Tag Archives: bottom plate

Loft in a Weld Up Steel Building

Loft in a Weld Up Steel Building

Reader CINDY in TYLER writes:

“I am constructing the interior of a welded metal house that’s 20x18x12. I am trying to figure out how to add a loft. The building framing is constructed of I-beams and the walls have 2 rows of heavy 8” C-channel per wall, Though the lower C’s will have to be cut for window installation. But the upper C is about the right height for the floor. I only want the loft to be 20×9. I’m going to give you my ideas and would like your response, ideas, thoughts and recommendations please. I have a 20’ piece of steel 8” C-channel that I could run across the building that would finish the square framing, though I don’t weld ad not sure how to best attach it to the walls. After that I can install, with screws, 2×8 along the inside of all the C’s. That will give something to attach joist hangers to which will be installed parallel to the C that was just installed. Does this sound doable and any ideas on how to properly attach the C channel? I was thinking I could cut the top and bottom part that curls, and bend it out of the way and attach some heavy duty angle pieces, but can only attach with 1’s onto the top and bottom of one channel and to the center of another. I would attach with bolts and nuts. Any help will be greatly appreciated. Thank you for all that you do for so many people with your blog.” 

Mike the Pole Barn Guru says:

If you are a regular follower of my blog posts, you will find I am a fan of weld up steel buildings only when they are fabricated from engineer sealed site specific plans with assembly done by a certified welder. While this may not be as important on a low risk shed, as buildings grow in footprint and complexity, it becomes significantly important.

Lofts can prove to be of special concern. They tend to be under designed (unless engineered) and over loaded, resulting in distinct possibilities of catastrophic failure leading to potential injuries (if not fatalities).

Trying to attach steel beams to steel framing members should not be done without an engineer’s design. There is an easier option:

Provided your concrete slab is sufficiently thick, my recommendation would be to frame 2×6 stud walls along each 20 foot side of your proposed loft. Use a pressure preservative treated 2×6 bottom plate. Studs can be 24 inches on center with a double 2×6 top plate.

Proper anchorage for stud wall to a slab has fasteners penetrating at least an inch into concrete. You could use 2-1/2″ Ramset nails.

Personally, I prefer using Tapcon screws 

What you’ll need:

Tapcon screws – Be sure to get 3/16″ x 2-3/4″
ones with hex heads. Don’t try to use a flat-head screwdriver to drive them! 

A hammer drill

Several concrete drill bits

A hex head bit for drill fitting Tapcon head size

How to attach walls using Tapcon screws

Drill pilot hole

Drill a hole through 2×6 bottom plate center, every 16″ to 20″ inches.

Hold the bottom plate in place by standing on it if possible.

Use firm pressure, but don’t push too hard. Save your body, drill will do the work!

If using 2 3/4″ screws, put a piece of tape on bit 3″ from tip. (Drill 1/4″ deeper than depth of anchor plus 1 1/2″ for bottom plate.)

Attach screw

For best results use a hex-head attachment on your power drill to secure screw. (Even the correct size flat-head screwdriver attachment will slip off frequently.)

Start off slowly until you’re through the bottom plate.

Speed up drill and drive anchor deep enough into concrete so the screw head is flush with bottom plate. 

Make sure you have enough drill bits on hand. You’ll go through several as tips eventually wear

Another method of attachment entirely avoids penetrating your concrete – construction out or break off. Repeat this process with each wall section adhesive. Make sure the slab is thoroughly clean and use a polyurethane adhesive. Polyurethane works if there is any moisture in the concrete or bottom plate and it has gap filling properties.

Assuming you will have no loads on loft greater than a 40 psf (pounds per square foot) residential load, 2×8 #2 floor joists can be spaced on top of walls 24 inches on center.                                                                                https://www.southernpine.com/app/uploads/SPtable2_060113.pdf

Use 3/4″ OSB (Oriented Strand Board) or CDX plywood for your floor decking. 

Why Pre-cut Studs are 92-5/8″ Long

Why Pre-cut Studs are 92-5/8” Long

Growing up with my Father and six framing contractor uncles (my Dad’s five brothers and Auntie Darlene’s husband Vern) all of us male Momb cousins (myself, brother Mark, Kim, Randy and Scott) eventually became M.E.I. (Momb Enterprises, Inc.) teenage slaves. My beloved Uncle Gil even has on his Facebook profile, “Former Mean Boss at MEI”. Whilst our generation worked hard, we were generally looked upon as strong backs and weak minds – there was very little explanation as to why things were done a certain way, and lots of do it, do it quick and do it right.

In framing stud walls, Uncle Gil would give us an evil eye if we had a stud even a minute fraction of an inch off being directly between his lay out marks on top and bottom plates. Never was there a discussion of why it was we were framing with studs 92-5/8” long, when all other framing lumber came in even two foot multiples (albeit those were always ½” to 5/8” greater in length than an exact two foot).

Now an average small home takes roughly 400 studs, can you imagine how time consuming it would be to have to trim back all of these if eight foot material was ordered and 92-5/8” was desired? 

It wasn’t until I went to work managing Lucas Plywood and Lumber’s roof truss plant, where I became exposed to “P.E.T.” – Precision Trimmed Lumber. This was one service provided for by our lumber remanufacturing (aka reman) operation. While there, since I was good at math, I taught members of our lumber sales team how to do material takeoffs for stick frame home lumber packages.

Helpful hint to those of your reading along at home – want studs 16” on center (o.c.)? Take lineal footage of walls and order the same number of studs as feet of wall. 24”o.c. take lineal footage x 2/3rds. Works out to be remarkably close in actual use.

Anyhow, back to why studs are 92-5/8” long.

Interior Wall FramingAnecdotally, supposedly the company who first pre-cut studs couldn’t close their 1943 delivery truck’s tailgate with eight foot material – so studs were cut to fit the truck bed.

When 92-5/8” studs are placed upon a single 2x bottom plate and a double top plate, wall height becomes 97-1/8”. This allows for 5/8” drywall on ceilings and keeps wall drywall ½” above the subfloor. This gives space for drywall to expand and contract without affecting flooring, as well as from absorbing any moisture on the floor.

Even though post frame buildings, with interiors to be finished, should be properly designed using bookshelf (horizontal girts) for exterior walls, these same rules are best followed for determining floor-to-ceiling heights. By use of heights 1-1/8” greater than whole feet, material use is minimized and drywall sheets can be run vertically without need for cutting. For extended reading on why this is best: www.HansenPoleBuildings.com/2019/09/11-reasons-post-frame-commercial-girted-walls-are-best-for-drywall/.