Minimum Header Requirements in The Great White North

[Zoobie777]

A bit of background to my question:

I have seen on house plans (architectural and structural) minimum header requirements of 2-ply 2x10 for <6' span and 3-ply 2x10 for >6' span or some similar variation. I have also had people tell me that these are code requirements (BCBC 2024, etc.). When I first started sizing headers someone told me, make sure you use 2x10s for over 6'. I recently did a roof truss design where the structural engineer specified something like this, so even 18" bathroom windows have a 2-ply 2x10 header. If there are no stamped structural plans, I generally spec. what is min. required.

My question:

Does anyone know where this comes from? Is there a bare minimum rule of thumb that everybody uses that I don't know about? Is this just lazy or cover-your-@$$? Or is this just making it idiot-proof for the framers?

Lumber might be relatively cheap right now but if I was the homeowner and found out extensive larger sized dimensional lumber or EWP was used unnecessarily I would be some kind of ticked off.

 

[phamENG]

Is this just lazy or cover-your-@$$?

Could be either, or neither. There is a not invalid school of thought that seeks to use the least number of individual sizes - be they steel beams, truss depths, framing lumber, etc. It makes it a bit more idiot proof - for the engineer, drafter, and builder - if you just pick the worst case and apply it to all. When you consider the cost differential between a pair of 2x6s and a pair of 2x10s, even if you're looking at 40 windows and doors vs. the potential cost of an error, the risk mitigation can have enough value in some cases. Especially when it comes to larger members, shipping is easier when everything lines up on the truck. Could be that this mindset has carried through to their design of headers.

Then there's the possibility of accommodating other framing methods. If the floor above is going to be 2x10s, keeping the headers all 2x10 allows the framing to frame flush headers, utilizing the rim joist (appropriately strengthened) as the header.

Or, they're just being lazy. Impossible to know without studying the plans and interviewing the engineer.

 

[XR250]

Many contractors want to use 2x10 headers in 8 ft. walls as there is typically no need for cripple studs.

 

[Eng16080]

I agree with the comments above.

If I were to design a simple house which, by calculation, needed some 2x4 headers, some 2x6 header, and some 2x8 headers, I would almost definitely specify 2x8 headers everywhere. The increased cost due to more material is small and there's a greatly reduced risk of error by the builders and likely less labor since the same detail is being repeated over and over. In general, I find there's a huge benefit in minimizing the number of unique details on a project.

In terms of code requirements specifying minimum header sizes, I can't really comment on that. I typically design every header beam for the loads acting on it. Most of my work is higher end residential, though, so not you standard cookie cutter houses. For simpler houses, I think what you wrote above might make some sense in some contexts. There are obviously limits, though. In some cases, "use a 2x10 over 6 ft" might make sense, but what if you have a 16 ft header supporting 2 floors and a roof? There are also plenty of times I've needed something like a triple 9.25" LVL header for a 3 ft span. These are unique situations though.

In the US, at least, the IRC code has a lot of useful guidelines for standard houses.

 

[Zoobie777]

Many contractors want to use 2x10 headers in 8 ft. walls as there is typically no need for cripple studs.

Thanks. Didn't occur to me.

 

[Zoobie777]

I agree with the comments above.

If I were to design a simple house which, by calculation, needed some 2x4 headers, some 2x6 header, and some 2x8 headers, I would almost definitely specify 2x8 headers everywhere. The increased cost due to more material is small and there's a greatly reduced risk of error by the builders and likely less labor since the same detail is being repeated over and over. In general, I find there's a huge benefit in minimizing the number of unique details on a project.

In terms of code requirements specifying minimum header sizes, I can't really comment on that. I typically design every header beam for the loads acting on it. Most of my work is higher end residential, though, so not you standard cookie cutter houses. For simpler houses, I think what you wrote above might make some sense in some contexts. There are obviously limits, though. In some cases, "use a 2x10 over 6 ft" might make sense, but what if you have a 16 ft header supporting 2 floors and a roof? There are also plenty of times I've needed something like a triple 9.25" LVL header for a 3 ft span. These are unique situations though.

In the US, at least, the IRC code has a lot of useful guidelines for standard houses.

Thanks. I generally start with a 2-ply 2x8 and upsize as loads dictate. I also try to make as few unique things as well, especially when designing trusses, as there are real savings to be had. I guess my irk is probably related more to my own personality. My scope is usually design of the floor system, the roof system, and whatever structural components (beams, headers, columns) that are required to support them. I also prepare the quote so I see how things add up. Sometimes 'blanket' specifications and ridiculously conservative specs add up to thousands of dollars. Having said that, I also work on a lot of high end custom homes and these people don't seem to have a shortage of funds. This past year it was all about the golf simulator room. A couple of years ago, everyone was putting in yoga studios.

 

[Eng16080]

Sometimes 'blanket' specifications and ridiculously conservative specs add up to thousands of dollars.

No doubt. For projects which are a crazy rush or ones with a client who wants to pay the bare minimum for engineering services, this is often the result. Engineers don't have time to fine tune the design, so they play it safe.

 

[RontheRedneck]

In my not-at-all humble opinion there's no reason to oversize headers for the sake of convenience. It wastes lumber and money, and reduces the amount of insulation that can be put in the walls.

We used to stock insulated headers, and used them in walls when possible. But they never caught on, and are hard to get now.

 

[EngDM]

In my not-at-all humble opinion there's no reason to oversize headers for the sake of convenience. It wastes lumber and money, and reduces the amount of insulation that can be put in the walls.

We used to stock insulated headers, and used them in walls when possible. But they never caught on, and are hard to get now.

Typically if there are similar windows throughout a wall with similar conditions I keep my header depths the same, ply's can vary as required. Keeps the framing details all the same.

 

[EngDM]

A bit of background to my question:

I have seen on house plans (architectural and structural) minimum header requirements of 2-ply 2x10 for <6' span and 3-ply 2x10 for >6' span or some similar variation. I have also had people tell me that these are code requirements (BCBC 2024, etc.). When I first started sizing headers someone told me, make sure you use 2x10s for over 6'. I recently did a roof truss design where the structural engineer specified something like this, so even 18" bathroom windows have a 2-ply 2x10 header. If there are no stamped structural plans, I generally spec. what is min. required.

My question:

Does anyone know where this comes from? Is there a bare minimum rule of thumb that everybody uses that I don't know about? Is this just lazy or cover-your-@$$? Or is this just making it idiot-proof for the framers?

Lumber might be relatively cheap right now but if I was the homeowner and found out extensive larger sized dimensional lumber or EWP was used unnecessarily I would be some kind of ticked off.

Also depends, is the building part 4 or part 9? You can get away with different headers under prescriptive design.

 

[Eng16080]

We used to stock insulated headers, and used them in walls when possible. But they never caught on, and are hard to get now.

I'm surprised those headers never caught on. Seems like a great idea to sell them. Most architects I work with want exactly this. My default header in exterior walls is a double 2x8 box header with 2x6s top and bottom and rigid insulation inside.

 

[Zoobie777]

I'm surprised those headers never caught on. Seems like a great idea to sell them. Most architects I work with want exactly this. My default header in exterior walls is a double 2x8 box header with 2x6s top and bottom and rigid insulation inside.

Also depends, is the building part 4 or part 9? You can get away with different headers under prescriptive design.

I mostly do part 9. Almost all the part 4 stuff I do has a structural package with it so the headers are usually out of my scope.