Did I Make a Major Framing Mistake?

Question

I am an absolute ameteur trying to frame my basement remodeling project by myself and I've learned a lot since the start of this project, but I am worried the parts I didn't know are going to come back to haunt me now. When I first started this project, I didn't know about things like fireblocking. I also didn't know about using a blocking technique to nail 2x4 lumber directly to the foundation when you encounter overhead obstacles that would prevent you from nailing your header to joists above. Without this knowledge, I intentionally placed 90° bends in my frame to step away from the wall a few additional inches to go around some overhead obstacles. At the time, I thought little of it, but I now realize I have created a nasty air pocket behind the wall that effectively makes fireblocking a major problem.

The issue, as I see it, is the massive air cavity behind my frame, with effectively no easy way I can think of to address it other than hanging some drywall on the backside of the frame. This would be difficult because even though there's space behind the frame, it's barely enough for a small person to fit behind. Still, it's not out of the question. The other option is tearing down the original wall, removing the bend, and placing the frame a normal distance from the foundation. This has a domino effect in the sense I will have to completely redo every single wall/soffit that comes after it because it will impact the 16" OC spacing, and/or the walls that follow will end up being too short, for obvious reasons.

My area requires fireblocking to be applied in two different ways (the first is referred to as fireblocking and the second is referred to as draftstopping). The first hopes to prevent a potential fire from spreading between floors. This is typically achieved by attaching plywood to the top of your header before it gets nailed to the overhead joists. This piece of plywood extends from the outside edge of your header to the foundation. I didn't even realize fireblocking was a thing when I started this project, so I'll have to place plywood under the header and notch it out to account for the studs. This is a pain, but it's doable and that's not the part I'm worried about. I'm concerned with how to approach draftstopping. Since I've moved the frame so far away from the foundation, I've inadvertnly created a vast amount of space between the frame and the foundation. You'd typically place something like this mineral wool between studs to prevent drafts and effectively (hopefully) suffocate a potential fire before it has a chance to spread. As you can see in one of the pictures, there is 15½" of gap between the foundation and the outside of the frame, so there's no good way to fill the air gap with mineral wool unless I pile a ton of it behind the frame. Said another way, you'd typically place the mineral wool between the frames, but there's entirely too much space behind the frame for that to work. Important note, allowable fireblocking materials are outlined and they specifically prohibit blown insulation.

I have attached some pictures I hope can help explain what 1,000 words are otherwise incapable of explaining. How bad did I mess up? Is rebuilding from scratch my best/easiest option?

• Header from below

• Bump out from foundation

• Air gap behind frame

• Distance shot

• Another distance shot

• Speaking of distance, it's 15½" from the foundation to the outer edge

• Doorway in wall that follows on next wall in line

If anybody is curious about the bottom, the basement walls are floated.

Edit: I'm glad everybody got a laugh out of design decision I made, but two important facts that have been overlooked here are 1) the pipe I went around is thicker than a single piece of 2x4 lumber 2) the basement walls are floated, so the frame won't be supported by the bottom plate.

Answer 1

Oh jeez

Honestly you overthought all of this. This isn't a bad framing job but it certainly is odd. Why would you want to get rid of a foot of space everywhere. If you leave it like this you certainly need to use it as a secret passageway. Definitely scooby-dooish wall.

Choice 1 (preferred) - Move wall

• cut off or pull all of the top nails and scootch your wall 1-2 inches from the wall.
• Yes you will have to add some more framing to perpendicular walls.
• You will then stuff some mineral wool into the upper gap.
• may not be any requirement for draftstop if framing touching existing insulation. if there is you just stuff some mineral wool every 10 feet into the frame gap.

Choice 2 - Leave it

• for fireblocking... I would install a 2x about 10" down from ceiling all the way across. then attach long strips of plywood that touch wall/insulation. then stuff mineral wool up into the top cavity until covered. this gives you fireblock plus a ton of insulation exactly where a basement needs it.

• draftstop... Now you will install strips of plywood vertically every 10' (or less). You will then add mineral wool to this and its gaps.

• this is totally goofy and not standard but I have given you the ability to meet code. There is really nothing wrong with a huge gap other than you lose sq/ft but if you are happy doing all this extra work instead of moving the wall over... go for it. I would inform your local inspector of both of the techniques I have given you and get his take. I would not have him inspect it without a good pre-warning as there may be a shock value... He needs to know you made a planning mistake and you want to meet code... not that you are hillbillying your way around to pass your permit.

Side note: There are no framing requirements for stud spacing in basements (that are not load bearing). You can basically do whatever you want. Sure some inspectors might ask you to have at least 24" so people don't fall through walls if they trip. But you can frame a wall at 12"-16"-8"-20"-13"-14". Yea its goofy, yea it makes laying drywall harder... but its less goofy than having framing 15" from the the wall.

Side note #2: You didn't need that blocking technique. You could have run cross blocking to the last joist to the outside wall. Just like you did between that joist and the 2nd one. Yes it is harder to secure but there are various ways to do this. Also it is an external basement wall. The baseplate of the wall will keep 90% of the movement from happening. You don't have to over secure the top. Honestly when I am "blocking" out walls like this... If I cut my 2x4 to be dead tight to the wall and give it a few nails in the joist, there isn't much securing needed in the area I can't reach.

Answer 2

Too much for a comment, so it's going as an answer.

There's nothing particularly magical about 16 inch on-center spacing for framing. It's not enshrined as gospel deep down in a building code, for example.

It just happens that, at least in the USA, sheet goods like drywall and plywood are dimensioned in 48 x 96 inch sheets (4x8 feet). Since sheet goods need to be installed so that their end joints fall on framing members, the framing is arranged so that an 8 foot long panel covers four (24" spacing), five (19.2" spacing), six (16" spacing), or eight (12" spacing) framing gaps. The 19.2 and 12 inch spacings are usually seen only in floors, not in walls.

Sometimes the spacing doesn't work out. A stud gets put in the wrong place or the wall isn't an integer multiple of the spacing, etc. We cut the 8 foot sheet a little shorter and cover what we can with it, then pick up another sheet to keep on going.

If your spacings are a little goofy that's fine. You'll have a little more wasted drywall material but the basement is only so big and the additional cost due to waste will be insignificant. The floor space is far more valuable than the cost of a few pieces of lumber and odd-sized drywall cuts you'll incur by moving those walls closer to the foundation.

Answer 3

Fireblocking is required at 10’ on center both vertically and horizontally. (See R602.8)

Acceptable materials are 2x material or 1x material with joints backed up, or one layer of 23/32 structural panels (plywood), 3/4” particleboard, 1/2” gypsum board, 1/4” cement based mill board, but must be secured. Batts and blankets of mineral wool or glass fiber installed in a secure manner. (See R602.8.1)

Loose fill insulation is not approved.