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-   -   Rafters need to be raised higher... (http://www.hotrodders.com/forum/rafters-need-raised-higher-38003.html)

Cliff Elikofer 04-19-2004 01:09 PM

Rafters need to be raised higher...
 
I'm in the process of getting a 2 post Rotary lift for my shop. But before I purchase the lift, I have to raise or modify two rafter's higher for the lift to clear. My rafters are 10ft off the concrete and I need 13ft of clearence to clear the top of the lift. Anybody have any idea's or a link to tell how to modify rafter's? The link below is the lift I will be getting. On another idea floating in my head. I have 5 inch's of concrete where the lift will be bolted down. Just thinking, would spreading the weight out like using a bigger diameter 1/2" steel plate under the post, would that be a good idea or possible over kill on that idea? I'm thinking about getting a 2' by 2' by 1/2" steel plate and bolt it down and then bolt the lift on top of the plate. I would feel better having those plates and knowing that I did all I could before I installed the lift. So, If the lift falls over, I won't feel bad...lol. Over kill and safety is my main concern here.

Thanks for any input.

http://www.northerntool.com/webapp/w...5511&langId=-1

30desoto 04-19-2004 01:47 PM

Cliff
Just a suggestion on the rafters you can figure out which ones need to be removed, and put 2x6 cross bracing at the top of your exesting rafters that are left over from the bottom to the top every 2' and if you only need to clear half the area of the rafters not the full length then you can cross brace in the center of the peek of the rafters, also instead of flat plate on the hoist at the bottom you could run L brackets out away from the bottom and bolt to hoist and the floor on each side just use a heavy steel L bracket, then if you need to remove it for some reason you just have to unbolt it.
30 dee

Cliff Elikofer 04-20-2004 01:08 AM

1 Attachment(s)
This is what I've came up with so far. I'm still tossing up idea's but I'm leaning more toward this idea for the rafters. As for the L bracket at the bottom of the lift, I might just do that. I'm going to speak with a factory rep before I make my final decision for the weight distrabution of the lift.

Thanks,
Cliff

Kevin45 04-20-2004 01:27 AM

That would work but add the wood BEFORE you ever cut the existing rafter. Also use 1/2" OSB for your tie plates instead of the small metal plates that the gussets are normally put together with. Add the OSB on both sides of each rafter for rigidity. Also make sure the 2x's that you install are installed symmetrically. Post some pics when done. What you are wanting to do is no different than a factory made truss.

Kevin

Cliff Elikofer 04-20-2004 12:36 PM

Just a little bent right now. Just got off the phone with a local rep and he said my shop is almost too small for that lift. I think he's trying to sell me a 4 post lift which was more money. He's not a rotary rep, just a local vendure. My shop is a poll barn style and its a 30x40 with 10 ft ceiling(concrete to bottom of the rafter). I have few pictures of the inside of my shop and one of the outside. Pay no attention to my truck and car. There both a work in process.

Does my shop look too small for a two post lift? This is a picture of the outside.
[url]http://community.webshots.com/photo/73650696/74858593EcCvZp[url]

You can see some what the inside of my shop. The lift will be going where the black car is.
http://community.webshots.com/photo/...73651134xlCOnK

Total album of pictures.
http://community.webshots.com/album/73650696fnhtIi

30desoto 04-20-2004 01:52 PM

Cliff
Your shop is more than larg enough to hankle that lift, I would just redo those rafters:thumbup:
30 dee:P

60convert 04-20-2004 05:50 PM

lift
 
I would say as long as you plan it for your intended use the 2 post will work to your expectations. also remeber that when the hoist is at its maximum height the car or truck on it will also be taking up all the space where the rafters use to be so make sure you make a (hole) in the rafters large enough to accomodate any of your projects.
Jesse

30desoto 04-20-2004 07:02 PM

Cliff
I really can spell better than the last post.
You should be fine with what you have just make sure you have the room in the rafter space, with good support. Your design looks like it will work great:thumbup:
30 dee

olsixrod 04-20-2004 07:20 PM

professional help
 
Hi Cliff, try a short walk in the yellow pages,find the closest truss manufacturer in your area, a half dozen dough nut's will buy you a conversion with the resident planner/ engineer, show him/her a sketch, with dimentions, of what you have, two min. or less in a design "cook book" style program, ( read that SALES TOOL ) will get you an engineered print to follow. this ensures that you will do no harm, and might even gain more vertical height than you need. You live in snow country, so minimize the risk,this is a lot more complicated than it looks from the floor, ask a pro.C-YA Paul

5window 04-20-2004 08:00 PM

Your rafter plan should be okay as drawn, as long as you use a board of adequate depth for the lower chord in your drawing. This would depend on the types of wood available and the expected snow loads in your area. You might ask a local builder or rafter company for their advice. You could use a board the same size as your rexisting rafter, but this might really be undersized and you wouldn't know it without checking

With all due respect, I wouldn't
use OSB for anything in structural construction. It has absolutely no strength-you can break it barehanded. If you aren't going to use structural connectors manufactured for the purpose, at least use 1/2" exterior grade plywood and galvanized construction screws. But Kevin45 is right, you want to brace both sides.

