Drop in frame for whirlpool

OK, this is my first drop in frame.

Water damaged sub-floor repaired, joists reinforced with blocking, even put sound proof insulation down.
Now I have a question on the correct height for the drop-in tub.
Here it goes.
Height of the tub deck is 19", lip edge is 2" so the height from the floor to deck lip edge is 17". Now for the vertical frame calculation using 2x4s: Bottom plate 1 1/2, top plate 1 1/2, plywood 3/4, cement board 1/2, tile & mortar 1/2, vertical 2x4s at 12 1/4. This gives me a height of 17". Bottom of deck lip edge is 17" so I should be good, right? (1 1/2, 1 1/2, 3/4, 1/2, 1/2, 12 1/4, = 17) What I did not calculate is the mortar bed the whirlpool will sit in. Do I add another inch for the mortar bed? Meaning the height to the deck lower lip would be 18" and my frame needs to come up another inch? Or do I ignore the mortar bed with the idea that pushing down into the bed will displace enough mortar to make the bottom of the whirlpool practically sit on the sub-floor. The whirlpool is a jacuzzi primo if that matters. comments &/or suggestion appreciated.

questions:
1. Am I building to the correct height?
2. Do I mortar & tile after setting the tub in mortar bed or before? (current plan is to set in mortar bed first & use 1" scrap wood to leave space for the cement board & tile & mortar.

If you can tile the tub deck first that is dream. Then your life will be easier.

If you want to tile after then 5/8" spacers work well for 3/8" tile and 1/4" thin-set.

The mortar mix under the tub should be higher than needed. The tub set overtop and squished down to resting position. The tub should sit on it's feet and the mortar mix serves as only bonus strength between the feet.

We use poly to keep the mortar from bonding to the tub.

Just installed one yesterday.

I'll look for the pics.

JW

JW, thank you for the response and the pics. I get nervous when measurements have to be exact especially the first time I am doing something. This really helps. Gives me confidence I am on the right track. Did not think about the poly, I will incorporate that into the project. Pics really helped. Thanks again

clapfc said:

JW, thank you for the response and the pics. I get nervous when measurements have to be exact especially the first time I am doing something. This really helps. Gives me confidence I am on the right track. Did not think about the poly, I will incorporate that into the project. Pics really helped. Thanks again

Click to expand...

Your welcome.

The poly is key. Once you set that tub run it through it's paces. If you need to remove it because of a leak you will be glad the tub is not stuck to the poly. The poly is a bond breaker here.

The mortar mix does not hold up the tub but only prevents it from sagging in the middle. It will feel more solid this way.

JW