[DIYguy2000]

I'm looking to add a storage loft in my double car garage over top of the garage door and door opener rails. The span is 20', and the shelf will be somewhere between 3 and 4' deep to the front face wall of the garage.

Question is, what is the best way to support this structure on the three sides where it touches the walls?

I'm envisioning a doubled up 20' beam across the span supported by threaded rod from the ceiling at a few locations along that span.

Where the beam attaches to the side walls, can I simply lag a 2x6 horizontally across a few wall studs and have the beam rest on that, or is it best to use a doubled up jack stud to rest the beam on? I'm guessing the jack stud is the best way to go, which is fine on one side of my garage, but on the other shared wall with my house, there's drywall ontop of plywood. Should I take the drywall/plywood down and do the jack stud?

Similarly, where the joists are supported on the front face of the wall, can I lag a 2x6 horizontally across the wall studs and rest the joists ontop (or use joist hangers), or can they rest on the header overtop of the garage doors?

Or am I really trying to overkill this support structure? Does anyone see an issue with the design in the picture I pulled from a website? If not, I may just keep it simple and do it that way.

Thanks!

 

[TarheelTerp]

Does anyone see an issue with the design in the picture I pulled from a website?

Yeah... I don't see enough support on the outer edge.
The threaded rod from above (if well supported) is a good start
but there should be a lot more of them.

Were it me... I'd stick with a 3 foot shelf cantilevered off the load bearing structure walls
and probably some bracketing there too... and let the center space go.

 

[joecaption]

Unless you plan on just storing some strafoam up there 2 X 4's are not even close to being wide enought to support any weight with that long a span.

 

[Ironlight]

I'm with Joe. I would not put more than 100-200 lbs. of stuff up there, even with the support rod in the middle (I assume that is one of two across the entire span) unless I wanted it all coming down, and probably taking my whole garage door opener along with it. That looks much deeper than 3-4'....more like 6-7' based on the door opener rails.

 

[sublime2]

If it were me,I would add joist hangers or similar bracing to all 2x4's more strapping from the ceiling around the perimeter to spread the weight load.
Something like this:

 

[Daniel Holzman]

The required support for the storage is totally dependent on the weight of the material you want to store up there. If you are storing newspaper or books several feet high, the load is far larger than if you are storing batts of insulation. But you have not told us what you want to store, so I have no idea how anyone on this forum can begin to address whether your proposed support system makes sense.

If it were my system, I would calculate the distributed load based on my storage program. Then I would compute the required size of each structural element. In your case, if you are not comfortable doing structural calculations, you may want to at least look at some span tables for floors with similar loading to see what size elements make sense. Bear in mind that supporting joists with threaded rods reduces the effective span, so you can generally use much smaller structural elements, but you HAVE TO CHECK rod failure, which can occur either due to tension in the rod, failure of the nut, or tear through of the wood, and is certainly a possible failure mode in your design.

 

[DIYguy2000]

I will likely be storage miscellaneous household materials and seasonal items, such as artificial Christmas tree, Christmas lights, skis, snowshoes, lawn chairs, golf clubs, hockey equipment, etc. Nothing overly heavy in itself, but combined weight would have to be considered. The depth of shelf (3' to 4') and clearance to ceiling (2.5') will also limit what I can place and stack.

I will do some more digging into the structural calcs before I attempt anything. Thanks for the advice.

 

[cortell]

Here's some additional perspective. Don't design this for what you're planning on storing up there. Design it for what could conceivably be put up there. In other words, I suspect you won't be the only person in the household putting things up there. Looking more long term, take into consideration what the future home owner might store (assuming you're not planning on tearing this down in the event you sell the house). Designing this to expected needs is, IMO, short sighted. You might store relatively light things like skis and lawn chairs, but someone else might put bowling balls, boxes filled with books, etc. This is why seriously over-engineering something like this is far better than building to meet expectations. Failure of this shelving unit could have very dire consequences given bad timing and circumstances.

