Exsisting joist change to scissor type joist?

Redwolf947 · Feb 28, 2015

Hey all,
I have a 22'x22' attached garage. The structure was built in the 50's. The ceiling height is 9'-4"ish. There are 17 sets of rafters including the gable end rafters. There are 5 rafter ties that are 20' with a 2' extension 2x4 on the ends.

So, what I want to do is add scissor type joists where there aren't joists. Then change the 5 over as well? I'd think this would add more support and make a little more room for lift height and make it easier to insulate.

Is this possible?

Redwolf947 · Feb 28, 2015

bump
Anyone think this would be a good idea bad idea? Any thoughts suggestions..
anything welcome.. Thank you

Denwood · Feb 28, 2015

A ridge beam will get you a lot more height and be easier to do.

The first page of my build thread has all the details. I left a 4ft loft section at both ends so also installed cross beams to take the ridge load to side walls.

Turned out pretty cool:

Redwolf947 · Feb 28, 2015

Wow that would be Cool.. Turned out pretty Awesome. What does one of those beams cost if you don't mine telling or PMing? that's a lam beam right?

Nakashige · Mar 1, 2015

Can you do anything like this with a hip roof

Denwood · Mar 1, 2015

The 3 "VersaLam" beams totaled $650 delivered. I included the load specs and engineering data on page one of my build thread.

Sure you could this with a hip roof. You would need the cross beams for sure, and likely would leave the hip itself alone.

Dan in Pasadena · Mar 1, 2015

Dennis,
I'm curious, hope you dont mind a few questions:

The rafters just sit on the roof beam, there's no connection, toe nailing, etc?

It seems like the beam perpendicular to the main ridge beam; the cross beam, would have greatly reduced weight bearing capacity because it's section has to be reduced in order to make it bear on the walls. Is this correct or am I misunderstanding?

Also, the way the ridge beam load is transferred to the cross beams seems to bear on the two 2x4's or 2x6's and the other two are just to lock it/keep it in place. Is this correct?

CNGsaves · Mar 1, 2015

Probably good that Denwood is replying to OP since Denwood is in Canada while OP is in Wisconsin . . . . both of which will have snow loads on roof.

OP . . . what is construction of outer roofing material . . . shingles or metal??

Overbuilding like Denwood did in Canada would be good idea for OP as the old rafter setup of OP looks pretty skimpy when considering snow load in WI.

+1 to pursue beam idea (ie LVL or 2x12's sandwiched) and spray foam directly on underside of roof.

Redwolf947 · Mar 1, 2015

CNGsaves said:
Probably good that Denwood is replying to OP since Denwood is in Canada while OP is in Wisconsin . . . . both of which will have snow loads on roof.

OP . . . what is construction of outer roofing material . . . shingles or metal??

Overbuilding like Denwood did in Canada would be good idea for OP as the old rafter setup of OP looks pretty skimpy when considering snow load in WI.

+1 to pursue beam idea (ie LVL or 2x12's sandwiched) and spray foam directly on underside of roof.

....
Well not sure about the 'code' here if i could do that? :dunno:

The roof is Architectural shingles.

I agree when I saw that roof system the first time I was surprised at how weak it looks..

I wont be doing the spray foam tho too expensive :sad:

But will use R-19 bat at least.

I see his main ridge board is sub level to the rafters. and looks like 2x material. I think mine has 1" board as the main ridge board so I wouldn't be able to 'rest' my main board on the LVL beam..

Redwolf947 · Mar 1, 2015

Denwood said:
The 3 "VersaLam" beams totaled $650 delivered. I included the load specs and engineering data on page one of my build thread.

Thank you Denwood and CNGsaves for your reply's.

Denwood where did you get that heater in the first pic?

Denwood · Mar 1, 2015

Red, the heater is a hanging Reznor space heater converted from propane to natural gas. It came with the shop..likely 20+ years old. It heats the shop very quickly.

Dan, the supporting ridge beam is sitting under the original ridge, and secured to it using metal straps (like larger hurricane straps). The ridge beam load is taken down to the cross beams using 4x4s, strapped in turn on all four sides with PL premium bonded/screwed 2x6s. The cross beams are cut to sit over the existing wall, and I've added two additional 2x6s at each wall (glued and screwed) to add support down to the garage footing. The beams and install was engineered to take our snow load which can be very high. Page one of my build thread has engineering detail. Here's are pics of some structure stuff. A lot more in the build thread linked in my signature.

Spray foam can reduce racking movement in stick frame structure by over 50%. I'd say that is the case here as even in the worst we've had this winter, I haven't heard a single creaks or squeak. It's definitely a lot stronger now than it was previously.

Redwolf947 · Mar 1, 2015

Thanks Den

Denwood · Mar 1, 2015

You're welcome. Just posted this in another thread which may be helpful. It's a screen grab of two truss alterations done during Cinevate's net zero (ish) building project. The top section shows clerestory truss mods, the bottom section shows the truss mods to attain an 11ft ceiling in our film studio. Studio is about 30x30, double walled STC 60 sound rated, blah, blah.

