Demo - Does a vaulted roof push out at the wall-plate? 

I'm curious, how does calling them "a millennial couple" add to your narrative? I've seen boomers build garages without a collar tie in sight, and in the following years the wall rack and start to spread apart.

😄😄😄😄😄😄

It's not a vaulted ceiling if you fill it up with rafter ties. You might as well just put in a regular truss roof. I just built a 10x10 addition with a vaulted ceiling that I *know* is fine, but I still had to have a lengthy discussion with the inspector about whether or not that doubled 2x10 will be strong enough to hold up three packs of shingles.

12 pitch is getting near the point of almost being self supporting. At least the collar beam could be installed closer to the ridge IF there wasn't a floor joist. We built an 18 pitch A frame but it was attached to a 2 X 8 knee wall only 30" tall AND we had a lotta intersecting, perpendicular walls as well so spread load was not an issue. This was out of 2 X 10 with no ridge beam. those beams were still pricey because they were special order 28' long back in the early 70's. We were actually considering plank & beam but it was even pricier. This was in Saint Lucie County. Yep that building is still there and in fact it now sports metal roof cover. I knocked on their door and said guess who? The female owner started crying because I asked them if the bed was still supported on chains and that blew her away. They were the 2nd owner but I knew that from checking county property records out of curiosity. Yep the bed was still supported by black chain!

That's called a scissor truss and it works great.

​​@@madmat990absolutely correct. I've built massive A frames and you must use a massive beam that is supported at two ends all the way thru to foundation and the steeper the pitch the less deflection of load live and dead on the eave walls.

@@madmat990 I thought that was what they were called, the whole time watching this I figured that is where they would go with it...

In a 2 story Victorian home I looked to buy. A stone wall bowed out enough to see light. The purchaser dug out and reinforced the foundation. Then using long threaded rods, washers, and nuts tightening slowly from bottom up. Over a period of a few weeks the wall was within 2 degrees plumb. Remortored, painted, interior walls fixed. It was resolved for a profit.

I have seen this happen in older, and even newer, car garages. The real problem is that wood is excellent under compression, and lousy under tension. I have “saved” a few of those garages with some relatively easy fixes. Depending on the length, several tensioning cables are run between the tops of the walls, parallel to the bottom runner, or “ceiling joists,” to stabilize the sag and outward pressure. Turnbuckles were placed, and standard cable clamps were employed. After placement of the cable/turnbuckle combination was assembled, the turnbuckles are tightened. Just an inch, they are tightened. Then they are left for a few weeks, maybe a month or so. Go back and tighten again, and another period of time, adjusted to the observation of the effect on the structure. When the turnbuckle has no more to give, the cables, in steps, are loosened, and the cable clamps are loosened, slack taken out of the cables, and the process repeats. This is done until the walls are true vertical again. The cables and turnbuckles are left in place to keep the sagging from happening again. Proper eye bolts and plates to spread the force out on the existing structure would be employed when the cables are first set. Any novice engineer knows of the tensioning vs compression formulas, as old wooden bridges were designed and constructed with this in mind. A cursory glance at some of the old exposed truss bridges that are still around can teach volumes with a little imagination and vision of what the engineer was doing to design the structure. Good luck!

I am not sure that churches can be compared to regular homes people live in. When you compare these buildings they are so very different, it just doesn't work. 1. Windows in homes were small to make heating easier and big glass was expensive. In contrast, most churches tried to have big windows. 2. The Ceiling in homes was low to make heating easier and save building costs. Churches have high ceilings and are higher buildings in general. 3. More than 2 Floors was uncommon for homes. Churches commonly have no upper floor in the middle. This makes church wood frame very unstable and much harder to construct. And any mistake in the lower structure will affect the roof. Also: are you referring to Roman or Gothic style churches? Always keep in mind: medieval wood frame usually combined oak for the wall structure with lighter wood for the roof and EVERYTHING was connected with wood nails. Steel is a modern invention and iron was only used for emergency fixes and would rarely have the same stability.

