Cutting One Pine Root for a Deck Foundation: Is It Safe?

Minimal Impact from a Single Root Cut

A contractor needs to cut one large root of a mature pine to pour a deck foundation. The root runs under the house, about 10 feet from the trunk. The homeowner fears the tree will die or fall.

Tree Root Biology

Pines have a taproot plus a spreading root system extending roughly 1.5 times the canopy width. Roots are concentrated in the top 24 inches of soil. Cutting one root—even a large one—removes far less than 30% of the total root system, the threshold for significant dieback.

Verdict

• The tree's health will not be affected.
• Stability is unchanged—the taproot and remaining roots provide ample anchorage.
• The tree will not fall on the house from this single cut.

Proceed with the deck work. No special treatment needed on the cut root end.