I’m looking to build a 2-car detached garage that’s 24ft wide with a loft above for storage. I’ve been searching and I can’t seem to find any lumber that spans 24ft. If I had 2×6 (or 2×8 or 2×12) that are 20ft long (longest I can find) can I stagger them and attach two together? There would be 20ft of overlap that’s attached and 2ft on either side that’s just a single board. Is this safe? Or do I have to do more of a truss system to support the beams?
Two-car garage construction
carpentryframinggarage
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The most important question here is, 'do you have a building plan?" Building a structure with 13 to 14 foot walls and a 12 foot door is quite a reach for an inexperienced DIYer. You should start by selecting a set of building plans at your local lumber yard or maybe online. There are a lot more considerations than what size studs you should be using. You are going to need a foundation detail to support the added weight of this large building. The wall details will most likely be 2X6, fire breaks, and 1/2" to 5/8" sheathing, ground built then lifted into place. Your design may use roof trusses or rafters with collar ties, and substantial posts and headers for a 12 foot door.
A building of this size is most definitely going to require a building permit. To get this permit, they will need to see your blueprints or plans.
With all that said, I personally would not build 14 foot walls with 2X4's. I would use 2X6's 16"OC, horizontal stiffeners 48" OC, 5/8 CDX sheithing, double 2X6 plates(upper & lower) and an engineered truss roof. Door headers minimum of 4X12 @ 12 feet, preferably a LAM.
The wall seems to have 'full dimension' studs and the markings of old lath and plaster. I don't see plywood sheathing on the exterior walls. All in all I'm guessing that your house was built prior to WWII and is either 'post and beam' or 'balloon frame' construction, both of which are radically different in terms of structure and loads from modern techniques.
Here are wikipedia links for those techniques:
- post and beam construction
- balloon framing
- platform framing ("typical" modern wood framing)
Can you post some photos that show the original framing for the original windows? I'm guessing the original construction did not include headers above the windows. Also I do not see any indication that jack studs were used in the original construction.
If your house is post and beam, then I don't think there are any significant structural issues.
If your house is balloon framed, this is how I would 'fix' it, with the jacks (red) and cripples (black) going through the floor to bear on what ever the existing old studs bear upon. The header (green) consists of two 2x10s sandwiching two rippings of 1/2" plywood (or whatever).
Based on the current state, achieving this is rather quick and simple. It does not require starting from scratch: the window and existing new 2xs do not need to be removed.
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Best Answer
I suppose there must be a way you could splice dimensional lumber and make a longer span, but... why?
Have a look at wood I-joists. Boise Cascade (BCI), LP Building Products (SolidStart) and Weyerhaeuser (TJI) are three options widely available in the US. (photo below from lpcorp.com)
As a single point of reference, a BCI span table shows spans up to or exceeding 24 ft with joists 11-7/8, 14, or 16 inches deep with spacings of 12, 16, 19.2, or 24 inches on center. You'll have to consult the table yourself to see the effects of joist family, spacing, allowed deflection, and loading.