Complete load of nonsense, a steel ridge member isn't going to solve the issue of flexing rafters. There are two solutions, joists or tie beams. Also purlin and cross members over a limited length or roof or commensurate with the size of purlins used.

@@dangeary2134 I can’t see the wood breaking under tension unless it is flimsy but I can see the join giving way if it is just a screw.

​@@jimdavis8391can you explain why you think flexing rafters are involved? I can't work out what comment you are responding to.

That’s a weird place to cut off. I see the algorithm is pushing this video hard the past few days. Basically you can use an I beam or engineer spec’ed wood beam and support it with a load bearing wall or post on each end (imagine at the siding and in front of the camera) so all loads are simply transferred out to those 2 points.

The ridge can’t flex with a steel If the ridge Doesn’t defect. The wall-plate can’t move

A steel ridge beam stops all roof spread because there is no horizontal component to the forces any more. See the next video here for an explanation: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BtsZk0UR2EI.html

Imagine a solid post or pillar going from the beam all the way down to the foundation.

The model in the video has a "ridge pole" and NOT a "ridge beam." A ridge BEAM absolutely WILL solve the problem. It will need to be designed to handle the load and for many buildings can be wood and not steel. Do not confuse a "ridge beam" with a "ridge pole". A ridge pole is what is shown in the video, typically a plank running on edge at the roof ridge and mostly serves as a nailer for rafters. It does not intended to carry the roof load and can simply be a single 2x plank. A RIDGE BEAM is different. A RIDGE BEAM is designed to carry a load which is why they are ALWAYS supported by posts, usually at the ends. So for example, imagine a shed 12 feet wide and 16 feet long. If you do the ridge pole approach, you might use a single 2x8. It may be supported on the ends, but only to hold it in place but not to carry any significant weight. The weight of the roof is carried by the rafters which transmits the weight diagonally to the walls, thus pushing down on them but also pushing outward. The ridge pole method needs ceiling joists at the bottom of the rafters, or else collar ties no more than 1/3 of the way to the ridge. HOWEVER, if you use a ridge BEAM, it WILL be supported at the ends and is much heftier than a mere ridge pole, hefty enough to bear up to 1/2 the roof load. So for this shed instead of one 2x8, a ridge BEAM might be three 2x10s sistered together. A ridge beam carries some of the roof load and eliminates the sideways push on the walls. A ridge pole doesn't carry any load to speak of and thus the rafters end up pushing out the walls. Big difference.

Finally!!! I can’t believe no one else mentioned this. Most barns use this concept. Bravo to you👍

@@richardsilva-spokane3436 thank you, good sir. I just thought it odd that no one considered that. I looked through some of the comments, and thought something should be said😬

Or pinnacles, or a hammer-beam roof (I'd love a dining room with one in my modest house!) - which is the equivalent of pinnacles along the length of the roof - the spreading force being applied part way down the wall.

The other design that solves the problem of rafters is the A-Frame, with the rafters extending all the way to the ground. Although, perhaps that would be a special case of the truss with the bottom cord being the floor of the building.

The Collar tie will absolutely help....! he's using a flimsy 2x2.... Try it with a 2x6... This "test" is completely pointless with 2x2's.

It’s not rocket science it’s just basic common sense

Yes, and if no ceiling joists are present. Such as in old Garages and I owned one built in 1953. There were at least wall ties every six feet. And these ties are still required on new garages that are built with conventional cut and stack methods. Now instead of wood collar ties Simpson strapping tying rafters and ridge together are used prior to installing roofing. After all this time There is still confusion about Ridge Board, Ridge Beam, what collar ties are actually used for. And it is important depending on the where you live and build. I live in earthquake country. Lol. And of course learning the buildings codes of the land is never a bad idea.

I've read it very clearly stated in numerous places that collar ties are NOT there to reduce wall spread but to prevent wind lift, even lower down. I am glad he pointed that out.

