loft me! :)

[asifnyc]

Hi, hoping for some guidance. First let me say that I searched for loft/mezzanine threads on the site and read a ton of them. I still have questions for my situation though.

I have a quonset hut style steel shop. 25x40. I have a car that I need to store in it. I realized the other day that it would be awesome if I built a storage loft to capture the space above the car. The car is on gojacks which make it easy to pull out when I need to use it or work on it. The dimensions of the loft would be roughly 17.5 ft long x 7.5 ft deep x about 57" high (that's the BOTTOM of the loft). Doing this would give me about 130sq ft of storage space that I couldl really use. what would be on it? spare wheels/tires (say 10), lot's of plastic totes full or stuff, some car seats, my propane heater (in the warm months). stuff like that. oh, and POSSIBLY a long rack at the back for steel sticks 10' long (tube, angle, bar, etc). At 57 ish inches high I should be able to grab a lot of stuff by just walking up to it (I'm 6'4"+ and long arms). for stuff in the middle I'd just need a step stool...

I was really hoping to get it done for a few hundred bucks but don't know if that's realistic. It can have walls/posts on 3 sides but, obviously, has to be completely open on the front side. Seems like I need steel to span the 17.5'. Below is a CRUDE sketchup drawing showing my rough idea. The end walls and back posts are 4x4 wood posts. the floor would be 1/2" osb or something cheap. The cross beams are 1x2 (.120 wall thick enough?) steel. I added some corner bracing (would do this in steel too). Depending on the length of the braces I could cut the free span down to more like 12'. I put a couple of angle braces from the back wall but I can't decide if they really make any sense. should I delete them? I'd love no bracing if I can get away with it. I don't want to overbuild this for cost and complexity reasons BUT I can't afford a failure...

so, how should I build this thing? what materials? thanks for any input! Here's some pics that hopefully tell that story...

 

[asifnyc]

here are the pics...

 

[38Chevy454]

Make it a little taller in case you have a different vehicle in future. As for the construction, as you said it basically the beam spanning the opening that is the only critical part. You'll lose height clearance due to the height of the beam. It would also be wise to make it a little longer, for ease of getting car in and also for future different car lengths.

I think your design using long joists parallel with the car will be more money to build, unless your goal is a smaller height beam on the open front side. If the beam is sized right, you can just use some cheap 8 ft 2x4 for the joists running perpendicular to the car. Your internal braces can be located to the outside to prevent interference inside, at least the way your picture shows them. Their purpose is to triangulate the structure. Make the box opening to be clean rectangle with no internal brace pieces. If you tie into the end wall, it will solve most of your bracing concerns.

You could also make the structure 6 ft depth and use 2 ft overhang. The top sheets at 8 ft length is just convenient. Steel will increase cost a lot vs using wood. Minimize the amount of steel used. 1x4 wood or some 3/4 plywood is fine for your triangulation. If you mount the flooring and make a solid side wall (opposite the hut end wall) you have created shear surfaces and no need for any triangulation. That solid side wall can also provide shelf or hanging space area.

 

[asifnyc]

38Chevy454, thanks for the reply. This is exactly the kind of feedback I was hoping for and I really appreciate it!

here's version 2 which I think/hope is the direction you were pointing me. this design is all wood except for the front beam. still not sure what I should use but I did price 4x2 .120 tube and 4x1 3/16 channel. don't know if either are strong enough or if I need to go bigger or thicker?

I didn't change the dimensions much because I really don't want it to take any more floor space in the shop. I will skin the 2 side walls and could skin the back wall if that's what's recommended. Also I can tie it to the wood back wall of the hut but not exactly sure how/where I should do it...

anyway, thanks again and if you (or anyone else) has any suggestions for this revision I'm all ears.

 

[bad_idea]

I'm not an engineer.

How about using the same LVLs on the front and back - skip the headache of working with steel. Then set your joists down between the LVLs. Attach the joists to the LVLs with joist hangers mounted lower on the LVLs. Not sure how that would impact the load capacity of the LVLs, perhaps an engineer will pipe up. Would simplify the build and a couple LVLs can be had cheap enough. Setting the joists lower than the top of the LVL gives you clearance to the top of the car and still gives you some decent storage height.

 

[38Chevy454]

I would have to search what the steel beam requirements would be, but my gut feel is a 4 inch height may need to increase to 6 inches for your span, at least to prevent being too springy flex at the storage floor. A wood beam would be easier for construction than steel, but would be taller height. BadIdea's suggestion to lower the storage floor is a good one, although that makes for a step at the front for putting stuff in and out; instead of being able to slide in and out from the storage floor. Wood beam will be less than a steel beam, unless you can find used steel or salvage type beam for cheap. But cost may be second to saving height clearance.

