Laying Bluestone Over An Existing Concrete Base
by Paul Grassi
(Broomall, Pa.)
Is it ok to lay a blue stone patio on an existing concrete pad? If so what is the proper technique. Should i place a mortar bed and set or is there an exterior thin set that can be used?
ANSWER
Hi Paul,
You can set the bluestone on a concrete pad as long as the pad is in excellent condition. The concrete pad should be 4"-6" thick. Beneath the concrete there should be 6" compacted aggregate, laying on undisturbed or compacted soil.
I would then set the bluestone on a 1"-2" mortar setting bed.
Double check all of this with a qualified mason if you can. This information is taken from Timesaver Standards - cut or field stone detail for installation, wet laid.
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Bluestone Over Concrete
by Mr. B. Don
We have a roof covered patio on the back of our house, built c. 1950.
The floor consists of 3 sections of cement (with strips of wood in
between each ). There are also
cement stairs leading down to the basement entrance .
The mid section of the floor has a huge crack that has been there for years.
We would like to facelift the patio and are considering using bluestone.
A couple masons have suggested to lay the blue stone over the existing concrete patio.
What would you suggest?
Demolish/remove existing cement patio first?
Or would it be okay to bluestone on top without removing the cement?
We live in northern new jersey and have v. cold winters.
Thank you in advance for any advice you can offer.
B.Don
ANSWER
Hi,
I hate to go against what masons say, but if your patio has a crack, I would never lay bluestone over concrete in this situation.
It's difficult enough to do a proper job of laying bluestone in cement, especially in northern NJ (where I am from!).
This is what I would suggest.
Remove the existing concrete. This will be an added expense, but you can save money by dry-laying the new bluestone. Regardless of the costs differences between installing bluestone in concrete or dry-laying it, I would opt for the dry laid method anyway.
It IS less expensive, but beyond that, you will never have any problems with cracking. The bluestone pieces can be laid very close to each other, as close as 1/4 inch spacing. This spacing (or a little wider) can be filled with loose stone or else you can choose a polymeric sand, which hardens.
I rarely specify bluestone to be set in concrete, not that I don't like the look, but for the above reasons.
Take a look at this page.
http://www.landscape-design-advice.com/patio-designs.html
It shows an example of a bluestone patio, dry laid. The color of bluestone is called full range, where you get various colorations. You could also choose full blue, where the stones are all the same...blue.
I hope this was helpful. If you have further questions, just post back here under Comments.
Susan
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Bluestone on Concrete
by Michael
(Syosset, NY)
Can I have bluestone "dry laid" on a cement base?
I had planned to mortar the joints, but I do prefer the look of a dry lay and it would also resolve the problem of cracking mortar in the future (I live in the Northeast).
Thanks...and your site is awesome.
ANSWER
Hi Michael,
Glad you like my site!
Yes, you can do this. However, the existing concrete base must be in good condition...no cracks or settling.
You might consider using polymeric sand in the joints. It resembles regular sand used for dry laid applications, but hardens. When you think about it, this makes sense for stone applications over concrete, because it's better if the water does not percolate through the joints down to the concrete and sit there. The polymeric sand helps with this.
Also, be sure that your existing patio is pitched properly for drainage.
It would probably cost you about $800+ to just remove the concrete and start over again.
Take a look at this page with questions and answers on Laying Bluestone Over Concrete.
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