How are the various wooden parts of a roof jointed? Is it always mechanical fasteners?

[Flyover]

I'm just curious, with regard to both stick and timber frame construction.

Mainly I'm wondering if nail plates or gussets is always how they do this, and if it's for any reason besides cost. Wouldn't proper jointing be stronger, and potentially give less room for the contractor to screw up?

I'm especially curious about how rafters are jointed to the ridge beam if it isn't with some kind of plate or gusset. None of the diagrams I've seen in online image searches tell me this.

 

[user 4883]

It all has to do with time and money.
Least expensive and fastest way to manufacture.
Least expensive and fastest way to build.

 

[Snoonyb]

I was a stick framer, 16D's ridge to rafter, 3-16D's rafter to top plate, 5-16d's rafter and tie to top plate.

Open beam, dap the ridge beam, 24" Simpsons over the top, on top of the sheating

 

[billshack]

I was a stick framer, 16D's ridge to rafter, 3-16D's rafter to top plate, 5-16d's rafter and tie to top plate.

Open beam, dap the ridge beam, 24" Simpsons over the top, on top of the sheating

I don't think most people even know what you said, you should translate to normal speak.

 

[Flyover]

I don't think most people even know what you said, you should translate to normal speak.

+1

 

[Snoonyb]

I don't think most people even know what you said, you should translate to normal speak.

+1

What I found interesting, from post #1; "I'm especially curious about how rafters are jointed to the ridge beam if it isn't with some kind of plate or gusset. None of the diagrams I've seen in online image searches tell me this."I'm especially curious about how rafters are jointed to the ridge beam if it isn't with some kind of plate or gusset. None of the diagrams I've seen in online image searches tell me this."

These, among others, are available from GOOGLE;
https://www.jlconline.com/training-the-trades/cutting-common-rafters_o
Wall Framing Basics
https://www.thisiscarpentry.com/2012/11/09/common-rafter-framing/
However, back to an explanation of methods, from a self-taught stick framer, (10yrs., USN, electronics).

The roof pitch is/has been determined by whoever prepared the plans, and handed to a framing carpenter/s;
Framer-The carpenter contractor that installs the lumber and erects the frame, flooring system, interior walls, backing, trusses, rafters, decking, installs all beams, stairs, soffits and all work related to the wood structure of the home. The framer builds the home according to the blueprints and must comply with local building codes and regulations.

The structure is "framed", the rafters and ceiling joist are laid out, (marked and labeled on the top plate), the walls are stood, squared, (plumbed and lined), and braced, the ceiling joist are crowned, high edge up, rolled and nailed with 3-16D over each top plate they cross.

The rafters are then crowned, racked up, (set on saw horses), and laid out, I preferred a framing square and stair gauges), the table of your saw is set at the angle of the roof pitch, the birds mouth is the 1st cut, the rafters are rolled on their side and the plumb and seat cut are marked using a pitch block, (a short section of 2X that is cut to match the prescribed roof pitch, with a piece of 1x attached to the top), the rafters are cut, the ridge is crowned and laid out, on both sides, loosely set and braced, the rafters are placed and nailed in place, (I nailed thru the ridge, both ways, hip and valleys were often toe nailed w/16D's), no more than 4 rafters were set W/O a rafter tie nailed with 5-16D's.

Mechanical connectors are seldom called out W/O there being a high wind circumstance present.

Here are some definitions;
Rafter- Lumber used to support the roof sheeting and roof loads. Generally, 2 X are used. The rafters of a flat roof are sometimes called roof joists.
Rafter, hip- A rafter that forms the intersection of an external roof angle. The ridge joint, intersection is composed of 2 common rafters and the hip rafter, each direction.
Jack rafter- A rafter that spans the distance from the wall plate to a hip, or from a valley to a ridge. Sometimes referred to as cripple jacks.
Rafter, valley- A rafter that forms the intersection of an internal roof angle.
Roof valley- The "V" created where two sloping roofs meet.
Roof sheathing or sheeting- The wood panels or sheet material fastened to the roof rafters or trusses on which the shingle or other roof covering is laid.
Ridge- The horizontal line at the junction of the top edges of two sloping roof surfaces.
Ridge board- The board placed on the ridge of the roof onto which the upper ends of other rafters are fastened.
Sheathing, sheeting- The structural wood panel covering, usually OSB or plywood, used over studs, floor joists or rafters/trusses of a structure.

 

[bud16415]

I once made a plan for a good size addition to our old house and set out to find a builder to do all but the finish work. I spelled out how I wanted it framed and one thing I asked for was hurricane strapping of the rafters over the peak. It was pretty funny as no one did that then and they all but one acted like it was the craziest thing they ever heard of. I pointed out I would make the strapping and it would only take a few minutes to install and they still said it was a waste of time and money. Then there was one builder that said that doesn’t sound to bad and said he was surprised more people didn’t do just that.



