I am planning to pour an L-shaped concrete patio approx. 30' x 20' in our back
yard that will attach to our existing foundation in
Texas. (picture a 30' x 20' rectangle with a 12' x 12' square out of it which
represents the existing home). I have been told two
different things regarding pinning it to the existing foundation. I am already
planning to epoxy rebar into the existing foundation
to prevent vertical movement of the patio. I'm also planning to place fiber
expansion strips between the patio and existing
foundation. Some suggest that I use the rebar caps that will prevent the new
concrete from bonding to the rebar in order to allow
some horizontal movement in the new slab. ...but the L shape means that the
rebar will attach to the new slab in two different
directions, which would tend to prevent this horizontal movement anyway. Others
say to simply allow the rebar from the existing
foundation to bond into the new concrete. If I would do this, I'm not certain
what the purpose of the expansion strips surrounding
the existing foundation would accomplish other than to provide a cavity to place
SL-1 sealer and give a more finished transition
between the house and patio. The rebar I am referring to above is simply the 2'
foot sections of #6 that are epoxied to the house.
The remainder of the new slab will have rebar placed in a conventional manner.
A second question involves the placing of some concrete pillars around the
outside of the patio. On someone's advice, I've already
placed (3) 9" diameter by 3-4 feet deep concrete pillars with vertical rebar
reinforcement at the perimeter of the planned pour
where the slab will be the weakest. The top of the pillar is at the bottom of
the planned slab. The question involves the rebar that
is currently sticking up from each pillar. If I allow this rebar to stay, it
will bond into the new concrete (it will be cut 2"
below the top of the new slab). I am wondering if this is a bad idea as it will
lock the patio into place horizontally as well as
vertically - could this promote cracking by preventing all temperature related
I am planning to pour the slab 5" thick with control joints cut 1" deep with
hand jointers during the pour in both directions on
about 2' centers to mimic large tiles and to provide plenty of area for
controlled cracking. Our area in Texas has very little
freezing, but it does have plenty of expansive clay soil. All topsoil was
already removed from the new pour, and a layer of 6" or
so of crushed concrete was laid for a base. The new slab does slope away from
the home in both directions. The slab will eventually
be acid stained.
Thanks for any advice in advance.