Replies

1. 
   Bearmon_ | May 19, 2000 01:15am | #2

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   Alan, don't even think about fabric or plastic of any type. This is the stupidest suggestion I have ever seen, although I keep seeing it. It obviously comes from people who don't actually lay any pavers.

2. 
   Guest_ | May 19, 2000 04:44am | #3

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   Wow, between Mike and bearmon, I should be able to come to a sensible decision somewhere.

   First thing I will do is consult with the local stone yard to see what's available.

   The heavy clay base does have me concerned.

   Thanks a bunch, gents.

1. 
   Guest_ | May 19, 2000 05:02am | #4

   *Had some typos in my previous post…Mike gives good advice. Re gravel types, Crusher Run, or Crush-n-run (that's what they called it when I lived in VA) is a mixture of stone sizes from fines up to about 1". See this link. The VDOT (VA Dept of trans.) designation is 21A. Also see this link and scan down about 1/3 of the way to the "Aggregates" section. In NC where I live now at the local gravel pit, they call it ABC or some folks call it roadbed gravel and It's a mix of 3 sizes of stone - fines, ~ ½" and ~1". Both products compact extremely well and are suitable for sub-base of driveways, paver patios, etc. I'd say that you should consider using fines (gravel screenings) rather than sand under your pavers, as it packs well and forms a firmer base than sand. Or if you really want to go nuts, mix about 10% dry mortar in with your sand/screenings, and it makes a really firm base. As far as your original question, the fabric goes between the sub-base and the soil, to prevent migration of the gravel into the soil. Or it can go between the sand setting bed and the gravel if you are concerned that the sand will wash down into the gravel. This fabric is not essential to the success of your project unless you have problems with your soil or other parts of your sub-base. Dupont makes several similar Typar products for different applications including planting beds mulch underlayments and paving subsurface underlayment (your scenario). In road building applications they are used to improve the subbase stability and reduce the necessary thickness of the sub-base. For info on brick paving installation, go to this BIA (brick Institute of America)< page listing technical notes for brick products. Start by reading documents 14 & 14A. Also read this Ask the Builder article on brick paving.Also, plan on using a vibrating plate compactor to get the desired compaction of the sub-base. After you lay the pavers, you can sweep them over with sand, and then shake 'em down with the plate compactor to really lock them in. Finally, you will need some kind of a rigid perimeter edging to hold your patio together.

1. 
   Guest_ | May 19, 2000 05:08am | #5

   *Thanks a bunch, Matt !What I'm getting around this part of (S.W.) Virginia is crusher run, then concrete sand base, then sweep fine sand once the bricks are laid.The plate compactor would be used on the crusher run base and after the sand is swept over the pavers.

3. 
   Bearmon_ | May 19, 2000 05:47am | #6

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   Alan, good advice from Mike and Matt. Sorry for the tone of my first post, but I am tired of seeing misinformation spewed out over something that is not rocket science to begin with. (I've been doing this for 15 years, so the mystery has vanished for me.)

   Matt is correct about using fabric in the bottom of the hole to prevent select material from disappearing into the existing soil, but we only use it if it is very gooey. Certain wet clay conditions will "pump" and eat your new base material.

   Using fabric or plastic as weed preventer under the pavers is a complete waste of time, money and your sanity. First, weeds aren't going to come up through all that tamped base material. They can, however, arrive as wind blown seeds and germinate in the sand between the pavers. This is where they come from.

   Secondly, about the sanity part. The little drawing you often see shows a cross section of the installation with this fabric layer as a thin line. Picture wrinkles, overlap, etc., in the real world, and then picture trying to screed a 1" layer of sand over this mess and keeping everything flat and perfectly smooth. See where I'm going with the sanity part?

   Around here, crusher run refers to limestone that has been run through a crusher, then screened to various sizes. Crushed stone refers to the same material with the "fines" screened out of it. You want crusher with the fines, as mentioned above. It tamps very well, and is easy to work with. I prefer it to bank run, but you have to use what is available in your area. Concrete sand is what I use to screed for the setting bed, also, although some prefer screenings.

   Please feel free to ask any more questions that come up. (Proper pitch, cutting pavers, or whatever.)

   P.S. Alan, I hope your wiring project continues as planned! I put in a new 200 amp service last year. Good peace of mind. I used to be able to crank my stereo and have the lights blink to the beat! It was kinda cool, but scared the hell out of me!

4. 
   Guest_ | May 19, 2000 08:53am | #7

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   We used 21A (No. VA) and it compacts to the hardness of a basketball court. No way sand could get into it, and certainly not after everything got compacted at the end (ran compactor over the pavers). 1" sand over gravel just as a bedding layer, it forms itself to the back of the paver for even support, no break points. Sifted between the pavers, it locks them.

   We did put landscape fabric under the GRAVEL layer -- the bottom of the 6" pit, and given the density of our clay soil it probably was not necessary. It has slowed the lateral migration of grass (rhizomes) -- the small walk we did without fabric shows the difference. The patio substructure does act as a sort of dry well, absorbing a fair amount of water before there is surface runoff and also directing it away from the house. Solved our backyard flooding problem, anyway.

