Bluestone over concrete slab – what’s the proper technique?
Martino5150
| Posted in Construction Techniques on
I met with two different hardscapers about putting bluestone over my raised concrete slab. Both agreed that the slab is in good condition and did not need to be taken away. However, one said it should be dry-layed and one said wet. What is the better technique to protect my investment? Thanks
Replies
Martino
What's your location? Freeze/thaw or sunny southern california?
Calvin, Thx for asking. We're in Northern NJ, so we do have tough winters. We've heard with Poly it could heave, but would go back down. With wet lay we've seen a lot of cracked grout that look impossible to fix. Would love your opinion. Thx!
Poly?
What do you mean "with Poly"?
I'd mortar it down
My front porch is 14' by 16', bluestone mortared down over a monolithic pour. Joints grouted with a bag, then tooled. Zero issues over the past several winters. I'm in CT.
Back patios, about 1600', are dryset, but over 6-9" of stonedust, not a slab. My concern with drysetting over a slab would be ants tunneling through whatever thickness of bedding material you have. Of water not being able to drain, or being slow to drain, and freeze/thaw heaving. Sure it may resettle. But with limited dry setting bed between the bluestone and the slab, it just might be a pain. Or not. I do get ant tunneling. Weeds in the joints are an occasional problem. We planted a low creeping thyme in some of the joints. It's spread nicely. Too nicely in some areas.
My pool patio is around 1800 feet, but it's slate over a slab. I used Ditra between the two. Grouted with a bag. Zero issues after numerous winters.
Over a stable slab I'd vote for mortaring it down.