Ridge Beam Size Calculator

Behind the shingles is the ridge beam, a house’s spine. Does the roof collapse in the wind and snow? Or does it maintain its shape over time? While most homeowners plan for a build based off square footage, loads determines the structure’s form. Material properties also matter. Get the central member correct and avoid cracked ceiling (and other failed connections) down the road.

Once you know your beam span and roof width, calculator takes care of the math. Then you can get back to thinking about how space will look instead of worrying about how to keep it standing.

How to Choose Your Ridge Beam

A lot of folks misinterpret where the load comes down to. There are two types of loads: Dead (like materials and framing) and Live loads (like workers and snow). The tool also calculates different for sloped surface versus horizontal plan area. It does this because the latter impacts calculation. Entering loads as if they is applied on a sloped surface accounts for pitch, meaning the calculator will adjust values to represent actual structural demand. That’s important because your roof’s footprint is smaller then its actual surface area (more so for steeper roofs), meaning there’s more weight building up on that line until it hits the beam.

Now you’ve got the load; now what? How far apart do your support beams goes? Beam size depends primarily on span. Eighteen-foot ridges acts differently from thirty-foot ones. Doubling the span doesn’t simply double necessary strength. It demands vastly more capacity. Many long spans must of been built using engineered wood products such as glulam or LVL instead of standard lumber. See how high-strength laminates compares to other material grades in the reference table below. Knowing these restrictions will keep you from creating a span that may look good on paper but sags in real life.

And there are also deflection limits. Safety minimums are the codes, comfort is the other side of the coin. How stiff does a beam need to be before it cracks the ceiling below without breaking? If there’s a tighter limit, you’re going to have to choose stiffer (or bigger) pieces. That will increase your initial costs but reduce your repair bills down the road. This is a minor trade-off that pays off over time. Most people only care about how strong something is and forget they need enough stiffness to prevent cracking their finish work.

The other variable is wood type. For shorter spans and lower deflection requirements, spruce-pine-fir is fine. But long spans is typically glulam or LVL because they’re stiffer. Engineered products holds their shape better under a load than solid sawn lumber. You can switch among material types with calculator and observe the variation in section depth as the wood type varies. This example demonstrates why high-end materials tend to pay off more for big houses.

The same goes for bearings. If you have perfect sized ridge but it sits on too short of a bearing, or one that isn’t adequate to hold it up, it doesn’t do you any good. Another failure mode for ridges is crushing wood at support points, so the tool checks for bearing pressure at both ends. What people forget in planning is that those loads create reaction forces against your vertical supports. You need to make sure they are strong enough to handle them.

How do you size a ridge beam? Keep in mind 3 factors: structural strength, beauty & cost. Too weak and your house falls down. Too heavy or big and it costs too much money. The following is just a starting place, get a pro to review your situation since codes vary from one area to another. If you have a spine supported well enough then the entire building will stand tall, long past when paint dries.