Q: I’ve specified an imported travertine for an exterior patio in a non-freeze/thaw environment. One of the local suppliers said they would not warranty it because they don’t recommend travertine for exteriors. Why is there a prohibition of using travertine outdoors? Isn’t it just like any other marble?
A: Travertine, despite being referred to as “travertine marble” for decades, is actually a specific type of limestone. It isn’t the stone fabric that causes the concern, it’s the filler. All travertines have voids in them, which is just the nature of the product, and in nearly all cases those voids will be filled. The filler is commonly a resinous product, but since it is done in an overseas factory, we don’t have control or even knowledge of exactly what product is used to fill those voids. In service, we frequently see discoloration of the fillers due to UV light exposure, and sometimes we also see dislodging of the filler. In your climate, travertines are sometimes used as exterior pavement surfaces, but in many cases they don’t age well. That is likely the reason for the supplier’s apprehension about providing it for your project. For the record, I’m in agreement with him on this issue.