dave*99
Well-known member
Jack the entire building up and put a stem wall under it. Keep your attic.
Garage Ceilling joist removal.
- Thread starter Vladmakh
- Start date
Orionrising
Well-known member
Most scissors are designed not to mess with interior finishes so minimal deflection is speced.
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Exactly. You have to tell the truss guy that, or you will end up with some horizontal movement.
Let's take a step back for a moment because some of these posts are way WAY off. This isn't an impossible task, in fact it looks pretty simple compared to other jobs wanting the same thing (but dealing with a different design). Think about it, there are thousands of single story, open span gambrel roof barns (even balloon framed), garages and homes in the US.
Looking at the new pics and hearing an engineer is coming to check it out (good plan, btw), it looks like a bulletproof set-up would be something similar to haunch braces with lower collar ties that are run at every truss. Still, it may not even be needed. The beam and lally column are for the floor only, from what I can see.
That said, I don't know what the max span would be. But, thinking back I want to say we built a few 24' or so wide spans that were open.
Vladmakh, no one has asked, what's the width of your building?
Looking at the new pics and hearing an engineer is coming to check it out (good plan, btw), it looks like a bulletproof set-up would be something similar to haunch braces with lower collar ties that are run at every truss. Still, it may not even be needed. The beam and lally column are for the floor only, from what I can see.
That said, I don't know what the max span would be. But, thinking back I want to say we built a few 24' or so wide spans that were open.
Vladmakh, no one has asked, what's the width of your building?
New construction vs remodel is huge difference. If the gambrel like rafters were designed with the floor there to resist the thrust, then taking it out is going to change that design.
Comes down to do you want shoot from the hip, modify it, put some braces here and there, and hope it works forever,
or
follow professional advice (both here and the engineer he wants to hire) and be sure its done correctly.
Most times first option is fine, but its that 1-5% of the time that something drastic occurs and gets folks into trouble.
ard
Well-known member
Can you find a single design online without a ridge BEAM that has no floor/ceiling joist OR no collar tie in the bottom third of the rafter??
(What he has pictured is such a 'design', right? No ridge 'beam'; no low collar ties; no floor joists to resist the outward spread....no haunch braces either, looks like a minimal birdsmouth on the top of the outer wall plate, then daylight....)
OP- you might also take a good many pictures and find an engineer that would give you a quick review over the internet- might be cheaper and easier to schedule.
Finally I agree with the comments above about a new engineered roof- OP has a water leak there in the pictures, you wonder what else is in store with those shingles....
pitterpat
Well-known member
As pointed out above, you dont have to have the collar tie in the same direction as the rafter/truss. The plywood will transfer the load.
Go in a big box store and look a the roof. the joists all go in one direction, and then at the end walls, the last joist is usually about 5-6 feet away from the wall. The roof deck is what gives the stability to those buildings, just like the plywood is giving stability to this building.
OP...I am a structural engineer, and if you remove that plywood, there is nothing stopping the roof from pushing out unless you are certain the roof was designed originally that way. 99% of all other engineers are going to say the same.
LX-Markham
Well-known member
post #27
Engineer?
I'm not talking about shooting from the hip. Redesign happens every day. I worked with redesign in remodels for years.
I don't think any of us need to call it a gambrel-like rafter. It's a gambrel rafter. They're not all cookie cutter running the same geometry.
That's the point. A redesign could very well have a ridge beam put in place. Or, depending on the span something like this:
Adding to what I've just written another solution could be running raised rafter ties and doubling the collars.
I'm spit-balling, I know. It's just that I've seen enough remodels and engineered plans to get what is possible.
Point is, there are possible solutions; safe, commonly used solutions used every day in the trade. I guarantee (since it was my bread and butter for years) that with a couple days of labor this garage can be modified to do exactly what the OP wants. If it wasn't possible, I wouldn't say a word.
ard
Well-known member
^ I believe we agree.
The garage is 24x24
There was a water leak due to a couple of shingles flying of which has been repaired. Installing a new roof is definitely out of the conversation. My initial thought was that the building was designed without the attic storage space and previous owners added for extra room/ storage.