You only need to put the shear wall on either end of the back wall, it does not have to be continuous. A 2 ft wide sheet top top bottom at the end posts extending in would be sufficient; or thinking out loud here you could cut a sheet diagonal and have it triangle shaped going from lower corner to top corner to out 4 ft on the back beam. That would maximize the triangulation effect you are trying to implement. My suggestion to tie into the bldg was for the side wall at the right, where you have existing wood framing. Also noticed that you have a continuous floor base board, why? You can just get some of the steel brackets and anchor to the concrete floor. No need for the bottom board. Save some money there.

If using 7/16 or 1/2 OSB for the storage floor, I would not exceed 16 inch center for the joist supports. I would just go with 2x4x8 ft joists running front to back, on 16 inch centers, and no need for anything side to side except front and back beams. Use the steel joist hanger brackets, they make it easy. For all those steel brackets, look at your local bldg supply/HD/Lowes for the Simpson steel inventory. Those brackets can make it a lot easier without need for notching or other more complicated joints.

 

[Justind97]

How long of a term is the car going to be under there? I’d be tempted to build it out just a tad wider and add removable legs on the one side so you can slide the car out as need be.

The design you have pictured shows the bigger beam with the supports while the smaller one is left free spanning. For The sake of argument, if it was built like that, there’s your weak spot in the design.
Wheels weigh a considerable amount if you store them up there. I’d put them close to a corner or on top of a leg to make the weight bearing load go straight down and not stress the structure

 

[bad_idea]

BadIdea's suggestion to lower the storage floor is a good one

Someone write that down. I had a good idea.

 

[38Chevy454]

Someone write that down. I had a good idea.

Gotta give credit where it's due, even if that's a rare occurrence

 

[asifnyc]

The lower floor is a good idea but I really want a flat floor that I can slide items on/off... having to climb up and pick things up over a ledge is not what I'm looking for.

Justind97, the front beam is more shallow because the plan is for it to be metal. I'm assuming metal beams can be less deep than wood for the same span. Someone please correct me if that's not the case. And I really want to avoid any posts in the front. If I do get any deflection having to get a post back in once taken out could be an adventure...

I've discovered that I have several 2x12 @12 feet PRESSURE treated boards from some fencing that was removed. Thinking about using some for the rear beam (so it would not be one continuous piece but would be supported at the seam of course). Also considering if it makes any sense to use any of this 2x12 for other parts of the design like the end walls or rear supports (since I have it on hand and it's free).

also have (6) 4x4 @ 8 feet that I will use. And had a friend tell me the joists should be 2x6, not 2x4.

I'm going to work on version 3 with 2x6 joists 16" oc and no continous base board at the rear. Also will try a 2x6 steel beam for the front. If I can repurpose some lumber I have laying around I won't mind spending (ie <$300) for one steel beam. But that's only if the appropriately sized steel beam comes in a lot shorter than 12". If it turns out I need a 10" steel beam then I'll just go ahead and do 2x12 wood. BUT if a 6" steel beam really can hold the weight then it's worth it to me to use it...

thanks again for all the advice. I'm above my pay grade here.

*played around in sketchup more. if I have to go to a 6" steel beam (or larger) than I will just go with 2x12 for the front beam. the difference in overall height will only be 5.5" (64.5" with 2x6 steel front beam, 69.5" with 2x12 wood (1.5x11.5 actual). Now if somebody tells me I need 2x18 wood for the front beam then I'm back to looking at steel beams

 

[bad_idea]

In my last garage I installed a 6" tall I beam across the 14' width of my garage. It cost me ~$125. I do not remember the other dimensions to the beam. It was supported within each wall cavity by a post. I had my BIL (engineer) run the weight calcs for me and he came back with 3900 lbs w/ a 2:1 safety factor. My SIL divorced him or I would ask him for you. Long story short, short steel can support the load you are looking for easy enough.

I would use I beam for a couple reasons. One, all the cool kids do it, you typically see I beam used for heavy structural loads. Two, you can hang a chain fall from the bottom flange, could come in handy at some point. Three, I think it would be fairly easy to rest your joists on the bottom flange and then weld a piece of flat bar to the web of the beam to through bolt the joist to.

One more time, I'm not an engineer. Just throwing out ideas.