1. 
   Guest_ | May 22, 2000 01:07am | #8

   *Thanks, Bearmon and Andrew D -My main concern is the proximity of the patio to the house wall with a basement below - it will butt up to the wall, which also has two basement window wells.The 12x16 patio will be replacing the same sized concrete pad that was removed last year.A collapsed gutter drain underneath had caused the concrete patio to settle and break in half. It also caused moisture problems with previous owners until I disconnected drain and channeled it away from the house above ground.Let's say the patio is properly pitched away from the wall....Should this pitch start with the gravel base and continue on to the paver surface or can this pitch begin at the sand base (less work) ?Or should it start at the soil base ?Someone suggested a solid barrier such as plastic sheeting to extend out from the wall about 10 feet underneath the gravel base to prevent water from soaking into the sub soil too close to the house during heavy rain (not very often, but it happens.)Or would the densly packed crusher run base lead the water away from the house ?I hope you understand my concern -Water will seep down through the sand and gravel base, so it seems some sort of sloped barrier will help lead the water away from the house and perhaps into buried gravel channel along one side of the patio.I need to order the two cubes of bricks early this week and get rolling on it and this fabaric/sheet business is a snag.Thanks again for your help.Alan

1. 
   Guest_ | May 24, 2000 03:37am | #9

   *Alan,You have received some good information. I am adding my two cents only in an attempt to clarify the good information you have received.1. Each layer needs to drain. If the top of your patio will be at ground level (or slightly above) you need to dig a pit 4" min for base material (we use 1"(-) around here, includes fines plus 1" sand to set the pavers plus the thickness of you pavers. That should be nomially a six" deep hole. This hole needs to drain at the soil level, at the compacted base level, at the top of the sand and at the surface.If these levels do not drain you will have "soup" at that level. Read unstable. You do not need, but I strongly recommend that you use a fabric between the base and soil to prevent migration. If you do you will have a better, longer lasting job, However, you said that this is a short term fix. OK don't use fabric. But please do not use solid plastic sheets that will not permit the migration of water through to the soil. With a plate compactator, 1"(-} will compact to the consistency of concrete. But unless proper drainage is provided it will become soupy and not provide support. Note, solid plastic sheets laid into your 6" pit with the edges running up and over the edges will create a pool leading to saturation of your base material. This will also occur if your soil is not perfectly flat. Imagine dips caused by shovelling out the pit. You should already have your yard sloped away from the house. Just make sure that each layer maintains that slope. If you do not use fabric, the base and soil will eventually migrate together. The base provides support for the pavers. This support will be lost through this migration. But this will occur over time. Again, you said that this is a short term fix so don't worry about it. And should there be problems before you build the addition, the beauty of this product is that you can easily repair sunken pavers. Pull them up, add some more base, hand tamp, resand and reset the pavers. Hope this helps.

1. 
   Guest_ | May 24, 2000 03:50pm | #10

   *Thanks, Herb -I feel more comfortable with proceeding with this.Wanted to clarify the plastic sheeting.I would not form a tub with it.It would be used only 5-6' wide and run along the house wall under the base material.When the water migrates down, the plastic sheeting would lead the water away at least from the wall before the slope takes care of the rest.I would use the fabric under the base material for the rest of the patio.And, yes, it's a definite on starting the slope with the compacted soil and maintain that throughout the rest of the layers.As for the plastic sheeting along the housewall, this may change depending on what I discover on the base soil.Thanks again for everybody's feedback !!I will report back on my progress.The bricks will be delivered today.Alan

5. 
   Guest_ | May 24, 2000 03:52pm | #11

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   Hello -

   I am getting conflicting information from many difference sources while researching the use of fabric material between the sand bed and crusher run gravel when laying paver bricks.

   This is for a patio (about 12x16) that will be butted up to kitchen wall.
   Below the kitchen is the basement utility room.

   The sub soil is red clay as dense as lead.

   Some sources say don't bother with the permeable fabric.
   Some suggest plastic sheeting.
   (The sub base and the patio will be sloped away from the wall.)
   And some diagrams show the fabric between the sand bed and bricks, others between sand and gravel, and yet another variation between gravel and soil.

   This is the only detail that needs to be ironed out before the bricks are ordered.

   Also, any specific type of fabric that is preferred over another ?
   I've seen TYPAR but only in 3' wide rolls.

   This is a temporary installation that will be in place for several years until the house is bumped out.

   Thanks for any experience you can pass on.

1. 
   Guest_ | May 18, 2000 09:14pm | #1

   *there are a couple of things going on here...1st.. the purpose of filter fabric is to maintain a boundary beween dissimilar materials.. there is nothing dissimilar between the sand layer and the crusher gravel bed....gravel of course being GRAVEL.. not crushed stone..gravel is what comes out of a gravel bank.... commonly called bank run...it is usually coarse sand with naturally occurring rocks mixed in..if it is processed, it may be screened to remove the larger rocks.. or it may be mixed with clay to make it bind better..anyways .. the gravel will be so tight that there is not going to be any migration of sand into the gravel..now.. if what you really have is crushed stone....then you need a filter fabric to keep the sand from washing into the stone and creating a void..typar and house wrap are not filter fabric...filter fabric is a special weave designed to filter out whatever particles you are trying to retain..practicaly speaking...you could use the poly woven SILT fence they sell at good lumber yards..it will allow water to pass but will keep fines from passing thru (to keep from poluting streams, etc.)the dense clay layer will turn to soup if it is allowed to become saturated...make sure you are redirecting water from passing thru the brick/sand/gravel and ponding on top of the clay...in short...if you have gravel under the sand, you don't need filter fabric.. if you have crushed stone , you do..the poly may be an attempt to move water away from the clay layer.. but could just turn the compacted gravel bed into a bog of slurry...drainage is what you want...and ant control....the ants will move a lot of sand from under the bricks to the top of the bricks...a couple of treatments of diazanon each season will keep them in check...b but hey, whadda i no?