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View Full Version : Questions about concrete sub-base for Pavers


Juan if by land
05-12-2010, 01:22 PM
I'm a builder in NY.Many moons ago I receive a degree in Horticulture in Landscape Development at SUNY.Landscape is not my full time gig,but I try to get involved with it on most jobs because my clients trust me and because of the level of incompetence I see in the landscape industry.

About 20 years ago I started to see pavers installed on concrete sub-base slabs in these parts. Maybe an inch of sand or rock dust as a leveling base for the paver.Mortared down edging with open joints.

I recommended against this type of installation at the time.I was certain it would fail,because of frost heaving.Well,I've revisited these installations from time to time and they have held up and stayed true.Other installations,even with excellent edge containment have had settling issues.

So,I'm going to have to say that this type of installation seems superior.But I have some questions regarding the installation details.I will ask about top of the line installation methods,as these are the only one I would get involved in,anything below that I just won't get involved in.

So here are some questions.

In large installations,500 SF plus,are you using expansion joints on the concrete sub-base?

Are you using any type of drains in the slab itself to relieve water beneath the pavers?

If the slab is pitched and then terminates to a mortared down edge detail,where is the water going?

I was told of someone installing the edge pieces to the concrete with PL...huh?

tturbonegro
05-12-2010, 09:37 PM
the water is going where you tell it to go...just as if it were a white concrete pad
PL works great
drains & expansion when and where needed

Juan if by land
05-13-2010, 09:20 AM
the water is going where you tell it to go...just as if it were a white concrete pad
PL works great
drains & expansion when and where needed

That's the thing...the installations I have seen haven't taken any of that into account.Maybe pitch,that's it.I haven't seen any special sub-base drainage precautions done or any type of expansion joint.Our soils tend to be very sandy with excellent drainage,some of it like a sandbox.But how does that help,if the subbase can't drain in the first place,since it pitches toward an edge that has a wet-set border?

And believe me, the installations that I have seen were not done by outfits that put any type of engineering into it.They violated a number of common sense building rules in other areas of general construction knowledge for me to figure that out.

Stone Creations
05-16-2010, 08:01 AM
Consider that only about 1% of rain water actually gets thru the pavers to the subbase. If properly maintained and joints are sanded and patio is pitched right there should be no water reaching that subbase!

Juan if by land
05-16-2010, 10:13 AM
Consider that only about 1% of rain water actually gets thru the pavers to the subbase. If properly maintained and joints are sanded and patio is pitched right there should be no water reaching that subbase!

Yeah,the percentage is probably pretty low,most times,but say a 24" slow snow melt,or standing water after snow/then heavy rain makes me wonder.

Rex Mann
05-16-2010, 02:39 PM
When mortar or PL is used to secure the border weep holes must be left to allow water to exit. You can also drill 2-inch holes in the concrete, fill with pea gravel and cover with geo textile

Peace,

Rex

http://PaversInstalled.Com

Stone Creations
05-16-2010, 09:23 PM
Yeah,the percentage is probably pretty low,most times,but say a 24" slow snow melt,or standing water after snow/then heavy rain makes me wonder.

it should still not get thru properly maintained joints..it will runoff on top of the pavers...

Bru75
05-17-2010, 09:20 AM
it should still not get thru properly maintained joints..it will runoff on top of the pavers...

Properly maintained or not, some moisture is going to get through.

Stone Creations
05-17-2010, 09:42 PM
Properly maintained or not, some moisture is going to get through.

Not enough to cause any damage!!

Bru75
05-18-2010, 12:55 AM
Not enough to cause any damage!!

Suit yourself. As for me, I allow for drainage.
Why not drill some holes? It's cheap insurance.

Juan if by land
05-18-2010, 08:06 AM
When mortar or PL is used to secure the border weep holes must be left to allow water to exit. You can also drill 2-inch holes in the concrete, fill with pea gravel and cover with geo textile

Peace,

Rex

http://PaversInstalled.Com

Rex,are you recommending geo textile over the 2" drain hole,or over the entire concrete slab,like I believe I saw you recommend somewhere else? And where are you locating the holes?

For you,what is a proper weep hole?

Flapjack
06-02-2010, 01:57 PM
I am not a contractor - just a home owner with some real-world experience with this topic that I thought I would share.

We have a front walkway about 23' long. Clay bricks over 1" of stone dust over a cement base. Normal slight pitch away from the house. The bricks were layed against each other with stone dust swept over the top. No geotextile fabric, no weep holes, no expansion joints...nothing. Our soil is only fair drainage - some clay, and no sand. This was installed 19 years ago. I just removed the bricks and sand only because the edges were starting to dip because the plastic edging was installed on top of the dirt, and also because our driveway was paved and I had to raise the paver height.

Bottom line when I looked at the concrete: it was perfect - looked like they just installed it. And this is in Rochester, NY where frost upheaving and harsh winters are the norm.

I'm not saying this installation was done right; in fact, I'm going to use fabric, concrete sand, and poly sand when I put this back together. I just wanted to share some actual experience from a home owner.

jonesy5149
06-06-2010, 05:03 PM
"Consider that only about 1% of rain water actually gets thru the pavers to the subbase. If properly maintained and joints are sanded and patio is pitched right there should be no water reaching that subbase!"........................

Ok what kind of pavers are being put down because there is 4 % of water that a paver will bleed out of water and depending on what kind a grout sand ur using that can be 100% to the sub base...