I have an outdoor patio 11x40. The concrete slab has some 1/32" heat
unsightly but not really structural.
To improve the appearance I would like to put a layer of split pavers
(bricks, 1 1/4" thick) on top
of the concrete slab, without gluing them down and without joining the
bricks by mortar or grout. By abutting the bricks it should not matter if
cracks work a little in the future. The split pavers will be enclosed by
walls on all sides. Any tiny voids between the bricks will be filled in with
I do not have vertical space for standard pavers (thresholds).
Is this feasible? Thank you for any input.
I demolished a patio about 12X15 that was brick over concrete slab
pretty much as you describe except that mine had the perimeter bricks
concreted into place. The patio seemed solid enough but the sanded
joints were always sprouting places for weeds and grasses and that
ruined the look. I salvaged all the thin paver bricks and am still
trying to figure out something useful to do with them.
BTW I had to demolish two patios of similar size on my house because
both of them were very cleverly built so they were (or shifted so that
they) pitched toward the house which made for interesting waterworks
during torrential downpours.
What would be the advantage of a layer of sand? How thick a layer do you
have in mind?
If I lay the brick directly on the concrete, albeit with hairline cracks,
would that not be more stable and less apt to generate weeds?
Neither concrete slabs nor brick are perfectly flat. The high points
will concentrate stress and possibly crack the brick. Pavers are
stronger, so it'd be less of an issue, but the sand will make getting a
flat level surface to walk on easier. A 1/2" sand setting bed is fine.
No. Those little hairline cracks are enough to let material enter.
Material that will consist of plant matter (read foor) and seeds (read
food eaters). You might not get growth right away, but when you do
it'll be tougher to get rid of the weeds.
If you're really concerned about stopping the weeds, they make
fortified sand mixes for filling the cracks between pavers. It's
brushed in, sets by sprinkling with water - best thing to prevent weeds
from getting started.
It probably won't stop the weeds, at least if his weeds are similar to
mine. Invariably I had weeds in the sanded cracks which resulted from
windblown seeds lodging there and sprouting. The warm bricks and damp
sand provided an ideal seed-sprouting environment. Having the roofing
felt under the bricks might actually make the environment warmer (a bit
of insulation from the slab) and moister (keeping water from running out
the bottom) thus accelerating the sprouting.
I'd go with an Ortho product to kill weeds. You spray once a year &
it kills any existing weeds and prevents weed and grass seeds from
sprouting. The label says it is safe for pets and kids as soon as it
Heavy roofing felt is better if the concrete is cracked. Keeps out the
water/frost, protects the bricks, keeps out the weeds, and holds the bricks in
I like 2 layers of the heavy stuff. Not the thin paper crap.
You should have no problem doing this. I just finished a patio job over
Memorial Day weekend. I put 1-1/2" pavestones on top of an existing
concrete patio. I couldn't use the 2-3/8" thick pavestones because it
would put the patio too close to the level of my door threshold. I put
a 1" deep bed of sand on top of the patio and then laid the pavestone
brick on top of the sand. I then used a plate vibrator to tamp the
pavestones down and then swept sand into the cracks.
Don't just lay the brick on the concrete. The imperfections in the
concrete and brick will cause them "rock" and/or break when they are
I actually made my patio larger than the existing concrete. I had to
excavate down about 4 to 6" where the concrete patio didn't cover and
then filled in with decomposed (crushed) granite. The granite was
tamped down tight and made level with the existing concrete patio.
Here are pictures of my project from start to finish:
Walter R. wrote:
In looking at you photos, it appears that you left a gap of about 1/2 inch
between brick. It looks like this gap was then filled with sand.
Is there a reason why you used gaps between bricks. Wouldn't it be more
stable if the bricks abutted each other?
Thanks again for all your help. You have saved me tons of time and money.
Walter, you're replying to my post when n5psi is the one who posted the
link to his patio pictures.
If you look at one of his close-up pictures, you can see where two
parallel bricks but up against a perpendicular one, and you'll notice
that the joint lines all line up. If you buy paver brick, they're
usually made modular - the width is half of the length so you don't
need any joint space. n5psi used brick that wasn't modular and the
joint width is required to make things line up.
There are benefits and disadvantages of each style, but if you compact
the base and sweep in sand, compact again, then the wider joint will be
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