Extended bathtub defined
An extended bathtub is longer than the 60 in alcove tub that is the US standard. Extended tubs measure 66 in, 70 in, 72 in, and 78 in. Width runs 30 in to 36 in. Water depth from the overflow to the tub floor runs 12 in to 18 in.
Elongated Soaking Tub Guide: Length, Depth, and Fit
The extra length adds leg room for a person over 6 ft. It also changes the alcove opening, the framing, the drain location, and the water volume.
Common extended sizes
- 66 x 32 in: shortest extended alcove model.
- 72 x 32 in: most common extended alcove size.
- 72 x 36 in: wider deck and shoulder room. Needs a 36 in alcove.
- 78 x 36 in: largest alcove size sold at retail.
- 66 to 72 in freestanding: same length range, no alcove needed.
Check the spec sheet, not the marketing name. A tub sold as 72 in often measures 71.5 in at the rim so it fits a 72 in opening.
Space and framing
An extended alcove tub needs an opening the length of the tub plus 1/8 in to 1/4 in. Walls must be plumb and square within 1/8 in, or the apron and tile flange will not seat.
A 72 in tub passes a 32 in door when stood on end. Hall width and ceiling height decide if that turn is possible. Tubs that cannot pass go in before drywall or through a removed window.
Water weight drives the framing. A 72 x 32 in tub filled to 12 in holds about 80 gallons. Water weighs 8.34 lb per gallon, so the water alone is 667 lb. Add a 100 lb acrylic tub and a 150 lb person, or a 300 lb cast iron tub. Total load runs 900 lb to 1,200 lb over about 13 sq ft. That is 70 to 90 psf. A residential floor design load is 40 psf. Joists under the tub need a check by a structural engineer, plus blocking or a doubled joist in some cases.
Water supply and heater
The body displaces 15 to 20 gallons, so the faucet runs 60 to 65 gallons for one bath. Tub fillers deliver 4 to 8 gpm. A 60 gallon fill takes 8 to 15 minutes.
Hot water demand is lower than fill volume. At a 130 F tank setting and 50 F inlet water, a 105 F bath of 65 gallons draws about 45 gallons from the tank. Check the first hour rating on the water heater label. A 40 gallon gas tank with an FHR of 65 gallons covers one fill. Two fills in one hour may pull the tank cold.
Cost
- Acrylic extended alcove tub: $500 to $1,500.
- Cast iron extended alcove tub: $1,500 to $4,000. Cast iron weighs 300 to 400 lb.
- Freestanding acrylic: $900 to $3,000.
- Removal, rough-in, and tile labor: $1,000 to $3,000.
Prices vary by region and finish. Get the quote in writing with the model number.
Buying checklist
- Measure the alcove opening at the top, middle, and bottom.
- Record the drain center distance from the end wall. Match it to the new tub.
- Check the overflow height against the existing drain arm.
- Confirm the tub passes the door, hall, and stair turn.
- Note joist size, span, and direction under the tub.
- Read the spec sheet for exact rim dimensions and gallon capacity.