As you go around the country or world you find depending on what point in time you are looking at it was done differently. When we built my nephews house we did a truss roof and we were planning on doing the job just the two of us. To our surprise a friend of his that was a builder offered to have his whole crew come out on a Sunday morning and do the roof. We had made sticks with two nails spaced 24” to keep the trusses lined up and when the builders saw them they laughed. The boss said well they made them lets give it a try. So each truss we set we nailed a couple of these spacers on each side. It went fast and when they started putting on the plywood it really helped lining it all up. I never saw a roof go on so fast and the guys asked if they could take the straps as that’s how they wanted to do it after that.

There are a million ways its been done.

 

[zannej]

I will add another term: Bird's mouth. It's a notch cut out where the bottom of the rafter rests on the top of the wall. From what I saw, a lot of people seem to use nails to tether things together but some use metal fasteners & long bolts with nuts.
Some have Gusset plates (either metal or wood in sort of a triangle shape- some notched for a ridge board) to hold the rafters together at the top.

 

[Flyover]

OK so here's one thing I was wondering: are the rafters and ridge board joined directly, or only indirectly via gusset plates like @zannej said and/or rafter ties like @Snoonyb said?

If the rafters are also joined directly to the ridge board, how? Mechanical fasteners (how are they driven?)? Proper joinery (what type of joint?)?

And, why are ridge boards called "nonstructural"? Are they always necessarily nonstructural?

 

[Flyover]

@bud16415:

After some clicking around, I learned what "hurricane strapping" is. Basically it's another type of nail plate or gusset (or something similar that goes by a different name): a metal brace that's form-fit to hold pieces of wood together in a specific way, resist stress in a specific way, etc. Makes sense. How do you make your own?

And, how many types of nail plates/gussets are there? How many are different names for the same thing?

 

[Snoonyb]

OK so here's one thing I was wondering: are the rafters and ridge board joined directly, or only indirectly via gusset plates like @zannej said and/or rafter ties like @Snoonyb said?

If the rafters are also joined directly to the ridge board, how? Mechanical fasteners (how are they driven?)? Proper joinery (what type of joint?)?

A quote from post #6; "the rafters are placed and nailed in place, (I nailed thru the ridge, both ways, hip and valleys were often toe nailed w/16D's), no more than 4 rafters were set W/O a rafter tie nailed with 5-16D's.

And, why are ridge boards called "nonstructural"? Are they always necessarily nonstructural?

That is not necessarily the case, there are many structural roof designs.

 

[Snoonyb]

@bud16415:

After some clicking around, I learned what "hurricane strapping" is. Basically it's another type of nail plate or gusset (or something similar that goes by a different name): a metal brace that's form-fit to hold pieces of wood together in a specific way, resist stress in a specific way, etc. Makes sense. How do you make your own?

And, how many types of nail plates/gussets are there? How many are different names for the same thing?

To make them is to simply follow a design, however to use them you must have them tested and certified to meet ASTM standards and then have all of the test results approved by the ICBO.

It's less expensive to purchase them from SIMPSON or HARLAN, to name a few, who's connectors are certified.

 

[Flyover]

the rafters are placed and nailed in place, (I nailed thru the ridge, both ways, hip and valleys were often toe nailed w/16D's)

Oops, I missed that. Thanks.

And, makes sense about testing & certification. Thanks for that too.

What are some examples of structural roof designs (as opposed to nonstructural ones?) where the ridge board would be structural vs. nonstructural?

 

[zannej]

The ridge board isn't always necessary for higher pitched roofs but anything below 3/12 pitch requires a ridge board or ridge beam (beam being something like a 4x4 or 6x6 whereas a board is a 1x6 or 2x6. Sometimes you just have two rafter ends meeting one another and cut to fit together like an inverted V. They are generally nailed to one another, but sometimes there are special hangers designed for specific angles that will hold them in place. There are all sorts of different installation types. Nails are often used but they can split wood near ends. If you use a ridge board (which gives added stability) you can use angled joist hangers I think. I think they make hangers specifically for rafters. You can also add internal braces to gusset plates. You need a gusset plate on each side except on the end rafters. From what I could see, preferred method of installing them involved using structural bolts or screws-- big thick spax ones or something.

I was researching this when trying to figure out how to build a roof for a new shed. My idea was to have a ridge board and gusset plates notched for the ridge board. You can figure out what pitch you want and thus the angles of the rafters, lay them on the floor or on a cardboard template. Mark out the angles you need and get the ends cut so they will fit together, use that to determine the size for gusset plates (can lay over a cardboard or plywood piece and trace or just transfer marks). Make your gusset plates from a template, screw them on to the rafters at the ends to hold them in place. Use a small piece of wood as a placeholder for the ridge board if you include one (which, I would do just bc I'm paranoid).

