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Old 03-17-2009, 11:55 AM   #1
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Upgrade to steel joists?


Hi everyone,

We have an approximately 100 year old home in Toronto. We had an excellent inspector come through yesterday and delineate the "must do" projects for structural integrity. The list is pretty long: excavate around exterior basement to replace weeping tiles/waterproof; replace all basement windows and replace vertical sections of brick and mortar above each window where exterior has shifted and cracked; install soffits, replace entire roof within 3 years; get permit to remove tree on adjacent property whose roots are eroding our basement and worsening shifting...

Just a partial list, to indicate that it's a big job, and we are committed to repairing the bones right to prevent future problems. We're going to defer to contractors for all this big stuff. We have some money to work with but of course don't want to misspend it.

The area is also a termite hot zone. The wooden joists in the basement ceiling show some evidence of some past damage. The joists are also sagging and must at least be sistered.We were informed that spraying can stall termites for perhaps 3 years at best, and we are also very concerned about cancer risks with pesticides.

The home is only 14' wide by 30' deep. We know that steel joists are uncommon in residential properties, and that such a narrow home may not *need* steel. But we are paranoid about the termite issue, and aware that steel may be more affordable now that prices have plummeted.

Is this a terrible idea?

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Old 03-17-2009, 01:20 PM   #2
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Using steel doesn't completely eliminate the wood from your home, so the termites will just go 12" higher and eat your floor sheathing and wall framing.

Steel joists are nice for some things, but I don't know that the means justify the end result in this case. Furthermore, steel is awful in a fire, rendering the entire floor system very unsafe shortly after exposure (not the case with wood).

An option you might really look into when replacing the joists (since you have to anyway) is wood treated with borate. The termites won't touch it, and it is reasonably available in most areas.

No construction material is a good substitute for proper treatment of the soil surrounding the home. There are bait stations available that should put your cancer concerns to rest.

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Old 03-17-2009, 02:59 PM   #3
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Excellent points. I will look into the borate-treated wood and termite approach you mentioned.

Thanks!
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Old 03-17-2009, 04:09 PM   #4
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I agree with your post that the means do not justify the end but, if there was a fire hot enough to weaken steel wouldn't the wooden floor joist most likely burn in the fire?
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Old 03-18-2009, 09:08 AM   #5
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I agree with your post that the means do not justify the end but, if there was a fire hot enough to weaken steel wouldn't the wooden floor joist most likely burn in the fire?
Absolutely. A wood member will ignite and burn, but it takes some time for it to lose its structural integrity to the point of collapse...Often 20-30 minutes for 2x dimension lumber in full exposure to fire. Wood chars, which actually keeps it from burning all the way through in short order. A light gauge steel joist will weaken within a comparatively shorter (a couple minutes) time period when exposed to the same heat/fire. When light gauge steel weakens you don't want to be standing on it or have bearing walls sitting on it because it loses pretty much all of its structural integrity and ends up in a pile in the basment. At least the wood gives you some time to get out and gives the fire department a chance to save the structure, which involves entry into the structure.
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Old 03-18-2009, 10:44 AM   #6
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Before you deal with the "termite" problem, you should get a termite expert in to determine if you actually have (or had) termites, or some other insect like powder post beetles, or carpenter ants. The treatment for insects is insect specific, and you need to know what you have before you treat.

I moved into a 40 year old house some years ago that had been vacant for six months, and our inspector pointed to areas where powder post beetles had been active, as well as carpenter ants. No termites. Turns out that carpenter ants only attack damp wood, whereas true termites will eat dry wood. The solution in our case was to repair the exterior damage that was allowing moisture into the space, and treat the ants with borate (done by an exterminator). Nineteen years later, no ants, no further problems. But if you have termites, that is a whole different story.
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Old 03-18-2009, 02:54 PM   #7
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In an extension of the time-to-failure discussion of joists exposed to flame induced hi temps: I saw recently a news report comparing the composite I-beam joists (OSB web with wooden rails) to dimensional 2x joists. Because the I-beams lacked the ability for protective charring, and beause the glue used is flamable, the floor structure collapsed under fire quite quickly and without warning. The report cited several incedints of fire-fighters suffering injury. The manufacturers association is reportedly working on next-gen designs that will include flame retardants or something

Thought it of general interest.

Also, with reference to the poster above, is it true that dry wood is not subject to carpenter ant attack?
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Old 03-18-2009, 04:10 PM   #8
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Rizzo is right about I-joists. To address this, the next code cycle of the International Residential Code will require the installation of sheetrock on the underside of all I-joist floors, whether the area below is finished or not. The fire protection lobby got that pushed through the ICC's voting. Not sure if the code language will address light gauge steel framing, but it should.
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Old 03-18-2009, 08:14 PM   #9
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just a quick question. what exactly do you guys consider to be "light steel"? i work almost exclucivly with sleel stud frameing in New york city. we probably have some of the toughest building code when it comes to fire in the country. i find it odd that if steel was so weak we would be useing it in so many buildings. sorry for the bad spelling.
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Old 03-18-2009, 11:47 PM   #10
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just a quick question. what exactly do you guys consider to be "light steel"? i work almost exclucivly with sleel stud frameing in New york city. we probably have some of the toughest building code when it comes to fire in the country. i find it odd that if steel was so weak we would be useing it in so many buildings. sorry for the bad spelling.
They're 12, 14, 16 and 18 gauge.

Steel studs are incredibly common, especially in multifamily construction. They're typically used in noncombustible construction, and that type of building often has fire sprinklers as well. Not always, but often. As a wall system they're plenty strong, but in unrated construction where the members aren't protected they do in fact prematurely compromise in a fire. There's just less fuel contributed by a noncombustible structure, and suppression systems are often added, so the likelihood of a fully-involved fire is lessened.

This is fire protection 101. Even heavy gauge (red iron) steel structures are weakened in fire, often to the point of failure. Buildings framed from heavy timber will stand much, much longer than steel framed buildings given the same fire/heat exposure.
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Old 03-19-2009, 07:25 PM   #11
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Upgrade to steel joists?


Quote:
Originally Posted by rizzo View Post
In an extension of the time-to-failure discussion of joists exposed to flame induced hi temps: I saw recently a news report comparing the composite I-beam joists (OSB web with wooden rails) to dimensional 2x joists. Because the I-beams lacked the ability for protective charring, and beause the glue used is flamable, the floor structure collapsed under fire quite quickly and without warning. The report cited several incedints of fire-fighters suffering injury. The manufacturers association is reportedly working on next-gen designs that will include flame retardants or something

Thought it of general interest.

Also, with reference to the poster above, is it true that dry wood is not subject to carpenter ant attack?
I would take issue on the wet/dry wood issue! I stored some spruce studs on saw horses, in my garage (detached)over winter! Come spring some of these studs were completely hollowed out by carpenter ants!
It was like picking up a balsa wood 2X4.
No moisture came in contact with thgis lumber, as it was covered by a plastic sheet.
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Old 03-19-2009, 09:30 PM   #12
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Upgrade to steel joists?


thanks for the clarification Thekctermite. i actually did a little research on the subject today and came up with similar results. i'm just the carpenter; not the designer...

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