What is blocking? Why do I need blocking when framing a basement wall?

This guy is installing blocking, most likely so he can frame in a wall.

This guy is installing blocking, most likely so he can frame a wall underneath of it.

Honestly, I had no freaking idea what the word "blocking" meant when talking about framing a wall.

When I started my basement project my friend Tom was like, "how did the blocking go?"

I played it off real cool, like "yeah, not bad, totally blocked it".  But when I walked off I was thinking "what in the hell is he talking about… blocking?

I had just started framing the first room of my basement, the man office / sports room ( aka the gift wrapping room ).

The first wall was up and I as I rounded the corner to start on framing the second wall it hit me.  Blocking!  I needed some blocking or this wall was not going up.

Blocking for wall framing are short pieces of 2 by 4 that you install between two joists of the basement ceiling.  It's not a "building code" thing and it's not optional, you'll more than likely have to install some blocking to complete your wall framing.

Let's say your ceiling joists (or floor joists, depending on how you look at it) run north and south.  When you go to frame a wall going parallel to those joists then you won't have anything to nail the top plate of the wall in to.

If your brain is about to explode now, please stay calm, I do have a picture. Be sure that you've read the basic how to build a wall post first, so you know some of the terminology.  Once you see what framing blocking is you're going to be like "oh, that.  Yea, I get that."

wall framing blocking installation

This wall is secured to the main joist. If you wanted to move it over a 1/2 foot, you would have to install some blocking before you frame the wall.

Install your blocking before you start building your wall.  You want them at 16" or 24" on center because the drywall guys will expect them to be the same distance apart as your joists.  (they can work around it, but you don't really want them to have to, so keep it consistent)

To install blocking, take your framing gun and "toenail" (nail at an angle) a nail on each side of each end of the 2x4.  The main thing is the be sure that the blocking is flush with the bottom of the joist and straight and flat.  I measured the length of each piece cause I'm a bit of a perfectionist and didn't want a gap.

If you don't have a framing nail gun and are doing this by hand or with screws… I feel bad for you. Like, really bad.  Unless your Mike Holmes and you can swing a hammer like Thor, you aren't going to have fun doing this part.  Check out this framing gun from Bostitch from Amazon, it's got fantastic reviews, great price, free shipping, perfect for finishing your basement.  

They are not that badly priced and you can always sell it to someone else when you're done. Although I wouldn't, cause have a framing gun is like the pinnacle of being bad ass.

basement finishing jason 205That's it.  That's blocking.  See, not that bad, right?  Next up - installing a firewall!

Relax, it's not that bad either, but it totally freaked me out 'cause I thought I had missed my chance to install fire blocking and that I would have to tear down all of my walls.

Cheers - Jason

Hey, dudes and dudettes, do you still have a question? Even after my redonkulous written explanation? I thought you might. Go ahead and ask it in the comments below. I'm just sitting here doing nothing... waiting... for you.

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Questions and Comments

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  1. justin says

    How would you block against a concrete wall? I've got the concrete wall, then the first floor joist is 16" parallel off the wall. I suppose I could nail gun a 2X6 or 2X8 to the concrete, then block off of that, but was hoping to find someone who had some experience with this.

    • says

      Hey Justin - Welcome. You should not have to nail your blocking to the concrete wall. I'm guessing that what you need to find is your "sill" plate. It's a piece of wood (about 2" inches high) that is sitting on the very top of your concrete wall. It may be hard to see or covered with insulation, but it should be there. Find that bad boy, that's what you nail your blocking too. Hope that helps, let me know if this is not the answer.


  2. Brandon says

    I'm about ready to start framing my basement. This issue still has me puzzled a bit based on the situation of my sill plates and how the floor joists are positioned. My joists sit on top of the sill plates, thus I can't add blocking that is flush with the bottom of the joists. If I want the blocking flush with the bottom of the joists, then the blocking will be sitting on top of the sill plate, and I would have no way to nail the blocking to the sill plate because of very tight conditions. Any thoughts?

    • says

      Hmmmm... Brandon, I'm fairly good at visualizing and you wrote an excellent description. If your joists are sitting on your sill plates then you are working with a wall that is perpendicular to the joists... in that case, you do not need blocking for framing. Simply nail your wall top plate to the underside of the joists.

