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Support for a Heavy Tub

Q: Is our floor strong enough to support a heavy cast-iron tub?

illustration showing the guidelines for joists
Illustration by Harry Bates

I'd like to install a vintage cast-iron pedestal tub in our second-floor bathroom, but we're not sure if the floor is strong enough to handle all the weight. Our house was built about 1975. What do you think?
Connie Olson, Onalaska, Wis.


Tom Silva replies: Most likely you won't have a problem. The joists in houses that age and newer should be plenty strong enough to bear the weight of the tub, even when filled with water. However, it's possible that someone cut through the middle of a joist or two to install heating ducts, or drilled big holes to run drainpipe, or made notches for supply pipes. Or perhaps a persistent leak has weakened the joists. A sagging, soft, or loose floor, or a cracked, water-stained ceiling in the room below are good indications that something is wrong. But even if the floor seems solid, play it safe and investigate the situation before you lug that tub up there. Unless you're gutting the bathroom, it's usually easier to make some ­exploratory cuts in the ceiling of the room below.

If you do find ducts, pipes, holes, or notches, don't be alarmed. Some cuts are okay, as long as they aren't too big or in the wrong spots. The il­lus­tration above shows exactly what's ­allowed under the building code and what's not. If the cuts do violate the codes, call in a contractor to fix the problems before you proceed with your remodel.


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