My New House & Workshop

[1990RangerinSK]

@Jim Oaks

I’m about 100 miles away from home doing a property inspection on 81 acres in about a dozen buildings, so I can’t send you something right at this minute.

A few of your sketches are a disaster waiting to happen, but a couple of them have potential. And @1990RangerinSK Inspired me, with something you can change, something you can implement pretty easily with a little money. I’m swamped again tomorrow but I should be able to get you something by Friday

I'm guessing that the ones that are a disaster are the ones where the upper joist doesn't attach to the rafters. It creates a pivot point where the original ceiling level's joists end. Right?

As for me inspiring you, thank you. I'll be interested to see what you come up with.

 

[Jim Oaks]

If I just went with something like Example 7 or Example 8 below I could just drywall the joists and move the whole ceiling area up instead of having a pocket, tray, whatever. The good thing about that is I'd really only have to buy one long 2x6. Once I put it in place I could take out the original ceiling joist below it, cut it down to size, and mount it above the next joist to come out.

Here's an article I had found at https://www.jlconline.com/how-to/framing/raising-ceiling-joists_o

Q: A client wants to create a vaulted ceiling in an addition with a shallow, 4:12-pitch roof. The rafters are 16 inches o.c., with no structural ridge. Can I raise the ceiling joists to create the vaulted ceiling?

A: Darren Tracy, PE, owner of West Branch Engineering, in Saratoga Springs, N.Y., responds: Yes, you can raise the ceiling joists, but with restrictions. Because you do not have a structural ridge, you must utilize rafter ties. Ceiling joists can serve as rafter ties to resist outward thrust on the walls from the rafter loads if they are installed parallel to the rafters and in accordance with code.

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In a roof with a non-structural ridge, rafter ties (which resist the outward thrust of the rafters) can be raised a maximum distance (HC) that is no more than one-third the distance between the top of the supporting wall plates and the top of the ridge (HR). Collar ties (designed primarily to resist wind uplift) must be located in the upper third of HR.
Figure R802.4.5 of the 2018 IRC states that a rafter tie can be raised a maximum distance of “HC” above the top of rafter support walls. HC is determined by a simple formula in which that height is a function of the ridge height (HR): The ratio of HC/HR cannot exceed 1/3 (see illustration). For example, in a roof structure where the ridge height is 9 feet above the top of the support walls, the maximum height that a rafter tie can be raised is 3 feet (3/9 = 1/3).

Additionally, be sure to adhere to the specific fastening requirements in the 2018 IRC Table R802.5.2 for the rafter-to-rafter-tie (ceiling joist) connections. That table provides the number of 16d nails at each connection based on rafter slope, rafter spacing, and snow load.

Section R802.5.2 also states, “Where the ceiling joists are installed above the bottom third of the rafter height, the ridge shall be installed as a beam.” In other words, to raise the ceiling joists more than one-third of the ridge height, a structural ridge would be required. With a properly engineered structural ridge, rafter ties can be eliminated completely. Also section R802.4.4 states that a roof with a pitch less than 3:12 requires a structural ridge.

As a final note, do not confuse rafter ties with collar ties. Collar ties, which are designed primarily to resist wind uplift, are required in the upper third of the attic space. Unlike ceiling joists, collar ties can be made of less-substantial material (1x4 minimum) and can be spaced up to 4 feet apart. Ridge straps can be used in lieu of collar ties to resist uplift.

Misc Photos

Here's a couple of photos I found online of some raised ceilings.

 

[don4331]

@Jim Oaks

All the examples you are showing pictures for are examples of roofs with much steeper pitches that your building; that includes your and @1990RangerinSK's diagrams.

Per code: section R802.4.4 states that a roof with a pitch less than 3:12 requires a structural ridge - from what I'm reading in previous posts, your roof has a pitch of 2.75:12. Which means if you touch the rafters, you MUST are supposed to change the ridge to be a structural member to meet code. If you change the ridge to be a structural member, you have lots of choice after.

I know I'm party pooper.

 

[Jim Oaks]

What is a structural ridge?

Say basically you're saying the 1x8 board at the peak should be a 2x?. If I read the right thing, they're supported at the end. Thos is a hip roof. I haven't paid attention to the end.

So are you saying this roof wasn't built correct? Maybe I better double check my measurement.

 

[85_Ranger4x4]

 

[don4331]

What is a structural ridge?

Say basically you're saying the 1x8 board at the peak should be a 2x?. If I read the right thing, they're supported at the end. This is a hip roof. I haven't paid attention to the end.

So are you saying this roof wasn't built correct? Maybe I better double check my measurement.

@Jim Oaks: @85_Ranger4x4 's picture is worth 1k words: Basically it needs to be 4X material (or better, depending on exact length) and supported by post (on a pad) from ground to the beam at each end (If supported at end of the original building, you can get away with less).

