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Old 02-08-2009, 12:11 AM   #61
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How to fireblock framing


I definately encourage those of you working on framing basements, etc to post fireblocking-related pictures or questions on this thread. The more pictures there are, the more people will learn about how to do it right.

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Old 02-08-2009, 12:42 AM   #62
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How to fireblock framing


Another thing I thought of...

If the stairs of a structure are compromised in a fire you may lose your only way of getting out of the structure. Or, you might fall through. Or, a firefighter might fall through. It is definately beneficial to keep fire out of the stairs.

The concealed space between stair stringers must be fireblocked at the top and the bottom. More often than not, the framing method automatically takes care of the fireblock. Stairs often hang on a band joist or beam of some sort, which effectively keeps the opening between the stringers from being connected to the space between the floor joists. For instance, if you're framing with floor trusses you're hanging your stair on a truss that has openings. So, a fireblock would be required at the top of the stairs to prevent a floor fire from compromising the stairs.

The bottom of the stairs is fireblocked automatically if the floor is sheathed with 3/4" sheathing. If there are any holes or gaps of any kind (wires, pipes, etc), fireblock them.

Here's what we're aiming for...
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Old 02-08-2009, 12:48 AM   #63
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How to fireblock framing


When you have a wall adjacent to a set of stairs, you must prevent the wall studs from opening up into the concealed space under the stair.

Sometimes stairs are framed unconventionally. That is the case with winder stairs or circular (not spiral) stairs. A conventional stringer usually isn't used. Instead, each wedge-shaped tread is supported by horizontal framing that is supported by studs in an adjacent wall. A block is needed in this circumstance. I find it easiest to locate the block in the wall instead of under the stair. A 2x4 block between the studs just under the concealed space under the tread (and often just above the tread, depending on the wall) does the trick.

I'll work on getting a picture of this as soon as I can find one!
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Old 02-08-2009, 01:31 AM   #64
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How to fireblock framing


In your picture in post #62, should the floor joists under the floor at the top of the stairs be enclosed/fireblocked so that a fire underneath couldn't weaken the floor right there? It seems like the stairway is being fireblocked, but not the floor at the top.
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Old 02-08-2009, 08:59 AM   #65
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How to fireblock framing


Strange as it may seem, a fire is allowed to move around in a floor system based on the code requirements (not that the fire really cares what the code says). Fire can generally move freely through horizontal elements of the building such as soffits, floor systems, etc. So Gma2rjc, the answer to your question is that the intent of a fireblock at the stair is to protect the stair. An added benefit of the fireblock at a stair (when needed) is that it keeps a fire in one floor from moving to another floor within the concealed space between the stringers.
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Old 02-08-2009, 09:26 AM   #66
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How to fireblock framing


Discussing floors makes me think of another thing. Draftstopping. Draftstopping does basically the same thing as firestopping, although the requirements are a little different.

Here's the issue:
Draftstopping is required in basically two scenarios.

First, open web floor trusses. Since the trusses are webbed members as opposed to solid like 2x10's or I-joists, a fire in the floor on one side of the house could have incredible amounts of oxygen to feed itself since it can pull air from the entire floor system. If the floor area exceeds 1000 square feet and it isn't broken up by solid members such as beams, draftstopping is required to partition them off.

Second, framed dropped ceilings. It is common for basement ceilings to be dropped to allow space for HVAC, plumbing, and architectural features such as curved soffits. When these dropped ceilings exceed 1000 square feet, they must be partitioned off by draftstopping. So basically, no part of the concealed floor system should have non-partitioned portions that exceed 1000 square feet. Dropped grid-type ceilings with ceiling tiles do not require draftstopping.

Draftstops pretty much work exactly like fireblocks, but the material requirements are lessened. You can use 1/2" wallboard or 3/8" plywood/OSB, whereas a fireblock requires a minimum 3/4" thickness of plywood/OSB. On a dropped ceiling it is often necessary to frame something to attach the draftstop to. On a truss floor the draftstop is normally applied to the side of a truss.

