Bathtub Install

[DKAudio]

I got a Kohler Archer bathtub. I was reading through the manual and it says either use construction adhesive under the 4 wood blocks of the tub or use a 2" thick bed of mortar in between the blocks. Which is preferred? The manual says the tub need no additional support other than the 4 blocks but I guess personally I would feel better with a bed of mortar for the tub to squish into. If I use mortar should I use plastic under and on top of it?

Also, my floor (house built in 1954) has diagnal 45° guess is 1X6 or 1X8 boards across the joists, then plywood or real oak wood boards depending on the area of the house. I haven't removed the old cast iron tub yet but from what I can see the tub is directly on the diagnal boards with nothing else. Should I put some plywood under the tub as well to disperse the weight more or will it be fine leaving it alone? If so what type and thickness?

Thanks

[DKAudio]

I was right...I just removed the cast iron tub and there was no plywood underneath, just the 45° boards which are 1X8s. The floor right next to it (with the tile) has the diagnal 1X8s and then plywood as well. I assume I should add plywood where the tub will go to disperse the weight more? Good thing is there are 3 joists that are under the tub (one doubled up and then a single).

Still see my first post for additional questions.

Thank you!

[The Builder]

It seems like your saying two different things. Your saying the manufacturer said it don't need additional support, and yet your saying that it says do more than the four blocks. What ever the manufacturer recommends for their product then do it. As far as wanting to add plywood under where the tub is for support, you can if you want, but remember, depending on how the floor looks underneath when you take up the tub, that a CAST IRON tub was already there. So you know that the floor is will equip to handle the new tub. Again it depends on the condition of the floor when you take the tub up. But also if you want to level the floor by adding the plywood board its totally your choice. Have fun getting that cast iron tub out. ha ha

[DKAudio]

Already got it out, did you see the pics of the floor I took? It wasn't fun but not too bad either. It was probably 300+lbs but I got a buddy over and we are both pretty strong, it wasn't bad. The manual for the new tub does say use either construction adhesive on the 4 blocks (feet) or use a bed of mortar...it gives both options.

[Java_Bob]

DK, that floor looks in good shape I would go rite on top of it.

[HayZee518]

the four blocks distribute the weight over a large area so I wouldn't worry about it. on the far side I would nontheless install a ledger board along the wall. all of the weight is on the floor just use the ledger board for stability. use the construction adhesive route. if you use the quickset it won't do much just add to the weight of the tub in that one spot.

[DKAudio]

Ok, my brother in law got a cheap fiberglass tub and I told him to put a bed down...he didn't, 2 months after the install the bottom of the tub cracked and leaked. Granted my Kohler tub is much thicker, I just don't want the thing to squeek and crack a couple years down the road. I am going to put a sheet of 3/4" ply down just so the tub will be on the same plane as the rest of the floor. The four blocks or feet on the bottom of the tub are fiberglassed in and are just 2X4s. Should be fine though?

Thanks

[The Builder]

A number of times you pay for what you get. I give you an example. If you by a can opener at a dollar store, and if you by one at a supermarket for a much higher price, which one do you expect to break? ha ha. If his tub really did crack did he take it back? Your tub should be fine. I installed a fiberglass tub a couple of years back, and certain that bathed in it were heavy, but it still stood the test.

[HayZee518]

I have a jacuzzi that I installed in my bathroom. The floor is 3/4 inch MFB - the tub sits right on the floor - no quickset, no adhesive. the tub base is all fiberglass. I screwed the base down using four 1 1/2 inch sheetrock screws. I have a ledger board running the length of the outboard sill. when filled to a depth of 14 inches the weight is nearly a half ton. nothing has cracked, nothing has creaked under all that weight.

[DKAudio]

Ok, that makes me feel better. The bed is just typically used for cheaper thinner fiberglass tubs/showers then?

I will just use some construction adhesive on the four feet and leave it at that.

As far as the ledger...the manual says do not use any ledger support under the deck of the tub, doing so may cause failure.

[pushkins]

If it were me I'd be adding the 3/4 (treated) ply over the 1x8's, for three reasons.
1. Much better support base.
2. It will bring the floor up level with the remainder of the bathroom( you mentioned the remainder was 3/4 higher)
3. It will help stop critters coming up from below and under the tub.
I always add the 3/4 in as it makes a much better support base for tubs, we have all seen that old 1x8 material with cracks in it and "Murphy's Law" says the feet of the tub will sit right in the middle of two slats and in the middle of two joists.

I'd glue down the feet and then after all the install is done (plumbing, tile etc...etc... add some low expanding foam under the tub from the plumbing inspection hatch.

[Johnbear]

Again it depends on the condition of the floor when you take the tub up.







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