Before someone jumps in and says "well, should you foresee someone using it to store a palette of 80lb Quikrete bags?" My answer is no; I would hope someone has enough common sense to not use it for that purpose, and I wouldn't try to accommodate those sort of hypothetical and extreme scenarios.

 

[nhmckitt]

I am looking to do something very similar. DIYguy, what did you end up doing? Did it work?

 

[DIYguy2000]

Hey, project was completed and it's working great. I will have to take some pictures of the final product, though there's a ton of stuff on it now, so I'm not too sure how much you'll actually be able to see. Either way, I'll try my best to provide a good explanation of what I did:

(lumber materials can be bought anywhere. my hardware was purchased at either Lowes, Home Depot or Rona (in Canada), but you shouldn't have an issue finding these materials. Only Lowe's had the strut channel though.)

I ended up taking down the plywood on one side wall and put in doubled up jack studs to support both ends of the main 20' beam. The jack studs didn't line up with the existing studding, so I placed a king stud on either side of the doubled up jack studs to provide a little more support. I also used a doubled up joist hanger between the beam and jack/king studs, though I don't know if this was necessary. I didn't use any blocking, but could have to give it a little extra support against the existing studs. I replaced the plywood, and ended up drywalling the whole garage.

The beam was a 2x8 glued and screwed together. It ended up having to be in shorter pieces since I couldn't get a 20' 2x8 without getting some specialized like an LVL. So the 'front' of the 2x8 beam was 10' and 10', and the back of the 2x8 beam was 5', 10' and 5' so that the seams didn't overlap. I know this makes it very weak at those seam location, but I make sure to add a ton of PL Premium and screwed it from both sides alot.

To support the span of the beam, I lag bolted heavy gauge electrical strut channels to every truss above the beam (overtop of drywalled ceiling). I then drilled holes through the centre of the doubled up beam at 4 locations: over left garage door opener rail (about 5' from left wall), over right garage door opener rail (about 5' from right wall), and over both middle garage door tracks (about 9.5' from each wall - so spaced about 1' apart from each other in the middle). I did this so that when I'm up on a ladder between the door rails and opener rail, there wouldn't be threaded rod in my way.

I used threaded rod (1/2" maybe? can't remember) to hang from the strut channel using a threaded rod strut nut, when then passes through the drilled hole in the beam. I reinforced the beam at this location using a deck 4x4 post bracket (the ones with a hole in the bottom, so the threaded rod could pass through), and then the threaded rod was finished off with a double washer, nut and lock nut. I tightened and loosened these nuts as needed to get the beam level.

The joists were 2x6's. I supported them off the beam using joist hangers. For the other side of the joist against the front wall of the garage, I used jack studs. I don't recall if I used joist hangers or not. There was only a few inches between the garage door header and the bottom of my joists, so my 'jack studs' were very small.

I topped the platform with 3/4" plywood. (come to think of it, I topped it first, re-drilled the holes for the threaded rod, then inserted the rod again so there wouldn't be gaps where I had to get it around the rod).

The final 'depth' of the shelf was about 32". That way I didn't need to waste any plywood material when topping it (2 cuts in the plywood to create 3 48"x32" sheets. Plus I was constrained by a steel I-beam about 5-6' away from the front face of the garage wall that hangs down probably a good 16-18". If I made my shelf any deeper, I would have had issues while up on the ladder trying to get the right angle to squeeze large boxes between the doubled up beam and steel I-beam. It's the perfect depth right now to be able to access anything on the shelf from a ladder.

I couldn't believe how solid it felt while I was up on the shelf putting the plywood down and finishing the drywall. It is very sturdy. Like I said before about it's contents, I store all our camping stuff up there, christmas decorations, golf clubs, hockey bag, kids toys, sleds, snowshoes, etc. Since it's only 32" deep, and maybe 24" high (honestly I can't remember the height of it), I don't think I'll ever have too much weight on it of typical garage storage items, unless I'm storing a bunch of very heavy objects, such as multiple sets of tires, heavy tools, etc.

