Question re. Fireblocking gaps between joists

[mwsenecal]

I'm repairing a basement bedroom, which involved completely replacing an exterior wall, and as a side effect the city inspector is requiring that the entire room be brought up to code for a bedroom, not just the wall I'm building.

One of the walls is an interior bearing wall (i.e. the joists rest on it), so there is a vertical gap between the top plate of the wall frame and the sub-floor above of about 9". The width of each gap varies, but is about 13" between joists. I'm told that I need to put fireblocks in place in these gaps to prevent drafts and fire from moving from one space to another. Blocking off most of the gaps was easy (I used 2" X 10" x 8' cut to length), but some of the gaps can't be easily blocked off. Three have 6" ducts running through them, one has the 220V line from the street running through it, and another has a bunch of romex. Short of driving myself insane trying to cut a 2X10 to an exact fit, what can I use to block these spaces off?

Any help would be appreciated!

Thanks,

---Matt

[Joseph Meehan]

I wonder what he would think of spray in foam?

[Edwin Pawlowski]

Bedroom? Would the same code be needed if it was an office or den? Probably too late for that now.

I see spray in foam was suggested and I was thinking that also. I'd contact the inspector and ask him what he'd approve. Fiberglass or similar material may satisfy him also. It does not matter what we think will work, only what he approves.

[DanG]

I would have thought drywall would be the easiest and cheapest to cut, fit, and install. Close penetrations, cuts, perimeter gaps with either fire tape or fire caulk.

Unless you have quite a good fit on your wood blocking you may need to fire caulk any gaps.

There is a fire rated expanding foam. As with all fire rated items, they are pricey. Make sure to clear the product with your AHJ prior to using, they can be quite picky, clarify whether you working on a fire wall or a smoke partition and what materials would be best in his opinion.

[Joe]

How about cutting 13" pieces of blocking from the 2" x 10", scribing the outline of the duct ( or cable hole) on the face, slicing the blocking through the center of the scribed outline and cutting out the opening on each piece and then installing one piece on top and one on bottom to seal the opening. If nailing in place is a problem, construction adhesive would work. This might pass inspection better than cobbling up a wad of brick and mortar for example. HTH

Joe

[John Grabowski]

5/8" drywall should suffice. You can put in pieces and tape and spackle the joints. I have seen contractors use some fireproofing caulk around the joints, but I can't remember the name. I have also seen them use the sound proof type insulation and another type of caulk on top of it to fill bigger gaps. Sorry I can't remember the names of this stuff, but a building supply company may have what you need. I've never seen a spray foam product used for fire proofing, but that doesn't mean that there isn't any out there.

[MB]

Use mineral wool. My AHJ swears by it and requires it instead of wood for fire blocking. Your local contractors supply shop should carry it (not Home Depot or Lowes; a real supply shop).

MB

[John Grabowski]

That's the stuff. Mineral wool. When I did jobs in NYC the contractors would use that and apply some fireproofing paste or caulk over it to make it fire rated.

[3G]

| > One of the walls is an interior bearing wall (i.e. the joists rest on | > it), so there is a vertical gap between the top plate of the wall | > frame and the sub-floor above of about 9". The width of each gap | > varies, but is about 13" between joists. I'm told that I need to put | > fireblocks in place in these gaps to prevent drafts and fire from | > moving from one space to another. Blocking off most of the gaps was | > easy (I used 2" X 10" x 8' cut to length), but some of the gaps can't | > be easily blocked off. Three have 6" ducts running through them, one | > has the 220V line from the street running through it, and another has | > a bunch of romex. Short of driving myself insane trying to cut a

2X10 | > to an exact fit, what can I use to block these spaces off? | >

| > Any help would be appreciated! | >

| > Thanks, | >

| > ---Matt | | I wonder what he would think of spray in foam?

spray foam (great stuff) is flammable and unacceptable. unless it is icynene

a non flammable fiberglass insulation is what you want, and flame resistant caulking for around wires and pipes running through the top and bottom plates.

| | -- | Joseph Meehan | | Dia 's Muire duit | | |

[3G]

drywall is NOT fire resistant unless you use 5/8" with a skimcoat of plaster on both sides. it is typically more time consuming. fire rated fiberglass insulation is the best way to go.

| > One of the walls is an interior bearing wall (i.e. the joists | > rest on | > it), so there is a vertical gap between the top plate of the | > wall | > frame and the sub-floor above of about 9". The width of each gap | > varies, but is about 13" between joists. I'm told that I need to | > put | > fireblocks in place in these gaps to prevent drafts and fire | > from | > moving from one space to another. Blocking off most of the gaps | > was | > easy (I used 2" X 10" x 8' cut to length), but some of the gaps | > can't | > be easily blocked off. Three have 6" ducts running through them, | > one | > has the 220V line from the street running through it, and | > another has | > a bunch of romex. Short of driving myself insane trying to cut a | > 2X10 | > to an exact fit, what can I use to block these spaces off? | >

| > Any help would be appreciated! | >

| > Thanks, | >

| > ---Matt | >

| |

[RicodJour]

Drywall, regardless of the thickness, certainly is fire resistant. Gypsum has a lot of moisture in it (ever wonder why it was so heavy?). When the elevated temperature of a fire hits the drywall it releases some of that moisture which keeps it from burning/decomposing

- at least for a while.

