inorganic (man-made) polymeric sand

by peter
(bergenfield, NJ)

Can I fill joints that are 1 1/2 inch wide by many feet long on a concrete patio in New Jersey (freeze thaw) where the concrete squares are appox. 4 x 4 feet? there are presently 2x pressure treated slats in the spaces now and are not flush, move and are unsighlty. If i didnt use sand, should I use stone dust?
looking forward to your suggestions.
Peter


ANSWER

Hi Peter,
I feel that joints that are 1 1/2" wide are too wide for polymeric sand. I was just consulting with a landscape contractor that I have worked with and is pretty high end. We were discussing polymeric sand, and he also felt that it is not best for wide joints.

As time goes on, I am feeling that polymeric sand is not a great solution, particularly in areas that have extreme freeze-thaw conditions. I have suggested using polymeric sand elsewhere on this site, and I am sure that lots of homeowners have success with it, but I can just think of too many scenarios where it is not optimal.

I am a NJ landscape designer so am familiar with the winter conditions here (especially this past winter!). I have a dry laid patio of brick filled with stone dust. You would not believe how much it heaved this winter. Now it has gone back to normal. But what would have happened to those joints if they were filled with the polymeric sand? I fear it would have been a mess, filled with cracks.

I know concrete is a different material and of course should not heave. However, the joints of this material can still be subject to freeze-thaw conditions and therefore can crack since it is a hardened material...just my thoughts.

If you can remove the pressure treated boards successfully, I would recommend filling the joints between the concrete squares of the patio with stone dust. You could also fill the joints with a decorative small gravel.