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# how do you calculate how much stone you need for a circle perimeter?

#1
06-12-15, 01:09 PM
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Join Date: Oct 2004
Location: PA
Posts: 2,323
how do you calculate how much stone you need for a circle perimeter?

I found this pic online and my friend would like her pool to have the stones like that around the perimeter. but I have no idea how to compute how much I would need

she has a 14 foot pool and there's some tarp sticking out from under the pool with a sand base . of course id have to slope the sand but I think the stones are a good idea to make it look good. I guess where the tarp is 'lacking' I should put something under there to direct it away from pool as well?

http://www.foodmn.com/media/full/13/...yard-ideas.jpg

#2
06-12-15, 01:41 PM
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Join Date: May 2015
Location: USA
Posts: 3,345
OK here's the general idea. You want to calculate the area of a circle with the outside diameter of the stone, and subtract the area of the pool to get the area of the stone ring. They multiply by the depth of stone you want to get the volume of stone needed.

Example. Say the pool is 14' in diameter, and you want the ring of stone to be 1' wide, which means it's outer diameter will be 16'.

Area of 16' diameter circle = 3.14 x 8 x 8 = 201 sq feet (area of circle PI x r x r)
Area of 14' diameter circle = 3.14 x 7 x =154 sq feet

Area covered by rock = 201-154 = 47 Sq feet.

Say you want rock to be 3" deep, which is 1/4 of a foot.

Volume of rock needed 47 x 1/4 = 11.75 cubic feet which is a little less than half a cubic yard.

Now here's the rub...If you buy from a landscape supply place, stone is generally sold by the ton, and the conversion from volume to weight is different for every type of stone. But they will be able to estimate it for you.

But 11.75 cubic feet is not a huge amount...you could buy it in bags at the big box store. They usually have volume listed on the bag.

You should put something like landscape fabric (or geotextile fabric) under the stone to keep it from gradually sinking into the ground. And I suggest some type of edging to keep the stone from gradually workings its way out into the lawn. The kind used for flower bed edging would work.

Good luck!

#3
06-15-15, 06:08 AM
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Join Date: Oct 2004
Location: PA
Posts: 2,323
thanks for the math. lowes has .5 cubic feet for 4 bucks. and I think we only need it an inch so I guess about 4 cubic feet or so or 8 bags. but regardless. It seems lugging bags home makes more sense than the 1 yard for 50 bucks I see advertised on the local guys site. plus I can just under by and go back for a more accurate count then. plan was use the tarp coming out from the pool or some other kind of plastic under stone to have water drain away from pool

Shop GARDEN PRO 0.5-cu ft Pond Stone at Lowes.com

#4
06-16-15, 08:59 AM
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iirc, 1sy @ 1" generally weights 110#

#5
06-17-15, 06:25 AM
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Join Date: Oct 2004
Location: PA
Posts: 2,323
here's how it turned out. I tossed sand at the foot of the pool to fill in the gap and maybe add tad of support and I didn't want the rock up next to the liner in case one punctured it. id say its about 1 foot of rock with just one layer deep. I bought 14 bags but need 2 more to fill in the bare patches. I used whatever tarp stuck out from under the pool and added some where needed to try to keep water from backing up and washing out the sand

next year will not be fun because I have to take down and put the pool up the correct way. the teens that did it put like 3 inches of sand down and put the supports on bricks that are already leaning 'inward' because they put the base on the seam between 2 bricks. genius!

I did use the edging that doesn't require digging and I think it worked out pretty well

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