Site Preparation for a Passive House

Site Clearing for a Passive Home

Site clearing and preparation is different from site to site, and certainly different from urban to rural projects, but there are some common steps in the process.

Obviously, if an older building or set of structures first needs to come down, demolition work will happen, followed by a complete clearing of the site.

If there is substantial tree cover or brush, then selective removal of all vegetation will need to happen before any work on preparing the ground can commence.

In the case of a steep hillside or mountainous build, like the one shown here, there is a combination of activities around tree and brush removal and grading activity that needs to happen at the outset.

Tree removal on any property will include a focus on any trees that could fall on the home in a high wind, as well as strategic removal to support any passive orientation considerations. For a home with a septic bed, we also need to choose ground accordingly.

For any site, the essentials will come next, including roughing in the home’s footprint, site access (driveway), and space for a septic bed when required.

Planning the Driveway

We tend to advise keeping driveways as small as possible. In rural settings, the most common driveway length we find ourselves creating is roughly 200 feet. A driveway in the range of 50 to 100 feet will generally be more cost effective. (A gravel drive is roughly $100 per sq ft, meaning that 200′ driveway will cost around $20,000.)

In an urban setting, we’re obviously dealing with many more constraints and limiting factors that will often decide the driveway’s overall dimensions.

Site Prep Basics

We will generally need to dig six feet wider than the perimeter of the home in order to address frost protection, drainage, and for foundation system access for a home with a full basement (most of our homes are built slab on grade).

In a rural setting where retaining as many trees as possible is a consideration, we tend to recommend placing the septic bed on the south facing side of the home (assuming this is possible for orientation). Tree clearing would happen here anyway, so it’s a simple choice.

We strip away the top foot or two of top soil and then add a compacted gravel pad for slab on grade. A full foundation obviously involves more preparation. (We’re usually working with clay in our home patch, but soil composition will be a factor in this work wherever your home is being built.)

At this point, we call in a geotechnical engineer to approve the ground’s load bearing capacity for the home. This is called a sub-grade inspection and typically costs between $300 and $400. On firm clay, we’re looking for 75kpa minimum for this measurement.

Site prep also involves all allowances for the services required including trenches for phone / internet, hydro / electricity, well / water, and out to the septic bed if present. We tend to position incoming service trenches in parallel to the driveway to minimize disruption.

Site Plans for Urban Homes

For a home to be built in an urban or suburban area, standard services (water, electricity, gas, sewer, internet) should be included in a services layout on a site plan.

We’re sharing here a sample urban passive home site plan:

Site Plans for Secondary Dwellings

For a secondary dwelling**, the site plan will need to show the new dwelling in relation to the primary dwelling and the property boundaries, as well as include a services layout.

We’re sharing here a sample secondary dwelling site plan:

**Secondary dwellings are known variously as accessory dwelling units, coach homes, laneway suites, garden suites, etc. We currently have 13+ passive house plans for these types of dwellings.

Site Plans for Rural Homes

A rural property will tend to have a site plan that looks like this one: