Who Do I Hire to Size a Beam for My House?

You’re staring at that wall between the kitchen and living room, already picturing the sunlight pouring through and the island right in the middle. Then somebody says the phrase “load-bearing wall” and the fantasy screeches to a halt.

Now the real question hits: who do I actually hire to size the beam for this?Do you call a contractor? A structural engineer? The architect? Is there some mysterious “beam person” you’re supposed to know about?

If you’ve ever typed “who do I hire to size a beam for my house” into Google, you’re in the right place.

What “sizing a beam” really means

Let’s start by disarming one big misconception: sizing a beam is not “grab the biggest LVL the lumber yard has and hope it doesn’t sag.”

When someone properly sizes a beam, they’re answering a very specific question: what member will safely carry the loads across this span without overstressing or deflecting too much over time? That means thinking about how far the beam spans, what it’s supporting (floor, roof, deck, maybe another wall), how much area is feeding into it, what material you’re using, and how much vertical movement you’re willing to tolerate before cracks, squeaks, or bouncy floors show up.

In residential work, a huge amount of this can be handled with the prescriptive rules baked into the building code and manufacturer guides. The International Residential Code lays out span tables and limits for common situations. Engineered wood manufacturers give you design software—things like ForteWEB or BC Calc—that crunch the numbers for their LVLs and I-joists. For simple steel beams, methods from groups like AISC can be applied to straightforward, house-scale problems without reinventing physics.

So the real challenge isn’t just “what size beam,” it’s “who is the right person to use those tools correctly for this situation.”

Option 1: letting your contractor “just pick something”

In the wild, this is the most common scenario. You say you want to remove a wall and your contractor says something like, “We’ll throw in a triple 2×12; we always do that and it’s fine.”

Sometimes it is fine. Sometimes it’s not even close.

Contractors are usually excellent at building things. They know how to get lumber into place, how to shore up walls during demo, how to actually make the jobsite work. Some of them are also very sharp structurally. The problem is that a lot of beam decisions on smaller projects get made by habit rather than calculation. A “go-to” size that worked in one house quietly gets treated like a universal rule.

The catch is that houses are not all the same. Maybe the span in your project is several feet longer. Maybe the beam in your case is supporting not just one floor, but a floor and a roof. Maybe there’s a concentrated load landing near midspan from an upstairs wall. Those differences matter, and rules of thumb don’t always keep up with them.

If your contractor is sitting down with tables from the International Residential Code, checking manufacturer software, and coordinating with whoever is ultimately responsible for the design, that’s a very different story. But if the sizing process boils down to “this is what we’ve always used,” you’re basically rolling structural dice and hoping they come up in your favor.

Option 2: calling a structural engineer for every beam

On the other end of the spectrum is the “engineer everything” approach. You get told, “Any time you touch a load-bearing wall, you have to hire a structural engineer. Full stop.”

There are definitely projects where a licensed Professional Engineer is absolutely the right first call. Long spans pushing the limits of wood, complex multi-story framing, beams that are part of a steel frame, weird geometry, heavy point loads, big hot tubs or masonry fireplaces sitting on things—those are “real engineering” problems. And when the building department specifically says “engineered design required” or asks for sealed calculations, that’s not a suggestion.

The upside of going straight to a structural engineer is obvious: you get someone whose full-time job is thinking about load paths and safety. They can stamp drawings and calculation packages. Their seal carries legal weight with the building department and your lender.

The downside shows up when you’re dealing with small, house-scale questions. A simple LVL over a 12-foot opening in a typical one-story wall is not very interesting work to a lot of firms. Scheduling can be slow. Fees that make perfect sense for a complex project can feel heavy when all you wanted was “what size header do I need here?”

For big, weird, or obviously complicated projects, absolutely: call a structural engineer. But for a single opening between your kitchen and living room that’s clearly within the envelope of the residential code, you may not need to start at the top of the ladder.

The middle ground: a prescriptive beam sizing service

This is the part almost no one talks about, and it’s where most homeowners and small contractors actually live.

Between “contractor guess” and “full structural firm,” there’s a very practical middle option: a prescriptive beam sizing service. Instead of guessing or over-engineering everything, you deliberately stay inside the rules the code already lays out and let the code plus manufacturer tools do what they’re designed to do.

Think about the kind of projects you see over and over in residential work:

You want to take out the wall between the dining room and kitchen. You’re adding a 12-foot or 16-foot opening in an exterior wall for a big slider. You’re installing a beam under existing joists in a basement to get rid of a row of awkward posts. You’re building a deck and the spans and loads are ordinary, not some multi-level monster over a ravine. Or maybe wood is getting unreasonably deep and heavy, so you’re thinking about a simple steel beam instead.

Those are perfect candidates for prescriptive sizing.

What a service like this does is pretty straightforward, but it’s grounded in actual mechanics instead of vibes. You provide the address and jurisdiction, sketches or plans, the span, the spacing and direction of joists or rafters, and what the beam really supports. For existing houses, you send good photos of the framing and supports. On the back end, someone sits down with the IRC, the manufacturer design tools, and, for steel, the methods in the AISC approach, applies reasonable loads and tributary widths, checks bending, shear, and deflection, and then recommends a member that works.

