You need to clarify the location of the tub "deck"

Is this in an alcove, and three fixed walls surrounding that Underscore tub?

If this is an alcove, with those fixed walls, you are talking about a jiggle into the space, with a huge cut out and very little surface deck. Even transportation from the fabricator to the house implies fragility, let alone achieving the perfection on site.

Marble is fragile until set in place. It can chip, crack easily in transportation....

Did you ask as to the specifics of reluctance, which should have been the job of your "designer" and her communication WITH the fabricator.

I have to agree the fragility of a huge slab with very little around a large hole is asking for trouble even a tiny bit off in that fit can spell disaster . Pictures anywhere can be manipulated so just because you saw it on Houzz does not make it so. Alcove are rarely absolutly perfect no matter how many times they do the measure Even getting that piece into the bathroom can be an issue around corners . You designer should know this BTW and be tlking to the fabricator that I presume they chose

Do u know if this is the best fabrication company in the area? Do they have the best reputation? Maybe your designer hasn’t aligned herself with the best. OTOH, maybe he or she has, and that complicates things.

Would definitely suggest a freestanding tub instead of one with a deck.

I do not agree a FS tub is better for many ereasons but since we see nothing about the space we can only comment on the deck choice . BTW no idea what awaterfall tub deck looks like

I have a large one piece slab of marble around my tub, but my tub is a drop in not an undermount.(don’t know if that makes a difference, it’s still a large slab with a big cutout in the center.)
I agree with you that seams would look lousy.
If your fabricator doesn’t feel comfortable doing it in one piece, it probably means he lacks the skill to do it. I’d try to find someone else who has done this type of installation successfully.

Something to consider: doing in one piece on the deck means using a complete slab with a lot of waste, unless installer can incorporate the pieces elsewhere and match up.

Perhaps contact other companies and weigh feedback, pros/cons, costs and ask for pictures of their work, as you don’t have enough info to make this big decision. I’m not speaking from any experience, but you don’t know what you don’t know.

It uses a whole slab with a cutout, that is then cut in 2-4 pieces, and self seamed back together on site. This is 100% normal, and done every single day for logistics reasons.

The slab backsplash on the tub in the photo above, definitely allowed them some wiggle room in the fit, as it didn't have to be perfect because any gaps would be covered up by the slab backsplash.

OP, what are you doing above the slab deck?

chispa: Maureen's photo above (thank you, Maureen) is almost identical to our situation. It's an alcove, with an undermount tub, marble deck and waterfall/apron, and 4" marble backsplash on the three sides (milled from the same slab).

We've been communicating with the fabricator via the designer and the GC. The fabricator said they can try to cut and install it as one piece, but it's 100% at our risk. They say they're 90% confident it will break, and that any other solid stone would as well. It's a huge disappointment and one we're finding very difficult to overcome.

The designer business has a solid reputation (why we chose them and paid the big bucks to do so) and has been around since the 70's as a three generation business. We've dealt with several fabricators in the past; one we would definitely recommend to anyone and one we would not. We have not personally dealt with this one, but the designer business swears they are the best locally.

Thanks, everyone.

I think you are anticipating a disappointment that won't happen. They've advised you the very logical risks and are wise to protect themselves from that reality..

Minardi has it correct, above, and they should be able to show you how seams /veining will align.

A "three generation" design business, a name as any other , can't guarantee the talent or wisdom of all heirs. .....and the designer should not have made the guarantee. She should have been AT the fabricator with you, along with the tub specs, a drawing and the entire bath plan.

I would proceed and do it their way, with the guarantee on visually pleasing seams, that will be no more noticeable than they are on a kitchen counter top. With a laser template and a computer, they can show you this, well before the cut and polish. ( If you're wise, you will also talk about the inside finish edges. The under mount method ( any material including quartz or granite ) can result in sharp edges you will not enjoy leaning against. Consider some extra ease to those.)

Back to your concern......

When veining lines up? They're usually not noticeable seams and hardly anything you should visually search for!.

Chasing 100% Perfection in any build or remodel is often a fools errand met with disappointment- perfection is also overrated. Encountering a slight glitch, is not usually a fail. I'd prepare to be very happily surprised. Unless a reason you can not? A four inch riser around that much tub, EVEN with a low window? Feel in contrast to the luxury of waterfall slab front. I'd give that riser a BIG boost....unless you are short on material.?

I think minardi is correct so one slb cut to fit and perfect seams all done those should be close to perfect minus the saw width Still IMO the best way to avoid real issues and the cut out myabe can be used somwhere else who knows

You are 100% overthinking this if you have a good fabricator involved. You've been to their showroom, and seen their seams? Youve seen their work elsewhere? Then let them do their job.

I don't think you are over reacting. You are being cautious, which is prudent. Why are you caught in the middle? Why is the designer not guaranteeing their ability to produce for you what they designed? What is the designer saying about how four cuts will look? Who have they used in the past who has done this with no cuts and why are they not steering you to this fabricator? The designer concocted a nice idea for you. They should be able to execute it.

