What does a structural engineer actually review when I open a wall for an addition? The answer covers more than just the wall itself. The engineer determines whether the wall is load-bearing, calculates how much weight the wall carries, and designs a beam and posts to safely redirect that load once the wall is removed. If the addition also changes the roofline, the new roof load must be calculated as part of the same connected system — not as a separate project. Foundation capacity at the new post locations is also checked. All of these elements must appear together in the stamped structural drawings submitted for permit, because reviewers look for the complete load path from roof to footing. Missing any one piece sends the plans back for revision and delays the project.
How does an engineer determine whether a wall is load-bearing?
A structural engineer determines load-bearing status by tracing the building's load path — following how weight travels from the roof down through floors, walls, and into the foundation. The direction of framing above the wall is one of the first things the engineer examines. Joists or rafters that run perpendicular to the wall and bear on its top plate are a strong indicator that the wall is doing structural work.
Original blueprints can help, but we don't rely on them alone. Framing is often modified after original construction, so a site visit or framing investigation is frequently part of the review. In ranch-style homes built in Chesterfield during the 1970s, walls carrying roof load are a known consideration — we trace the specific framing conditions on site to confirm load-bearing status rather than assuming based on home style or era alone.
We also check what sits directly above and below the wall in a vertical line. A beam, post, or foundation element stacked above or below a wall is a strong signal that the wall is part of the load path.
What if the wall looks non-structural but carries a point load?
A wall can carry a concentrated load from a post or beam above even when the floor joists run parallel to it. In that case, the wall may look non-structural to the eye but is actually transferring a point load from one level to another. That's exactly why visual guesses aren't reliable without an engineering review — it's the kind of thing that looks fine right up until it isn't.
Physical clues engineers look for include framing direction of joists or rafters bearing on the wall's top plate, stacked structural members directly above or below the wall, wall continuity running straight through multiple floor levels, and beam pockets or bearing plates at the top plate visible when framing is exposed.
What happens to the load when a load-bearing wall is removed?
When a load-bearing wall is removed, the weight the wall carried does not disappear. It must be redirected to a new beam that spans the opening and transfers the load down to new posts and footings. The engineer calculates the tributary area: the portion of roof, floor, or both that the wall was supporting. That area is expressed in square footage and then converted to pounds per lineal foot acting on the new beam.
Posts at each end of the new beam concentrate the load into point loads. Those point loads then travel down through the structure to the foundation. Every element in that chain — beam, post, connection hardware, and footing — must be sized to handle the calculated force. If the load path passes through a floor system before reaching the foundation, we check whether the existing floor framing can accept the new point loads, and we review the existing foundation directly below each post location. Skipping any link in this chain is what causes structural failures and failed inspections — not just permit rejections.
Do both ends of the new beam always need a post?
In most residential wall openings, yes. Both ends of the new beam require a post or column to carry the point load down to the foundation. A pocket column — a post hidden inside the depth of the existing wall framing — is a common solution in finished interiors where exposed steel columns aren't desirable. We size the pocket column based on the calculated load and specify the bearing connection at both the top and bottom of the column.
How is the beam or header size actually calculated for a wall opening?
Beam size is calculated by determining the total load the beam must carry, the span of the opening, and the allowable stress and deflection limits of the chosen material. Two categories of load feed into that calculation. Dead load is the weight of the structure itself — framing, sheathing, roofing, and finishes. Live load is the variable weight from occupants, snow on the roof, and furniture on floors above. Both categories are required by building code and must be combined correctly before the beam can be sized.
Span has an outsized effect on beam size. Bending stress increases with the square of the span, so even a moderate increase in opening width can require a meaningfully larger beam, even when the load above stays the same. We see homeowners surprised by this regularly — the opening doesn't look that much wider on paper, but the beam size jumps considerably.
Material choice also affects the final dimensions. LVL (laminated veneer lumber) beams are engineered to consistent strength ratings and are common in residential additions because LVL is available in long lengths and comes in predictable, grade-stamped form. We specify not just the beam's depth and width but also the required bearing length at each end, the number of plies if the beam is built up from multiple members, and any required connection hardware at the bearing points.
Can I just use the IRC span tables instead of hiring an engineer?
The IRC (International Residential Code) prescriptive span tables, published by the International Code Council, work for straightforward, single-load-source conditions that fall within the table's scope. Additions that change the roofline or stack multiple load sources onto one beam fall outside those conditions and require engineered calculations. Confirming the local permit requirement before relying on a prescriptive table is always the right first step — and honestly, if your project involves an addition, there's a good chance you're already past what the tables cover.
| Opening Width | Typical Load Condition | Why Engineering Is Typically Needed |
|---|---|---|
| Short (up to 4 ft) | Single floor above, standard tributary width | May qualify for prescriptive table; verify with jurisdiction |
| Moderate (4–10 ft) | Roof load plus floor load stacked | Multiple load sources exceed prescriptive table scope |
| Long (10 ft+) | Roof, floor, or addition roofline extension | Span and combined loads require engineered beam design |
Why does adding onto the house change the wall-removal calculation?
When a home addition extends the roofline, the extension changes how much load reaches the wall being opened — so the two structural changes must be engineered as one combined system, not two separate projects. A roofline extension can increase the tributary area draining to the interior wall. That means the new beam must carry more load than it would if only the wall were removed with the original roof still in place.
New roof framing connections at the existing structure also create lateral and vertical forces that must be resolved at the point of attachment. We check that the existing structure can accept those forces without modification, or we specify what reinforcement is needed.
