Bricks over concrete patio?

[Walter R.]

I have an outdoor patio 11x40. The concrete slab has some 1/32" heat expansion cracks, 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 the small 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 brushed sand.

I do not have vertical space for standard pavers (thresholds).

Is this feasible? Thank you for any input.

Walter

[volts500]

I know that you don't have much space, but try to get a layer of coarse sand between the concrete and the pavers. In fact, concrete > sand >

pavers is how the pro's do paver driveways.

[John McGaw]

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.

[Tim Killian]

We put 1/2-inch of sand over an old, cracked concrete patio and then laid pavers. All is well after 2+ years, but as others mentioned, some weeds will try to sprout in the gaps between pavers.

[Joseph Meehan]

I suggest a bed of sand under the brick.

[Walter R.]

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?

Thanks

[RicodJour]

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. Cheap insurance.

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.

R

[Walter R.]

Great advice

Thank you

[Jimmy]

One or two layers of HEAVY roofing felt on the concrete will prevent weeds, support the bricks, and prevent them from shifting.

[Jimmy]

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 place. I like 2 layers of the heavy stuff. Not the thin paper crap.

[Joseph Meehan]

It would not be my choice. I doubt if it would hold up nor provide the ideal base.

[John McGaw]

snip...

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.

[n5psi]

Walter,

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 walked on.

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:

Regards,

Mike

Walter R. wrote:

[RicodJour]

Looks nice. Good job.

R

[Jimmy]

It works well here in the very rainy northwest. The problem with sand on concrete is rain and snow melt wash it away and create soft spots allowing bricks to sink and get uneven..

[Walter R.]

Hi

Thank you very much for your excellent and detailed advice, especially the photos.

[Walter R.]

Hi, again

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.

[RicodJour]

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 very stable.

R

[Walter R.]

Thanks for pinch-hitting, RicodJour :-)

Have a great Sunday

[n5psi]

Walter,

The bricks are in fact placed against each other. There is a ridge on the edges of the brick that makes the space about 1/8" between them when they are butted up against each other as mine are. The brick I am using is Pavestone brand and the model is the "Claylook Thin". They are not shown on their website

but Home Depot carries them. They are the same size (width and length) as the Holland Stone they carry, only thinner.

Regards,

Mike

Walter R. wrote: