I don't have a clear picture of his intent, but I'll toss this out:

As a tile backer and/or shower surround, a mud job is king. It allows the walls to be floated perfectly plumb and square, and with mesh properly embedded in and wrapped around the mud wall corners, you can actually grout your shower's inside corners instead of caulking them. It's rock solid construction.

Now moving on, he mentioned "acrylic or fiberglass" for the shower floor and or portions of the walls. I translate this as a manufactured acrylic shower pan and an acrylic shower surround unit. Installing an acrylic surround over a mud job doesn't quite make sense to me.

Or were those offered as two different choices?

In an ideal world, I'd use the floated mud walls as the base structure. Kerdi over that would give you topical waterproofing. Tile/glass over that and you have an installation that will last for generations.

An acrylic or fiberglass surround, it really depends on the quality of the unit. Lesser quality units, especially flimsy bases, can flex and crack around the drain, sometimes in a matter of years. Better quality ones can perform well for years.

As to a waste of money, I don't think a mud job is a waste of money unless it's to be covered by an acrylic surround.

I don't think Kerdi is a waste of money unless it's to be covered with an acrylic surround.

A cheap acrylic surround can be a waste of money, a failure in the unit can cause unseen water damage, if it's flimsy and the base flexes underfoot it can give an uneasy feeling when standing in the unit. A good quality acrylic surround can give excellent value for the dollar and perform very well. But it can be installed over drywall.

All totally my opinion.

Could he have been describing an acrylic or fiberglass waterproofing over the mud job?

I think I'm not fully understanding his intentions.

mongoct- thanks for responding. The gc is supposed to call me sometime this week. I will have to ask him to explain better. He definitely did not make it sound like it was one of those bath fitter surrounds but rather acrylic or fiberglass (I thought he said acrylic- hubby thought he said fiberglass) is somehow placed on the walls and will cover the bench seat as a waterproofing all before the tile job is done. The only other thing I recall gc saying is that when they come in to do the acrylic/fiberglass, the smell is really bad and the people working will be wearing masks. I somehow got the impression the acrylic/fiberglass is sprayed on... I will have to have him clarify when he calls

Gotcha. That clarifies things.

Sounds like they are going to do mud walls, a mudded in bench, and a mud sloped base. That's excellent construction.

Then it sounds like the acrylic/fiberglass is for waterproofing the seat area. The acrylic could be the waterproofing itself and the fiberglass could be fabric reinforcement for the corners.

I certainly don't want to intrude into his methods, as we all have our favorites. Personally, I've gone over to Kerdi for its 100% topical coverage. I have zero worries with Kerdi.

I'm not trying to sell you on Kerdi. As long as an installer isn't boneheading an installation, often times it's best for them to stick to their tried and true methods.

Mongoct

Again- thanks for your quick resoponse!! I got the feeling that although the gc was somewhat familiar with kerdi, he probably did not have much experience with its installation. He definitely said the purpose of the acrylic/fiberglass was for waterproofing and to make sure the walls are perfectly straight before tiling. SO assuming I dont do kerdi, any idea if this method would be good at keeping the shower waterproofed for years to come? any disadvantages? He thinks it will cost about $500 to the professionals do the acrylic/fiberglass? Your thoughts and advice?

THANKS AGAIN