Masonry sealer: To Seal or Not To Seal?

Gbenga asked us an interesting remodeling question:  

"Does an exterior sealer on a brownstone have any negative effects on the home?"

Masonry sealer can be extremely beneficial to extending the life of most man-made and quarried stone. You didn't specify the application, but "brownstone" is typically a form of sandstone. Sandstone is a quarried stone that tends to be particularly porous and can deteriorate over time when exposed to inclement weather conditions. Sealing any porous stone can only benefit its lifespan.

The only negative (or perceived negative) that we have dealt with in a masonry sealer is it can alter the physical appearance of the stone itself. Much like the difference between a piece of unfinished wood and varnished wood, sealer can darken and change the sheen of a particular material so you need to keep that in mind when choosing a sealer. Check out the image below to see what I mean:

If you have the option, test the sealer on an inconspicuous area of the stone and let it dry so that you can judge whether or not you like the finish much the same way you would with testing a paint color before painting a room. The difference being you can always re-paint a room, removing sealer isn't as simple.

I would also offer that before you apply any sealer, make sure the surface is properly prepared. In an exterior application I recommend pressure washing the surface to help remove any residues or staining. In an interior installation, I would suggest a mild soap & water sponging of the surface followed by a clean water rinse. In either situation, allow the surface to dry completely before sealing.

Always choose a quality masonry sealer! There are lots on the market and not every sealer is right for each application so make sure you do some research and don't swap quality for cost. A decent sealer should provide years of protection.

Hope that helped and thanks for Asking A Home Improvement Expert!