In my own practice with Slate Drafting, that’s exactly what I do for house-scale problems. I’m very explicit that this is not me acting as your structural engineer of record. It’s code-based, prescriptive design support for typical residential beams and headers using the same tools engineers use for that kind of work. When something clearly belongs in a structural engineer’s hands, I don’t try to shoehorn it into the prescriptive world; I hand it off through a formal structural desk arrangement with a Virginia-licensed PE.

When you truly need a structural engineer anyway

Even if you start with a prescriptive service, there are situations where everybody should agree, “Ok, this is engineering territory.”

If the beam is part of a moment frame resisting lateral loads instead of pure gravity, you’re out of simple territory. If you’re dealing with multiple spans, significant cantilevers, or supports that aren’t straightforward, that’s a warning flag.

If the beam is carrying columns and stacked loads from multiple stories instead of just catching joists or rafters, you want an engineer thinking through the whole load path. If you’ve got heavy or unusual loads—massive tile tubs, giant aquariums, commercial-style equipment, hot tubs on decks—you’re beyond the cozy confines of the prescriptive code.

And sometimes the deciding factor is political, not technical: the building department reviewer looks at the plans and says, “We need engineered design and sealed calculations for this beam.” When that happens, it doesn’t matter how confident you feel about the math; the jurisdiction is asking for a PE to take official responsibility.

The nice thing about working with someone who lives in the prescriptive world all day is that they can usually tell you quickly which bucket you’re in. They can also package all the relevant spans, loads, and sketches into something an engineer can review efficiently instead of making the PE start the detective work from zero.

If you’re a homeowner: what’s the smartest first call?

From a homeowner’s perspective, the decision often feels like a tug-of-war between wanting to be safe and not wanting to overcomplicate a straightforward remodel.

If you’re planning to remove a wall, open up a kitchen, add a large window or slider, or build a deck that’s not doing anything exotic, the smartest first call is often to someone who spends their time on residential framing and code, not to a giant anonymous engineering firm, and not to whoever happens to be selling cabinets this week.

A good beam sizing service will listen to what you’re trying to do, look at the spans and what the beam supports, check the jurisdiction’s rules, and then give you a very plain answer: this is a prescriptive beam we can size in-house, or this needs a structural engineer and here’s what that process looks like. You get clarity and a path instead of bouncing between contractors, engineers, and the building department while everyone points at somebody else.

If you’re a contractor or designer: why this makes your life easier

If you build or draw for a living, you’ve probably felt this pain from the other side. Clients want open plans and big glass. Reviewers want comfort that beams are legit. You want to keep projects moving without either guessing or burning your relationship capital with engineers by asking them to size a hundred tiny beams a year.

In that situation, having a dedicated prescriptive beam sizing partner is a huge relief. Instead of you taking responsibility for spans and loads you didn’t fully check, or clogging up an engineer’s inbox with micro-requests, you push all the house-scale beams through a consistent process. The prescriptive ones get handled cleanly, with documentation you can drop into your plan sets. Anything that crosses the line into engineered territory gets escalated with good background already assembled.

You stay focused on building and design. Your engineer spends their time on the work that truly demands their license. And your clients are less likely to experience that familiar feeling of, “We’re waiting on something, but I’m not sure what or why it takes this long.”

How a structured beam sizing service actually works in practice

Here’s how the whole thing plays out in real life when someone hires me for beam and header sizing in places like Richmond, Henrico, or Chesterfield.

First, you send the basics: the address and jurisdiction, a simple plan or sketch marking the beam, the clear span, what’s above it, how the joists or rafters run, and a handful of clear photos if it’s an existing house. If you already have drawings, great; if not, a measured sketch is often enough to start.

Next, I look at the geometry and the loads and make the key call: is this a prescriptive-style situation that can be handled with the IRC and manufacturer tools, or is it the kind of thing where a structural engineer should be in the loop from day one? I don’t sugar-coat that answer; it’s better for both of us to be honest about it up front.

For the projects that do fall inside the prescriptive envelope, I sit down and do the actual sizing work—applying reasonable dead and live loads, calculating the tributary width, using engineered wood design software and tables, and, when steel makes more sense, using simple methods based on standard wide-flange shapes. I check bending, shear, and deflection rather than just one number.

When I’m happy with the performance, I settle on a recommended member, put the assumptions and results into a short, readable summary, and attach any relevant printouts from the tools used.

You get that package back and can hand it to your contractor, use it for permitting, or let me integrate it into a full set of drawings if I’m handling the plans. And if at any point in that process something smells like “this really ought to be engineered,” I stop and say so, then help route it through a Slate Structural Desk arrangement where a Virginia-licensed PE takes formal responsibility.

The simple answer to “who do I hire to size a beam?”

Under all the technical detail, the answer is actually pretty simple.

If you’re dealing with a normal house problem—removing a wall, adding an opening, spanning a modest distance, building a straightforward deck—you don’t have to choose between a shrug and a skyscraper engineer. A prescriptive beam sizing service that actually uses the code and the right software can give you safe, documented answers and tell you when it’s time to step up to a structural engineer.

If you’re dealing with something big, strange, heavily loaded, or explicitly flagged by the building department, you should feel good about going straight to a structural engineer and letting them lead.

The trick is not guessing which world you’re in. It’s having someone whose job it is to stand at that fork in the road and say, “This one we can size prescriptively; that one needs a PE.” That’s essentially what my Beam & Header Sizing service is built to do: give you a clear, code-based path forward, and bring in the engineer when it actually matters.

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