Raising the roof

[Dr Stan]

Since I'm going to replace the roof on the shop due to hail damage I decided to raise it from 8' to 12' high like I should have in the first place.     I'll remove 12 to 14 ft of roof at a time and add 4' stem walls then reuse the trusses.  Will also replace the 7/16 thick OSB sheeting with 3/4 tongue & groove (also like I should have in the first place).

This will enable me to install a 2 post car lift inside and use my forklift w/o cutting it down.  I realize it will be a lot of work, but the advantages will be high and I'd been thinking about this for awhile. 

Part of the house has a 12/12 or close to it pitch which I'm hiring out.  The remainder is 4/12 pitch.

I'll have to wait until my heel is much better as I'm dealing with rejection of the artificial bone used to fill the hole in the heel bone. 

So I'm looking for suggestions.  I plan to install 4' stem walls built on the ground then lifted up instead of building them directly on top of the existing walls.

Has anyone done this and if so what approach did you use? 

What problems should I watch for?

Thanks in advance

Stan

[f350ca]

I've seen walls extended that way on OLD buildings Stan. With trusses it might work better as there should be no side load. The buildings I've seen had rafters, over the years the side load of the rafters flexed the walls at the joint. Mind you won't need to worry about snow load in Kentucky.

[Vinny]

I hired it out but only went for 10' due to also adding a second floor for office space.

[Dr Stan]

(07-24-2016, 01:07 PM)f350ca Wrote: I've seen walls extended that way on OLD buildings Stan. With trusses it might work better as there should be no side load. The buildings I've seen had rafters, over the years the side load of the rafters flexed the walls at the joint. Mind you won't need to worry about snow load in Kentucky.

You're correct about snow load as we have very little.

What I've read on some DIY construction sites is to pay attention to the hinge effect.  In other words the joint between the 8' & the  4' walls as much horizontal stress will try to separate the walls.  Nails are only to be seen as temporary fasteners and to use 1/4" diameter carriage bolts every 24" as connecting devices.  That's the same way I tied the top cap together as per code and I'll probably throw in some construction adhesive to boot.  New hurricane ties will also hold the top cap & the trusses together.

I'll also build a wooden jib crane to raise the prefab wall extensions.

Thanks for the input.

Stan

[f350ca]

Bolts will hold the plates together but the studs are still just nailed to the plates. Plywood sheeting on both sides of the joint extending past the plate to catch the studs might help.

[Dr Stan]

(07-24-2016, 09:41 PM)f350ca Wrote: Bolts will hold the plates together but the studs are still just nailed to the plates. Plywood sheeting on both sides of the joint extending past the plate to catch the studs might help.

The existing walls are sheathed with OSB on the outside and MDF on the inside (I found the MDF at a seriously low price on Craig's List).  The extension will have OSB on both sides with metal strips on the diagonal on each corner.  Construction adhesive will also be used between the sheathing and the studs.