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Discussion Starter · #1 ·
I have started a project of laying pavers in my backyard in a 26'x16' area. Is 1" enough sand. I am going to install 12"x12"x2" pavers.

Also, would it be enough to compact by hand or do i need to use a plate compactor? It will be hard to get the compactor into the backyard since i have to go through the house to get to the backyard.
 

· Civil Engineer
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If the natural soil beneath the pavers is granular (sand or gravel), then 1 inch of sand is OK if you are only planning to walk on it. If you think you may drive a vehicle on it, then you need at least 6 inches of subbase (usually a graded sand/gravel mix).

If the natural soil beneath the pavers is silty or fine sand, and you live in a northern climate, you are likely to experience frost heave, which over time will cause the pavers to become uneven. This may be OK, if not you will need more sand. If you absolutely cannot tolerate frost heave, you need granular soil all the way to the frost line, which is rarely done because of the cost and time.
 

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Discussion Starter · #5 · (Edited)
Another question

This is a patio just for walking and some movement can be tolerated.

So, my plan is to compact the natural soil first with a compactor. Then lay the 1" of sand. Then I will compact that after using a large 2x4 to even it out and make it level. From there, i assume i just put the pavers down by starting in a corner and then compact again (with a rug down or a piece of plywood so i dont break the pavers) after they are all done. Am i missing anything?
 

· Civil Engineer
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You indicated that the natural soil is somewhat clayey. It may not be feasible or necessary to compact the natural soil before laying the pavers. Usually you compact using a plate whacker (rent it at a U-Rent type store), a couple of passes each direction would be fine. You can compact the sand the same way, although you are not going to get a lot of compaction on only one inch of sand, still not bad to do it. Laying the pavers is simple, just put them in and hit them with a rubber hammer a couple times to seat them.

When you are all done, you can fill the gaps with some fine to medium sand, no need to use cement. Just sprinkle the sand in. We did our front walk this way using brick, although we put in about a foot of sand base (compacted) because we did not want any movement. The walk has held up beautifully for about fifteen years now, no movement, no problems.
 

· Licensed P.E./Home Insp
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IMHO 1 inch of sand on clay soil is going to bite you in the behind.

Our company spec on pedestrian pavers in NJ is excavate to pitch/depth and compact the soil with a jumping jack (hand tamping won't do squat to clay soil, neither will vibratory plate), 4-5 inches of compacted gravel laid in 2 drops, 1.5" of screeded coarse sand, followed by paver. Excavate 8-12" wider than the patio so you can install the edging over the compacted gravel and before the sand goes down. When you're done, backfill behind the outside of the edging with soil and plant grass seed or a flower bed.

Anything less than that is leaving yourself open to problems.
 

· Old School
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The desired level of compaction is best achieved by matching the soil type with its proper compaction method. Other factors must be considered as well, such as compaction specs and job site conditions.

  • Cohesive soils - clay is cohesive, its particles stick together.* Therefore, a machine with a high impact force is required to ram the soil and force the air out, arranging the particles. A rammer is the best choice, or a pad-foot vibratory roller if higher production is needed.
    *The particles must be sheared to compact.

  • Granular soils - since granular soils are not cohesive and the particles require a shaking or vibratory action to move them, vibratory plates (forward travel) are the best choice.
Reversible plates and smooth drum vibratory rollers are appropriate for production work. Granular soil particles respond to different frequencies (vibrations) depending on particle size. The smaller the particle, the higher the frequencies and higher compaction forces.
Normally, soils are mixtures of clay and granular materials, making the selection of compaction equipment more difficult. It is a good idea to choose the machine appropriate for the larger percentage of the mixture. Equipment testing may be required to match the best machine to the job. Asphalt is considered granular due to its base of mixed aggregate sizes (crushed stone, gravel, sand and fines) mixed with bitumen binder (asphalt cement). Consequently, asphalt must be compacted with pressure (static) or vibration.
 

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Discussion Starter · #9 ·
Measurement

Hopefully, this will be my last question...
The yard is about 26x17...How many yards of sand do i need to get 1" across the whole thing and some extra to sweep onto the top?

Thank You all for your help!
 

· Licensed P.E./Home Insp
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Just a question, have you thought about a structured gravel patio? I did one last summer and they are pretty amazing. It's ADA compliant for wheel chair access, which means it's pretty firm. Look up GravelPaver, gravelpave, something like that.
 
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