This combined-system analysis is a core part of home addition structural engineering in Chesterfield, where we coordinate wall removal and new framing in a single set of stamped drawings. Drawings that show the wall removal but omit the new roof framing connection — or show the new roof framing without addressing the modified interior load path — are routinely returned for revision. We see it happen more than you'd think, and it's almost always because the two scopes were treated as separate jobs.
Does the sequence of construction matter structurally?
Yes. We may specify whether the new beam must be installed before or after the addition framing begins. Temporary shoring requirements depend on which load path is active at each phase of construction. If the addition framing is erected first and begins transferring load to the existing structure before the interior beam is in place, the original wall may be carrying more load than planned during that window. The stamped drawings address this sequencing explicitly when it affects structural safety — it's not a detail we leave to the contractor to sort out in the field.
What role does the foundation play when a wall is opened for an addition?
The foundation must be able to accept the new point loads created by the beam posts — if the existing foundation cannot, we will specify new footings or a spread footing below the post locations. This requirement surprises many homeowners, because the foundation work isn't visible during the wall-removal phase of construction and is easy to overlook in early planning conversations.
In a slab-on-grade home, a new post may sit directly on the slab. A residential slab is generally not designed for concentrated point loads at arbitrary locations, so we evaluate whether a thickened slab section or a new isolated footing is required at each post location. In homes with basements or crawlspaces, we check the existing footing width and depth below each proposed post location and compare the existing capacity to the calculated bearing pressure. Soils vary across the St. Louis County region, and we may rely on local soil data or conservative code default values when a geotechnical report isn't available for the specific site.
What if the addition itself also needs new footings?
New addition footings and interior beam post footings are calculated separately because the two locations carry different loads. Both sets of footings must be detailed on the same permit drawing set, however, so the plan reviewer can confirm that the whole foundation system works together. Submitting addition footings and interior post footings on separate drawing sets — or leaving one out entirely — is a common reason plans are returned for revision before a permit is issued.
What must the structural drawings show to pass permit review?
Structural drawings submitted for permit must show the existing framing, the proposed beam with dimensions and material specification, post sizes and locations, connection hardware, and any new or modified footings. The drawings must be stamped and signed by a licensed Missouri structural engineer when the scope exceeds prescriptive code limits. Additions that open load-bearing walls almost always meet that threshold.
Plans must also show how the new framing ties into the existing structure at the addition connection point — not just the addition framing in isolation. Shoring plans or notes may be required if the existing structure must be temporarily supported during construction, and some jurisdictions require shoring details to be shown explicitly on the submitted drawings. Including a general notes sheet that references the applicable building code edition is standard practice and gives the reviewer immediate confirmation that the correct code version was used.
Structural drawings for a wall-opening addition typically must include:
- Beam schedule — size, material type, species or product designation, and span for each beam
- Post schedule — post size, material, and bearing length at top and bottom
- Footing detail — dimensions, depth, reinforcing, and bearing capacity assumption for each new footing
- Connection hardware callouts — manufacturer product numbers or equivalent specifications for hangers, straps, and anchor bolts
- Load path diagram or narrative — a clear trace of how load travels from the new roof framing through the beam, posts, and footings to the soil
Does the architect's drawing set replace the structural drawings?
No. Architectural drawings show layout, dimensions, and finishes. Structural drawings show load calculations, member sizes, bearing details, and connection specifications. Both sets are typically required for addition permits. An architectural drawing stamped only by an architect doesn't satisfy the structural engineer stamp requirement when stamped calculations are required by the jurisdiction — and conflating the two is one of the more costly assumptions we see homeowners make late in the process.
Why do permit reviewers send addition plans back when a wall is being opened?
Plans are most often sent back because the drawings treat the wall removal and the addition as separate structural events rather than showing how the two changes affect each other as a combined system. A plan set that addresses the new addition framing on one sheet and shows a generic opening in the existing wall on another — without connecting the two structurally — gives the reviewer no way to confirm the load path is complete.
Missing beam or post specifications are a frequent deficiency. Showing a generic "beam" symbol without specifying size, species, grade, or material type leaves the reviewer unable to confirm that the member meets code, and the correction requires a full resubmittal rather than a simple field clarification. Omitting the load path from the new roof framing down through the existing structure to the foundation is another common gap — one that appears most often when the addition extends or modifies the roofline and the structural drawings were prepared without accounting for that change.
Stamping errors also trigger resubmittal requests. A drawing set stamped only by an architect — without a structural engineer's stamp on the structural calculations — doesn't satisfy the Missouri licensure requirement for engineered structural work. Catching these gaps before submission is one of the practical reasons contractors and homeowners bring a structural engineer in early in the addition planning process, not after the architect's drawings are already complete and coordinating changes becomes costly.
How long does a permit resubmittal add to the project timeline?
Each resubmittal cycle adds time: the deficiency must be identified, the drawings revised, the set resubmitted, and the revised drawings worked through the reviewer's queue. A complete first submission that addresses all structural requirements avoids that added time. The exact duration varies by jurisdiction and current workload — but we'd rather help you get it right the first time than watch a project sit while paperwork catches up.
Opening a wall for an addition is a connected system review — not a single isolated calculation. Load-bearing status, beam design, foundation capacity, roofline changes, and permit documentation all feed into one another. If your addition plan involves opening a wall, bring the structural engineer into the conversation before the architect finalizes the drawings.