I-JOISTS FOR RAFTERS


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Is anyone familiar with the sub fascia and fascia material used when I joists are chosen to frame a roof. Below are some screenshots of a cross section and framing overview I did. If 12" i joists are used as shown in my design, then the fascia boards are obviously going to have to be wider. I have a 2x12 sub fascia, but what can be used for the fascia, ripped plywood then paint it? I'm not even 100% positive my lookouts will work at 2x10's. This is a request from the homeowner by the way, I didn't chose this material for rafters.

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5 minutes ago, Joe_Carrick said:

2x14's should work.  OTOH, I would design that with "Square Cut Eaves" vs "Plumb Cut".  Cutting the ends of the TJIs would be very difficult.

I agree on the square cut, you mentioned a good point.

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1x2 nailer at top 1x10 fascia at the bottom and a a 1x6 shadow nailed to both at top for a built up fascia.  Alternative is 1x2 nailers top and bottom with rolled metal wrap 

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When we cut the I joists we almost always make a jig which enables easy cross cuts. For a shed roof the plumb cut more easily enables you to create a drip curf at the bottom of the fascia. That drip is pretty critical since the water wants to travel right into the vulnerable spot where the rafter meets the plate at the top end. Detail the beejeezus out of that to get some liquid flash a that point (don't ask me how I know).

 

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Many details for this on the TJI website. If your keeping the full thickness for the overhangs you can use TJI's rim board for the sub-fascia and then build the fascia however you want. I'd shy away from wide thin boards in your neck of the woods

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I just did one with 14" series 230 i-joist rafters, and wanted a somewhat less beefy roof edge.  Lotsa pieces, but in short, a rimboard subfascia is there, capped with a pad piece and 1x12 Miratec trim board fascia, and a 1x6 Miratec shadowboard to cover the top.

2022-08-04 15_51_47-Window.png

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Agreed. That's a nice way to cover a large structural member w/ a layer cake of fascia. 

 

For good measure, it's always helpful to call out flashing, even if it's just a simple drip edge. 

 

That type of roof condition is prone to allow for capillary action below the top course of shingles. 

 

Even if the builder may have an excellent roofer, simple stuff like making a general note will make sure that you're covered for any unwanted dribbles. 

 

 

 

 

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2 hours ago, VHampton said:

Agreed. That's a nice way to cover a large structural member w/ a layer cake of fascia. 

 

For good measure, it's always helpful to call out flashing, even if it's just a simple drip edge. 

 

That type of roof condition is prone to allow for capillary action below the top course of shingles. 

 

Even if the builder may have an excellent roofer, simple stuff like making a general note will make sure that you're covered for any unwanted dribbles. 

 

 

 

 

Thanks.  I'll wait until there's a decision about roofing.  Owner's builder will present costs after bids are in for asphalt shingles, exposed-screws steel, and standing seam steel.  I'll detail it accordingly.

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6 hours ago, GeneDavis said:

I just did one with 14" series 230 i-joist rafters, and wanted a somewhat less beefy roof edge.  Lotsa pieces, but in short, a rimboard subfascia is there, capped with a pad piece and 1x12 Miratec trim board fascia, and a 1x6 Miratec shadowboard to cover the top.

2022-08-04 15_51_47-Window.png

what type of simpson strapping would be correct?

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TJI's typically require a squash block in order for the ties to be able to fasten.

 

The clip in the screen capture is fairly common even though the rafter is shown on the lower plate. (Same thing happens on the upper).

 

...and you're welcome Gene.  It's always good practice to leave nothing to chance when it comes to water infiltration. But from the aesthetic standpoint, usually exposed flashing always comes up in conversation at a later date, ...and since drip edge typically comes only white or brown aluminum, (or lead coated copper) there's always the chance for hemming and hawing in case they have to paint it to match the fascia.  

 

I could be wrong, but that type of roof flashing usually has a special riglet so that the top course of shingles gets tucked into a small notch.

 

 

Snip20220805_21.png

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4 minutes ago, VHampton said:

TJI's typically require a squash block in order for the ties to be able to fasten.

 

The clip in the screen capture is fairly common even though the rafter is shown on the lower plate. (Same thing happens on the upper).

 

...and you're welcome Gene.  It's always good practice to leave nothing to chance when it comes to water infiltration. But from the aesthetic standpoint, usually exposed flashing always comes up in conversation at a later date, ...and since drip edge typically comes only white or brown aluminum, (or lead coated copper) there's always the chance for hemming and hawing in case they have to paint it to match the fascia.  

 

I could be wrong, but that type of roof flashing usually has a special riglet so that the top course of shingles gets tucked into a small notch.

 

This is a link to a legit web site (home inspection forum), and the discussion was specifically about this type of roof and the flashing involved: https://forum.nachi.org/t/flashing-on-shed-type-roof/47043

 

 

Snip20220805_21.png

Those look a tad larger than simpson H2.5a's. I will research. Very helpful now that I see the squash block.

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You're quite welcome.  The Simpson site has wide variety of clips which meet the codes, but that one is pretty standard for high wind zones. 

 

A quick search will show pretty much all of the options. "seismic ties" or "hurricanes strapping" yields helpful results. 

 

 

 

 

 

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