The lower image shows the profile of glue/screw plywood added to the trusses (both sides) in place to effect the new ceiling profile. It went from 8ft to 11ft at the vault. Very cool space now as the entire studio is painted flat black. I'm posting these as the truss company basically said an in place mod was not possible. It is! These drawings are from the architect, with an engineers stamp.

Redwolf947 · Mar 1, 2015

Yes I was reading that thread. That's pretty cool thanks for the heads up tho. You think a raised tie setup with glued and screw/nailed plywood work as an alternative.. the plywood covering all the truss joints for strength? If I had and could remember how to use a good cad program to draw it up.. maybe I'll have to draw and scan it in hurmmm..

Denwood · Mar 1, 2015

Definitely have an engineer run the numbers once you've baselined your existing setup. There is some framing detail (at the new ceiling line of the truss) to do as well if you clad a truss both sides.

Redwolf947 · Mar 1, 2015

OK I doodled up this sketch its not to scale.. The raised tie would be the max allowable I think that's 1/3 of the height of the rafters? The shaded areas would be plywood screwed glued over 2x material. I would be doing this for all 15 rafters effectively making them all trusses. As stated before there are only 5 tie joists as of now. I think I'd put in a pull down stairs near the back for running new drops or anything after the walls are finished. or at least a scuttle hole.

Sorry the scanner picked up the printout on the back :willy_nil

that's the 2nd image shown. That's my basic plan for outlets and lights.

And again thank you Denwood for your information.

Denwood · Mar 1, 2015

If you're going from 5 truss ties, to this structure x 15, the result would be much stronger than existing. It would be a lot more work than a ridge beam, but gives you plenty of room for standard insulation and venting.

Redwolf947 · Mar 2, 2015

Right now the ties are extended 2x4's would you suggest 2x6's and maybe 9 instead of 15?..

What type of ply OSB or?

Thickness of ply 5/16" or 1/2" or?

Still a lot of work but I do have a pneumatic framing nailer

.

My plan is for a portable 4 post lift. I'd move it to the middle for working I could then work on my Stang inside but lift my F250 outside.

Thanks again you've been a great help Den.

Kaizen · Mar 2, 2015

Red i did something similar in my kitchen with barn beams. From my research most say you can move the ties up 1/3 of the height of the roof. I had 2x6 rafters full dimensional lumber there and i gluedand screwed in a 2x8 if i remember right onto the edge of it cut to fit at the ridge and onto the wall. then i put in collar ties at the ridge out of 2x12s cut to fit about a foot down. I replaced 6 2x6 ties with 4 9x9 barn beams but right under the top ledger. did just fine this year with all the snow. i would recommend for you using bigger the 2x6 if you are going to put stuff up there of any weight. since i didn't get an engineered plan i overbuilt it. also my rafters were not all 16 on center. some were 2 ft some were odd so i did this on every one. you can probably get away with less
oh should go without saying but don't cut out old till new is done

Redwolf947 · Mar 2, 2015

Kaizen said:
.... I would recommend for you using bigger the 2x6 if you are going to put stuff up there of any weight... ..since i didn't get an engineered plan i overbuilt it... ..you can probably get away with less
...oh should go without saying but don't cut out old till new is done

Thank you Kaizen.. This would not be used for any storage just insulation. It never hurts to build it stronger than needed I'll probably do all 15 to make insulating easier and to 'overbuild' it. And you are correct I'd install all (or as much as I can) new framing before removal of the old :thumbup:

.. But that's always good to add some don't think that far..

Redwolf947 · Mar 22, 2016

Well I've saved some cash and am looking at this part of my garage upgrade again. I'd love to go with a ridge beam like Denwood but don't feel I could acomplish this without alot of help. Also my garage is somewhat wider and the larger lvl bears get fairy expensive. Installing 15 2×6's 1'9" higher and simply nailing them in like a standard rafter install would be stronger than what I have.

The issue here is I'd like to be able to get a lift and raise not just the mustang but my truck too.

Here is the question is it possible to raise the rafters and frame an 8' square in the center for the cab of my truck to raise into? :dunno:

any suggestions thoughts comments???

Redwolf947 · Mar 23, 2016

Bump... ^^^^
Any thoughts of this? Is it possible or just too far fetched? 8' square double joists on each side maybe even double headers?

Note: This is an attached garage so one of the walls the joists are attached to are also attached to the house.

View media item 52777
The dry walled section is the wall between the house..

Thanks to anyone willing to try to answer or comment on this..

Redwolf947 · Apr 22, 2016

Seeing as I'm no longer trying to go with a Scissor type joist setup I started a new thread:

Raised tie ceiling joists in attached garage
http://www.garagejournal.com/forum/showthread.php?t=324278

This has my progress on this project!

Exsisting joist change to scissor type joist?

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