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Splicing loft floor joists

9.9K views 38 replies 20 participants last post by  Sark  
#1 · (Edited by Moderator)
I'm adding a 15'x15' loft over one side of my shop. I'm using 2×8x15 wood joists. However, the pieces are too long to put into place as a whole piece. I was thinking about cutting them down and splicing them back together once in place. Roof is already on so there is no way to do it the easy way.

Here's my plan:

  • Cut the wood into two pieces
  • Put the two pieces together in place and splice them using 1/2" plywood, glued and screwed (both sides)

Would it matter if all were cut in the center or should I stagger the cuts of each board? How long should the splice be? The span is 15'.

Any better ideas?

The loft will be used mainly for storage (scraps of lumber, holiday stuff, etc.). There is no crossbeam running down the center.
 
#8 ·
+1 Would not cut them under any circumstance

Splice load bearing joists are supposed to be supported under the splice area per IRC. There are approved methods for repairing a damaged joist. These require addition of sister joist(s), adhesives, and fasteners. Need to consult a structural engineer or your local building inspector for methods approved locally. Splicing joist usually means putting up 3 boards instead of 1. With current lumber costs, would try hard to avoid splices.

+1 Double check size of lumber .vs. weight loading capacity.
Typical 2×8 length limit used as load bearing floor joist 16" OC is ~10-12ft for SYP. SPF framing lumber is shorter. Might want to look at IRC (building code) chapter 5, Floor Joist spans table.

+1 Add a ledger board,
and use face mount joist hanger's.

Have you tried to fit a 15ft board in that space yet?
Appears the garage door and track are above the header plate on walls.
hmm?
Where are you going to attach the loft joist, half way up the roof framing? Then can not use ledger plate and hangers. Plus, Will roof joist anchor point support the weight? Due you have hurricane, coastal wind, or snow loads to accomidate on roof/walls, that subtracts from possible loft weight loading?

Don't shoot the messenger.
Am sure there a many *********************************** ways to slap loft floor up there that might work for awhile,
until it comes crashing down on top of your vehicle or tools parked in garage. :(

Be safe, not sorry.
 
#9 ·
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Best case scenario is you must put the loft on the back half of the building. As Capn K pointed out your door is going to be in the way of doing anything up front.

Now you are saying you are building a 15×15 loft, then you say a 15" 2×8 won't fit? So what is the actual measurement side to side on the top of your top plate? Whatever that is is where you will set the joists. Actually all of this should have been done before you put the roof on, A lot easier, and probably to a better end.

I also am wondering where you got info that on a 15' span a 2×8 was sufficient to bear weight of a loft, much less put anything on the loft floor? You could use a 2×8 if you were working on 10" placement, but if this is to be looked at for code, you should be looking at 2×10. Back the width to 10 or even 12' you might be ok, at 15 2×8 is light. I am talking side to side width, the measurement I asked for.
 

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#10 ·
Plywood won't work. Splice plates are usually 1/4 or better cold rolled steel 24" long and full width. Agree 15' unsupported is too long for 2×8's.

You should have saved the cost of the 16's and just bought 8's if you have to cut them.

What are you going to support this with? You can't splice a cantilever (well YOU can but I won't walk on it!)
 
#11 ·
Read the "Captain's" post carefully.

Now, you don't say what this loft is to be used for. Do you intend to use it as work space, as in walk in it? Or is it to be just ab open shelf you set a ladder against and store a few light items? Empty boxes, x-mas ornaments etc. The following is the assumption you want to use the space.

If you were in an agricultural zoned space and no building codes, I might double sister with a 10 foot 2×8, but I am sure that would net meet code. Remember code is MINIMUM. Anyone who does not like trampolines for floors goes one size larger.

I do not see how you think you are going to get a minimum 8 foot garage ceiling below a loft floor. That door does not look like an oversize 8 footer, so I am guessing, correct me if I am wrong, but your walls are only 7 foot.

Look at code for the stairs. There are minimum head-rooms. Stairs that meet code can take up a lot more space than you expect, especially when a sloped wall or ceiling is in the way.

Remember, all lumber is not the same. The junk sold at the local stores in not the same strength as what it used for pre-fab roof trusses. Again, the code will tell you max span for various options.

