Jim’s Tip: Marble Floors – What We Need to Know

Based on pictures shared with us from HOUZZ and PINTEREST by our clients, we are seeing more and more marble in upscale baths. The walls and countertops are not an issue, but the floors provide some challenges for both designer and builder.

The Tile Council of North America, TCNA, requires that any floors with natural stone applied must be designed with a deflection of L/720, twice as stiff as code requires L/360 (“L” is the length of the clear span of the floor joist in inches). The challenge is that we have no idea what your client is going to select when we lay out the structure for the house. If we know ahead of time, stiffening that floor area is simple. After the fact it may become very expensive.

Changing the subfloor or the backer board isn’t going to provide the required rigidity, you’ll have to add additional joists. This may mean removing and replacing HVAC, plumbing and electric to get these joists into place.

The simple solution for designers and engineers is to add a disclaimer to the plans, but that doesn’t help you one little bit. The best choice is for all of us to be aware of the potential problem and attempt to get a determination or at least a direction on floor surface selections from the homeowner before we complete the plans. If homeowners know there will be a lot of extra cost to change the floor later, that may help them make some decisions earlier. 

Let’s work together on solving this one!

I never recommend social media links to anyone but recently I came across Build w/Matt Risinger, a channel on YouTube with a lot of detailed construction information. He’s a custom builder in the Austin, Texas area and he is talking about performance vs. prescriptive codes; contemporary interior trim details, soundproofing tricks, hidden door ideas, etc. All in all, this is a very informative group of videos. His channel publishes new content twice a week so you can watch what interests you.

Below is a link to a short video from Matt on traditional framing vs. high-performance framing techniques. He walks you through two houses while talking about and pointing out the differences.

https://www.youtube.com/watch?v=UDsaMFY3OcE   I hope you find it as interesting as I have.