[Shop-talk] reinforcing roof joists

[Jim Franklin]

On Mar 17, 2012, at 11:07 AM, Tim wrote:

> A qustion for engineers here maybe?
>
> I want to hang a Datsun Roadster car body from the joists above my shop
> and garage space so I can start working on a frame in the shop.
>
> The joists are approx 2' apart and made of 2x4s. The roof is a 4 12
> pitch. The car body might weigh as much as 700 pounds but I have yet to
> get an accurate answer. (I thought I had read at one point that the body
> weighed between 400 and 500 pounds.)


It's important to get some terminology straight before answering this. Rafters
form the pitch of the roof; joists are parallel to the floor and stop the
walls from spreading out (and occasionally are strong enough to support
storage up there):

http://www.carpentry-pro-framer.com/images/anatomy-of-a-common-rafter.png

The span of the joists is important. How long are they? 2x4s will hold a lot
of weight but not if they're 20' long.

Trusses are pre-manufactured as a triangle and might support a car body, might
not. It depends how they are held together.

What do you have up there?