Question
QUESTION: I live in MA. and recently installed pavers over my exiting concrete slab and stairs using SRW, a concrete adhesive. My question is what type of sand or should I use stone dust too sweep in between the pavers.

ANSWER: Hello,

You should not use sand or dust between the pavers. You should set the pavers in mortar.  Setting pavers in sand over a concrete base will trap water between the pavers and the base because there is no place for the water to drain. The water should drain down vertically and thats how things would take place if there were gravel or earth under the sand but it cannot take place with a concrete base.

Setting the pavers in mortar will create an impermeable surface that sheds water. Good luck. Let me know if I can be of further help.

Mark  Harshman
http://www.harshmandrafting.com

---------- FOLLOW-UP ----------

QUESTION:  

Hi Mark, Thanks for your advice: Since I have already installed all my pavers with SRW I think I have only a few choices of getting some type of mortar in between them, and if you know of any others could you please share them with me. As I look at it, I could purchase the mortar in a tube and try to get it in between and down as far as possible, or I could purchase a bag of mortar mix and sweep it in dry hoping light moisture will harden it to the point where it will keep water out. (This is my top choice) If this is possible is there any special type of mortar I should use? I probably should have talked with other professionals before I started this project and get there advice. I抦 a pretty handy person and try and do all my work myself with great results. This paver job looks awesome, my wife loves it and I would like for it to last for years. If we lived in a warmer climate water and ice would not be a factor. Your input would be appreciated.

Best Regards,

Rick


ANSWER: Hello,

A dry mix swept into the joints will not obtain the hardness necessary to make it impermeable and you will still get moisture penetration into the joints. These type of dry joints are typically used on flagstone and other paving set on sand and gravel beds.

The recommended minimum joint width for mortared paving is 25mm(0.98 inch)but you might still get good results with a narrower joint width. Use a Class 1 mortar. This mortar may also be labeled as type 60. I used this type of mortar on some "crazy paving"(broken pieces of concrete to form a path)in my own backyard about a year ago and the joints are still holding well. The size of the joints there varies from about a half inch up to 2 inches. The mortar bag label will state if the mortar is good for paving.

Mortar purchased in a tube will get very expensive. It would probably require not much more effort to simply trowel the mortar into the joints.

I suppose the adhesive may give you some advantage in avoiding delamination (the shearing of the pavers from the base). Water penetrating the joints will foster that and the freeze/thaw cycle will aid the process. Actually,in colder climates,a sand/gravel base can be better since concrete and mortared joints tend to dislodge and crack in temperature extremes. The ground under the paving is always expanding and contracting.
Good luck. Let me know if I can be of further help.

Mark Harshman
http://www.harshmandrafting.com



















---------- FOLLOW-UP ----------

QUESTION: Hi Mark,
I ended up using mortar in between joints. It was kind of a pain and time consuming finishing the project, however it looks really nice. Hopefully it will last for years. time will tell.


Regards,
Rick

Answer
Hello,

Glad to hear it worked out. A less time consuming method would have been the slurry method. With this method a lump of mortar is dumped on the surface and then pushed into the joints with a spade shovel and brush. The mortar then has to be hosed and brushed off. However,this method tends to leave stains and mortar residue that then hardens. The residue will eventually wear away but that could take a very long time.

With the slurry method,the joints still have to be hand checked for settling or voids and this method produces a weaker joint because the mortar has a higher water content and is thinner.

Mark Harshman
http://www.mahdrafting.com
Email: [email protected]

http://www.scribd.com/markscrib47