In other words, an open loft "shelf" makes sense for light storage in a garage. I do not think anything else would be wise in the building as I see in the picture.
 
#12 ·
2 by 8 shouldnt span 15 feet. in the pics in the link it appears there are 2 in place already. those are collar ties. their purpose and load are different than floor joists. they are intended to keep the walls from bowing out so have no load on them on them.
rule of thumb i was taught quite some time ago:
2 by 6= 6' span
2 by 8= 8' span
2 by 10= 10' span
2 by 12=12' span

ive added loft space to a structure with a gambrel roof. we were able to get the floor joists in with full bearing on the walls. tricky but doable

itvrgeek brought up a good point about about quality/species of lumber used between framing and trusses. typically the bottom cord will be yellow pine. the top cord and webs are syp BUT that syp isnt the same as big box junk. it will have tighter growth rings.

if you were to use yellow pine, youd still want 2 by 10 for floor joists
 
#14 ·
no header on overhead door, could be an issue, what is loft used for, perhaps divide in two, beam in middle, hang joists on beam side to side then joist short way, one can splice a beam if done correctly, or build a flitch beam to carry load. if spaning the 15 ft, diaghram block it, on joints of plywood, will help with load.
good luck, give it a whole lotta thought of use and design
rj in az
 
#22 ·
WoodZenStudent
Went back to your previous post on new shop, and found more pictures.
Looking at everything, that building was not designed/built to have a serious loft?

Don't have any dimensions, but the lack of headers over garage door and side door, makes it appear the top plate is only 8ft above concrete? Very hard to use conventional ledger plate/hanger method for 15 foot span, as you will loose nearly foot in ceiling height, ending up with 7ft ceiling under the loft. :(

One solution might be to build a 'deck' loft, using support posts. Since deck post would be placed couple feet from walls to reach up into roof space, could use the space between posts for storage shelves/cabinets, and/or side closet(s) for things like DC/compressor. Would essentially be building a 12' wide room with 8ft ceiling, between the existing 16' wide space. Would make a nice finishing room, or pleasant hand tool workshop with some double doors on end?

IMHO - cost to build a smaller room inside the building could be high enough, might be cheaper to unscrew the metal roof panels on a loft portion of Gambrel roof, cut out portion of plywood panels, install proper sized joists on header plates (don't forget earthquake structural ties), then rebuild/repair roof? Sucks to tear apart new roof, but sometimes it is cheapest method, and wastes less space than other options.

BTW - Am not a contractor, carpenter, or home builder. Just an engineer with some experience on home remodeling, and a ton of industrial facility projects. Please consult a professional in your frigid Alaskan area for best advice to met local requirements.

Best Luck.
 
#25 ·
Thanks everyone! I greatly appreciate your feedback and enthusiasm. I can't wait until I can actually start working on wood projects.

To reiterate, I planned to use the loft area - above the garage door - for storage (Holiday/seasonal stuff, clothing, etc.). I don't plan on anything really heavy.

I did some research prior to posting and read lots of mixed recommendations. I knew that span was going to be challenging but found something that said it would be ok at 13' or 14' as long as it was not taking a heavy load. Again, I knew it would be a challenge. It does appear I need to reconsider the size and perhaps opt for 10" or 12" if I can do this at all.

Background: This shop was built prior to us buying the house. I would have done quite a few things differently but I'm trying to make the best of what I have (safely and within financial reason). Some of the things done, frankly, have my head shaking.

I thought about a ledger board, but with 7' walls, that would put the ceiling really close to my head and the top of my side-by-side so I'm not sure that is an option. I would end up with something like 6 foot or less ceiling clearance.

Yep. The garage door is above the top plate (hmmm, indeed) which is why I planned to raise the joists. But as someone pointed out, the gambrel trusses(?) might not be able to support that added weight.

I made a miscalculation. I bought 16' boards and did not cut them down. The opening to place the boards on the top plate is roughly 15'. So if I trim down the boards a bit, I should be able to get them to fit and sit on top of the top plate. That said, it really sounds like my 2×8 is too weak. I may just end up building a separate storage unit.

Again, thanks for all the input!