What is fire blocking? How do I fire block when framing my finished basement?

Not sure how to install fire block? I'm your huckleberry. I know that's a movie quote from somewhere but I can't remember where. I think it means I'm your man or something southern macho like that.

how to fire block a basement wall

If you're reading about fire blocking then I know you must be either:

1. Someone who plans way ahead (kudos to you!)


2. Someone who is presently freaking out. Perhaps because you missed a major step in your basement finishing project.

Either way, I know I can help you. During my basement finishing project I was the latter. The guy freaking out.

I remember, it was a Monday. I mentioned to my friend Tom that I was done framing my basement walls and had scheduled my framing inspection for Thursday. He goes, "Cool. You are really doing it." then casually mentions as he walked away. "Don't forget fire blocking - they'll fail you for sure."

WHAT!!!  What the hell is fire blocking? Can I do it in 3 days?

The purpose of fire blocking is two fold. Starve a fire of oxygen and prevent it from spreading. Ironically, fire blocking material does not have to be fire-proof. It just has to keep the fire from getting fuel (air/oxygen).

basement wall with no fire block

Here's my best attempt at visually explaining what fire blocking is and where it goes. In this example there is NO fire block. The fire can get air and move freely. (not good)

When you're finishing your basement, you need to install a fire block in the gap between the top plate of your framed wall and block wall of your house foundation.

basement wall with fire blocking

Ok, same diagram but with fire blocking installed right near the top plate of the wall. That's it, a little strip of drywall. Not that magical.

Believe it or not, that's the best explanation I was able to write after 30 minutes of my hamster brain running. Read these other sections and it will make more sense.  I know, you're probably thinking "what the hell is he trying to say???"

What material can I use as a fire block?

I recommend using drywall as a fire stopping material. You can also use 2x4s, plywood, rigidly packed insulation, fire foam and sometimes sheet metal. I used drywall for my basement. I was a bit short on time so drywall was easiest to cut to the right width and length. It passed inspection without any issues.

How do I "install" fire block?

Fire blocking isn't something you'll see at the Home Depot labeled "fire stopping stuff" or "fire block". It's just material (drywall in my case) that's nailed into the gap between your top plate of your framed walls and the foundation of your house.

So you're going to cut a strip of drywall (or other material) the width of the gap from the block wall to the framed wall, probably 4 to 5 inches. Then push that strip of drywall up into that space.  Take a few nails or screws and secure to the material in there so it doesn't fall. It doesn't have to hold Andre the Giant, just its own weight, so a couple of screws or nails should do it.

If you have small enough gap just use some fire foam and it will expand to fill the space. Plus, it fun to squirt.

Fire Block Space around Holes for Pipes or Wires

fire foam used to fire block holes for electrical wiring

photo from : http://joshbasement.blogspot.com (thanks Josh !)

If you drill a hole in the top plate of a wall so you can run plumbing pipes or wiring you need to stuff some rock wool or insulation in the remaining space.

Yes, even a little tiny space. Don't shortcut it.

If a fire is burning behind your wall and that space is open the fire will suck air into the gap and go burn crazy.

No hole... the fire should just smolder or even go out.  Giving you, your family and your fire department time to react.

Not sure what you can use to fire block? Ask your Inspector!

If you're not sure about what you can use in your area for fire blocking, ask your inspector. Don't be afraid to call, they are there to help you! Call them. Here's what you say. I wrote it down for you.

You:   "Hello, I'm finishing the basement of my house and I have a question about fire blocking ."

Inspector Receptionist:  "Okay, no problem, hang on while I get _____ (Fred).

Fred: "Hello?  What ?  (Fred is a little hard of hearing, due to that one air show he went to where he stood right next to the engine while it "warmed up".)

You: " Yes, Hello... Fred... What material do you recommend for fire blocking if I'm finishing my basement? Is it okay to use drywall?

Fred:  "Yes….yeah... drywall is A-okay! Thanks for checking."

See. That was easy. He even said thanks for checking, so you know you are good to go.

3 Questions, 3 Answers - About Fire Blocking

Q: Do I install fire blocking before or after wall framing?
A:  After. You can also do it as you go along. I didn't even know about it so for me… after was good.

Q: What if I don't install fire blocking?
A:  You will fail your framing inspection. Well, you "should" fail. Not a huge deal, you don't get penalized or anything - you just have to install the fire block before they will pass you. In most areas they'll come back for another inspection at no extra charge.

Q: What is horizontal fire blocking?  Do I need to worry about it.
A:  So, the fire blocking we've been talking about is vertical. It stops fire from moving up. Horizontal fire block stops fire from moving sideways. My county did not require horizontal fire blocking. It wasn't even mentioned at all in the building codes. Check your code, but it seems like it's not required in many areas for basement finishing - check your code though.

basement finishing jason 205I hope that helps. I know for me fire blocking was a tricky topic to grasp at first.

