Douglas Fir Root Threat to Stem-Wall Foundation

80-foot Douglas fir, 30" diameter, 12 ft from stem-wall foundation. Nearby patio slab lifted 4 ft away. Soil: 2 ft topsoil over blue clay.

Foundation Safety Analysis

• Stem-wall footings typically below frost depth (>2 ft)
• Tree roots concentrated in top 2 ft
• Roots unlikely to reach footing depth
• Branch spread ~20 ft (roots 1.5× = 30 ft), but outer roots small/diffuse
• Foundation slab thicker than patio—more resistant

Conclusion

Root damage to foundation highly unlikely. Patio lifting occurs because thin slab on shallow roots. Foundation footing depth and construction provide protection. Monitor but no removal needed.