Joist Sistering

What This Service Involves

Joist sistering strengthens a floor or ceiling by fastening a new joist alongside one that is cracked, rotted, notched, or undersized. We assess the damaged members, then bond and fasten matching sisters full-length so the pair shares the load and stiffens the span. This targeted repair is often the cleanest fix for the sagging, bouncy floors that show up in older Puget Sound homes with moisture-worn framing. Where rot is involved we address the moisture source so the repair lasts. The reinforced joists restore stiffness and bring the floor back toward level.

Benefits

Weak or damaged joists reinforced to full strength; Bouncy, sagging floors stiffened and flattened; Full-length sisters that share the span's load; A targeted fix that avoids replacing whole floors; Moisture cause addressed where rot is present

Our Process

1) Inspect the joists and confirm the extent of damage; 2) Cut and fit full-length sister members alongside; 3) Bond and fasten the sisters to share the load; 4) Address any moisture source and verify the floor stiffens

What Affects the Cost

Number and length of joists to sister; Extent of rot, cracking, or notching present; Access to the joists in a crawlspace or ceiling; Material matched to the existing framing; Moisture remediation where rot is involved

Best Time of Year

Joist sistering happens year-round; correcting moisture-driven rot at the same time protects the repair through wet seasons.