How to use marble as a surround over a cast iron tub?

Do you have any pictures, its hard to visualize.

Is it a free-standing tub? If it is I think the best way would be to mount the marble under the lip of the tub. If not, the marble will need to be cut and smoothed to form a smooth edge to the tub. I would check with a company that installs marble to find out the best way to do this.

You would need to build a framework around the tub from floor to tub top out of 2X4's. The marble/quartz would be placed on top of the 2X4's with a bead of caulk. Then cover the framework with plywood. Prime, paint, and seal with three coats of a water based polyurethane.

Something like this

https://www.addicted2decorating.com/diy-tub-skirt-decorative-side-panel-for-a-standard-apron-side-soaking-tub.html

https://www.thespruce.com/before-buying-a-tub-surround-2718960

https://www.youtube.com/watch?v=q7OWuvGHZ-c

The framework would be built custom around the tub out of a sturdy wood product with the purpose of supporting the surrounding area and not the tub. A skilled carpenter could do that, then the quartz or marble would be cut to fit and glued to the framework. Caulking would be needed where the tub and base come together, either under or over the lip, which ever you chose. Best to you.

Hi Tracy, hope these helps you out,

https://www.diynetwork.com/how-to/skills-and-know-how/masonry-and-tiling/how-to-install-a-marble-floor-and-tub-surround?soc=sharepin

https://www.johnbridge.com/vbulletin/showthread.php?t=30426

You should be able to use a sealant like silicone to deter leakage, you don't want the marble to flex,

Here's a post that might help - https://www.thegritandpolish.com/blog/diy-tutorial-install-tiled-shower-surround

Hello Tracy,

This might be a project for an expert Stone cutter...........

It's the framework that would support the marble slab not the tub. The weight of the stone could crack/crush the tub or cause it to sink into the floor. The feet on the tub would not be able to carry the weight. The weight needs to be evenly distributed hence the framework.

Hi Tracy, I think it would look stunning. If cutting the marble proves to expensive, perhaps you can swop the marble for the skirt and use something like cedar for the top?

They don't laser cut stone. They use a diamond blade water saw. The bevel edge is ground with diamond carbide router bits.

Hi! Stone is tricky, and you need not only the right tools, but, the support for the weight. I would speak to a local company that works with these materials, and ask them how much it would weigh, for one thing. Keep in mind that the cast iron tub is already heavy. Fill it with water, heavier. Add stone, and unless you have a concrete slab under it, you may have to beef up your floor. Get a contractor who knows what they are doing, and it should be lovely! Good luck!