      Am I under thinking this? Hopefully that helps, if you're still stumped or I'm not fully comprehending, shoot me a picture "jason AT ifinishedmybasement.com" - Jason

      • KevinB says

        Jason. I think I know exactly what Brandon is talking about since I just ran into this myself. Here is a picture which describes the scenario.


        The wall in this case is parallel with the joists so you need blocking between the sill plate and the 1st I-Joist. But the bottom of the I-Joist isn't even with the sill plate. It's 1.5 inches lower so you have to bump it up a bit to do the blocking correctly above the flanges. TJI recommended to not nail blocking into the flanges but instead above them so that they sit on the flanges.

        • says

          Ah... yes, good diagram. Yes, you would definitely want to level the blocking (not have it angled). My only concern with that diagram is that the drywall for the ceiling doesn't have a level block to nail to on the end. If you toe-nail the blocking to the "flange" then you have a solid backing to secure the ceiling drywall. - Jason

    • says

      Framing first, then electrical and HVAC. For the most part they are separate phases. You'll have to get your framing inspection done "before" you start your electrical work. If you have a lot of HVAC work to do, like adding a whole new trunk line, then you may have some framing to do to accommodate that. Good question. - Jason

  3. Mike says

    Great article...went to turn the corner framing and the said "Oh #$%@". So now I know about blocking. I was having a heck of a time trying to toenail with the framing gun and was read to give up, but decided to try screws with a cordless driver. I had some 3.5 inch deck screws left over from a fence project, and they did the trick! I highly recommend using screws if the space is tight and if you are not used to toenailing upside down.

      • Mike says

        Some of my joist areas were so tight that I couldn't even get a cordless driver in there. I went to lowes and picked up the "BOSTITCH PN50 Mini Impact Nailer", which is basically an air-powered palm nailer that allows you to drive a single nail at a time...it was a life saver, and only 40 bucks.

        • says

          Mike - That's a great tip. There were definitely a few times I had to do something similar. I turned my hammer sideways and smacked away for 10 minutes, a $40 palmer nailer would have been well worth the money. Plus it's just so bad-ass that you could nail something with the palm of your hand. - Jason (here's a link to that same Bostich PN50, if anyone else needs one)

        • cris longfield says

          good one Mike im more into finish work ===but the framing helps when its straight & level when most needed Learned blocking way back its a necessity

  4. Chris says

    Hey, Jason, yours is my new go to site during my basement renovation. I have a neat one. My house is sixty plus years old. And a previous owner, used mortar to build a pretty ramp up the exposed edge of the sill plate and the top of the cinder block wall, so it slopes up and back at forty five degrees. I hope I don't have to chisel all that out of the forty foot wall requiring blocking

    Yours truly

    Chris Stallaert

    • says

      Hey Chris - Ummmm.... a ramp of mortar? That's very interesting. Interesting is the nicest term I can give it. Thanks for visiting the site and good luck on your basement renovation! - Jason

  5. Pete Koutoulas says

    Is there a particular reason why you suggest toenailing the blocking to the joists? Why not just nail through the joist from the other side, straight into the blocking? Seems easier to me.

    • says

      Pete - Good point, actually I had to toe nail where the blocking meet the sil plate because you can't get to the other side. But where it met the joist, I could have just nailed through. I think the reason I didn't is that my joists bottoms (they're engineered, not all one pieced) are pretty thick and I wasn't sure my nail/screw would go all the way through. - Jason

      • Pete says

        Thanks for the reply. That makes sense. I was wondering if I was overlooking something. Thanks for sharing your experiences here. Great tutorials.

  6. jason says

    So I have a section of duct that comes off the main and runs for about five feet inside the rim joist/sill box where it attaches to the floor vent on the floor above. I obviously can't block in this part of the sill box. How do I frame the exterior wall at this part?
    Jason 2

    • says

      Hey Jason - Good question. So is the bottom of the duct even with the bottom of the ceiling? Absolutely no room for even a 1x4 block? If it was just a foot or so you could get away with no blocking, but at 5 feet the ceiling drywall would sag, we need to have something to nail the drywall into. Maybe a 1/4 inch of plywood attached the bottom side of the joist and then you'd have to get creative and use a piece of 1/4" drywall just for that section? I think I'm envisioning what you're saying but if you want to send a picture that might help.


