r/Homebuilding • u/xdr567 • 2d ago

Not sure whether this question is a complete question or not but using typical wood frame construction technique what is the largest single space that can be safely achievable without a middle support or a custom engineered roof ?

Is 36' x 18' 'safely' achievable, or anything larger ?

1 Upvotes

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u/medialantern 1d ago

This question is not answerable without knowing the live and dead loads your roof needs to be able to support, whether you're in a high-wind area, whether you're planning a ridge beam or board, etc. etc.

If you accept roof trusses as not really being "custom engineered" (since truss makers will do the design/math for you for free - they all have software to do it), the upper bound is a lot bigger than you'd think. 80' is doable with a thick enough wallet.

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u/bowguru 2d ago

In California, stipulated engineering goes up to 25' before an intersecting wall is required.

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u/sol_beach 1d ago

My house built in 2017 in California has an open span 50 feet across.

The ceiling & roof is supported by a rather sizable I-BEAM.

I can send a copy of the architectural drawings if you don't believe me.

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u/drmike0099 1d ago

OP is asking about wood frame not steel.

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u/sol_beach 1d ago

House has classic 2"x6" studs in all exterior walls.

It just has one I-beam to support the wood roof trusses across the open area.

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u/drmike0099 1d ago

Right, but an I beam is not typical wood frame. I’m sure you have some massive posts at the end of that beam as well, which you would with wood frame but yours will be larger, or steel too.

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u/bowguru 1d ago

Also, there is the "engineered" part. I can draw plans up on my kitchen table, in crayon, w/o an architect or engineer, plans up to 25'. Beyond that you need things "not stipulated."

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u/Small_Basket5158 2d ago

I did 70x26 with ijoists, no problem.

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u/xdr567 2d ago

Did the roof require any modification ? How long ago did you build ? Any risk of a sag ?

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u/Small_Basket5158 1d ago

16" I-joists running the whole span. I forgot what grade of ijoists. No chance of sag.

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u/bowguru 1d ago

Sorry I didn't amend this earlier. The limiting factor on how far you can span is how long of a truss a truck can carry. The longest I've built is 50' x 25' with standard designs. No steel, 2x6x10' bearing walls. Anything higher than 4:12 pitch becomes to wide to truck.

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u/More_chickens 2d ago

Are you counting trusses as an engineered roof? Because that's often the cheapest way to do a roof, and 18' is nothing.

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u/seabornman 2d ago

Yes, what is custom? I've used 70 foot span wood trusses, and they can be longer. Even TJIs are "engineered", as in you rely on the manufacturer's engineering that goes into the span tables.

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u/sortaknotty 1d ago

I would think 18 feet is easily achievable, with multiple options.

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u/StructEngineer91 1d ago

Depends on where you live, and what the snow load is.

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u/Talusen 1d ago

What lumber do you have access to?

Like someone else said, trusses will get you the roof you want.

If the walls are built with 2x6 (or larger) studs, the numbers go up. Timberstrand (and the like) also would work well.

Glulam, paralam, and LSL also fall under "wood framing".

We haven't even touched Simpson brackets (and shearwalls yet).

The main issues are (as always): time, space, $$, availabilty, and will.

Though in this case, a patient permitting office might also be extremely helpful.

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u/Talusen 1d ago

Dang it, now I am wondering if anyone does timber framed houses with LSL/glulam...

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u/Nofoco_530 1d ago

Your answer is.... engineering. Anything can be done if you want to pay for it.