shower tub renovation求建議 -續 （Plumber 也要掙40萬）

https://bbs.wenxuecity.com/fdcj/1869517.html

Bathroom remodeling companies all too busy to take cheap job like fiber glass tub replacement. They all want to offer $8k and upper new tub.  I have to wait until nov or end of Oct for fiber glass tub replacement from these companies. I can not wait that long. My normal contractor is busy with his house project. 

Thumbtack gave me 2 good connections. I found out my plumber could demolish and replace tub too. Without tub/plumbing kit, labor about $2500, 2x of what IEbird paid (Plumber 也要掙40萬lol). With it, about $3500 +-200. Compare this to resurfacing of $1450 (about 1mm thick sprayed coating), I will go with new one (worried about old valve would give me trouble down the road and joint between old tub and drain is a concern too). 

Tub support: some plumbers put in mortar bed underneath and some would not. I asked my plumber to put in mortar so the parts under pressure would not settle/become soft down the road. One plumber said: manufacturer says ok not to put mortar, but nice to do so. Another plumber said Sterling tub has more support underneath. I still insisted. 

ChatGPT: 

When you install a fiberglass tub or shower unit, the base usually needs support underneath to prevent flexing, squeaking, or cracking over time. The "code" doesn’t usually specify exact material names but requires that the tub be installed per manufacturer’s instructions and that it rests on a solid, stable, load-bearing surface.

Here’s how it’s typically done:

Commonly Used Materials Under a Fiberglass Tub

1. Mortar bed (most common & recommended)

   • Mix a pile of mortar (or floor leveling compound) on the subfloor.

   • Set the tub into it so the mortar spreads and supports the base.

   • This gives full contact support and is required by many manufacturers.

2. Structo-Lite® or similar plaster base

   • A lightweight alternative to mortar, sometimes used for easier handling.

3. Expanding foam (ONLY if manufacturer approves)

   • Some installers use minimal expanding spray foam, but it must be the type that won’t over-expand and lift the tub.

   • Not all manufacturers allow it, so check instructions first.

4. Wood shims or pads (for leveling, not as main support)

   • Can be used just to level, but you still need a mortar bed for strength.

---

What Building Code Says

• IRC (International Residential Code) doesn’t list “mortar” specifically. Instead it requires that fixtures (like tubs) be “installed in accordance with the manufacturer’s installation instructions” (IRC P2708.1, P2709.2, etc.).

• In practice → if the manufacturer says mortar or setting material is required, then code requires you to use it.

---

Best practice: Use a mortar bed under the entire bottom of the fiberglass tub for long-term durability and to meet most manufacturers’ instructions.

Do you want me to give you a step-by-step guide for setting a fiberglass tub on mortar (including mixing, placing, and leveling)?