Can I just clarify Benjamin, (diyer only) are you saying that if a post is put from a load bearing wall up to each end of the ridge (on a four way hip), that would be sufficient to reinforce/strenthen the whole roof? Do hope you see this and reply, on a 'I need to know" basis :). Thanks hopefully?

Hi@@jesshothersall, it wont provide stiffness to the ridge unless the posts you mention are continuously being extended all the way from the bearing wall to the ridge. Like another bearing wall in the attic so to speak.

@@jesshothersall do you have ceiling timbers running from plate to plate or a vaulted roof with sloping ceilings? If the former then a traditional roof configuration may be possible with ceiling joists tying the rafters feet together to prevent spread, and binders running perpendicular to the ceiling joists to tie that direction. If vaulted then yes, provided your ridge beam is strong enough, and often overlooked, the hip beams are strong enough to carry the load from all the rafters fixed to them, then yes posts at the end of the ridge at the intersection of the hips could support that but hip and ridge beam sizes need to be designed by a structural engineer and are usually huge compared to what you might expect

@@jesshothersall -- You cannot put your post just anywhere on top of a bearing wall. Any such post is almost certainly carrying 1000s of pounds of weight. So if your post sits on a bearing wall and the nearest studs are 7 or so inches away, then this post, which is bearing 1000s of pounds, will severely compromise your top plates. Even if you have a stud in your bearing wall directly underneath the added post, the building code will tell you that you need a double or triple stud to support that post. You absolutely must have a post built into the bearing wall directly below the post you are adding, a double or triple stud. But it doesn't stop there. You need to verify that the bottom end of the this post in the bearing wall is also being strongly supported from below. Most houses are built in a platform style, where there are floor joists covered with plywood or USB, and then you build the walls on top of the floor. So if you have a post carrying 1000s of pounds of roof weight, it could easily punch a hole through your OSB floor unless you put support underneath the post. So if this post is directly above the foundation, you can simply stick a block the height of your floor joists on top of the mudsill and under the flooring to support this post fully. Otherwise in your basement or crawl space you should have doubled or tripled joists under where that post comes down, or equivalent. Every structure is different so you really need to understand and analyze what is the right approach for your situation. Structural engineers refer to this subject as the "load path." You need to think about every load in your structure and make sure that every load is transferred all the way down to the foundation and thus supported. Here's another quick example. Why do they put headers over windows and doors and sometimes the framing around those openings have multiple studs? Well, the rafters bearing a heavy roof sit on the wall and also ceiling joists that bear the weight of drywall etc. Over an opening your going to need some kind of beam to support all this weight so that it doesn't crush your opening. So you put in a header, which is really a small beam, and that header may need 1 to 3 jack studs. So ALL the weight of the roof and ceiling over that window is carried by the header beam. And since the beam is supported by jack studs, all that weight on the header is now transferred to the jack studs and downward onto the floor. So now you need to determine if those jack studs have adequate support underneath. It all depends. A lot of times a bearing wall is spanning joists but also rests on the rim joist which gives it a huge amount of support and there are no issues. But you have to look at every case individually to verify.

​@@dennmillsch Those are great points. In retrospect, I think it is best to avoid giving general ideas about the physics and legal issues behind structural work as they may give a false feeling of security to the DIYer. You are best to hire a local engineer ma'am.

Thanks Nenad. That's a great solution. I think in countries where earthquake is an issue they also use concrete ring-beams.

Collar ties can do both functions, if rafters and ties are sized properly, and then you don't need a ridge beam supported on the gable ends.

It seems like rafter engineering is pretty important. I wish he switched from 2x2 boards to 2x4 boards to show the difference in flex a different board dimension offers. What he's doing only exaggerates the wall flex because he's using such small boards that have a high degree of flex. You also can't forget that attached walls add to the flex resistance as well.

