Saturday, July 12, 2014

Two Hour Fire Wall

Tim Uhler and Kyle Davis layout, frame,sheathe and lift rake walls on a daily basis. They make it look as simple as tying your shoe laces. I had a two hour fire wall (1600 pounds) to lift this last week, so I asked Tim for the correct way to attach the lifting straps to the wall. I didn't want to jack up the wall and attach the lifting strap on the underside of the wall.

Sim,
We use nylon lifting straps we bought at whitecap.
Make sure they are rated 10,000# or greater.
On this last house we used Simpson screws because they are bigger then the Ledgerlok http://www.strongtie.com/products/connectors/SDWS-SDWH.asp?source=fastenhp
I would use 4 screws per pick point minimum. If the bottom plate on the way stays down, the pick points, and forklift will "see" less load as the wall goes up.

We've thought about making rips of 1.75" x 5" Lvl to use instead of 2x6 to screw to the top plates. We haven't had anything break yet. 

Tim
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I went by WhiteCap Construction Supply on the way to work, but they didn't carry any of the Simpson Timber Screws. So I bought some GRK 3/8" x 8" timber screws that are rated at 4364 lbf  for side grain tear out. I was worried about the the top plate of our two hour fire wall ripping off the rake wall, because we only had two layers of GP DensGlass Sheathing (sheetrock). If I had structural plywood sheathing nailed to the rake wall top plates  I would not have been concerned about the top plates ripping off the studs.

Note: This two hour fire wall required 6 building inspection.

  1. Screw inspection on Base Layer on outside of wall.(1 1/4" min screw length, 6-12 O.C.)
  2. Screw inspection on Face Layer on outside of wall. (1 7/8" min screw length, 6-12 O.C.)
  3. Frame inspection after we lifted the wall.
  4. Shear wall sheathing nailing.
  5. Interior Screw inspection on Base Layer on inside of wall.(1 5/8" min screw length, 6-12 O.C.)
  6. Interior Screw inspection on Face Layer on inside of wall.(2 1/4" min screw length, 6-12 O.C.)


Outside base and face layer inspected.

3/8" x 8" GRK screws , 3 each side of rake wall top plates, screwed into our 4x4 post. With 4- 4 1/2" SDS screws on each side of the strap, that's rated at 12,800 pounds in the basket position.






Third inspection on the framing and anchor bolts.


Fourth inspection on the plywood shear wall nailing.

Fifth inspection on the base layer on the inside of the two hour fire wall.


Sixth inspection on the face layer of the two hour fire wall.


After using Tim's method of attaching the lifting straps to the top plates, I would only place the lifting straps on the bottom side of the two hour fires walls when they weigh more than 2,800 pounds.  Tim's method made lifting this rake wall as simple as tying our shoelaces.


Here's some pictures showing how we use to lift our walls, by jacking up the wall and placing the lifting straps on the bottom side of the wall. Or by cutting slots in the plywood for the lifting straps.








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