor.

A repair man that is familiar with the building said the floor structure was 2" x 10" floor joists.

The floor has been replaced sometime in the past because in the year 1969 chipped wood press board had not yet been invented.

There is water damage at the corner where the wall meets the bath tub. The seller is going to remove the finish floor and the sub-floor.

He then is going to let me have time to inspect the floor joists.

I am going to have to lay down on the floor [belly first], shine a flash light between the floor joists, and then look underneath the bath tub.

I was going to take a screw driver, reach up under the bath tub, and try and jab it into the floor joists. I don't think my arm is long enough to reach the floor joist all the way at the back of the tub.

How can I be reasonably sure that the wood floor joists at the back of the bath tub are not rotten?

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Old 04-23-14, 02:29 PM
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Put a level on the tub and see if it is way out of wack which would indicate issues with the support mechanism.

Truth be, that most of the issues in bathrooms are not found under the tub, but at the curtain lip where water spills over and at or near the toilet which is a constant problem area. Other area to inspect is the front area of the tub where the drain and supply lines are. These can be viewed through a service panel that is many times found in an adjacent closet or room.
Old 04-23-14, 03:39 PM
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Checking the levelness of the tub like Crizzi mentioned is a good tip especially if you don't have access to look underneath. I look for cracking of the caulk or grout where the tub meets surround which can also indicate that the tub has sunk. And, if you're a brave person get in the tub and hop up and down (while still keeping your feet on the tub) and see if there is motion between the tub and surround.

Since you'll have access below your eye & screwdriver will tell you more. Wood that has been dry all it's life will have a nice light color. If the joists have been wet for long there will be water stains that remain even after the leak has been fixed. Stains don't necessarily mean the wood has been compromised but should be inspected further. Your screw driver will quickly tell if the wood has softened/rotted and how extensive the damage.

Most tubs have a lip around the perimeter that extends up and behind the surround so water rarely gets down behind the tub. The front where careless splashing can seep into the flooring is more common. Another problem area is under the faucet and drain where a slow leak may go unnoticed for years.

The difficult thing is that the subflooring is put down then the tub on top. It is difficult to replace the subflooring underneath the tub without removing the tub. Often they will cut right at the edge of the tub and only put down new subflooring for the area you can see and leave the old under and supporting the tub.

Another thing to inspect is the toilet. Sit on the toilet and notice if it moves under your weight. Give a little wiggle and see if it moves. Often the wax ring will leak and the water seeps through the subfloor rotting it. The toilet, without a firm floor underneath wiggles which makes it almost impossible to keep wax rings from leaking. A wiggling toilet can also be from a broken toilet flange so there is nothing for one or both hold down bolts to grab.
Old 04-24-14, 07:13 PM
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I think the floor is okay. The seller removed the comode and tore up part of the floor.
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Old 04-25-14, 07:41 AM
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Will you be repairing the floor or the seller?

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