You're doing awesome! Keep going with your basement finishing! It's going to be so worth it.

If my awesome explanation wasn't good enough, although I can't see how that would be, feel free to leave a comment or question below this post.

Cheers - Jason

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Questions and Comments

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  1. Nick says

    I installed fireblocking before framing as recommended by the inspector. I simply cut 8 foot drywall sheets into strips and screwed them to the floor joists (or blocking going the other direction) along where my exterior framing would go. Then the top plate of the wall was screwed to the joists through the layer of drywall.

    I think Jason's way might be easier in the long run since I may have to shave off drywall and make it even with my top plate where I left it a little too wide.

    You'll also need to make sure to fireblock any exterior wall framing that runs under a soffit, it's the same idea, but visually is different and for some reason was hard to wrap my head around.

  2. Jian from Toronto ON says

    Hi Jason, Thanks for everything you posted on your website. I am about to remodel my basement myself. Luckly, I found your website, and now I am learning and digesting from your DIY day by day. The drawings and picture in regard to fire blocking are very helpful.

    • says

      Jian - That is awesome! I'm so glad it's been helpful, theres more on the way. You've got the perfect attitude, make some progress each day, each week and before you know it you're looking at a great finished basement for a third of the price. Plus a primo set of tools and skills to boot. Have fun! - Jason

  3. Jon says

    The walls of my basement came with insulation already on the walls so I'm framing my walls on the outside of the insulation. The inspector here (Colorado) says the insulation on the walls can act as the fireblock so I don't need to add anything special...YAY!

    • says

      Thats... interesting.... I'm not sure how that qualifies as fireblock for the vertical space? But, if they say ok, then it should be good. No big deal if they aren't being clear, they'll just tell you what you need at the framing inspection. - Jason

  4. Dan says

    Jason, I a bit slow...do you mean that the sheetrock should go on all the vertical ceiling boards (and horizontal boards, if required)? Dan

    • says

      Dan - I'm not 100% sure I'm following your question. For fire blocking you do need to install it along the entire perimeter behind your wall, there shouldn't be any gaps where a fire could spread vertically. If you have a picture email it to me and I can probably comment more better. - Jason

  5. Jeff says

    Hi Jason,
    Is 1/2" thick drywall acceptable for fire blocking in the stud cavities or does it need to be 5/8"?

  6. Jared says

    Hello Jason,

    You post was awesome and just what i needed. I was like you and freaking out that I had finished my framing with no fire-blocking. Thank you so much for your post! I just wanted to say thank you for your drawings and pictures also, they helped me understand exactly what I needed to do.

    You da man!

  7. Ed says

    Hi - Thanks for your article. I understand that 1/2" drywall would be acceptable to use as fire blocking where I am located. However, it shows the 1/2" drywall tight to the joists and then extending to the exterior perimeter sill plate, then the top plate of the basement framing fastened through the 1/2" drywall into the joist above (top plate of basement framing would be under the drywall). Even though the basement wall will not be a load bearing wall it seems odd to fasten through the drywall to catch the joist - do you or anyone on here have any experience with this method and its long term viability?

    • says

      Hello Ed - Although I haven't seen it done this way too often it would seem to me that should work just fine. It sounds like what you're describing is that they drywalled the ceiling first then framed the wall. In this way the fire-blocking is already in place? Once the walls were framed you would just have to drywall the walls and you're good to go. Seems okay.

      Anyone else seen this? Please chime in. Good luck with your project! Cheers -Jason

      • Robert says

        Hi Jason,

        I put my fire block (1/2 drywall in first then caulked with fire resistant caulk to fill gaps along the concrete wall. I then built my walls and nailed them in place. I used a 6' level and a straight 2x4 to determine how wide to cut my drywall (fire block) so that I would not have to trim the drywall after the walls were in place. This passed in Stafford county VA.


  8. Tom Bennett says

    Jason, great article and your writing style is very easy to understand and makes perfect sense. Now my wife and I can stop discussing fire blocks on our project...she won. I had to laugh at the very beginning when you talk about the statement "I'm Your Huckleberry". The movie was Tombstone and it was what Doc Holiday (Val Kilmer) said to Johnny Ringo during the movie. It's in reference to Huckleberry Fin of the Tom Sawyer books, Huck Fin being Tom's back up and best friend. Doc was Wyatt Earp's very good friend in the movie.

