Building a House - Grading - Land Development 101

The first step in building a house is the grading! Once we got our grading plans stamped and approved, we finally got our grading permit (we will discuss these steps in more detail in a future post). Now we were able to get started with building our house.

Outline of flag lot from a Google maps view showing property that the future house will be built on. — Google Maps view of lot

Photo of empty lot from the street with for sale sign. — Google Maps view of lot

Point of view of empty lot standing from back rear corner looking down at a sloping dirt property towards front neighbors. — Rear POV from back of empty lot

Because the natural terrain of our property sloped upward from the front to back (a total elevation difference of about 30 feet!), it was going to require quite a bit of grading. We needed to do some cut in the back and fill in the front. And since we could not slope the sides to match the existing surrounding grade around our property, this was also going to require retaining walls. With this lot size only being 0.23 acres, we did not have much of a choice.

Plan view of house sitting on lot. Grading plan shows a sectional cut view B-B. — Grading plan showing house layout and retaining walls.

Plan sectional view of the lot from top to bottom showing slope of existing topo overlayed with new proposed grade. Also shows retaining walls. — Sectional view of lot from the street to the back of the property. The proposed grade (in pink) is overlayed with the existing ground (in yellow).

But before your grading begins, there are a few things you MUST do:

1. Make sure you call your Underground Dig Alert Service

You need to mark out on the road with spray paint where you plan on doing construction. You can indicate with 90-deg arrows to mark out the limits along with a distance, which also indicates how far back into the property it will go. (See example in photo). This will allow all local utilities in this area to come and mark out where their utilities are so you don’t accidentally tear up their pipe when digging.

Aerial view of the empty lot where the future house will be built. Markings in white shown in road to alert Underground Dig Alert services — Aerial view of empty lot showing white spray paint markings in road to alert the Underground Services Alert (“USA”) prior to building a house.

2. Call a surveyor

You must call a surveyor to come out and stake a few things so your grader will know where to work. Your surveyor will most likely come out a few different times to stake various things. If they come and stake everything all at once, you will most likely lose things during construction. So, the first thing they must stake are the boundaries of the pad. And in this case, since we had slopes on either side, that meant staking the top of slopes, toe of slopes, and retaining walls.

3. Set up source for construction water

The closest source for water was a fire hydrant off the road a few houses down from our property. After contacting the water utility company and paying a fee, they came and installed a temporary water meter for us. Keep in mind, some agencies may also require for you to install your own backflow preventer.

TIME TO BREAK GROUND

Once we had these things, then we were able to officially break ground! Immediately our grader used the excavator to start cutting the high parts of the lot in the back, and moved that dirt to the low area in the front (the “fill”).

Excavator starting to dig into the existing ground to cut a slope on an empty lot. — Beginning to cut in a slope in the rear of the property. Notice the marked out white line.

Excavator cutting in slope in rear of empty lot. — Excavator cutting in the new rear slope in the back of the property.

But because the front of the pad required retaining walls, we obviously could not completely raise the front edge of our lot up to the proposed finished grade elevation. We just had to slope it down until the retaining walls could be installed and backfilled later.

Excavator grading property. Front of pad is sloping downwards where a future retaining wall is outlined in red. — Front of pad showing future retaining walls.

Downwards slope in the grade of the property towards a future retaining wall as drawn out in red. — Slope graded downwards towards future retaining wall in front.

You typically need a laser or something to help you determine/maintain your grade elevation throughout the pad. We had a GPS Trimble system, which also quickly helped us know when we reached our ROUGH GRADE ELEVATION.

MOISTURE AND COMPACTION

During the excavation, don’t forget to constantly spray the dirt to get enough moisture. This helps with the compaction. (It also helps for dust control so your neighbors don’t get mad at you.) Usually you would need something for compaction, but in this case the excavator is heavy enough to provide enough compaction while rolling around on top.

CERTIFY THE PAD

Once the lot has been graded to the rough grade elevation, a licensed surveyor must come back out and certify the lot. Meaning that he’s checked the elevation using his GPS system to make sure it is correct and then he records it.

Excavator sitting on new graded property in empty lot. The pad needs to be leveled prior to building a house. — New graded pad with retaining wall back cuts.

OVER EXCAVATION (OX)

But we are not done yet! Now, it’s time for the over excavation. This means to excavate further below the rough grade elevation in order to get a competent foundation for your house. For this house, the soils report recommended 2’ below the subgrade.

Excavator bucket digging into the ground right at a green spray painted line. — Over excavation to begin for the house footprint.

Excavator bucket in ground pulling dirt from the ground prior to building a house. — Over excavation to begin for the house footprint.

Excavator machine digging a hole in the dirt about 2' deep. — Over excavation (2′ deep) for the house footprint in progress.

Once we got to the bottom, the soils technician was required to check the compaction and buy off on it. By doing this, the technician hammers a hole into the ground about 12″ (varies), then they use a nuclear density gauge which sends a probe into the ground to read the density. If we reach the minimum compaction, we then put the dirt back in.

Person is hammering at rod in the ground of the foundation to test compaction prior to building a house. — Soils tech performing a compaction test for the over excavation.

This step was especially necessary for a “transition” lot (which means your house sits on a pad that has both cut and fill), such as ours. And because this was a transition lot, it was best to grade to the rough grade elevation and THEN begin the process of over excavating. But if we had a pad that needed to be raised up entirely, then we would’ve just called the soils technician to inspect the OX subgrade elevation PRIOR TO EVEN REACHING OUR ROUGH GRADE ELEVATION.

Excavator machine digging into ground about 2' deep. — Excavator performing over excavation for house foundation.

Excavator machine on new dirt that was placed back in a hole for building a house. — Excavator performing over excavation for house foundation.

BUILDING A HOUSE – GRADING SUMMARY

Once the soils technician buys off the over excavation and the rough grade elevation has been certified by the surveyor, your grading is complete! And you’re one step closer to building a house. Now you’re ready to start the retaining walls.