Construction of Patio and Concrete Pond
After living in our house four years, we decided to add a bluestone patio and circular concrete pond to add more interest to the entrance. We broke ground in April 2003 and worked off and on through December 2003 to complete the main part of the project.
The soil next to the house was fill that had 4 years to settle. I pounded the bare soil with a cinderblock; the gravel was further compactified with a rented plate compactifier. Drainage tile was run underneath the gravel and around the edge, allowing drainage of the front of the house (via French drains) and the perimeter of the patio. I tacked asphalt expansion joints around the edge of the slab. The slab is not tied to the foundation of the house. The rebar is 1/2"; the idea of the large amount of rebar is to make the slab rigid in case there is settling in one area. The slope of the patio is the standard 1/4" to 12" away from the house. The bluestone pattern of the finished patio (not shown) is a continuation of the porch and step. The electric tool on the yellow cord is a vibrator that was used when the pond walls were poured.
Rebar cage for the pond. The vertical bars are 4' lengths of 1/2" rebar that I first pounded in the ground every 8". The bottom bars are 1/2" rebar. I used 3/8" rebar to bend for the circular parts. I probably could have bent 1/2" rebar also, but it would have been more difficult. I worked wire mesh over the whole business. It was all very rigid, and you could walk on it at the end.
The inside form for the pond is 92" diameter, 20 1/2" high. I built this in our garage. The circular rings are two layers of 3/4" plywood, cut with a reciprocating saw. The outer circular form is 1/2" plywood scored with a radial saw. The whole business is held together with a ridiculous number of screws. I coated the surface with a clear sealer to make it easier to remove the forms at the end.
My good neighbors Bill and Dan helped me to lower the inside form into the hole. Dan gave me the idea of the 3/4" plywood circular rings to hold the inside form, and he clued me in about reciprocating saws. It was a good excuse to buy a Milwaukee Sawsall. Of course I had measured everything, but I was much relieved when we dropped it in and it fit perfectly. I adjusted the level with shims. I built the outside circular form, 12" high, after the inner form was in place and leveled.
Three pros! Kevin, Daniel, and Roy from the Abrahamse Construction Company did the hard work of pouring the concrete. Gerry, also from Abrahamse, suggested the 2x10" supports to eliminate any possibility of movement of the forms when the heavy concrete was added. We ordered 6 1/2 yards at 3500 psi and 3" slump (a bit stiff). Pouring the pond was tricky. They started on the walls. Care had to be taken that the inside form was not embedded in concrete at the bottom. Short hits (a few seconds) with the vibrator helped to get out the air pockets. Too much use of the vibrator is not good.
The circular walls came out 8 1/2" thick, the concrete base is about 10" thick. I took the forms off after 3-4 days. The inner form came off in two pieces. To do this, I cut through the inner plywood rings at places where the form had joints, and then the two pieces popped away from the concrete. We kept the concrete under plastic for a month to cure. I used some Quikrete and a sponge to fill in the small holes. Then I put on 3 coats of a rubberized pond paint with special primer designed for concrete ponds (Herco No. P-SC Primer and Herco no. H-55 Grey): this essentially puts a rubber liner in the pond.
The finished product!
The final step was to add coping on the pond. We decided on Indiana limestone, 3" thick in eight circular pieces. This was ordered from a stone center in Indianapolis, and we solved the shipping problem by hauling it to Virginia in our pickup truck. The coping is held in place with Powerseal SB-10 Paver Bond Adhesive. I added the two walkways to the entrance to our house. The walkways are made with 18x18" pieces of bluestone set in brown gravel.
We have a few goldfish in the pond, a water lily, and a filter that also runs a water spout (there is a power outlet on the far side of the pond). The pond is a frog haven, and they serenade us on spring and summmer evenings. In the spring of 2006, I dug up and enriched the original soil around the pond. We visited a local nursery and brought back a collection of annuals and herbs. We also started some bearberry ground cover for winter greenery. This photograph was taken in August 2006.
Sofie taking a nap.