Building specs evolve with time - the latest rendition dates from 2018. So, it might have met code when built and code updated since. And if you're that close, you should be doing it correctly, not double checking measurements.

 

[Jim Oaks]

I checked it again holding a level up to the underside of the roof and measuring up at the 12-inch mark. Still 2.75".

 

[Jim Oaks]

Did a quick search to see if there were any discussions online about roof pitches below 3-12 without a ridge beam.

Read this:

"Saw a 3/12 pitch roof today with a ridge board instead of a beam. I think it should be a beam, not a board for that little of a slope."

Reply:

"A 3/12 slope is the lowest acceptable in the code for a ridge board. If no sagging, and the rafters line up opposite each other, should work.

From the 2006 IRC. (underlining is mine)

- R802.3 Framing details.

Rafters shall be framed to ridge board or to each other with a gusset plate as a tie. Ridge board shall be at least 1-inch (25 mm) nominal thickness and not less in depth than the cut end of the rafter. At all valleys and hips there shall be a valley or hip rafter not less than 2-inch (51 mm) nominal thickness and not less in depth than the cut end of the rafter. Hip and valley rafters shall be supported at the ridge by a brace to a bearing partition or be designed to carry and distribute the specific load at that point. Where the roof pitch is less than three units vertical in 12 units horizontal (25-percent slope), structural members that support rafters and ceiling joists, such as ridge beams, hips and valleys, shall be designed as beams."

Another Reply:

"As usual JP is right on. Many older houses in this area have ridge boards, mostly T&G 1/2" x 6" (sheathing boards), regardless of the roof pitch (pre-date the modern codes). Some real old ones have no ridge boards at all, remember that wood shingles on nailers common then are a a pretty light roof covering.
If there are no sags in the roof it should work."

Discussion:

Ridge beam or ridge board

Saw a 3/12 pitch roof today with a ridge board instead of a beam. I think it should be a beam, not a board for that little of a slope. Asphalt shingles over ice and water shield from top to bottom. Very cold today not above 10F.

www.inspectionnews.net

When I'm done remodeling the building I plan to replace the shingles with a metal roof. It's also my understanding that metal roofs are 50% lighter.

At least my rafters line up.

 

[Jim Oaks]

"To resist thrust, the IRC calls for a structural ridge (required for any roof with a pitch less than 3/12) or for each pair of rafters to be securely connected to each other by a continuous ceiling joist (R802.3, 2006 IRC)."

Rafter Ties and Shallow-Pitch Roofs

Q. My clients have a garage with a conventionally framed 4/12 roof that they want to convert to living space. They like the idea of a vaulted ceiling but not the expense of the new structural ridge it would require. As a compromise, can I replace the existing ceiling joists with rafter ties?

www.jlconline.com

I do have continuous ceiling joists.

There is a 2x6 ribband that runs the length of the building in the center of the joists that I guess keeps them from twisting.

 

[Jim Oaks]

Cut the roof from one side to the other as wide as you want. Run a strong-enough cross member under both sides. Jack it up, and set it on stub walls. You’ll have to run angled braces from the middle or lower half of the stub all’s to minimum 2’ into the bottom rafter to keep the elevated section from folding over. I can help you with what the “string enough” support etc looks like when you have your dimensions for elevation (how wide & how tall, and what the angle braces should look like.

I'm not understanding what you're saying.

I like example 6, personally. Except that I see a problem. The end of your existing ceiling joist is unsupported. I'm not an engineer, but somehow I don't think that hanging the ceiling joist off of the new joist will be enough. I would think that you'd need to support it from underneath. @don4331 what do you think?

This might work better (note that it's not drawn to scale):

I've eliminated the need for supporting the inside end of the existing ceiling joist. Now, the end of the joist (or is it now a rafter?) is attached to, and supported by, the collar tie, and the opposite joist (rafter?).

This looks like a scissor truss. Can I modify my ceiling joist / rafter in to this?

I think this guy did something similar to what you're suggesting:

 

[Rick W]

Here ya go, obviously I did this very quickly. The strength is in the triangle, whether it’s one or a combination of several. Right angles are very week if not part of a triangle. The shorter the short side of the triangle, the weaker it is.

@Jim Oaks examples 2&3 will fail, dangerous. Examples 4,5,6 & @1990RangerinSK second/horizontals example are weak, but they’re covered in my second example, you could use that.

Snowy’s example one will also fail, but it was the inspiration. It is not a scissor truss. In a scissor truss the lower angled members have to tie in to the higher angle member on the opposite side directly. The way Snowy has it drawn, under a heavy load, the two lower angles would push up into the horizontal and snap it in half just before the whole roof came down. But it was a valiant effort and I honor him, except for the whole roof falls down part.

First, DO NOT remove the existing crossmember until the new pieces are glued and screwed and glue is set (typ 3 days). Weatherproof liquid nails, a lot, 2-1/2” torx deck screws.

