Setting tub

Replacing old cast bath tub with new tub the old cast didn't have a mortar bed. New tub will have apron. Sub floor is not perfectly level, it is 1x8 boards. Have some questions about a mortar bed for tub install.
1 Just mortar mix?
2 How wet or loose should mud be?
3 Do i set the bottom of the apron in the bed also? (Do i spread the mortar the whole area of the tub)
4 How thick?

Thank you. Larry

Lightweight concrete like Gypcrete is good, heavy but fluid consistency.

BUT, first, determine if the tub you are using REQUIRES or PROHIBITS underlayment. Varies greatly by type of tub.....get the manufacturers installation instructions.

Do not bed the apron. You need to have a more or less level floor. The apron supports the front, and a 2x4 ledger across the back supports that. After those items are in place, then the mortar bed issue is per instructions.

A bed does two things...compensates for an uneven floor and supports tubs that aren't real sturdy from deflecting. A CI tub is strong enough to stand on its own and doesn't 'need' a mortar bed. The feet do need to be supported.

tub

What kind of tub. I have never used a mortar bed under a cast iron tub, and seldom use one under other materials either.

I've never bedded a cast iron tub either.

I put a 2x4 on the back wall using a level,
And then if needed, shim the apron. The apron like hj mentions touches the floor.

With some fiberglass tubs, I may use some mortar.
I don't use a full spread, but piles which can spread out a bit when the tub is dropped.

What material do you use to properly shim a cast iron tub? I want to make sure that my shims do not compress over time due to the weight of the cast iron.

Thanks!

Terry said:

I've never bedded a cast iron tub either.

I put a 2x4 on the back wall using a level,
And then if needed, shim the apron. The apron like hj mentions touches the floor.

With some fiberglass tubs, I may use some mortar.
I don't use a full spread, but piles which can spread out a bit when the tub is dropped.

Click to expand...

tub

You do NOT shim it. The back edge rests on a ledger board and the front side rests on its apron. If there are legs they are a bonus, but do nothing to support the tub.

Am planning to install Sterling Vikrel Ensemble on ground floor slab. Haven't torn out the old 1 pc fiberglass so don't know how level the floor is yet. Have recommended spun bonded underlayment as recommended by Sterling and may use if slab is ideal for that material. The install instructions don't suggest how much or if you multifold the stuff. They do say place the felt pad if provided. Many pros suggest throw it away and mortar. I also have mortar on hand and plan to use it as an option as Sterling suggests. You posted using visqueen poly for a cover over the mortar in another place but not so here. I was wondering if it depends on other conditions, type of tub, etc., that dictates use or not. Not to get crazy but could you quantify how much you would use in creating those 'piles' which spread when tub is set in. Also how many mil thick would you go on the poly? Like some others who have commented the waffle like molded tub bottom can affect how the mortar spreads, I wonder if this influences the decision for using poly either under, over or both sides of the mortar base. For a lot of us DIY'ers this seems to be a never ending dilemma. Having search extensibly for a consensus, I get the impression the pros go with the mortar. Appreciate all the good scoop on this forum. I don't think I would have tackled this project if not for the freely shared expertise passed along here. Thanks.

I installed my sterling ensemble tub without mortar. It has been in for 3 weeks and cracked on the top edge. I don't think this is caused due to no mortar but now want to put mortar under the tub. I have access. Any suggestions that are proven with the exception of resetting it. I have all tile installed.