Fire-rated assemblies are usually built with 5/8" Firecode, but your standard 1/2" drywall on wood frame is good for about half an hour of rating.

Here's one you might appreciate: about 20 years ago, when I was working as a construction manager in NYC - NYC is notorious for whimsical and strict code - a subcontractor produced a testing agency report that showed that standard 5/8" drywall lived up to the ratings as well as the 5/8" Firecode drywall. Hmmm, how odd. I can't imagine why a company would sell what is essentially an unnecessary "upgrade" for an markedly higher price. ;)

R

[3G]

| >

| > drywall is NOT fire resistant unless you use 5/8" with a skimcoat of | > plaster on both sides. it is typically more time consuming. | > fire rated fiberglass insulation is the best way to go. | | Drywall, regardless of the thickness, certainly is fire resistant.

the paper on 1/2" is different than 5/8 " and unskimmed drywall does not meet fire codes.

| Gypsum has a lot of moisture in it (ever wonder why it was so | heavy?). When the elevated temperature of a fire hits the drywall it | releases some of that moisture which keeps it from burning/decomposing | - at least for a while. | | Fire-rated assemblies are usually built with 5/8" Firecode, but your | standard 1/2" drywall on wood frame is good for about half an hour of | rating. | | Here's one you might appreciate: about 20 years ago, when I was | working as a construction manager in NYC - NYC is notorious for | whimsical and strict code - a subcontractor produced a testing agency | report that showed that standard 5/8" drywall lived up to the ratings | as well as the 5/8" Firecode drywall. Hmmm, how odd. I can't imagine | why a company would sell what is essentially an unnecessary "upgrade" | for an markedly higher price. ;) | | R

the paper on 1/2" is different than 5/8 " |

[DanG]

BS, Mr. 3G

I let yesterday's comment go, but now it gets ridiculous. If you have good information, please share it; but if your information is inaccurate, back off.

Remember, this is supposed to be a helpful source of information for construction/home issues. The OP simply asked for something easier than cutting wood blocks. I originally suggested drywall and/or fire rated expanding foam. I did not attack yours or anyone else's suggestions until you start making things up. At issue here is whether this is a fire rated wall or a smoke partition. It can almost not be a fire wall, so I assume it to be a smoke partition. Anything we come up with here has little to do with what OP's AHJ will accept. If the AHJ will buy blocks of Thermafiber, great! The inspector would seem to be asking for fireblocking just like putting cross blocks in stud chambers, I think he will require holding them in place, I sure would. Reference: If you have UL documentation to the contrary, I would like the information for my own uses.

I am not aware of any fire rated fiberglass batts or purposeful use in a fire rated assembly so do not understand your statement: skimcoat of

[Just Joshin]

I saw Lowes now sells spray in foam that has a 'fire blocking' rating.

tom @

[3G]

| If you have UL documentation to the contrary, I would like the | information for my own uses.

last time we did recessed cans in a garage ceilng the local inspector made us build a box out of 5/8" drywall and insisted that the entire box inside had to have 1 coat of plaster to meet firecode. He said and I quote "1/2 in. drywall is not sufficient for fire blocking and unplastered 5/8 in. drywall does not meet standards"

this is why I commented on this issue having been told this by an inspector. maybe code is different where you live,and maybe both of us are right in our areas. but BS it is not.

keep singing DanG

| | I am not aware of any fire rated fiberglass batts or purposeful | use in a fire rated assembly so do not understand your statement: | skimcoat of | > | > plaster on both sides. it is typically more time consuming. | > | > fire rated fiberglass insulation is the best way to go. | > | | > | Drywall, regardless of the thickness, certainly is fire | > resistant. | >

| >

| > the paper on 1/2" is different than 5/8 " and unskimmed drywall | > does not | > meet fire codes. | >

| >

| > | Gypsum has a lot of moisture in it (ever wonder why it was so | > | heavy?). When the elevated temperature of a fire hits the | > drywall it | > | releases some of that moisture which keeps it from | > burning/decomposing | > | - at least for a while. | > | | > | Fire-rated assemblies are usually built with 5/8" Firecode, | > but your | > | standard 1/2" drywall on wood frame is good for about half an | > hour of | > | rating. | > | | > | Here's one you might appreciate: about 20 years ago, when I | > was | > | working as a construction manager in NYC - NYC is notorious | > for | > | whimsical and strict code - a subcontractor produced a testing | > agency | > | report that showed that standard 5/8" drywall lived up to the | > ratings | > | as well as the 5/8" Firecode drywall. Hmmm, how odd. I can't | > imagine | > | why a company would sell what is essentially an unnecessary | > "upgrade" | > | for an markedly higher price. ;) | > | | > | R | >

| > the paper on 1/2" is different than 5/8 " | > | | >

| >

| |

[mwsenecal]

I checked and mineral wool is indeed the stuff! Thanks for the tip! I picked some up yesterday.

Thanks to all of you for helping me out with this. I appreciate it!