I recently replaced my tub in my master bathroom. The tub I used is a Sterling tub with side panels that went with the tub. The tub itself had what I can best describe as a pedestal or a plastic foot frame that went on under the tub. The customer service people from Sterling indicated that if I had a solid and even floor I would not need a bed of mortar for the tub. I installed the tub without the mortar because I had new decking under the tub and it was flat and even. However after installation the area from about 6-8 inches from the drain and back from the drain about 8 inches seems soft and springy. I was told I could shoot foam insulation under the tube to form a more solid surface. I was wondering if anyone else has an opinion?
i have seen this work to stiffen tubs before if it is in a spot that gets a lot of foot pressure, closed cell foam is best "2 part foam comes in two bottles that mix in tube as sprayed" but i have seen someone use the great stuff and said it had worked it was under tub for a year when i talked to them and was still fine