Youtube is full of videos on how to make rafters, gusset plates, etc. I had a mini marathon earlier but I need to cut back on videos bc I've already used 20gb of my 150gb limit & we're only 3 days into the billing period.

 

[bud16415]

I started learning about framing in the 1960s as a kid watching my dad build our family home and neighbors doing the same. Then there were a couple local builders putting up 3-4 homes a year for the people that were not DIYers. These places were all stick built and the guys like my dad cut every stick with a man powered hand saw and drove every nail with a hammer.



Previous to the post war building boom the method was balloon framing and starting in the late 40s –50s platform framing took over. I never saw a truss or any kind of a pre made framing gusset until the late 60s-70s. Someplace in there plywood replaced planks for sheathing and drywall replaced plaster. For me the low point was the 80’s when they started to really get cheap bringing in the foam sheathing and just using plywood on the corners and every other aspect of framing was cheapened up IMO.



A lot of great homes were built with nothing but 2X and nails and there was for the most parts not many blueprints or engineering done. These guys overbuilt when in doubt and I remember reading after a bad hurricane down south once most of the 80’s homes blew away and the 60’s owner built places made it thru.



No one cared back then how you built a house and quite a few were all made from blocks.

Most of the balloon framed homes I have owned and worked on had rafters around 3x8 and were butted and there was no ridge board. The roof sheathing was mostly 1” thick rough sawed sometimes not edged with bark showing. All the platform framed homes I have seen have a ridge board. And now of course with trusses there is no ridge board again.

 

[Flyover]

Why would they ever build without a ridge board? In that case the roof sheathing is the only thing resisting horizontal force on the trusses/rafters, right?

 

[zannej]

Flyover, the ridge board is not necessary to carry load in higher pitched roofs. But I do think zone matters. If you're in an area that gets a lot of snow, you'd want a ridge board or beam. If you're in an area with moderate weather & have a 6/12 or higher pitched roof on a smaller structure, the board is not needed. I personally would go with a ridge board, but I'm not an engineer or expert.

Bud, so much was done differently back in the day. My house was originally built in the 30s or 40s as near as I can tell. As near as I can tell, my room & my mother's room were later additions & there's a beam below the house that says something like 2-27-47 FAT (Can't remember the middle number for certain, but I remember it was 2 and 47 and the initials were FAT). I don't know if the people who remodeled took out insulation in walls or if it was never installed. I do know there are open gaps under the walls all the way through the floor. They didn't use 2x4s on the bottom of the walls. They just put studs over the plywood floor. There were renovations done in the 70s (I'd guess by the avocado green & the printed wall panels that mimicked wallpaper).

I found out that some jurisdictions allow sheathing that is basically cardboard. I don't know how anyone would think that was OK. There's a guy on Youtube who was showing a house under construction & pointing out how it had cardboard sheathing that was torn, electrician punched a hole in it with a hammer rather than cut so there was a huge gap around stuff. Just absolute garbage. If I had to build a house now, I'd probably use the ZIP system (even though I'm not a big fan of OSB). At least it's better than cardboard.

I really babbled... LOL.

 

[bud16415]

Why would they ever build without a ridge board? In that case the roof sheathing is the only thing resisting horizontal force on the trusses/rafters, right?

If you think about it all the rafters attached to the ridge are a bunch of parallelograms and will all fold together. In the homes I have owned without a ridge board the sheathing on the roof was a full 1" thick or thicker. Way back they were covered in wood shingles so they wanted the space between the planks for air. When modern shingles came along the spaces were a problem and the one house I owned i had the whole roof covered in .5" plywood and then the roofing. So that roof was between 1.5-2.0" thick.

Often when you look at old places done without a ridge you will notice a swayback to the ridge line from outside. That should give you reason to start looking deeper into the framing of the walls and attic area.

 

[zannej]

Yup. The top ends of the rafters press against one another to resist downward force. The ridge board/beam seems to help more with keeping them straight up and down (rather than having them lean sideways) if that makes any sense. I'm just guessing here from my understanding of physics. A ridge board or beam spanning all of the rafters does give a little added stability in larger structures & ones with heavier loads. It takes more work to incorporate them, but IMO it's not a bad idea to use them. Reminds me I need to reinforce my workshop's roof rafters.

 

[Flyover]

@zannej: That makes sense. One set of rafters joined to the ridge beam sort of "holds up" the rafters on either side of it (via the ridge beam). So it helps prevent that swayback @bud16415 was talking about.