Land and site assessment

The parcel decides more than the plan does

A house design can be changed until it is submitted. The land cannot be changed at all. Everything it imposes, it imposes permanently, and the imposition is priced into every subsequent decision.

That asymmetry is the argument for doing site work first and doing it properly. A week of due diligence before closing is the highest-return week in the whole project, and it is the one most often skipped because it happens while the buyer is still excited.

Access and services at the boundary

Two questions, both answerable by standing on the site and making three phone calls.

Can a truck get here. Specifically: can a concrete truck, a lumber delivery and, if you are building offsite, a low-loader and a crane reach the position where the building will stand. Width, overhead clearance, turning radius, bearing capacity of the approach and any bridge or culvert on the route are all real constraints, and any one of them can add a line to the budget larger than a kitchen.

And what is at the boundary. Water, sewer, power, gas, and communications either terminate at your property line or they do not. The distance from the boundary to the nearest connection point is a cost that scales with distance and with what has to be crossed to get there. A road crossing, a neighbour's land, or rock changes the figure entirely. Ask each utility for a connection assessment in writing rather than assuming that a pipe in the street is available to you.

Where sewer is absent, the question becomes whether the ground will take a septic system, which is a soil and water table question answered by a percolation test and by the local health authority. That test can fail, and a parcel where it fails is a parcel you cannot build a house on.

Soil, slope and water

Soil decides the foundation, and the foundation is the least visible expensive thing in a house. Bearing capacity, expansive clay, fill from previous use, rock at shallow depth and a high water table each push the design in a different direction and each has a cost attached.

A geotechnical investigation is the way to find out, and on a small residential project it is often skipped on cost grounds. That is a defensible decision on a flat, well-drained site with neighbouring houses of similar age and no history of fill. It is a bad decision on a slope, on made ground, or anywhere a neighbour mentions water in a basement.

Slope is worth its own thought because it compounds. A sloping site raises the cost of the foundation, the access, the drainage and the retaining, and it does so together rather than one at a time. The reasoning for what to build on top of it sits under foundations in the structure series.

Flood exposure, and why the date matters

Flood risk in the United States is mapped federally, and the authoritative lookup is FEMA's Flood Map Service Center, which publishes the effective flood insurance rate map for a location.

Two cautions travel with any answer it gives. The map has an effective date, and mapping is periodically revised, so a determination is a statement about the current map rather than a permanent property of the land. And a map showing a parcel outside a mapped flood hazard area is not a statement that the parcel does not flood. It is a statement about a modelled event on a published map, which is a narrower claim than most buyers hear.

Where the answer matters, and it always matters, get the determination in writing, note its effective date, and ask the local floodplain administrator whether any revision is in progress. That office exists in every participating jurisdiction and it is the only one that can tell you what is happening locally.

What a survey establishes, and what it does not

A boundary survey establishes where your land is. It locates the corners, the boundary lines and, depending on the type commissioned, improvements, easements of record and encroachments.

What it does not do is tell you what you may build. Zoning does that, and the two are separate documents from separate offices. A survey will show an easement running across the middle of the lot; it will not tell you that the setback from it forecloses the only sensible building position. That conclusion is yours to draw by overlaying the survey onto the zoning requirements, and it is worth drawing before closing rather than after.

Order the survey early enough that the result can still change your mind. A survey delivered the week before completion is a formality. A survey delivered during the inspection period is due diligence.

A sequence that fits inside a contract period

Day one: pull the zoning designation and read the dimensional standards for that district from the jurisdiction's published code. Day two: call the utilities and the health authority. Day three: walk the site with a builder and look at access. Then order the survey, and order the geotechnical investigation if anything in the first three days suggested you should.

None of that is expensive relative to a land purchase, and every item can kill a deal on its own. Finding out afterwards is how a buildable lot turns out to be a very expensive garden. The rest of the sequence, once you own it, is on the front sheet under planning.