I'd call someone else and get an opinion. My understanding is that marble is very porous and must be sealed. I have a client who had marble installed for her island countertop during her kitchen reno three years ago, and it's completely a mess with water rings already.

Is there a chance that your marble was sealed at the factory?

ML

They will be installing the sink and the toilet etc. and I fear with their boots and plumbing parts etc. the floor will get scratched

Sealing doesn't do anything to prevent scratching.

I was visiting my best friend this summer and her DH was re-doing a bathroom. It's a historic home and she wanted me to help choose the flooring, and marble was our choice. After installing, her DH immediately sealed it. Since we brought home the tiles, he had no contact with anyone re:a question of sealing, so he must have known this is something which needs to be done on completion. Hope this helps.

Not marble but....My son had ceramic tile put in their kitchen with white grout. Their installer did not recommend sealing the grout....said it was easier to clean without the sealer. I had never heard of that.

I think marble tile is supposed to be sealed before grouting but I don't know for sure.

Sealing won't prevent etching. My marble powder room floor of Carrara is etched. That's a property of marble. My marble counters are etched, too.

I installed my mother's travertine marble backsplash with my brother who is a contractor. We sealed the marble before installing so that the grout would not stain the tile. I think we did two coats of sealer because the first coat sucked in. We had a choice of sealer, one was more shiny and one was matte. We choice matte.

I sealed my Carrara marble hex floor (after grouting) with a product called 511 on the advice of the marble retailer. It's a liquid and very easy to apply. I try to do it about twice a year. It still looks like new.

I think you can find more info. on this in other threads on GW. Try doing a google search for marble sealing Garden Web.

You might also consider putting cardboard down to cover the majority of the floor before the plumbers arrive.