How To Reinforce A Floor Joist For A Clawfoot Tub

If you re worried about the joists under the tub i d head to a local welding or machine shop and get them to cut you some lengths of 1 4 or so steel that you can frame around the joists under the tub.

How to reinforce a floor joist for a clawfoot tub.

A 300 pound tub never mind the weight of the water when it s filled will place extra strain on aged joists even those not compromised by holes notches or insect damage. Both floor systems are normally strong enough to support the weight of a cast iron bath filled with water. The time to address these structural issues like reinforcing floor joists is at the time it was built or during a retrofit or remodel. The floor framing for bathtubs requires special attention.

Upgrading the surface of a subfloor is not the only possible solution for reinforcing a floor to support a cast iron tub. Older houses pre 1980s have wooden floor joists covered with pine floorboards. The tub will weigh around 500 lbs. The floor system is 2 10 joists spaced 12 inches on center.

A subfloor may also be reinforced from beneath the floorboards. The most common way to reinforce a bathroom floor is to double the joists. You must consider all of the weight the floor joists must be able to support. Note the photos show a recent bathroom remodel where we relocated the tub drain across several floor joists.

A standard bathtub can hold between 40 and 60 gallons of water. Add extra support to a floor beneath the floorboards by adding additional joists to the floor. Put those on either side of the joists that the tub will sit on and run bolts through the lot and it won t be going anywhere. Water weighs 8 lbs per gallon so 20 gallons in a tub would weigh 160 lbs.

You should be able to check the floor joist situation without crawling around under the house. If the floor joists are at least 2 x 10 on 16 to 24 centers with a 3 4 thick sub floor you should have no problems.