control joints for blue stone pad over concrete.

[ks768]

Have to install a 30' x 20' bluestone patio. The bluestone are approx 1" thick in different size squares and rectangles. Plan on mortaring them on concrete pad in a random pattern. Not sure exactly how to consider possible control joints. If I poured a 6" concrete pad with either #3 rod or wire, could I get away with using no control joints? My thinking was if any shrinkage cracks did develop, it would happen early and the reinforcment would keep them from getting any bigger so it wouldnt effect the mortared bluestone. Not sure if I'm safer breaking it into 4 equal sections with a metal key type joint and cutting a neat saw blade width joint over exposed bluestone. Also wondering if I put dowels through the metal control joints, I wouldn't have to cut any joint on the exposed bluestone.

 

[hokie66]

If you put joints in the slab, match the joints in the finish. Dowels wouldn't make a difference in this regard. If it were my patio, I would cast it in one piece, wait as long as possible before setting the stone, and hope for the best. Are you using a flexible adhesive?

 

[ks768]

I was planning to match a joint in the finish if I went that route. I would feel safer puttng in a control joint somewhere, but with the pattern of the stone (see photo) it makes it difficult. Want to avoid a continuous running mortar joint anywhere and I would like to avoid having a saw cut running through anywhere. If I did go with no control,would the #3 rods be a better way to go? Was also thinking about adding fiber mesh-it would only add about 80 bucks.

If I didn't use any control joints, what could be the possible outcomes?

 

[ks768]

And no I wasn't plannng on using a flexible adhesive. Planned on using a type m mortar. The bluestones will be different thickness. Some bed joints could be 3/4 inch thick. I don't know if they make any kind of flexible mortar for this type of application. Thanks

 

[hokie66]

I don't think there are any joints in the patios shown on that site you attached. Yes, the more reinforcement you use, the finer the concrete shrinkage cracks should be, and thus the less chance they will telescope through the finish.

Your method of laying the stone over a concrete slab is considered the "Cadillac" option. The contractor in the link you attached lays pavers and stone over a compacted granular base. I have done it that way with pavers, using cement stabilisation, and had a successful result. The varying thickness of the stone would make it a bit tricky.