My garage was built without rafters. :bloated: So the lateral strength of the block walls has been the only thing keeping the roof from going flat over the last 50 years. The drainage was also suspect. As a result, the corners have sustained a bit of movement and a lot of the mortar needs to be repointed. No problem, but I’m going to address the cause before I repoint the mortar.
So I added the back gutter that was never there. Again :bloated: I also made sure the yard was graded as well as possible in good old spongy clay earthed Tonawanda. Now I’m going to add the missing rafters before fixing all the damaged block and mortar.
I haven’t measured yet, but I’m pretty sure my garage is longer than 16’ from front to back, and even getting 16’ 2x4’s home is going to be a pain in the ass. What’s the proper way to couple 2x4’s? In theory these guys will only be in tension, so it shouldn’t be much of a challenge, but am I thinking about this properly? What about running diagonal supports from the rafters to the roof?
Anybody know what I’m talking about or have a good online resource?
there are various brackets on the market thata allow u to join 2x4s together with nails…either at 90 degree or 45s or 30s…i am trying to find them for u
I don’t have time for a decent drawing, but here’s the general idea. No rafters. In red is a big ass maybe 6x8 timber that runs lengthwise, sits on top of the block walls, is supported in the middle by basically a jackpole from the floor, and has a 4x4 running from the timber to the peak of the roof.
So what I’m thinking is, in theory :ohnoes:, adding 2x4 rafters that would be in tension and thus stop the roof spreading from stressing the walls. Yes? No? In blue. Holy crap this drawing sucks. :headbang:
what would be much simpler would be cables. This will also allow you to put some pretension on them. That would be hard to do with wood. Also, the cables will be cheaper than the wood, and less hassle, i’d imagine.
So if the 2x4’s need to be longer than whatever I bring home, any problem with just joining them end-to-end somehow? I have some sort of steel box in my mind as being the thing to use.
not feeling the cables?diagonal supports will help
because you will effectively make 4 triangles instead of two. And we all know that the triangle is a very strong geometric shape.
I think I may have my terminology wrong. The rafters are the diagonal boards that make up the roof? If so those are there. And the horizontal boards are joists? If so, my garage has no joists.
Not so much. I think wood will be cheaper and easier in this case. If nothing else because of my own skill, or lack thereof. I don’t have a severe problem. I’m just theorizing that the design is putting some extra stress on the walls. Most of the problem probably just stems from Tonawanda’s shrinking/expanding/settling ground, the lack of a gutter on the back adding to the moisture and thus frost heave, and general neglect by previous owners.
Good point. Plus if I do it the way it’s drawn, it will transfer some stress to that center beam, and thus to the center of the walls. Which I think would be a good thing?
Thanks, but probably unnecessary. This isn’t a real serious problem so I’ll probably just toss up a few supports, then repoint the mortar and see what it looks like in 5 years. If it still looks good…I’ll sell the place and move somewhere with more stable soil. Like Amherst. :ham:
I have almost no formal mechanical engineering training, but I will say this from my experience with old houses.
Just because the monster timber approach has been abandoned in favor of multiple smaller supports in modern designs does not mean there was necessarily a problem with the old designs. There are several reasons why huge beams aren’t used much now:
Cost, because you’re talking about an old growth tree.
Space savings.
Weight.
Difficulty to work with (that beam probably weighs as much as your Jetta).
Look at it this way… how old is your garage? What makes you think that a more modern design with more bracing, but much smaller lumber would have held up any better to your shifting soil? There are tons of new builds in this area that aren’t holding up nearly as well as your old (I’m assuming old) garage.
Eh, from a statics standpoint, the old way really isn’t that efficient.
The it loads the walls in two directions
A majority of the roof weigh is transferred all the way to the end of the building
it puts excess stress on the joint at the top.
James,
If your garage is not much longer than 16’, you could always raise the beam up a bit, so you wind up with an A vs a delta.
Reason #1 why I’m interested in your advice! :biglol:
Yeah it’s about 50 years old. Which is probably why I should just repoint the mortar and stop trying to over-engineer it.
Actually now that you mention it, another reason why I should just do that is because that’s what my professional and experienced home inspector told me to do when I bought the house. :bloated: :lolham: (The home inspector’s opinion was that the problem was mostly caused by a lack of a back gutter.)
I’ll probably toss up a few joists just because it’s a cheap and easy way to add a bit of strength, but that’s about it.
Newman I see where you’re coming from. Your design will add a ton of tension immediately, halting all spreading of the roof. But I’m not even positive that there is a spreading problem. It’s just one theory. Another theory is that the ridge beam is properly supported and there is no spreading problem, only a moisture related shifting problem.
Maybe I’ll just leave it be until 6 months before I want to sell the place, then repoint the blocks so it looks nice and pretty and :gtfo:
yes i am the architect. Newman’s idea is probably the fastest acting solution to spreading if in fact that is your problem. putting tension on the roof immeditely will even have some reverse effects rather than just stopping it from getting worse. cables would be SOOOO easy to do and wouldnt take any more than a good crescent wrench and a bag of hardware. you dont even need a truck for it lol. In theory putting “rafters” in would only have the added advantage of giving you some type of storage space over your garage which i could see doing for that purpose.
putting in the diagonals from the rafters to the roof is less about the spreading problem and more about helping in live load dispersment such as a crapton of snow so that it doesnt cause the middles of the roof to sag inward to hold even more snow and cause a failure.
IMHO, if its only about fixing a spreading problem and you have no need for the extra storage space do cable tension members across the width evenly spaced front to back. if its not about that then go with rafters so you have a nice storage space.
NOW, about the fact that if its wider than 16’…
the CORRECT way to connect two beams is called to “Sister” them, you overlap them about 2ft at the center and bolt them together or use a lot of good wood screws.
The middles of the roof are sagging a bit. I can’t really quantify it. It’s not too hard to see if you’re standing near the garage. Maybe a maximum 2" deflection from “flat.” :gotme: Maybe not even that much.
I’ll probably toss up a few rafters and diagonals. Seems like the best solution for a bit of extra tension against spreading, a bit of extra strength against sagging, and a bit of storage space. Won’t hurt anything.
Then I’ll have at the block, and see what it looks like in 5 years. If the problem comes back I’ll consult a professional. Which by that time will be focusinprogress again. :tup: Thanks for the info!
^ yea no problem. i would go with the rafters and diagonals if you have some sagging. if you need more in depth explanation on how to sister two joists let me know. the other thing i would just like to add is you dont need to go overkill on the rafter size…generally a 2x4 is a bit undersize, but for your needs i think thats perfect. if anything dont go bigger than 2x6. i would also probably only do it every other roof joist in your case as it doesnt really need much more considering its an old design that has held up for 50yrs and adding so much of the new tech is overkill. maybe even every third joist.
I don’t have a severe problem. I’m just theorizing that the design is putting some extra stress on the walls. Most of the problem probably just stems from Tonawanda’s shrinking/expanding/settling ground, the lack of a gutter on the back adding to the moisture and thus frost heave, and general neglect by previous owners.