You can modify the existing pieces into a scissor truss. Before you proceed, I’d need to know the size of the 2xs, and lengths. If it’s too shallow, it will fail, but I know several ways to strengthen it. So this is a start.

Important: if the free space between the ridge board and new lower angle boarded is less than approx 3ft, we have to rethink it. If it’s 4-5 better. So, pull a couple strings where these scissors will be and measure up from the floor to see if you get the clearance you want at the 4 corners.

See “blueprints”

While I put in the option of just moving the crossmember higher, I cannot impress upon you enough that the entire weight of the roof and anything on top of it will be at a point load where that new crossmember ends. I fear it will snap a 2 x 6 or 2 x 8 like a toothpick with 6 inches of snow on the roof. And, without strengthening (scabs) the walls will still be pushed outward. If you choose that option, you need to scab another 2x whatever the same size on at least one side of the free part of the angled 2x, extending 24 to 36 inches upward past that point on the lower side, it has to be cut to exactly match the existing so it ends up resting on top of the wall plate. A variance of that is to use some half-inch plywood (plywood, not waferboard, not a 1x). While that might be stronger, but it is much more difficult to get it right.

On the lengthwise double 2x4 straps, us walk studs, and I can show you how to glue it in a slight arch, so load is transferred to the neighboring indisturbed rafters

If you hear cracking, don’t stand underneath it looking up with a flashlight looking for the problem.

If you pick one, I can provide much better details

Good lock!

 

[85_Ranger4x4]

Probably not "up to code" but after all this talk about rafters I have been gawking at my barn roof as I work on my camper. It seems to be sort of a hybrid. Looks like a structural ridge with lengthwise running beams that are supported to the floor.

May or may not have room if it is legal to do it that way I don't know.





Barn has seen roughly 150 years of upper midwest snow loads, you can see the track for the hay trolley in the second pic...

 

[Jim Oaks]

@Rick W

In Regards to R4:

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NOTE: If I move the rafter up I'll go 10" or 10.5".

If I'm understanding this correctly, you're saying to mount (scab) a 24" long 2x6 along the opposite side of the rafter that the ceiling joist is on, and mount it to the top plate next to the original rafter. This I'm guessing is to keep the rafter from cracking under the down force of the roof. Does it have to be screwed to the top plate as well, or just screwed and glued? What size screws and what kind of glue? While I'm thinking about it, is there an advantage or disadvantage between wood glue and construction adhesive like liquid nails? Every time you say glue I keep thinking construction adhesive.

If I'm understanding the point of this correctly, the higher the pitch the more force that's pushing the wall down and less force that's forcing the walls and rafters to spread apart. Since the pitch is so low, it wants to push the rafters and walls out, which is why there has to be a single solid joist as low as possible to hold them together.

I saw this picture (above) on garagejournal.com (unfortunately the site is down today to get a better pic). You'll see that the person added a 2x between the joist they placed higher on the rafter and the top plate. Does this accomplish the same thing? Is one method better? Your method looks easier. I'm assuming with this method I'm removing the old joist completely. The advantage to this method is if you mount these short stubs first, it gives you something to set the joist on and hold it up. Especially if you're working alone. It also looks like the person bolted the new truss in place with (5) bolts. Is there an advantage to bolts over screws? Especially since there's so much concern about load force? Don't screws have clamping strength and bolts have sheer strength? Would I be better with bolts versus screws and glue?

I'm not questioning your suggestions. Just making sure we're looking at every possible option and the pros and cons before I choose a direction to proceed in. It's easier for me to do something when I understand the how and why it works or doesn't work.

In Regards to R2 and R3:

Are you telling me to keep part of the original crossmember because I need it, or because you think I want a ceiling there? Is the 2x4 parallel 'strap' meant to support the remaining section of original ceiling joist and drywall? At this point I'm thinking it would be easier to ditch all of the old ceiling and joists in the areas where I install raised joists. The peak in this design gives me some room for the GMRS antenna mounted in the center of my cab. LOL. I'd have to piece in 2x4's between the joists at the peak to screw drywall to. This method looks like it may be a little more difficult to put together than the R4 idea.

 

[don4331]

@Jim Oaks:

Just like we don't provide recommendations to individuals to tow/haul at limits greater than Ford's GCWR/GVWR, we don't provide recommendations that don't meet current code - electrical, building, etc.

Last thing we want is your daughter suing us, after the roof collapses and crushes you and TRS2.​

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The actual load of the roofing materials isn't the issue. The design load case is a repeat of the ice storm, where you have ice sticking to the roof material and then 4+ inches of wet snow on top of that (30lb/ft^2 or more).

As your roof's pitch is under 3:12, if you want to make modifications, you need to change the ridge to a structural member, and that will become real ugly given the hip roof. The support column would be right in the middle of the area you would like to park your truck.

 

[Jim Oaks]

I plan to switch to a metal roof so branches slide off of it easier. Although we got snow this past February, it's an extremely rare event.

Do you really think the 1/4 inch is that drastic?