^^

You can't and you don't, in this business, "promise " a design on .ANYTHING for which you won't have 99.5% control. You assume responsibility "guarantee outcomes", when you have in writing from whatever source, that they can produce quality exactly as designed. The designer did not do, due diligence with this aspect of her design.

Promises, made with no wiggle room, intent of all good things to come .......can and do go awry. Having the " last slab on earth" in a stone yard.....it shatters... Splits at a fissure! The entire bath designed around a slab and you go to plan B. WHAT plan B!!? Some things are annoyance, some are human error, and some are yes indeed , big problems. LARGE or small, they are the nature of build and remodel - neither of which is for faint of heart as we all know.

If we may assume the OP has a slab she adores, a bath layout she loves, all her other selections are in place for the room, and is on the way to a gorgeous bath of her dreams? This will turn out to be a nit! Or she can force the hands of fate and risk the TOTAL outcome , based on an ill researched......promise.

Or she can force the hands of fate and risk the TOTAL outcome , based on an ill researched......promise.

Yep, bounce it back to the designer. Ask them to oversee this installation of the seamless marble top and ask them what their remedy will be if it cracks. Who will be on the hook for the cost?

I have an expression I use all the time with each and every one of the sources that allow me to execute nearly............anything. " Expertise DEFER!" It might be a beautiful mat and frame on a treasured piece of original art, or a gorgeous broadloom carpet where someone insists on wall to wall carpet in a primary bedroom. Maybe it's a mantel surround?

We're at two beautiful options at my framer. .We laugh..they're both great! "You pick, ! You do this every day, I love them both and so will my client.

The bedroom......." Jan.....don't do it. It's just not going to seam well". Out comes his pokey awl. "Look"...( he runs that awl thru the rows of the luscious wool with the fabulous texture .....and I take his word !! He's been at his job for forty four years, more yards of carpet installed than we'd ever be able to count.

Lets use the mantel surround /true example below. SOAPSTONE.

ALL four sides. I wanted no seam. It's a long ride from the shop to the home, ......answer? "No. We don't recommend. Good possibility it cracks on the way. " That surround has seams. Imperceptible seams.

Wrapped views · More Info

I'm out with only this to the OP.

You designed this bath for your best friend. Same tub. Same advice on tub deck...........And you tell her what? : )

"I'll oversee your install!! " Which might mean you get to witness a crack? : ) What now, Kimosabe?

Self seams are done every single day in stone so that they are transportable, or handleable. All the full height splashes? Multiple pieces, cut for transport and then seamed back together. Same with most tub decks. Some even need 2 bookmatched slabs for that. All of the 14’ walls of stone around a fireplace? Bookmatched slabs, seamed together. Seams, done well, are never ever a problem.

What you are really saying here is that you do not trust your fabricator. And that means you didn’t do due diligence on the front end, to develop trust. Did you just go with the cheapest quote? A questionable neighbor’s recommendation? How did you select them?

If you can’t trust them, find a different fabricator. The MOST important factor in getting a good result, is a good fabricator.

Ask what trade industry associations they belong to? MIA, SFA, ISFA, BSI, etc. What about continuing education? What was the title of their last seminar? What industry trade shows do they attend. The only wrong answer is none.

Do they have their work anywhere public they can see? (Many have it on display in commercial projects, kitchen and bath showroom, or have a showroom at the shop)

What is their process? Minimum is they offer basic advice about suitable wholesalers to shop, advice on specific stones, discuss seam placement preference, overhang supports, and allows you to view and discuss the template placement on the slab.)

What fabrication machinery do they use? (CNC, or water jet are acceptable, angle grinder snd cutting in site are not)

Can you view the fabrication shop? (should be a OSHA approved WET fabrication shop, with zero dry cutting or polishing, and everyone wearing goggles, respirator, and hearing protection. Just google silicosis and quartz to understand why.)

What is your process if my home is damaged? What risks am I responsible for dealing with? (Liability insurance if they drop it and ruin your wood floor, but your responsibility for touching up paint)

What if I have an issue with the install? Who do I call? ( wrong color being delivered, or wrong seam location—DO NOT LET THEM INSTALL IT!)

Do you have a follow up procedure for repairing chips? What is the charge for that? (Chips are not warrantied by any manufacturer or fabricator, but many good fabricators will do a fill or file the first year. And charge after that.)

This is a risk bearing issue, nothing more, nothing less. Someone has to pay for the risk of damage and/or failure. The fabricator is cutting his risk at the possible expense of the look you want. If you can't compensate him for the additional risk with more money and a waiver, shop another fabricator.

My most profitable jobs were those that other fabricators/installers insisted "couldn't be done". Music to my ears and wallet and the most appreciative customers as a bonus.

^^

The classic Price, quality, delivery pick two.: ) Win a puppy from Joe if it takes you more than three seconds to figure out which two you get when he works some magic for you.....?

Pics or it didn't happen!

I love the update! As I mentioned, my marble tub surround had been successfully done in one piece, and I was very surprised that there were so many wonderful design experts who were such naysayers in your thread!
Enjoy your new bathroom!