The short answer

If your project changes how your house carries weight — a wall, a floor, a roof, a foundation, or a new load on top of any of those — you almost certainly need a structural engineer, not just a contractor’s opinion. If nothing structural changes, you probably don’t.

Call before you start if you are

• Removing, moving, or cutting an opening in a load-bearing wall, even a “small” change.
• Adding a room, a second story, a dormer, or a rooftop deck.
• Changing the roofline, raising a ceiling, or vaulting a ceiling.
• Adding a heavy load: stone finishes, a large tub, solar panels on an older roof.
• Building or rebuilding a foundation, retaining wall, deck, or porch enclosure.
• Converting a garage, attic, or basement where framing or floor loads change.

Call promptly if you notice

• Wide, horizontal, or stair-stepped cracks, or cracks that keep growing.
• Doors or windows that suddenly stick or won’t latch.
• Floors that slope, bounce, or feel soft; walls that bow or lean; a sagging roofline.
• Water, rot, or insect damage where beams and walls bear on foundations.

Hairline drywall cracks that don’t grow are often cosmetic. The patterns above are a reason to get an evaluation, not a patch.

Also call after an earthquake, flood, major storm, or fire — even if the house looks fine — and before you buy if an inspection flags anything structural. A targeted evaluation tells you what is actually wrong and what can wait, before you close.

What an engineer gives you that a contractor doesn’t

A contractor knows how to build. An engineer is licensed to say, in writing, that a design is safe and meets code, and to stamp drawings the building department will accept. Ask which deliverable you are getting:

1. Evaluation / report — visit, findings, recommendations. Good for buying decisions and “is this serious?” triage. It does not authorize construction on its own.
2. Calculations — the math behind beam sizes, spans, bearing, and foundation loads.
3. Stamped drawings — plans a contractor can build from and a department can permit. Removing a load-bearing wall without these is guessing at the beam — and an undersized beam shows up later as sagging, bouncy floors, and doors that won’t close.

What happens next

Most structural work needs a permit, with engineered drawings and calculations. Expect: engineer visit and design, permit submission and review, then construction — with temporary shoring in place before any bearing wall comes down — inspections before drywall, then final sign-off. Skipping the permit can mean stop-work orders, forced rework, and trouble at resale.

Costs vary by scope and region, so get a written quote stating what’s included (visit, drawings, calculations, revisions). And bring the engineer in before demolition and before a contractor prices the structural work — sizing a beam on paper is cheaper than fixing one in place.

Disclaimer: This guide is educational information, not a stamped design for a specific house. Requirements vary by jurisdiction and existing conditions. For a specific project, consult a licensed structural engineer in your state and your local building department.