I'm very pleased with how it turned out. Not sure if I would have changed anything. Maybe try to get it a couple inches lower for more clearance up top, but I was getting pretty tight to the garage rails as it was. I could have went with a 2x6 doubled up beam to get a bit more clearance, but it probably wouldn't be worth the risk.

Good luck on your project. Let me know if you have any more specific questions on how I built mine!

 

[nhmckitt]

Thanks for the detailed reply. Congrats on the success. If you get a chance for some pictures, it'd be interesting to see. Thanks again!

 

[DIYguy2000]

Here's some pics I took this morning. As I mentioned, I drywalled it, so it's difficult to tell how everything got attached, but hopefully my description above explains it. And yes, the drywall was a pain! I put it up first before the plywood.

You'll see the middle most joist is supported by a joist hanger on the garage door wall since there was a double stud at that location that I used.

I also should trim the bottom of the threaded rod. You'll see I have lots of clearance to the garage door rails, but there's only a few inches of clearance to the opener rails (this was my limiting factor in gaining additional storage clearance).

There's not much ontop right now, alot of it is on the garage floor as I was going through a bunch of boxes.

The strut channels are in 3 pieces, but I overlapped them at the seams and made sure it was at a truss location to lag bolt both ends.

Also turned out I used the same dimensional lumber for the beam as I did for the joists. I think those are 2x8's. I didn't measure, but they don't look like 2x6's to me in the photos. I was considering using 2x6's for the joists and lining up their bottoms with the bottom of the beam, so that the top of the beam was 1-3/4 higher than the top of the 2x6. That way when I put down the 3/4" ply, there would be a 1" lip at the beam to prevent things from 'rolling' off. I didn't end up going that route. I'm sure either would be fine, but I'm kind of glad there's no lip right now. I probably could have trimmed off a bit of that plywood overhang though.

I also said that I used a lock nut, whereas I actually used a lock washer between two nuts. You'll also notice a piece of plywood on the back side of the 4x4 'post supports' since they're meant to accept a 3-1/2 post, not a doubled up 3" beam, so I slid a 1/2" piece of ply in.

There was one thing I was considering to do though to make it stronger. At the back of the plywood, there's nothing supporting it between the two joists. Based on what I have up there, I'm not concerned. However, I should have but blocking between the joists up against the drywall to support the plywood. There was nothing behind the drywall to really support this blocking through, so it would have to be screwed into each joist. If I ever notice sagging in the plywood, I'll reinforce it then.

Oh yeah, it's 24" spacing between joists so that it would match up with the 24" stud spacing on the outside wall. There was a small jack stud placed on the header right up against the wall stud. It also helped since the plywood was 48" wide, so the seams lined up nicely on every other joist. If you were concerned about the seams, you could always put a doubled up joist to support both ends of the plywood better, but again, I didn't think it was necessary as I was building it and saw how sturdy the 3/4" ply actually was up there.

Enjoy the pictures!

 

[DIYguy2000]

The other thing I noticed when I was adjusting each nut on the threaded rod to get it level was that some were harder to tighten than others. The beam wasn't perfectly level or perfectly straight when I built it. I was pretty darn close, but there are no 'exacts' when dealing with this. To get it level, it meant that some theaded rods likely had more tension on them than others.

I'm not sure how you would determine if the load is equally spread over the 4 nuts. It would also change, depending on how much weight you had up there, and where.

I suppose you could possibly torque the nuts so they're all fairly equal, but this is no guarantee that the load is equally split among the 4 threaded rods. I basically went with my gut and got the beam as level as possible, and made minor adjustments if I felt one rod was supporting too much of the weight.

Either way, as I said, the load will change depending on your storage, so just do your best to try and make each rod support an equal amount of weight.

 

[MarkSindone]

Glad to see that you managed to get quite a number of things packed away into the storage area after everything is done up. Thanks for posting up pictures for us to see as well. It really helps with the understanding of how you went about to do everything and it sure helps that I was thiking of putting up some overhead storage in my garage too. Will definitely be taking some of the advice here to heart in my project!