A Stormwater Management Solution with Style
A Courtyard Built to Manage Stormwater
Andrew Soto, LC/DBM
The owners of a Boulder, Colo., residence hired TLC Gardens, LLC, to build them a backyard living space in an area with stormwater management problems. A complete drainage system, concrete paving, seatwalls, and custom water feature were installed to create an intimate outdoor living space.
TLC Gardens is a full service landscape firm offering design, build and maintenance services. The Colorado company is led by Cheri Stringer, APLD, owner and lead designer. The firm specializes in projects ranging in size and complexity from small residential landscapes to large estates. This work has earned TLC Gardens the experience to tackle a wide variety of project styles and build restrictions while partnering and fostering relationships with others in the landscape industry.
"We are the GC on all our projects and our landscape construction partners are part of our integral team in producing our finished product," said Stringer. "Our construction partners are so much more than subcontractors we prefer to identify their commitment to our team with the term, 'landscape construction partner.'"
The project goal was to create a sustainable landscape solution for the home's expansive backyard by installing proper drainage in an area prone to flooding. To that end Stringer and her landscape construction partners, transformed a 1,200 square foot area between the garage and main structure into a space for outdoor living and water management.
The team began by excavating down 12", prepping the foundation for a level grade. The build team then set the drainage runs and linear drains. After testing the water flow, a road base was set to 6" above the leveled and graded foundation. This base was compacted and reapplied several times to get the required grade for water flow. Framing of the concrete areas and rebar work was performed shortly after.
The prep work for a pour of this size takes about a week. This includes the time used to make the forms for the concrete paving. The pour was completed in a single day. Expansion joints were integrated into the patio at critical areas where the concrete meets the house. In addition, the build crew also installed a carefully concealed recessed concrete transition zone with linear drains, one for each of the concrete patio segments.
This was done to channel water to a pair of established water swales on the north and south sides of the property. It is important to note the recessed area was excavated 12" below the main patio to allow for drainage to this area. All patio surfaces were sloped to the concrete recessed area as it contains three tandem linear drains.
The concrete recess handles water overflow during heavy rain, while also serving as a transitional zone to move from the breakfast nook area to the master bedroom segment leading to the backyard and garage. The area was finished with flagstone steps mortared in place and filled with polished beach pebbles and accent boulders.
Raised seatwalls, which double as planters, are filled with a plant theme selected to incorporate a pallet of sustainable and low water plants suited to the region for long lasting color. The build crew had to excavate down below the frostline at 36" before concrete could be poured.
The paving was poured with thickened edges and increased rebar, a standard recommendation by engineers in the region for seat walls set on a concrete slab on grade. The thickened edge is 24" and has rebar on center at 10". This is integrated into the main patio slab, which is 6" thick and has a standard rebar spacing of 16" on center. The seatwalls were built with concrete masonry units on the thickened edge of the concrete patio, finished with stucco and capped with flagstone.
Fighting the Frost
The water feature was a design Stringer wanted to implement for some time. The main feature piece is constructed out of a select STK 6" nominal cedar set with 5/8" gaps between the boards. Four main cedar posts were embedded into the concrete patio to support the horizontal boards on the face and on the sides.
The basin for the water feature was constructed with a sleeve just under the cap at the back for the water connections leading from the pump within the basin up to the spillway. These connections are hidden by the screening fence detail. Stacked CMU block supports a clear poly sheet, which the polished beach pebbles sit on. This reduces the splash of the water feature and protects the pump.
A diffuser at the back of the spillway allows the water to spread out and flow evenly over the spillway. An LED light strip highlights the spillway and is plugged into a GFCI outdoor outlet behind the water feature that also supports the pump electrical power. The water line zone is set to run daily for 15 minutes but will only run if the float is open.
Implementation of the design was challenging because the space had limited access. Due to the narrow area between the main structure and garage, as well as the changes in elevation, smaller equipment for excavating, grading and hauling had to be brought in to do the job. The crew relied on a compact walk-behind front-end loader to do most of the heavy digging and lifting.
The drainage installation had to be very precise, posing another challenge for Stringer and her team. The crew had less than 3" of fall to work with. The pipes had to be installed dead on level (they have internal grades) to account for the finish concrete heights to achieve proper drainage of the patio surface.
"Even though we took up space creating the courtyard, it felt bigger than it did before," said Stringer, "a hallmark of good design."