    • says

      I'm glad someone has my same level of movie intelligence, knowledge of history and recall. Thank you for the wonderful compliments on my writing, I really appreciate the feedback. Clearly you're a man of great character and savvy.

      As for the fire blocking - like you I always let my wife win arguments - this makes getting permission for my annual 4 day golfing trip to Orlando that much easier.

      Cheers - Jason

  9. Steve says

    Very entertaining writing style!
    In Colorado, horizontal fire blocking is also required, or draft stopping, especially after these huge fires we've had. They're slightly different, but go together. The principle is that only 100 sq ft of wall or ceiling should be air-flowing. So less than every 12 linear feet of wall, there should be a sealed barrier (on the outside walls, preventing air from flowing along between the basement wall and the framing. Like you've said, you can do it with wood (2x or 2 1x) or drywall or structural board, and seal the seams with fire caulk or compressed (packed) fiberglass insulation.
    And you've already covered the vertical blocking--separating the cavities in between the floors from the walls, and from each other. With these huge fires, one of the things that happened is that a deck caught fire, the fire entered the area inside the exterior wall under the first floor and...spread like crazy, resulting in the loss of the whole house and fuel for the next house down the street. Embers that could start new fires were flying up to 1/2 mile!

    • says

      Steve - Great info. I didn't even think about fire creeping in from the outside but you're 100% right. These seemingly small fire blocking tips can be the difference between a small fire and the total loss of your home. - Jason

  10. frank says

    Hi, Jason,,

    I am not sure I understand correctly

    "Then the top plate of the wall was screwed to the joists THROUGH THE LAYER OF DRYWALLl."

    any picture will be helpful.



  11. Cliff says


    Can you walk us through fire stopping soffits? I can't seems to visualize it at all. I'm also in Loudoun County so I'm glad to hear I don't need to fire stop horizontally.


  12. Geoff says

    Hey Jason,

    I'm wondering about fire stopping for a basement in which we plan on having an open/painted/industrial looking ceiling (In other words... no drywall... just rafters, pipes, wires, etc. shown bare). I'm still in the planning stages of my project so I'm not in a rush but I'd love to hear your thoughts.


    • says

      Hi Geoff - Okay, here's the deal with fire blocking your basement with a no drywall ceiling. It's the same as if you had a drywalled ceiling. Fire blocking is for the ceiling space behind your basement walls (which I'm presuming are going to be drywalled). There will be a 3-5" space between your concrete wall and the framed-drywall walls. It's that ceiling space that MUST be fire blocked with drywall or some other material.

      The reason is that that space is hidden. Because the drywall for the wall goes up to the ceiling the space behind it is hidden. IF your design has some kind of openness to the top of the walls then perhaps you would not need fire-blocking. Any concealed space must have fire stopping materials at the top to prevent the spread of fire to the next floor.

      Hope that helps to explain it. It's a great question - and I really like the no drywall ceiling option - let us know how it turns out.

      Cheers - Jason

  13. Ran Parikh says

    My family member did basement without permit. When he went back to get CO, the city is giving hard time to pass inspection without fire stopping. walls are up and painted. Is there any other way to install fire stopping without destroying walls??

    • says

      Bummer... that's a common issue that trips people up who don't get permits. There's no way that I know of where you can add fire-blocking without removing some drywall.

      This page talks in more detail about some of your options for fire-blocking after drywall has been installed. Good luck! - Jason

  14. Don says


    I am finding myself in trouble before I get these permits started to finish my basement. Last year my pipes were blocked solid from the Kitchen to the Basement from 50 years of bacon grease and who knows what else from the previous owner. My friend and I tore out the Cast Iron and Copper piping and installed PCV in a day but needed support for the new 2" pipes so we built an open frame, 2x6 studs and 24" apart along the wall to the existing cast iron stack for the plumbing. My friend and I didn't know anything about fire blocking until I read what I need to do for finishing my basement this past week. From what I see from the town here in NJ and on other websites, people are attaching 3/8 plywood, Drywall, or a 2x4 before putting up the framing to go between the floor and the Fire blocking. I see what you did in that one picture which looks similar to my situation where you had existing framing but no Fire blocking and you added Drywall and Spray Fire resistant foam underneath the 2x4. Will or did it pass code for you?

    • says

      Hello Don - Yes, I used drywall and some spray foam for fire blocking and both methods passed code. I've also worked with guys who like to use rock wool, and that has passed. I can't comment specifically on NJ - but I would guess their allowable methods for fire blocking are similar.