I was thinking of something similar. I like this idea more and i would also leave 3 joist on each side and add additional 3 joist in front and back to tie it all together. I was thinking of also installing plywood on top which would strengthen it and i could use it as small storage place as a bonus.
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I found this when i was looking around for car lifts. It seems like his garage has similar structure and doesn't have anything to support the roof trusses.
I'm not talking about shooting from the hip. Redesign happens every day. I worked with redesign in remodels for years.
I don't think any of us need to call it a gambrel-like rafter. It's a gambrel rafter. They're not all cookie cutter running the same geometry.
That's the point. A redesign could very well have a ridge beam put in place. Or, depending on the span something like this:
Adding to what I've just written another solution could be running raised rafter ties and doubling the collars.
I'm spit-balling, I know. It's just that I've seen enough remodels and engineered plans to get what is possible.
Point is, there are possible solutions; safe, commonly used solutions used every day in the trade. I guarantee (since it was my bread and butter for years) that with a couple days of labor this garage can be modified to do exactly what the OP wants. If it wasn't possible, I wouldn't say a word.
You should send him some drawings so he can do it right.
Trey T
Well-known member
That's likely the case. It's pretty unconventional to design ties to resist lateral force by spending ~90% of the costs on joist (+ girder) and only 10% on plywood sheet. And to think that the plywood is the primary structural member to resist the lateral force is crazy. Even folks w/o engineering background would think that's a stupid design.Vladmakh said:
The point is, none of the guys on here have given you a solution that will work or you'd accept, you just gotta go with your common sense or hire someone to do it!!! Go w/ your first instinct - just don't let this thread confuse you!!!
Plywood is used all the time as diaphragms for buildings, attached to joists, even commercial buildings. Its an engineered product that has design values that are confirmed thru testing.
I dont think any engineers on here are going to do a "design" for anyone. Will advise and point out if wrong, but this is not a freebie for engineering.
Hopefully no one on here takes advice from folks when it comes to building design - Would you go on a medical forum if your heart was hurting and see what everyone would say?, no you would contact a professional.
I think the best suggestion is to remove the joists over the lift, leaving a few each side, creating a 'deep beam' that can transfer the load to the end walls. Numbers can be put to that easy enough by an engineer.
Even though I've read a lot of bad advice on forums, I disagree. There are quite a few knowledgeable folks that have worked in the trades around here. Advice that actually gives real-world options by people that have experience is valuable. Weeding out the hot air salesman is the difficult part.
Vladmakh, at a 24' span you're definitely in the ballpark to make it work for you. I'm interested to hear what your guy says after he pulls measurements.
Some folks are not knowledgeable to week out the hot air. Its eventually going to cause issues.
firebirdparts
Well-known member
True of all forums that I frequent. If you ask a serious question, you will need some real wisdom to pick the one person giving good advice. Those are not trusses, and I think May Pop just made a typo about that on page one. Typos can also tilt the discussion off axis.
Personally, I would call this a very poorly designed building as-is. The problem with using plywood to carry that load in this geometry is that the load has to get from the plywood to the rafters or at least to the wall. The plywood is very strong but you need strong joinery to go with that. If you go upstairs you can see just how that load is connected to the rafters. I can't see but you can. My guess would be not at all.
Personally, I would call this a very poorly designed building as-is. The problem with using plywood to carry that load in this geometry is that the load has to get from the plywood to the rafters or at least to the wall. The plywood is very strong but you need strong joinery to go with that. If you go upstairs you can see just how that load is connected to the rafters. I can't see but you can. My guess would be not at all.
firebirdparts
Well-known member
Ps the floor appears to go all the way to the wall. What are the rafters sitting on?
Zeke
Well-known member
I like this post. Now, firebird, I can see that the plywood runs under the top plate that the rafters bird's mouths sits on. I personally think the plywood is a structural system.
The suggestion to take this to a civil engineer is just about imperative. While many a jackleg idea may work, you never know about the ultimate stresses and loads, like wind load.
dave*99
Well-known member
OP, any update on your project?