setting tub in mortar?
 

I am installing a fiberglass bathtub. From the searching i have done it is recommended to set it in a bed of mortar for support. Should i lay down some 6 mil plastic or is it ok to put mortar directly on the wood subfloor? Thanks and feel free to share any other advice about setting tubs!

I put plastic over the mortar to keep it away from the fiberglass. I can put the tub down and stand in it to set it, then raise it up to make sure there are no low spots and the mortar doesn't stick to the tub.
Ron

Thanks Ron. So i don't need to worry about the concrete ruining the sub floor from the moisture in the concrete?

No. It will be fine.

Only thing I have noticed is it seems to set faster when on wood than on plastic. Maybe it was just me. Also - I built a little dam out of cardboard to keep the mortar where I wanted it. stapled it to the ply deck.

Not just you; it will set faster because the wood will absorb the moisture from the mortar, whereas the plastic sheeting will prevent this, so the only drying will be from evaporation . I doubt if the moisture from a one time application like this would premanently harm the wood sub floor, but I routinely throw down some sort of barrier. Just whatever is around..felt, visqueen, house wrap.