We have written before about why it pays to talk to a builder before you buy land, and about the covenants and design controls that come with it. This one is about the ground itself. A lot can be perfectly legal to build on and still be an expensive place to put a house, and the reasons are usually visible to someone who has done it before.
How the water leaves
Start here, because everything else follows from it. Water moving across a site decides where the house can sit, what the foundation has to do and whether you end up with retaining walls and drainage structures that never appear in anyone's picture of their dream home.
Walk the lot after heavy rain if you possibly can. Standing water, a soft low area, a channel cut through leaf litter, silt fanned out across a flat spot: these tell you more in ten minutes than a plat will.
Slope, and the difference between a view and a problem
Grade is not automatically bad. A well handled slope gives you daylight on a lower level and a house that sits into its site rather than on top of it. What costs money is the combination of slope and access: a steep driveway that has to meet the street at a workable angle, equipment that cannot reach the back of the lot, foundations that step repeatedly, and soil that has to be moved rather than simply cut and balanced on site.
The question is never just how steep it is. It is where the steep part sits relative to where the house wants to go.
Soil, septic and what the perc test decides
If the lot is not on city sewer, the soil decides what you can build before an architect draws anything. A septic permit is tied to a specific number of bedrooms, and that number can come back lower than the house you had in mind. On a marginal lot you may be looking at an engineered system rather than a conventional one.
Two practical points. Get the soil evaluation done before closing wherever you can, and understand that the septic field and its repair area occupy real estate that then cannot hold a house, a driveway, a pool or an accessory dwelling. On smaller parcels this is often what caps the whole plan.
The buildable envelope is smaller than the lot
Take the parcel, subtract the front, side and rear setbacks, subtract any easements, subtract stream buffers and floodplain, subtract the septic field and its repair area if there is one, and subtract whatever tree conservation applies. What is left is the buildable envelope, and on some lots it is startlingly small.
Easements deserve particular attention because they do not show up when you walk the property. A utility or drainage easement across the middle of a lot can split the envelope into two pieces, neither big enough for the house.
Trees
Mature trees are usually why someone fell in love with the lot. They are also a constraint. Tree protection requirements vary by jurisdiction across Wake, Durham and Orange counties, and specimen trees can carry their own rules. Beyond the ordinance, there is the practical matter of root protection zones during construction, which limit where equipment can travel and material can be stacked.
The trees you keep need to be chosen deliberately at the start. Trees that are damaged during construction tend to die two or three years later, which is the worst possible outcome: you paid to protect them and lost them anyway.
Floodplain and stream buffers
Check the flood maps, and check for a stream or drainage feature at the property line or just past it. Riparian buffer rules apply in much of the Triangle and they push structures back from the water regardless of where the lot line sits. This is the kind of thing that can eliminate the part of the lot you wanted to build on.
Where the utilities actually are
Water, sewer, power and gas have to reach the house. The distance from the connection point to the building site is a real number with real cost attached, and so is what sits between them: pavement to cut, a creek to cross, a neighbour's easement to negotiate. A lot that looks well served from the road can still be a long run to a building site set back in the trees.
Rock
In parts of the Triangle you will find rock close to the surface. It affects excavation, foundations, utility trenching and septic. It is not a reason to walk away from a lot, but it is a reason to know before you own it rather than after, because it changes the approach to the foundation rather than simply adding a line to the work.
Access and staging
A house gets built by equipment and deliveries. Concrete trucks, lumber packages, a crane if the design calls for one. Narrow frontage, a tight turn from the street, an overhead line across the entrance or a neighbour's wall close to the property line all constrain what can physically reach the site, which in turn constrains how the house gets built.
The useful order to do this in
Look at the lot before you fall in love with a plan. Most of what is listed here can be assessed in a walk of the site and an afternoon with the county's mapping, and it costs nothing compared with discovering it during design. The lots that work are rarely the ones with no constraints at all. They are the ones whose constraints you understood before you bought.
If you are weighing a specific parcel, send us the address. We would rather look at it with you now than redesign around it later. You can also read how we handle pre-construction, which is where this work properly belongs.
Written by the team at NG Custom Builders, a licensed general contractor in Raleigh, North Carolina.
