05:47AM | 05/28/04
Member Since: 02/08/04
16 lifetime posts
Hi, I want to build a concrete block wall (only two courses high) using an existing concrete patio.

1) Can I use the existing concrete patio and lay the blocks directly on them? If so, what sort of surface prep would I need to make sure the mortar will stick?

2) Or, do I need to dig and pour new footers next to the existing patio?

I live in Florida, frost footings are not the problem. The existing patio has adequte depth.



04:03PM | 05/30/04
Member Since: 11/06/02
1281 lifetime posts
I can't see a problem as long as your building dept says it's OK.

to gain mechanical adhesion with the mortar bond, lat a chaulk line down both sides of the wall to see where you are working. Then take a cold chisle and big hammer ( with gloves and goggles) and just nick it full of chips every few inches.

Or use chemical processes. If there is much staining or resiudue buildup, wash with acid and rinse, or use a degreaser if oils from auto or cooking ar present. Then apply an acrylic bonding agent to the existing the morning you start or the day before

Excellence is its own reward!

Glenn Good

10:29AM | 06/10/04
Member Since: 09/10/03
314 lifetime posts
An even easier method to securely attach your block to:

1) Snap a chalk line in the center of the wall down its length

2) Drill a 5/8” diameter hole, 3” deep, every 24” on center on a chalk line (Start with the first hole 4” from the end of the wall)

3) Drop a piece of #4 rebar 6” – 10” long in each hole

4) Lay the blocks over the rebar (the rebar should be near the center of the open cell) and fill the cells containing a rebar with mortar to lock them in place

This method is less labor intensive and will work well.


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