Travertine and marble are also porous stones. They are also not rated for outdoor use because of how fragile they are. Limestone, sandstone and granites are all good selections for outdoor stone, it all depends on taste and application.

All stone left outdoors eventually will weather with time. Some people like the weathered look associated with natural stone. If you are one who doesn't, you will simply have to pull the pressure washer out every 3-5 years to expose the pre-weathered surface.

Travertine is probably not a good selection unless you are in a warmer climate. Most contractors here in Chicago have stopped using it because of issues with cracking and shaling. Limestone, slate, sandstone and granite will be better selections.

The stone source is important too. Although we quarry a lot of limestone in Illinois, it's primarily used for gravel. We use limestone from Wisconsin and Indiana for most of our natural stone projects or bluestone from Pennsylvania.

Good luck with your project!