Collar ties by definition are located within top 3rd of rafter. Rafter ties must be within lower 3rd of the rafter to be sufficiently effective. Ridge beams can be, and typically are, wood. Doesn't have to be metal.

If the ridge beam is supported at the gable ends, then you don't need the collar .ties@@RobindeJongh

Correct 👍

It also provides more/better insulation options as well as providing room for utilities.

Be aware thst dynamic loads, wind and snow, are very different for a flat roof vs a pitched roof. Make sure that you have sufficiently reinforced it for high winds and that you have strapped the roof down to the walls and not just the wall plate, and that the walls weren't damaged too much by the movement.

Yeah it’s unclear to me how that solves the problem - at least with the scale model he is using here.

@@Pseudify The beam is supported at both ends so the peak of the roof is resting on a beam that is transferring all the load down to the foundation. If the peak can't move down, the rafters can't push the walls out.

@@bradley3549 Yep I figured that out soon after I posted this. Thanks.

Those are great points, Paul. No reason why any collar tied roof can't work as long as it's well designed to control the deflection.

@@RobindeJongh I have a possible roof to put on an old 20x25’ stone building. We want a vaulted ceiling ideally if possible. I would love some thoughts on this.

Exactly Paul.I work from India for clients in UK - since 2004.On one refurbishment job,an existing roof had a collar tie and some dummy posts to support ceiling lights.The new owner wanted the dummy posts removed and I explained that no additional structure was required based in collar tie and cavity wall + deflection check.The builder did not listen and energy ahead with loads.of steel purlins !

General common sense until you get to the I beam then no explanation vid ends….

and no clues as to how to attach it to the wooden beam overhead either @@diogenes1815

Hi Robert. I quote the author of the book "Structures, or why things don't fall down": Naturally, the buildings we see and admire are those which have survived.

​@@RobindeJonghgreat book👍

We have to think about what can happen not what has happened. For example, how long does it take a building to collapse in a fire? And how does it collapse when it is damaged?

Exactly! And this is because years ago things were done correctly! The roof in the demonstration doesn't even have purlins! If all the correct components are in place then this shouldn't be a problem

@@mattschannel1502 yeah and a vaulted roof needs ties, bracing, or ridge beam support, an unsupported roof will absolutely spread the walls unless its a very small roof. O.p's building probably just has a type of bracing to resist the wall spread that o.p. doesn't recognise

It is a great idea. That’s what the video starts with, and as you can see there is no roof spread.

This is pretty much a scale model.

I agree, the rafters are to skinny (not really to scale) 6”, 8” and or course 10” rafters would be much preferred with way less deflection and collar ties would work better .( But load bearing understood for this demo… )

no, it's a good representation of the physics. What you describe would add unnecessary resistance to the model which would make the results erroneous. We want to look at the lateral effects at the base when gravity loads are applied and this video achieved it perfectly. If the thicker rafters with multiple bolts were used in this small model, the distance between the bolts would be significant enough to add moment resistance basically creating a rigid frame. If you were to build a house with 24 inch rafters and ties (±your proposed scale), the same effect could develop in the connections, but that in turn would be unrealistic because nobody builds with these dimensions. I recommend you find a real interest in the physics because once you get a good grasp, it is truly a mindblowing experience. I've never quite seen anything like it.

As others have said, sure it would work better but at a real roof scale and load, it would require very large timber and connections.

Hi John. Thanks for your question. If you would like to send an email and include some photos and sketches I may be able to take a look for you.

@@RobindeJongh Many thanks for the reply, when I realised how long ago you made the video I wasn't really expecting one tbh, so it's much appreciated. I'll email something over in the next couple of days when I've got together as much accurate information as I can.

Would this also be the solution to dropping the ceiling height to allow for a loft conversion without compromising the roof?

They could, although they would need to be designed for minor axis bending because they would resist both vertical and horizontal forces

plumb cut if tied roof sat on top if structural ridge beam

Yes that's a great solution.

Thanks Tony - glad you liked it!

