Just realized that old trick of following the discolored soil lines saved me hours last week on a site in Mobile.

I was trying to map out a 1930s foundation and kept digging in the wrong spots until a retired surveyor told me the dark streaks in the dirt show where wood rotted in place, so I just traced those instead and found the corner posts in under 20 minutes - has anyone else tried this method for old building footprints?

3 comments

3 Comments

green.noah2d ago

Wait, is this actually reliable or was the retired surveyor just messing with you? I get that wood rot changes the soil, but wouldn't old foundations leave way more obvious signs than a dark streak?

torres.blair2d ago

Have you ever actually dug into one of these spots? I have, and it's not just a dark streak - the soil changes texture completely, gets greasy and almost spongy from all the decomposed organics. The old surveyor was probably right, because the real giveaway isn't the color alone, it's how the ground feels different under your boots. You'd expect bricks or glass but wood foundations just rot away entirely, leaving nothing but that dark stain and a slight dip you can only feel if you're walking barefoot. Test hole is the only way to know for sure, dig down about a foot and you'll either hit solid undisturbed soil or that soft black crumbly stuff that smells like a damp basement.

the_eric2d ago

Wait, hold on. The guy walked you right up to a random dark patch in the dirt and said "that's a 200 year old house"? That's wild. I mean, I've heard of soil discoloration from old privies and trash pits, but a whole foundation? You'd think there would be a clear depression or at least some broken bricks or glass around. Not just... a slightly darker line in the mud. Did he point out what kind of wood it was, like old growth oak or something? Because that stuff rots completely different than the pine they use now, but still, a dark streak feels like a stretch without digging a test hole.