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

What is the best way to build a

vaulted

ceiling? We're going to do some

demo

s here to see the various options for creating a voltage ceiling within a ceiling. Here we have a model of traditional beams tied to the

wall

. board, so what we're going to do is apply some load to this and see what happens to the

wall

. The problem with this type of setup is that when you apply the load to the ridge or the rafters, it

push

es the walls outward and that's called

roof

extension, so here we're applying some load to the top and you can see if you look down here the walls are actually being

push

ed outwards and moving outwards now, if we zoom in again now while applying some load we can see that the whole wall is rotating so it will crack along the lines of mortar into your wall and could potentially even push the wall down, so with a traditional

roof

what you have is a roof that acts as a link, so in this

demo

we are just going to connect the roof rafters to the rafter and to the wall

plate

, so what I'm doing here is not particularly good practice in terms of building full scale, but it just connects this in a similar way to what it would be. done on site so we can see what the structure is doing, so we are connecting to both the wall

plate

and the beam.

We would probably do this with nails on a traditional roof, so the roof here now acts as a tie down, so If we apply the load to the roof, so this is the weight of the shingles and potentially the snow and wind , the wall is not moving at all and what we have here are the beams that are compressed and the ceiling is tensioned, so we take In a close up view we can see that when we apply the load there is no outward movement, but that It's not a very good arrangement for a voltage roof, so a common solution that builders use is to provide a tie with a collar fairly close to the ridge, so let's put this tie in there and see what it

does

once we apply the tie. load, so for this mockup we'll only place it about a third of the way from the ridge to the ridge. wall plate and now we're going to take out the ceiling beam and watch how the structure relaxes once we take it out, so let's see now if when we apply the load this makes any difference in how the walls push up well, not really.

Look closer and we can see that there is as much rotation in the wall as before, so this solution is not going to work and the recommendation that is always given is, as a general rule, to tie the roof and tie the collar in two. thirds of the way down, that is, one third of the distance up from the wall plate, so let's try that and see if it makes a difference, so this new fitted ceiling will sit one third of the way down . distance, the problem, of course, with this is that we're not actually getting a truly

vaulted

ceiling, so we'll remove the top tie, apply some load like before and see if this has made any difference now that there's not as much rotation. on the wall but it is still too much and if we look closely we can see that the wall is still cracking so this particular solution still needs to be designed by a structural engineer because the amount of rotation in the wall depends on the stiffness of the rafters used so really the only way to achieve little to no rotation in the walls is to have a steel ridge beam and this solution allows you to have a completely vaulted ceiling with no tie downs to reduce headroom so that's what I recommend. a steel ridge beam