Hi Cory. It may be achievable, with the ridge beam as small as possible and the rafters as deep as possible. Maybe detail it with timber either side of the web, bolted through, with face-fix joist hangers for the rafters. A flitch beam might also work.

@@RobindeJongh great this is similar to what I had in mind! All about the positioning and levels I guess. One I have in mind is only a small span so could even potentially use doubled up timbers in all honesty. Again demos like this are great to see!

@@RobindeJongh How about with Scissor truss?

Great suggestion! Hope you're getting your droopy gables looked at?

@@RobindeJongh Robin, I will strip the gable end back in the Spring and then fix it myself. If you want to feature the problem in a 'Gable End Ladders' video then I can send you the video once stripped back. I want to keep the structure open with no A frame or cross-bracing. It is a bungalow near Totnes in Devon

Yes that's an option, however it would make no difference most of the time.

It is a bit of a generalisation/simplification that you need a steel beam. Depending on how far the ridge beam needs to span between supports, it may well be possible to use an LVL or glulam beam. And it's possible that a steel ridge beam won't work either, if there are no appropriate support points.

Hi Carlos. You could achieve this with a ring beam at wallplate level that ties all the hips together.

A collar tie can work as long as the roof has been calculated by a structural engineer to be able to support the load without a large deflection at the eaves.

I don’t think the collar tie is stretching at all. It’s all in the bending of the wood below the tie.

Thanks again for the info. This video was a great demonstration. @@RobindeJongh

That's it. I've used use thin lath rafters and a string tie to mock up this demonstration, the bending is easier to see and the role of tie is clear. As others have commented above, you need deeper rafters if the tie is raised. In the US codebook rafter tables, in the footnotes is a small chart of size increase factors to use as the tie is raised above the plates. This is to help resist the increased bending force in the rafter as the tie is raised. For instance a dougfir 2x6 can span 12'1" if tied at the plate but can only span 8'1" if the tie is raised to 1/3 roof height. The rafter needs to be deeper as the tie is raised. At the end of those tables is the "Heeljoint connection table". It tells how many nails to use to connect rafter to tie as the tie is raised. As the tie is raised the force on those connections increases. Using the same example the connection table might require 6 nails at each rafter/tie connection if the tie is at the plate but would increase to 9 nails per connection if the tie is at the 1/3 mark. But! they called out 16 penny common nails. We shoot smaller gun nails... head off to the equivalents table to see how many more times to pull the trigger and we are going to be up to 12 shots per end or so. Here, if you keep the tie in the lower third of roof height and understand how to use those tables the solution is "prescriptive", the engineering has been done for you.

@@donp5774 Thanks DonP, it took me a while to break down your comment. Those charts were super helpful. Your explanation was super helpful. Thanks again for replying. I am starting the project in a few days.

No, because then there is little or nothing to stop the rafters pushing out at the eaves

Hi Michael. Are the I-Beam manufacturers ok with their product being used for this application?

hes not talking about a truss system

See my explanation here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BtsZk0UR2EI.htmlfeature=shared

Hi Jonathan. That would be different -- I assume if the ridge is supported at the wall.

A ridge beam is supported at each end on the gable walls.

It’s a beam supported at each end.

Ridge beam carries the load to the end walls.

Don't mess with all of that just anchor The ridge and anchor the end of the trusses with clips

@@guruofendtimes819 the tie beam was on the plans, so we were obliged to put it in. It didn't do anything other than be aesthetic. Fitted RR47 ridge beam clips and rafter clips at the bottom. Nice, simple, effective.

Yes, no sideways force at the eaves.

Yes use a Ridge Beam not a Ridge Board. Entirely different Roof Dynamics.

Hi Mark. Counterintuitively, the stiffer you make a structural element, the more load it attracts. So by making the rafters stiffer and the wall taller (therefore less stiff) it may avoid cracking. Otherwise a ridge beam or purlins. A third option I haven's discussed here is a ring-beam to take the lateral force at the bearing.