Structural Engineering Coordination: When You Need an Engineer, Calcs, Wall Removal and Costs

How the code decides when engineering is required

Most US houses are built under the International Residential Code (IRC) or a state version of it. The IRC is a prescriptive code: it gives tables for joist sizes, header spans, wall bracing and footings, and a builder who stays inside those tables doesn't need an engineer. Engineering comes in when a design steps outside them.

The engineered design rule

IRC section R301.1.3 says that when a house of otherwise conventional construction contains structural elements that exceed the code's limits, or that don't conform to the code, those elements must be designed using accepted engineering practice. The engineering only has to cover the nonconventional parts, and it has to work with the rest of the conventional frame. That is why a mostly ordinary house may need just one engineered beam, one steel post and one footing.

California states the same idea in licensing law. Business and Professions Code section 5537(b) says that if any part of an otherwise exempt wood-frame house departs from conventional framing rules, the building official must require plans or calculations for that part from a licensed architect or registered engineer, with their stamp and signature.

Common triggers on house projects

• Removing or shortening a load-bearing wall
• Openings wider than the code's header tables allow, such as large sliding or folding doors
• Adding a second story, which adds weight to the walls and foundation below
• Long floor or roof spans, vaulted ceilings, or roof decks
• Steel beams, steel posts or moment frames
• Hillside lots, retaining walls and foundations on poor soil
• Repairs after foundation movement or storm or earthquake damage
• Heavy loads such as rooftop solar or large equipment

HomeGuide's list of reasons to call an engineer covers many of the same items, from additions and wall removal to foundation cracks, sloping floors and solar panels.

Wind and seismic design

Location can require engineering even for a simple house.

High wind

Under section R301.2.1.1 of the 2021 IRC, as compiled by FEMA, the IRC's own wind rules stop applying in regions where its wind design map requires design, or where the ultimate design wind speed reaches 140 miles per hour or more in a special wind region. In those places the house must be designed for wind using one or more recognized methods:

1. The AWC Wood Frame Construction Manual (WFCM)
2. ICC 600, the standard for residential construction in high-wind regions
3. ASCE 7, the national standard for design loads
4. AISI S230, for cold-formed steel framing
5. The International Building Code

Your building department can tell you the design wind speed for your lot and whether it falls in a region where wind design is required.

Earthquakes

The IRC assigns each site a seismic design category based on expected ground shaking. In the most severe category, E, the residential code sends seismic design to the International Building Code, unless the site can be reclassified to a lower category under the code's rules. If any part of the lateral system in a lower category falls outside the code's tables, the engineered design rule above applies to that part. Ask your architect or engineer which category applies before you settle on a layout.

What the engineer delivers

The engineer's work usually shows up in the permit set in three forms.

The engineer stamps the calculations and structural sheets. HomeGuide notes that most engineers won't stamp work they didn't prepare or supervise, so a stamp from someone who only glanced at a drafter's plans is rare. If the building department asks questions about the structure during plan check, the engineer answers those comments. Our page on permit drawings explains how the full set and the correction rounds work.

How architect and engineer coordinate

HomeGuide describes the split this way: the architect designs the space, look and function of the house, and the engineer is responsible for strength, safety and the load-bearing parts. The handoff happens in design development, when the architect works with engineers on the structural, mechanical, electrical and plumbing systems.

Good coordination follows a pattern:

1. The architect sets the layout and marks walls that may come out or openings that must grow.
2. The engineer visits the site or reviews existing drawings to learn how loads travel to the ground.
3. The engineer sizes beams, posts, footings and shear walls, and flags anything that doesn't work.
4. The architect adjusts the design, for example adding a post in a closet instead of a deeper beam.
5. Both sets of sheets are checked against each other so dimensions, beam depths and ceiling heights match.
6. During construction, the engineer answers contractor questions and reviews changes, such as a substitute beam.

Problems usually come from skipping step 5. A beam that is 4 inches deeper than the architect assumed can lower a ceiling, block a duct run or clash with a window head.

Removing a load-bearing wall

This is the most common reason homeowners hire an engineer. HomeGuide puts the total at $4,000 to $10,000 in a single-story home, and $9,000 to $15,000 in a multi-story home. Some complex two-story walls cost $20,000 to $30,000. A non-load-bearing wall costs $500 to $2,000 to remove.

What the job involves

HomeGuide says the engineer has to size the beam and check whether the footings under the new posts can carry the extra weight. Without that, the result can be sagging ceilings, uneven floors or worse. Beam material alone runs about $3 to $12 per linear foot for LVL, $6 to $22 for glulam and $6 to $24 for steel. Recessing a steel beam into the ceiling so it doesn't hang down costs $170 to $450 per linear foot. HomeGuide also warns that wiring, ducts or plumbing found inside the wall can add about 20% to the cost.

How to tell if a wall is load-bearing

Only a site visit settles it. HomeGuide notes that all exterior walls are load-bearing, and that a contractor needs to inspect the home before giving an accurate estimate. For interior walls, have an engineer check how the framing above and below carries loads before anyone opens the wall.

Ways to keep engineering costs down

• Bring the engineer in early, before the layout is final, so the design works with the structure.
• Ask for existing drawings or permits for your house from the city, which can save site measuring time.
• Accept a post or a dropped beam where it doesn't hurt the room, rather than a flush beam over a long span.
• Group the work: one engineering package for the wall removal, new windows and addition costs less than three.
• Get two or three quotes and confirm the engineer is licensed in your state, as HomeGuide advises.

Estimate total design fees, including engineering, with the architecture calculator below.

For related project guides, see additions and remodels, residential design, ADU design, commercial design, 3D renderings and, for California homes, Title 24 energy compliance. The architecture overview covers fees for every project type.