      Hopefully that helps - good luck with finishing your basement! - Jason

  15. Jaysen says

    I am finishing my basement that had the insulation attached to the exterior concrete walls. I have put up the exterior walls and was wondering how to do the fire blocking. I looked at putting a 2X4 in between the studs horizontally, but that left a gap below between the studs where the plastic over the insulation compressed and also left noticeable gap behind the studs. I believe that defeats the purpose of fire stopping, but it does block gap to the trusses above. Any suggestions on how to approach this with out tearing down the walls and starting over

    • says

      Hi Jaysen - Yes, I have suggestion. In fact I did my fire blocking AFTER framing as well and I also had insulation on the exterior walls as you are describing.

      What you want to do is use drywall as your fire blocking material. You just need to cut long strips of drywall 3 to 4" wide. I didn't even need to nail the drywall strips to anything they just fit snuggly between the top place of the framed wall and the sill plate (wood beam) on top of the exterior wall.

      You are correct that you do not want ANY gaps behind your wall - you can use some rock wool to fill any holes or spaces that are too small to cover with drywall.

      Hope that helps out - you should be fine but just to double check you might want to call or look up your local building department to ensure they accept drywall as a fire blocking material.

      Good luck!


  16. Drew says

    I too have the majority of my walls framed before learning about fire blocking. The building inspector in Ohio said that drywall cannot touch the foundation walls. In that case is there a trim to go around the drywall or a special type of drywall (i.e. cement) that can be used to fireblock? Is there a reason you can't just use Rockwool along the whole exterior of the wall instead of struggling to fit drywall or plywood pieces to the top plate and behind studs?

    • says

      Hi Drew - Not touch the foundation?? That's a first for me. I guess technically mine was touching the "sill plate" not the foundation but still. Yes, from what I've read and heard from other rock wool is acceptable, even all the way around to fill in major gaps. I would call the inspection office and confirm but that may be the best solution for you (others in Ohio, may want to double check this). - Jason

  17. Steve says

    Thanks for the insight. My basement framing is about an inch from the concrete, so if I was to do the same as the pictures post above would there not be gaps behind the 2x4? Also in my case, my foundation only runs up about 90% of the wall. If i was to attach the drywall to the underside of the top plate the front edge of the drywall would be pressed up against wood and not concrete. It doesn't seem effective? Am I missing here?

  18. Theodore says

    Hi Jason, Excellent site. I'm currently finishing my basement and getting stuck on fire blocking above the main electrical panel. I often find examples online of one or two discreet wires or a plumbing pipe penetrating the basement wall's proposed top plate. But above the electrical panel, there's 20+ armored cables going up and into joists. My first challenge will be to frame a wall around this mess. And after that, I've no idea how to fire block 20+ penetrations. They're so close together that it won't be individual penetrations. Any suggestions?

    • says

      Hi Theo - The framing part is a whole topic in itself, but to fireblock those gaps between the wires and the framing you just need a bit of rock wool. This stuff is soft like insulation and (wearing gloves) you can just pull a bit off and gently place it into any air gaps. Good luck! - Jason

  19. Matthew Lemmon says

    Some of the exterior walls in my basement are half concrete half exterior framed, do I have to install fireblocking on these walls? Basically I'll be installing fireblocking between the top plate of the wall I built and the 2x6 exterior wall the builder put on top of the concrete 1/2 wall?

    • Cal says

      Following. I did same thing. I did not know about this requirement when I started project. Will I just have to run particle board behind wall now?

  20. david says

    Is this only need on framing up against the exterior walls? I'm trying to figure out where I need it. I put 2" XPS right on the concrete and will be framing right up next to that, so there really won't be any gaps like in your pictures.

      • Aaron says

        I realize there will not be gaps between the rigid foam and framing but don't inspectors assume that in a fire the hot gasses melts the foam almost instantly , therefore leaving a gap? Don't they require the fire blocks to go through the foam and to the foundation or sill plate?

  21. Kirk Varra says

    "ill be your huckleberry" is a quote from Doc Holiday. a huckleberry is a little flower typically left on a grave. Doc Holiday would say "ill be your huckleberry" before a gun fight. He was basically saying that he would be the flower on their grave. so yes, manly. good article on fire blocking by the way.

  22. Erich says

    Our contractor failed inspection because horizontal fire blocking was not installed at the top of the metal furring. The building is all concrete block and bot a basement. It is one story and she said to install wood fireblocking within the top of the furred space. The roof framing is wood trusses. In the building code fire blocking is only related to combustible construction. Do you think that because the trusses are wood and the rest of the building is not is what is triggering the requirement for fire blocking? The building is one story, utility building with concessions that servsd premade food, a small office for the park director and restrooms with no interior furring.

    • says

      Hi Erich - I can't say for sure. I only comment on basements and this sounds like a shed or out building for food, etc, which could have completely different code. Sorry I couldn't be of more help. - Jason

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