We just installed pavers over a concrete slab with an inch of sand between the layers. There is fabric under the sand to keep it from washing away, and drainage seems to be working well with moderate rain.

Now we're wondering whether to fill the joints with polymeric sand or just regular sand. We're in PA so there will be freezing over the winter if that matters.

Are we likely to have problems with one vs the other?

 

I am not a fan of polymeric sand. It has not been needed for years and I question why it would be needed on a proper interlocking concrete paver installation. I have not seen it used on any high strength critical projects where conventional fine sand (masons sand) is the rule and specified.

I am curious about your project -

1. Are you installing interlocking concrete pavers?

2. Do you have the normal tight joints?

3. Why was a mesh used and where is it placed? - on the concrete or on the setting bed sand?

4. Since you have a concrete slab you must have free drainage around the sides. Does your edge restaint permit free drainage?

It is always a challenge to install pavers over a slab instead of a conpacted base and I try to find out what people are using and why.

Dick

 

Thanks for the reply!

I'm considering polymeric for two reasons: To help keep weeds from taking root in the sand between the joints, and because I'm worried about always having sand all over my patio every time I try to sweep the leaves off it. The local E.P. Henry guys seem to love this polymeric sand, but they're most often not installing over a pre-existing slab.


1) They're E.P. Henry rectangular concrete pavers in two sizes ( 6x6 and 6x9 ).

2) The joints are tight, yes.

3) We put the layer of geotextile fabric between the sand and the slab with about 2 inches folded up between the outer pavers and the edge restraint. This was all recommended to keep the sand from washing out the sides as water drains away.

4) We have free drainage around the edges of the slab. We glued slightly larger pavers around the perimiter to form our edge ( angling the glue to allow water to pass )

We went with 3/4 inch of sand under the pavers, and after running the packer over it, it turned out nicely. Just have to get something in the joints now.

-o-
Neil

 

Neil -

E. P. Henry is a good, knowledgable supplier, so I would tend to go with them.

Your pavers are in someway "antiqued" or "rustic" and not the typical paver with squared corners and edges that do not permit the migration of sand. The polymeric sand could help with the sand movement, but weed seeds are very small, so you may need a shot of Roundup once or twice a year.

Usually high performance pavers have very tight joints and as much contact as possible for maximum strength. For a patio, your pattern/unit will work just fine. - For a street or airport taxiway, no.

You are right about most pavers not being installed on a concrete slab is correct. For heavy loads, pavers on a concrete slab do not perform as well as pavers on a well compacted base. For large installations, the concrete impeeds the drainage and actually decreases the stability and strength.

Dick