As for needing foot plates to distribute the load, you can figure the load by adding the weight of your lift and the weight of your vehicle and dividing that by the cross sectional area of your lift posts to get a pounds per square foot calculation. The are lots of tables for calculating the supporting strength of concrete. A call to your local concrete supplier could probably tell you if you need a wider support or not. Good luck.

Beenaway2long 04-21-2004 09:25 AM

Since its a relatively new building, ask the manufacturer of the trusses what you would have to do to accomodate your request. I would think that they could give you some "off the record" suggestions. Or ask them how the truss would be designed,if they were building it. Ask them for a price and the sketch, so the codes person can inspect it.
Either way, I would sandwich the existing truss w/ 1/2" plywood. Glued and screwed on all chord members.

'35 Sedan Delivery 05-02-2004 10:21 AM

Instead of modifying the trusses, I'd open up the whole space. Trusses don't take well to "field" modification, and I doubt that the mfgr. would give you any advice on how to do this, informal or not. Besides, opening up the whole space would give you a lot more flexibility.

Here's how to do it.

Assuming the trusses are on two-foot centers and are centered over the bay where the lift is going, remove the metal roofing 4 feet to either side of the center truss. Remove the center truss and the ones on either side of it (three total). Take two of these trusses and "sister" them to the remaining adjacent trusses (screw them together every foot along their entire surface, using #8x3" galvanized deck screws).

If the plate on the top of each side wall where the rafters have been removed isn't at least a 2x8, replace it with a 2x8 and bolt it into each concrete block cell that is filled. This may be overkill, but it is intended to prevent the wall from bowing out where the rafters have been removed, hence the walls are no longer "tied" front to back.

To fill in the space, use 2x6 "purlins" (beams going lengthwise between the rafters). Place them at the ridge (peak), above the side walls, and where the short truss elements join the long elements along the roof. They should be angled so that they are perpendicular to the roof line. Fasten the purlins to the trusses with joist hangers.

Then nail a 2x4 diagonally to the underside of the purlins on one side from where the top purlin joins one truss at the ridge to where the bottom one joins the other truss at the side wall. Do the same on the other side but in the opposite direction. Again, this may be overkill, but it is intended to prevent the roof from "racking" due to the 8' gap between the rafters.

Finally. replace the metal roofing.

Now you have an 8' wide "cathedral" ceiling over your lift, along with a roof system that will take the snow and wind loads the original structure was designed to handle.

Good luck.

Bill

daimon1054 05-02-2004 12:13 PM

I would at least run the new rafter all the way to the ends of the roof. Look at how a try ceiling is done that is what I would do.

http://playfair.homestead.com/files/house/tray.html

Cliff Elikofer 05-02-2004 03:16 PM

1 Attachment(s)
Thanks Bill

I went to the company that built my shop and I talked to the engineer that works for them. He said the blue print that I have now will work fine. I told him I was going to build a support around the lift to support the trusses bottom cord. The blue print in the above post is what I was going by from memory and is wrong. I went out and did some measuring before I went and talked to the engineer about my new blue print (the company calls that 10' and I have no clue why they do that, it's 9'6'...not 10'). The bottom cord is actually 9' 6'' from the concrete to the bottom cord. As of right now, I have the support up and the lift up as well. I don't have the lift totally installed and the bottom cord has not been cut yet. I just have the side post put up and the top bolted on the lift. The support that is built around the lift is treated 4x4 lumber and is nailed together with 2x4 purlin hangers. The bottom and top cords that are in my shop are 2x6's and the purlins are 2x4's. My trusses are 4' off center. I have two trusses that will be modified. Before I cut the purlins out and cut out the bottom cord. I will nail some 2x4 together and put them up to support the top cord. Then the middle cord will be cut to length and them put up using truss hangers. I will then cut the purlins angles just like the factory did and nail them up as well with the hangers. After that is done, I will cut the bottom cord out. Now the middle cord will be the bottom cord, which will set right on top of the support that is built around the lift. The only problem I might have is the pull up door can not be opened all the way while a long bed vehicle is on the lift like a long bed truck or extended cab truck. I have a heater that is in front of the lift that I will have to relocate cause I don't wont the heat from the heater blistering the paint or getting the grill hot to the point it starts to melt. Once I relocate the heater, I can move the lift forward and that will clear a long bed truck and the pull up door can be opened all the way. That takes care of one problem but it will generate another problem. My heater has a 20' long tube that comes from the heater. The heater is bolted to the trusses and when its on, the heat is shot straight down and a vehicle can not be to close to the heater or the paint will blister. I will probably leave the heater where's it at. But I will not be able to open the pull up door all the way. I can open it about 3/4 of the way. To me, that is not a problem. But its the other person that I'm worried about. If a friend comes over and were working on something and I forget to tell them about how high the door can be raised when a long vehicle is on the lift (that is what I'm worried about). What I could do is, put some kind of stop in the rails so that the door will only raise so high. That way, I don't have to worry about it. But I will have to get used to the door being only raised only 3/4 of the way up even thou a vehicle is not on the lift(Ooo...the decisions I have to make...I know I created them...lol).

Cliff Elikofer 05-02-2004 03:21 PM

1 Attachment(s)
Support that is built around the lift.


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