  7. Jeff says

    I've been reading along and took your advice and just built a wall. Funny how hard that first one was. Now moving forward with the basement, I had a concern about building a wall that butts up to my foundation. I'm not finishing the outside walls and don't know if I need to put any kind of barrier between the foundation wall and the wood stud? Also if anybody has good ideas on how to cover the insulation between the rim joist I'm all ears as I want to paint my ceiling when done. Love the blog it's be a real life saver.

  8. Shawn says

    First I want to say thank you for the strength . You are an inspiration, if I used two top plate for my wall like the builder did, do I still need to fire block. I'm confused . I have pictures I can send you. Thanks in advance for the answer.

    • says

      Hi Shawn - Yes, the fire-blocking is for "behind" the top plates. Having 1 or 2 top-plates doesn't matter. It is confusing, until you get it, then it's easy. When I say behind I mean between the top plate(s) and your basement foundation. You are basically "blocking" the top of that empty space with a fire stopping material. - Jason

  9. Umer says

    Hi Jason,.
    Awesome site...thx..looking forward to building that first wall...but
    the area where i want to start need blocking, but the area above the sill plate is drywalled..and there is wood behind the drywall....so...i would think that i would remove the drywall and then install the blocking?
    i can email you a pic too if that would help visualize.

  10. Matt Kiesel says

    So I really appreciate your website, I have decided to use steel studs to frame for the convenience and seems there may be less errors. But I have two questions.
    1. For blocking my joist have a lip to them. The bottom looks like a T would my blocking go above this lip? There is a blue plastic water pipe attached to the lip as well running to the other water spout. So just curious your thoughts there.
    2. Since, I'm using steel studs could I just purchase the previous palm nailer for the blocking or use 3.5 deck screws with a typical drill?

    • says

      Hi Matt - Congrats on starting your basement! I wish I could answer you steel (metal) stud questions but I'm afraid that's outside my knowledge zone. I've only built with and support lumber framing. Good luck! - Jason

  11. Brian says

    Jason - Don't know if you're still monitoring this blog, but thought I'd ask you a question and see if you're still out in cyber space! I need to install blocking into a tight space above my foundation, between the outer rim joist and the next joist in towards the basement room (does this make sense?). It's a fairly large space, but the opening between the inner joist and the foundation is only about 5-6 inches so I cannot toenail into the outer rim joist. I'd only be able to attach the blocking with a nail/screw to the inner joist and I'm stumped on how to attach the block to the outer rim joist. Any advice at all on how I can add blocks?


    • says

      Hi Brian - Yes, I'm definitely still here and monitoring for any basement finishing questions. It's a bit tricky to answer this particular question without seeing a picture but I think I get what you're saying.

      Make sure you couldn't possible attach the blocking to your "sill plate" - that should be wood and run along the top of your foundation - it may be hidden by insulation, that's typically what you would toe-nail to on the outside (so to speak). If that doesn't seem to work- email me a picture and I'll take closer look.

      Cheers - Jason

  12. Melanie says

    Great info! I want to do as much myself and this really helped! Need advice though - hvac is currently vented from the ceiling. Is it better to run the venting down the walls to the floor? I live in a cold climate will this help keep the basement cozier?

  13. says

    Hey Jason. YOU'RE REALLY FUNNY! You should have a TV show or somethin. I'm a TOTAL NEWBY with all this stuff. My boss at work told me to Google "blocking" and "framing" - and THANK HEAVENS - Your site popped up!! Or it could've been a very dry and boring night. Thanks!

    • says

      Thanks Rachael - My sister is always telling me that I should try stand-up comedy. Maybe for my birthday I'll write 5 minutes of stuff and give it a shot! - Jason

  14. Jason Harris says

    Thanks for the great site Jason. I'm working on my basement as well and confused about the blocking between the open web joists and the foundation. Below are some links to the different setups that I have. Under a cantilevered section, I could just make my wall talker and attach to the top of the joist, however that would not be possible in a majority of the basement. Reading the comments above, it sounded like I should try and attach to the sill plate and then find a way to level off the blocking below, but I'm just not sure how I would go about doing that. Any help would be greatly appreciated. - Thanks!

    In case it helps, my plan is to install 2" XPS and a 2x4 wall, so I would still be a 1/2" from the bottom of the floor joist with my top plate.



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