Compare the ground under two addresses
Two ZIP codes, side by side. Useful when you are choosing between houses, when you are moving to a state whose ground you do not know, or when you want to see why the same weather produces a wet basement on one street and not on the next.
If you are choosing between two houses
The three numbers point at three different questions to ask the seller:
| High moisture or water table | Ask what happens in the wettest month, whether there is a sump, how old it is, and whether it has a backup. Ask to see the basement in spring if the timing allows. |
|---|---|
| High foundation movement | Ask about cracks that have been repaired, and look for fresh patching and fresh paint on foundation walls. On expansive clay, a seller who has watered the foundation consistently has done you a favour; one who let it bake has not. |
| Both low | The ground is not your risk factor. Spend the inspection budget on the roof, the service lines and the grading instead. |
Why neighbours differ
Within one ZIP code the soil survey often maps several units, and the boundary between them can run down the middle of a street. That boundary is invisible and it is frequently the whole explanation. The soil map draws it.
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