What fill should we use to withstand the weight of an 800 lb. clawfoot tub?

QUESTION

We have a customer that has terrazzo in their home. We removed the tub surround and a closet area and there was no terrazzo underneath it, so it is at least a 1-1/2″ drop down that we need to fill before installing floor tile on top. We will be installing a very heavy claw tub on top of the floor tile. What do you suggest we fill the hole with that can withstand the weight of the tub that is at least 800 lbs.? Concrete would have to cure and my customer is not willing to wait the 30 or 60 days unless it is the only solution. Is there anything else we can use?

ANSWER

I suggest that a thick bed (mud bed/dry pack) would be the best alternative to fill the void. Most require a 72-hour cure time at the longest. Some pre-mixed versions can be tiled over (or have membranes applied) sooner. If using a wet-bed method, it is tiled immediately.

Details for installing a thick-bed method can be found in the TCNA Handbook. Use the Method Locator for Ceramic Tile near the back of the book to locate the Floor methods then find the type of substructure (i.e. wood framing), and you will be directed to the page number(s) for the appropriate methods. 

Mark Heinlein

Mark Heinlein is Training Director for the National Tile Contractors Association. He is Certified Tile Installer #1112 and currently a Ceramic Tile Education Foundation evaluator for the Certified Tile Installer program. Heinlein was the owner of Mark Heinlein Surfaces of Negaunee, Michigan.