Tandem House was conceived to be a sustainable home that is achieved in every respect from using SIP panels, solar panels, and an efficient HVAC system (among numerous other things).  The house will be LEED-certified (we should have the certificate any day now) and the landscape is a major component to receiving the necessary points required for the certificate.

We see the landscape as an extension of the home and the sustainable concept flows through every exterior detail.  By opting to eliminate the need for irrigation the plant selection includes all Colorado native and adaptive species.  Once established the plants will sustain off the ebbs and flows of the environment that it’s meant to thrive in.  The artificial turf lawn requires zero maintenance and no water.

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The grading and flow of water on-site is a big factor in plant selection, ensuring that plants that require less water are at a higher grade and those that thrive off more water are at low points. The water diagram below shows the flow of water on-site and from the roof downspouts.  The water that is handled on-site, flows to the native grass rain garden that can handle large water events with droughts in between.  The landscape acts as a sponge, soaking and cleaning water as it flows through the site and into the groundwater system.

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Once we plant the few remaining plants and complete construction site cleanup we will have the landscape professionally photographed.  Stay tuned!

Now that Tandem House and the landscape are almost done it is hard to remember what existed before this all started.  This post requires a look back at the original one-car garage that we demoed two years ago (pt. 2).  If you remember, we saved the brick and stacked it for future use.  We used the red brick (the inside layer of the old garage) to pave the ribbon driveway.  In a few weeks, we will fence in this area to give the front house a side-yard (stay tuned).

Back in May, we conquered the concrete pathways and back patio.  Once the subgrade material was compacted and set to 3 inches below final grade per the site Grading Plan and concrete details, we were ready for concrete formwork!  Because the landscape design is fairly complicated (from a grading and pavement perspective) it was important that we had a detailed Layout and Materials Plan (per the landscape drawings) and use this as a tool when getting bids for subcontractors.  Because concrete itself is a simple material, its crucial that the contractor is detail-oriented and doesn’t deviate from the drawings unless otherwise instructed on-site.

The most important time to be on-site was to oversee the building of concrete formwork to ensure that layout and grades are set correctly. Once the concrete is poured and set it’s difficult to correct which is why it’s crucial to get right beforehand.

After two days we were ready to pour!

Once the concrete forms were stripped, it’s easy to see the 4″ gap that is left between each concrete pad.  This 4″ border was further accentuated and held in place with steel edger and lined with filter fabric.  The border was filled with decomposed granite to complete the look.  The final product breaks up the mass of hardscape for a soft and contemporary feel that matches the house aesthetic.

This summer has been focused on the landscape and exterior of Tandem House.  We have two open permits that have yet to be closed pending Zoning and SUDP (Sewer Use and Drainage Permits) final inspection and approval.  Once these permits are closed then we will finally have our Certificate of Occupancy.

Zoning has already confirmed that the building fits within the bulk plane and setback requirements (among other things), but a few items have yet to be done.  In order to get our Zoning permit closed the City wants to see that all landscaping be complete, that no lingering construction material be on-site and that they approve all exterior lighting.

The Sewer Use and Drainage Inspection ensure that the flow of water is away from the house and handled either on-site or directed properly towards the alley.  It also dictates that sump pump discharge is handled on-site and inspected per the City’s detail.

A good landscape design understands that both subjects go hand-in-hand.  A successful landscape design acknowledges grading and drainage from the very start because it dictates cut and fill, site retaining, steps, access points, circulation and the flow of water.  A major factor in our landscape design was dictated by the final Finish Floor Elevation of the house which is 3.5′ lower than what was existing.  Hense excavation and the hauling of dirt off-site was a huge endeavor and a major cost.  This was a big learning experience for myself as a landscape designer.  From this personal experience as the homeowner, I now understand the importance of limiting the amount of cut on-site by finding creative and resourceful grading solutions that limit the need to haul dirt away.  In the middle of a construction boom in Denver, hauling dirt away is more expensive than ever because everyone is building basements and underground parking.  Most construction sites are getting rid of dirt (cutting) not filling.  Hence the problem.  Dirt has to be loaded one truck at a time and hauled away 40 miles north.

This Spring we prepped the site for landscape.  All major excavation was complete so we began by installing a wood retaining wall at the south property line.  The wall now holds back the 3.5′ of dirt from our neighbor’s yard; preventing it from eroding or collapsing onto our site.  With the wall up, it allowed us to prepare for what would become a large rain garden.

Step 1:  The Rain Garden

The rain garden is the foundation for site drainage and a major landscape component.  To build the 200 SF rain garden we had to excavate another 2.5′; that’s on top of the 3.5′ that was originally excavated.  Once the garden was dug, we directed roof run-off via downspouts.  As the water exits the downspout it enters a catch basin and that leads under the now sidewalk and into a dry rock well at the bottom of the rain garden.  We also directed the sump-pump water to the rain garden.  If there is ever excessive groundwater from a rain event, the sump will pump the water up and away from the house foundation into a second dry rock well at the bottom of the rain garden.

Once the water was directed to the rain garden we filled it with a soil mix that promotes drainage.   The mix is made up of 30% sand, 25% compost, 25% topsoil, and 20% clay.  To complete the rain garden we planted two Rocky Mountain Glow Maples and a mix of Colorado native grasses (little bluestem, blue grama, and switchgrasses among the ten different species).  This rain garden is not irrigated and once established it will be fully supported by natural rainwater events.

Step 2:  Fine Grading & Artificial Turf Prep

Below is our SUDP plan.  This is subsequent to the more detailed grading plan and shows where water is flowing.  The ‘infiltration swale’ is the rain garden.  Downspouts and flowlines (FL) show where water is being directed away from the house foundation.

SUDP

Below are images that show the aggregate base for the artificial turf detail and the sloping landscape away from the house with french drains that lead runoff towards the rain garden.

We chose not to irrigate our landscape and to make that come to fruition we installed an artificial turf lawn.  The manufacturer is synlawn which is a great product.  The proper foundation for artificial turf is crucial for efficient drainage.  To prep for the lawn, we removed 4″ of earth where the turf is installed, filled the area with 3″ of 3/4″ aggregate, compacted that and added 1″ of pea gravel.  We lined the area with a steel edger which completed the prep work.  To install the lawn we rolled it out in place, made a few cuts and seams and pinned the lawn down with 6″ non-galvanized steel nails.

The lawn is now a fantastic place for our one-year-old daughter to play.  We completed it just in time for her first birthday!