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dpdrive 03-30-2012 08:42 PM

Synthetic stone over precast concrete
I have precast basement walls and I'm questioning whether or not any special pre-treatment is required over the precast concrete such as water blasting, sand blasting or acid etching. I intend to ask the wall manufacturer but for several reasons I don't put much faith in their advise. I am also wondering if it is okay to run the stone to or just below finished grade. We did that on my detached garage with no ill effects after one Buffalo, NY winter. No brick ledge was used and the stone was placed with a scratch coat over a poured concrete wall. I want to do the same thing to my new house with the precast walls. Thanks

Tscarborough 03-31-2012 11:11 AM

If they are fresh, they may have form release on them. A good quality polymer modified thinset is what I have used, unless you want to lath it.

TRUEPRO 04-10-2012 08:50 PM

Easy rule of thumb. Masonry bonds to masonry. Scratch coat, then stick stone. If you have any worries, use type M mortar, the highest strength available without additives. Good to go = )

concretemasonry 04-10-2012 09:28 PM

Truepro -

A high strength mortar is the last thing to use since it has a high compressive strength (not needed here) and does not have the other desired properties that Types N and S have for a veneer (non load bearing) type application. Stronger or bigger and heavier is only good for dumb work where a sledge hammer is used.

Thinset or a polymer in the mortar is best to insure a good bond.

Precast concrete is NOT masonry.


stadry 04-11-2012 05:48 AM

what dick & t-scar said !

& in buffalo, depending on the individual stone's weight, i'd be adding mechanical anchors & applying silicone siloxane when done - or, at least, that's what i'd be doing if back home in binghamton - good luck !

TRUEPRO 04-11-2012 09:12 AM


Does mortar not bond to precast? When i say that masonry bonds to masonry im referring to any porous surface (brick wall, block wall, concrete wall) that stone and mortar could be applied to. Yes, you can stick stone on precast i do it all the time. And who in the world would use thinset to apply stone veneer? Yes i agree its very doable but that not common practice AT ALL. I feel bad for the user who wanted some solid advice cause now you have complicated things by suggesting all these additives blah blah blah. Its a simple project that does not need to be overkilled. Thanks for the input dick.

jomama45 04-11-2012 09:42 AM

Do not use Type M, it's far too strong for this application, as stated by others above.

A few ounces of bonding agent per batch will go a long way, and will work far better than additional, un-needed Portland cement....

concretemasonry 04-11-2012 12:42 PM

High strength mortars (Type M) do not have properties necessary to bond properly that the lower strength mortars do, so often additives (bonding agents) are necessary - blah-blah-blah.

In the Buffalo location, it could be a "superior" foundation with little horizontal continuity on a gravel foundation and high density/low absorption concrete panels that present bonding and adhering problems and cracking possibilities. If it is a series of larger (wider) garden variety precast slabs placed on a concrete footing, the concrete is usually not a dense, is easier to bond to and cracking possibilities due to the shadowing of the panel joints to the surface exist.

It never hurts to improve the bond by using the right type of mortar and cheap additives for exterior applications that can be hard to repair.


stadry 04-11-2012 03:23 PM

you looked better when you posted a picture of your wife's car, the bugatti veyron :thumbup:

concretemasonry 04-11-2012 04:33 PM

That car was the one I sold before marrying my first wife (Joy1) of 25 years. My second wife (Joy2) of 22 years drive a Blazer almost identical to my Jimmy. Joy1 and Joy2 are great friends and control the family social matters and menus.

I do enjoy cars, but drive what works best for me. With my Jimmy, I can go cross country after a good dirt track race or can tailagate after a good road race (deinitely not NASCAR tank racing).

Since we are getting into the fishing season, I will use my trophy fish avatar soon.


jomama45 04-12-2012 08:40 PM


Originally Posted by concretemasonry (Post 896806)
With my Jimmy, I can go cross country after a good dirt track race or can tailagate after a good road race (deinitely not NASCAR tank racing).


Do you ever get a chance to get to Cedar Lake by chance??

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