How Floor Joists Support Your Home’s Foundation

Have you noticed squeaky floors or other problematic signs around your home? Basements and crawl spaces require durable floor joist systems for support. These structures uphold your flooring, furniture, and everything else above the foundation’s underground area.

This page explores floor joists, common issues that cause damage, and the repair methods that stop the squeaks for good.

Floor joists are horizontal framing supports essential to your home’s structural integrity. They span between beams or load-bearing walls to support the subfloor and the floor above. Properly sized and spaced floor joists create a robust and stable platform that distributes weight evenly throughout the home’s structure.

• Solid Lumber Joists: These are a traditional option with span capabilities depending on the size and lumber grade.
• I-Joists: These contain solid wood flanges and a web of oriented strand board (OSB) or plywood. They are durable and typically span longer distances than solid lumber joists of similar size; however, they offer minimal flex comparable to solid lumber.
• Open-Web Floor Trusses: Made from dimensional lumber (like 2x4s) with diagonal webbing and metal connector plates, these offer utility accessibility and longer spans than solid lumber joists. Though they flex more than I-joists, proper engineering and installation can reduce this to acceptable levels.

• Sagging floors 
• Misaligned window and door frames 
• Overspanned floor joists

• Wood rot
• Mold growth
• Squeaky or bouncy floors

• Poor Design: Poorly designed and installed joists, using too few joists, over-spanning, and improper spacing cause insufficient load support, weakness, and sagging.
• Weight: Joists have a weight limit. Adding extra weight during renovations can crack joists, affecting your home’s stability.
• Moisture and Humidity: Excess moisture leads to wood decay, a common cause of floor joist failure.

• Vapor barriers
• Dehumidifiers
• Sump pumps
• Drainage systems and matting
• Crawl space insulation

Crawl space support jacks, like our IntelliJack™ crawl space jacks, are essential for reinforcing and stabilizing your home’s foundation. For peace of mind and a stable foundation, contact JES Foundation Repair for a free inspection and expert recommendations tailored to your home’s needs.