It makes sense to locate the draftstops so that they're as minimal as possible. Using features such as stair openings and beams to your advantage will really minimize the length of the required draftstops in most cases. It also pays to pick areas that have as few plumbing, HVAC, and electrical penetrations as possible...Those are no fun to cut around when placing a draftstop.

If you're finishing what was an unfinished basement with trusses or a framed/sheetrocked dropped ceiling, your house didn't have draftstops and didn't need them until now. That's because the floor system wasn't concealed until you decided to conceal it. As with fireblocking, draftstopping is only required in concealed spaces. So now that you're concealing the ceiling, plan on draftstopping if there are 1000 square foot sections of uninterrupted floor.
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Old 02-08-2009, 09:34 AM   #67
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How to fireblock framing


I doctored a picture from earilier in the thread to illustrate how a draftstop would be applied in a truss floor system.
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Old 02-08-2009, 11:40 AM   #68
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How to fireblock framing


not that is necessarily means anything coming from me, but;

I'm impressed KC. You put on a great demo via this forum (I realize how tough it can be) and you have shown yourself to be very knowledgeable on the subject at hand.


great job
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Old 02-08-2009, 01:25 PM   #69
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How to fireblock framing


Well said, nap.
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Old 02-08-2009, 02:24 PM   #70
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How to fireblock framing


Thanks for saying so Nap. Much appreciated. Hopefully it helps somebody out and saves them from failing an inspection!
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Old 02-08-2009, 08:24 PM   #71
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How to fireblock framing


Quote:
Originally Posted by thekctermite View Post
Thanks for saying so Nap. Much appreciated. Hopefully it helps somebody out and saves them from failing an inspection!
Actually, the inspection, to me, is secondary to the real reason fireblocking should be done properly and that is;

to prevent the spread of a fire so as to save as much of the building as possible and to save lives.
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Old 02-08-2009, 08:28 PM   #72
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How to fireblock framing


Absolutely!
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Old 02-09-2009, 12:17 AM   #73
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How to fireblock framing


Are there materials available on the market to build a house that is almost fire-proof? For example, foundations are already made of cement, but what about above-grade and second-story walls, second-story floors, etc.?
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Old 02-09-2009, 08:26 AM   #74
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How to fireblock framing


Quote:
Originally Posted by gma2rjc View Post
Are there materials available on the market to build a house that is almost fire-proof? For example, foundations are already made of cement, but what about above-grade and second-story walls, second-story floors, etc.?
There definately are, although costs make it largely prohibitive.

First, fire retardant treated lumber is available and widely used in commercial construction. It is southern yellow pine that is treated with chemicals that essentially render it fireproof. Dimensional lumber and plywood is available with this treatment. Here is the website of one manufacturer: http://www.frtw.com/

You can even get fire retardant treated lumber with an exterior treatment for use on decks, pergolas, etc.......... (it isn't beautiful).

When talking about non-combustible residential construction, a lot of people instantly jump in the corner of light gauge steel framing (steel studs, steel joists, steel roof trusses). Although steel has its attributes, I think that is a mistake. The benefit of steel is that it won't contribute fuel to a fire, a fire has a hard time spreading in concealed spaces, and fireblocking is not required if the home is built completely noncombustible. However, homes are full of fuel whether their construction is combustible or not. If the carpet, furniture or stored items catch on fire, the heat from a fire will compromise the steel building's structural integrity in very short order because the light gauge steel quickly softens. A wood structure may burn like crazy, but won't completely lose its structural integrity right away because it takes time for the wood members to burn through.


C-channel light gauge steel joists.

There are some spray-on chemicals that will make combustible products fire-resistant (such as furniture, wood, drapes, etc), but that's a topic for another thread.
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Old 02-10-2009, 07:01 PM   #75
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How to fireblock framing


While on the subject of stairs, as an owner of a rental property, I was required to install 5/8" drywall on the underside of the grade landing! It was a provincial regulation! The intent was prevent evacuees and firemen from falling through the floor, should fire occur underneath. I thought that this was a good idea and mention this as an adjunct to your post about fire blocking a staircase!

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