 

[asifnyc]

ok, here's my third attempt trying to use all the input that you've generously provided. I did price a 6" I beam at a local metal supply. $250 for 20 ft.

I tweaked the dimensions some more and will do the full 20 ft wide. For depth I really don't want to go a full 8 ft. So 7'4" is what I'm planning.

This version has 2x12 for the floor frame. The front 20ft beam I will need to purchase. The rest of the 2x12 I have on hand. Joists are 2x6 and will need to be purchased as well.

For the posts/columns I'm using TWO 2x12 sandwiched together (because I have it free) at different heights to create a ledge for the beam to sit on. In the front I"m using 4x6 (will need to buy) because I didn't want a wide post up front.

I've put shear walls at the back. I did it in the center as well but maybe that's not needed? also wondering if I need the side wall base boards I have in there?

Thanks again!

 

[bad_idea]

Hit up your local used steel yards to see if the have the I beam. I have a yard local to me that sells steel used, remnant, and new by the foot. Worse case you can buy new and only buy the 18' you need. The yard by me will torch cut it a couple inches long. Keep in mind you have to get that beast to the house. At $250 it is likely $1 or so a pound - meaning the beam will weigh ~225lbs.

 

[38Chevy454]

Third revision is looking good, using what you have to save buying materials. Don't need the rear center shear walls, but you do need to add some shear wall to the sides. Just move those rear center pieces to the rear corners on the side. Then you have secured the back plane and the side planes. The top flooring will lock in that whole plane. Being in CA, think of an earthquake with weight up top and what those forces will do, you are preventing the structure from folding on the 90 degree joints. Posts can be anchored to the floor, so don't need the floor beam. Use the Simpson steel brackets discussed earlier. Glue and screw the sandwiched 2x12 beams, and use screws for the rest of the assembly. It will make it better than nails, and is also easier if you need to make a change. Your dwg shows 2x12 beam at the front, but you said it would be a 6 inch beam or tube. Tube may be less cost if you have to buy new.

 

[asifnyc]

plan is 2x12 @ 20ft ($26 from home depot). I found a steel beam but it's $250... is it worth the expense? what's the strength comparison of 6" steel vs 12" wood?

also found this span table: https://www.decks.com/how-to/40/beam-span-chart-table

if I'm reading correctly I think it wants DOUBLE 2x12s... is that right? would still be way cheaper than a steel beam but trying to understand if a single 2x12 is gonna fly...

 

[asifnyc]

Forgot about this thread but wanted to close the loop. I did actually build this. Although construction changed from the sketchup plans. Ended up building two end walls (you can see detail in one of the shots below) and then used (3) 2x12 LVLs across the front unsupported span and (1) 2x12 LVL and (1) 2x12 pressure treated for the back beam. Back beam is supported leg at mid-span made of (2) sandwiched 2x12s. It is bolted to the floor at both end walls (3 bolts per wall) and the back wall of the loft is screwed to the back wall of the shop. Meant to use 3/4" flooring but accidentally bought 1.25" flooring (tongue and groove). Joists are 2x6 on 16 centers. don't have a pic handy but I have a recycled wood ladder from a kids play structure that lives mid-span. I just pull it down and it leans against the front beam and I climb on up.

I then skinned it in reclaimed fence boards. I'm happy with how it turned out. Feels incredibly sturdy. I can crawl around up there and feel zero deflection.

 

[bad_idea]

I like it. Looks good. What you got under the cover?

 

[gmcgeo]

If i was to guess, looks like Camaro or GTO. i would bank its a Camaro

 

[Jim_No_Garage]

I like it. Looks good. What you got under the cover?

Based on the picture I'm betting on an AMX Javelin. The nose is a little more square than a Camaro's, the front wheel arches are more pronounced, the rear end is a little longer and the rear spoiler is taller.




Nice job on the loft - I missed the original thread but enjoyed catching up and seeing the final result.

Cheers

Jim

 

[gmcgeo]

Based on the picture I'm betting on an AMX Javelin. The nose is a little more square than a Camaro's, the front wheel arches are more pronounced, the rear end is a little longer and the rear spoiler is taller.




Nice job on the loft - I missed the original thread but enjoyed catching up and seeing the final result.

Cheers

Jim

I would say you are correct by the picture on the front of the loft with 2 AMX

 

[asifnyc]

ding ding

 

[Jim_No_Garage]

I would say you are correct by the picture on the front of the loft with 2 AMX

I didn't see the AMX on the grill of the cars in the picture until after I posted - LOL