Tuesday, March 13, 2012

Should I fill deep saw cuts when staining exterior concrete, like sidewalks and patios?

Ask a Pro

   Q. -   What about sidewalks and concrete slabs with deep scores?  Can I keep them, but ensure that they are perfectly clear of dirt and dust before staining?  Would I need to fill the scores?  What do I fill them with?
Hello Cathi,
   A . -  I wouldn't suggest filling the scores, or saw cuts, unless that's the structurally correct thing to do. They could be expansion areas and any filler would just pop out later, or they could be water access points causing damage and need to be filled. 
   So first, ascertain whether or not and/or which ones should be addressed. If you do decide to fill them then you can use a concrete patching material, mortar, or crack repair material. Though you may want to consider using Deco-Seal. It's what they put between a pool deck and the pool coping at the inside edge of the pool. It allows for contraction/expansion, is custom colored at the time of application so it can be made to blend in or stand out artistically, is topped with a light sand covering which increases the attractiveness and the traction, and it's fairly inexpensive. Though it will usually need maintained about every two to three years, which can include repairs and/or complete removal/redo.
   Of course, you could also use hot oil, which would last longer, but would tend to be quite messy and much less attractive.
   If you use mortar or a concrete patching material and want to stain it as well, then you need to first know that it will likely stain a different color from the concrete, so you should make sample boards using a few potential filler materials, allow them to dry, and stain them to see what the colors will be, before doing the entire project.
   Once ready, you will clean the concrete well such as powerwashing and/or scrubbing with a stiff straw scrub brush and T.S.P. (tri sodium phosphate), rinse well and allow the concrete to dry.
   You can use leaf blowers to speed up the drying and also prior to applying the filler material to remove any dust.
   If you use a cement filler and want to stain it also, then apply the filler material before acid staining the project.
   If you use a non cementious filler like Deco-Seal or caulking, that can't be stained, or if you use a cement filler but don't want to stain it, then you should acid stain the concrete first, neutralize and rinse, allow to dry and then apply the filler.
   It is highly recommended that you seal the entire area, at least the first time, to help enhance and lock in your new look.
I hope this helps.