Flagstone patio--mortared vs. gravel/sand?????
colbyj
19 years ago
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AshaK
19 years agomustangsally52
19 years agoRelated Discussions
What layers of gravel/sand would I use for a patio?
Comments (4)This is how I go about patio prep 1)excavate down paver thickness plus +- 7" (for 6" gravel base) 2)apply geo textile fabric 3)add 6" of 0-3/4" 'cheap crushed' gravel base (4" is acceptable for a patio, 6" is better especially in Denver climate) seek recycled crushed gravel if available. 4)tamp gravel base with a vibrating plate over two layers (at 3" and 6") 5)top up low spots to make level grade (sloped slightly for drainage in appropriate direction) tamp. 6)apply 1" layer of sand or limestone screening. sand is preferable for flagstone as it shapes to irregular underside of flagstones and drains slightly better. 7)level off perfect grade playing with a 4' carpenters level or leveled pipes and 2 by 4. slope 1" over 4 ft in appropriate direction for drainage 8)apply pavers (tightly) or flagstone 9)sweep in polymer sand to fill in joints 10)tamp, reapply polymer to top up joints, moisten Alternative bases for flagstone- 1)geo textile fabric 2)4" crushed gravel (0-3/4") base 3)4"- 6" Concrete pad with rebar 4)apply thin set mortar with 1/8" notched trowel 5)place flagstone 6)apply mortar to joints, have sponge handy Least thorough option for thick flagstones (2" +) 1)excavate slightly more than 3" 2)apply 1" sand for levelling 3)drop flagstones in place, hammer down with deadblow mallet 4)fill joints with polymer sand, moisten Hope that helps....See MoreFlagstone Patio
Comments (10)Good morning Colby, Your base thickness sounds appropriate for your climate ( this is what we use and we are also located in N. CA.) I'd go closer to the 3" rather than the 2" for the 3/4" crushed gravel. If you have access to 3/4" class II base rock that would be preferable to straight gravel. Class II base has some fines mixed into the gravel that aids in binding the base together when it is compacted. Additional recommendations , : compact the soil below your sub base. Especially if it is highly organic. Loamy soil to clay like soil is made up of decomposing matter that continues to decompose as it ages. This is one example of why dry lay patios eventually become uneven and sink , it is one of the reasons why the topsoil layer is commonly removed when laying a patio. I support the filter fabric method between the compacted gravel base and the sand layer, especially if you use straight gravel which even when it is compacted still has minimal air gaps for the sand to filtrate downwards. 1x6 plastic border will warp out of shape very quickly once a downward and sideward load is pushed against it. You will need to either augment the 1x6 with additional shear or additional equal loading pressure or use a more appropriate size thickness to support the pressure. Some methods may include digging a perimeter concrete footing - sort of like a curb that is located below and under the edge of the flagstone. Or beefing up the edging to a 2x material or countering the side pressing load by edging the edging with rock or cobbles or some other stable + grounded methods....See MorePolymeric Sand -vs- SandLock
Comments (16)I'm trying to solve what I think is the same problem. I built a beautiful tri-color patio last summer, dryset on sand with a compacted "breeze" base. I then used breeze to "grout" the joints. Survived its first winter with little to no settling; my only complaint is that the larger pebbles in the breeze work their way up to the top and eventually on to the flags, so it's not very barefoot friendly. That's a long-winded way to say I'm exploring polymeric sand and other "joint stabilizer" formulas. What I've found is that (1) polymeric sand is virtually unknown west of the Mississippi River, and (2) the various liquid joint stabilizers I have found are designed for narrower joints, like with dimensional cut flags or pavers. A couple people have told me that they would not work for wider joints like mine (averaging about an inch between stones). Any ideas would be welcome....See MoreStone dust vs sand for laying pavers? Help!
Comments (41)25 years ago I had to choose between stone dust and sand when laying a brick patio using standard sized bricks. The underlying ground here in Virginia is fairly high content clay, I can absolutely state that stone dust is the way to go.... here are a few pointers; 1. Use a rigid but moderately flexible edge guard to define the area. I used aluminum about 4 inches tall. Don's use something softer like plastic or nylon as it will flex and your bricks will start to migrate all over the place no matter whether you use sand or stone dust. 2 . Use 4 inches of stone dust, but apply 2 inches first...then compact it with a manual or mechanical tamper....then thoroughly soak with water and wait a couple of days before applying the 2nd layer of stone dust and tamping and watering again. (BTW, I really don't understand the comments about stone dust not draining well....you will see the water soak quickly through the stone dust.) 3. Make the area as level as possible using a screed (look it up :) 4. Install some water permeable landscaping membrane on a fairly well leveled area. This will promote drainage and stop weeds from infiltrating from below. I will also make it easier to slide the bricks into place. 5. Install the brick. Either full size bricks or the thinner pavers. I used full size bricks which are more stable. To ensure that the bricks are level with one another, place a piece of piece of wood (approx 3" x 8" by 3/4" ) across the surfaces of the brick you are working on and its adjoining bricks...then hammer it with a large mallet until they all the bricks are even. Give then some good wacks...full-sized bricks can take it so long as you use wood as a buffer. Be gentler with the thinner pavers. 6. Depending upon your personal preference, you can butt the bricks directly up against one another or place a think spacer between them. I use pieces of asphalt roofing shingles to maintain uniform spacing. I like the look and using spacers allowed me to adjust the alignment for bricks which may not be uniform size. 7. Regardless of which way you go on item 6, sweep stone dust into the joints between the bricks. Wet the area, let it dry and repeat again. The irregular shapes of the stone dust will lock the bricks into position much better than sand, which is more round. Sand will not get into some of the smaller joints between bricks. 28 years later I am still VERY happy with my results. Occasionally a nearby tree root will distort things a bit but that will happen with either sand or stone dust. I just remove a few bricks and cut out the root. The only periodic maintenance I need to do is sweep new stone dust in the spaces between the bricks one ever 4-5 years. Good luck....See MoreAshaK
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