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The distributors here in MI recommend a 21AA gravel, which is basically crushed limestone. The gravel has sharp edges, so it sort of interlocks, and the dust hardens over time with exposure to moisture. I have both patios and driveway areas and haven’t had problems. I put 6 – 8″ under the patio, and 12 – 14″ under the drive. On top of the gravel, screed 1″ of 2NS or slag sand to set the pavers into.
More important is the installation. I put fabric under the gravel, and compacted the gravel in lifts. Don’t compact the sand, but do compact the pavers after they’re all installed. I set the pavers 1/2″ high, then compacted them down to height, which pushes some of the sand up between them. Then top off the cracks with dry silica sand (play sand in 40# bags).
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The distributors here in MI recommend a 21AA gravel, which is basically crushed limestone. The gravel has sharp edges, so it sort of interlocks, and the dust hardens over time with exposure to moisture. I have both patios and driveway areas and haven't had problems. I put 6 - 8" under the patio, and 12 - 14" under the drive. On top of the gravel, screed 1" of 2NS or slag sand to set the pavers into.
More important is the installation. I put fabric under the gravel, and compacted the gravel in lifts. Don't compact the sand, but do compact the pavers after they're all installed. I set the pavers 1/2" high, then compacted them down to height, which pushes some of the sand up between them. Then top off the cracks with dry silica sand (play sand in 40# bags).
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Rich,
What function is served by the fabric under the gravel? I want to do this and was thinking I'd put the fabric under the sand.
*Gerry:The fabric prevents the soil from migrating up into the gravel and the down into the soil. In other words, it separates the unlike substrate layers. Not sure if it makes as much sense to put fabric between the crushed gravel and the sand as they are very similar.Also, Rich says "Then top off the cracks with dry silica sand". I thought that it was necessary to put the fine sand on the brick before compacting to prevent the vibratory plate compactor from marring the brick surface - or at least that's the way I have done it???
*We used the same coarse sand for crack filling as the bedding layer. And I did run the tamper -- a medium-sized one at that -- over the pavers will no ill effects. More cautious folks use a sheet of plywood, but I figured if I cracked one or two I could just replace it. Those pavers are tough!The tamper-compacted pavers came out superb -- very smooth from paver to paver, sand forced in hard (and quickly, I might add).As for longevity of the patio, as with almost anything masonry, the base is everything. Incidentally we used fabric too, with the intention of keeping the gravel from becoming plugged with silt; soil movement could also undermine the base and cause settling, dense though the 21A is. Some here say the gravel doesn't drain at all so you don't need fabric... I think the manufacturer recommended it, and given the tremendous sweat equity we put in I was happy to use it.
*HEY YOU GUYS! - I have always liked the look of pavers but want to know if they get slippery when wet? We get so much dogged gone rain here that it is a real concern. What about it? Are they slick when wet? Thanks - jb
*Nope. I think they great all around. the only thing to be concerned about is oil-based staining, for which you can periodically seal them if you want.
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On brick pavers:
Some ideas I've never heard, and some responses: the "fabric" is landscaping cloth, sold by mason suppliers. It not only keeps crushed stone from clogging with soil; it bars deep-rooted weeds from coming up. When shallow stuff like grass grows in cracks, walk around with a spray-bottle of vegetation killer.
Given the usual 1/8-per-foot slope or more, a flat soil base (compacted by a vehicle or tamper) is a great drainage platform. The gravel lets all water drain through it, even heavy rain.
If you fit the bricks tight, there is no need for any sand. Some silt will blow across anyway, falling in and sticking in some cracks. That makes for more stability.
If you roll or finger-smooth the crushed stone (round river stone is unstable), lay the bricks on gently with up to 1/4-inch unevenness. Either vehicle use or tamping/rolling will make them billiard-table flat with eatchother. If you have a good eye, keep lying flat, chin on ground, until the whole drive (patio) looks beautifully flat. After a year of spot-settling (or static tire compression), you can pry up a dozen bricks and achieve permanent flatness with more gravel.
One caveat: Power steering spreads bricks. You have a constantly expanding driveway. The solution is not those cheap plastic channels, but an edging of six-inch-wide, two-inch-thick concrete with rebar, in ten-foot sections. Pack the soil tightly against the outside, and your power-steering creep is defeated.
Concrete pavers are crap. They look just like what they are, cheap and light grey. All the pretty photos are taken after a phony hosing. Deep color uses so much color-powder that it weakens them. Use brick, which adds only a few cents per square foot and looks just like the magazine ads for expensive cars.
Everyone is terrified (in central and northern states) of frost heave. What few realize is that the crushed stone layer is great insulation. It just about assures you that rain or melt seeping down to the soil will run off before it seeps into the soil and freezes.
Here in the northeast, masons swear by stone dust, but that fills the spaces solid and conducts soil heat right out in winter. Clean crushed stone is a much safer insulator, and just as stable against bricks tipping.
Pavers will tip when people stamping or heavy vehicles press them. But the nice part is that the next random loading will correct half of the problem. It all averages out to flat.
Pavers (brick, not concrete) are so beautiful and so practical that anyone laying a blacktop driveway or a concrete slab for almost the same price should be ashamed of himself.
--YankeeDam
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I have patio brick pavers which after a number of years are uneven, the previous owner installed them,the grade now sloped towards the house, and this year I am starting to get water in the basement. I plan to remove the pavers and reslope the yard away from the house as much as possible, what type of foundation should I put under the pavers?
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Our county uses concrete pavers -- which can look like brick or fancier shapes -- for sidewalks, crosswalks, etc. Durable and long-wearing.