1 hour fire rating on exterior deck post??
Hello to all,
I am performing a deck repair for a client that requires a new post be placed that lands on a new footing. It turns out that we will be placing this new post such that it falls within 24″ and 36″ of the property line. This condition can’t be changed. As such, our building department is requiring that the new post have a 1 hour fire rating. Normally, an 8×8 will pass the 1-hour fire rating but in this case, due to the load and height of the post, the engineer has calculated that the minimum size required is 8 3/4″ x 8 3/4″ so we are talking about a pressure treated 10x10x20. I’m finding this to be a tough stick to procur, not to mention how ridiculous it will look.
One distasteful and prone to failure option would be to use a 6×6 and wrap it in type X gypsum followed by cedar or Hardie panel. Another possibilty is an intumescent paint coating which I can’t confirm meets 1 hour fire rating.
Does anyone here have any experience with achieving fire ratings on exterior timber?
Replies
Cement siding would do it - it's the same stuff as the hardy panel just in strips. Keeps the wood look too.
If you go with cement siding, and use an air gap it might negate the fire rating.
Air gap allows the fire to get straight to the wood.
I'm not sure, but just thought you might want to make sure.
Shouldn't, if the seams are tightly sealed (either caulked with fireproof caulk or mudded with fiberglass tape and thinset or some such).
Yeah, either some sort of cementatious material (exterior gyp board, Hardi siding, etc) over wood, or a steel post.
The problem with the wrapped wood is that the wrapping will with near certainty promote rot. I'm not sure how to deal with that other than to use rot-resistant wood and put the wrapper over lath so there's a small air gap. (Wrapping in rubber will unfortunately hold in any moisture that gets inside.)
Maybe some kind of laminated post....
We have them here and I believe they are rated higher than solid lumber, but I'm not gonna bother to look it up as I live on the right coast and what we get here you don't get there.
We used some 10x10 T as beams. A 10' piece weighed about 300 pounds.
I would wrap a metal post in redwood or other rot resistant wood. We put little round vents top and bottom to let out moisture.
KK
Just a thought...
why not a steel column, then wrap with whatever you want for cosmetic purposes?
Jim
Edit: That was wierd - I post then two other posts show up above it suggesting the same thing - steel.
Maybe laminate six 2x8"s, all
Maybe laminate six 2x10's, all PT? They would resist the twisting that you usually get with a solid timber of that size.
There's no easy way out; whatever you're doing, the codes really don't want you to do it. That's what 'setback' requirements are all about.
It's a serious matter; anyone who watches western wildfires has seen them jump across fire breaks and six lane freeways; the requirements are inspired by real-world experience. Remember the Oakland fire - where one house stood intact, while every neighboring house was reduced to a slab?
It might help you to understand just what a '1 hr. fire rating' means. I simply means that an example of the construction has proven itself by withstanding one hell of a test fire for an hour. Not only did it survive ... it also failed to get hot enough on the 'protected' face to ignite stuff near it. If it was supporting a load, it continued to support that load.
With that in mind, it's not just the post that has to meet the test; EVERYTHING near the property line does. This means the roof, fascia, decking, etc. This goes well beyond simply wrapping everything in drywall; you really need to have a professional sign off on the plans. We're out of DIY territory.
While I agree with you, I don't think the Oakland Hills fire is a good example.
That was primarily caused by Eucalyptus deadfall debris which hadn't been cleaned up from a heavy frost the year before. Dry brush, winds, and other difficulties.
If you pile up highly flammable debris around any house / neighborhood it is dangerous. Especially a windy, winding, hillside.
A 1- hour fire rating won't help you in a 107 alarm fire...
I do agree with the spirit of your post though. Fire = dangerous.