A Fix for a Sagging Ceiling

What to do when a new beam goes up and the ceiling starts to sag.
sagging ceiling beam illustration

New beam, sagging ceiling.

"My ca. 1930 bungalow once had a room-dividing colonnade. I contracted with a well-known cabinetmaker to create a period version. After installation, the glass-front cabinets and piers looked great. But a significant sag in the ceiling, unaddressed during measuring for the project, required the 'beam' to be scribed more than could possibly look reasonable, marring the effect."  —Roseann Ferrini

The Fix

The homeowner is reeling with regret that she had not noted and addressed the significant sag in the plaster ceiling. But she’s also unhappy that a professional cabinetmaker visited, measured, drew plans, and then built a room-spanning colonnade without accounting for the sag.

sagging beam illustration

If you have an existing colonnade or any other period trim, leave it be!

“After installation, I knew I couldn’t live with the scribed beam,” she says, “and an architect–neighbor was sufficiently troubled by the sag itself that he told me I needed a structural engineer.” Undersized joists in the attic floor had bowed, and then the keys in the plaster ceiling pulled away from the joists. At the time of construction, nails rather than screws regularly were used to attach wood lath to joists, and the nails had slipped right out.

A general contractor sistered new joists to the existing ones. He used specialty clips to attach the lath back to the joists. He was able to raise the sagged ceiling two inches (of the total three inches the ceiling bowed at center). This exposed a gap over the scribed beam, which had been cut away to follow the sag.

The cabinetmaker has since created an overlay trim piece, which is neatly scribed to the ceiling and covers the gap at center. It’s not perfect—but what is, in an old house?

“The lesson,” says the homeowner, “is this: If you have an existing colonnade or any other period trim, leave it be! Because it’s not easy to retrofit a house that has settled.”

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