Tag Archives: green roof

Green roof and blocking – Part 2

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The 2nd floor load bearing wall reinforcement moves along for the sake of a future vegetable garden on the roof.

While we opted for removing and rebuilding the load bearing wall in the back 1/3 of the building, it made sense to reinforce the wall in place for the front 2/3. The existing conditions such as ceiling joists and perpendicular wall connections didn’t lend themselves to remove and rebuild.

To replace the two by four top plate with a two by six header, we cut off the top of the wall studs, removed them along with the top plate, and fitted the new header. The bottom of the wall received the almost identical treatment, except that we left the two by four bottom plate in place and just set the new two by six header on top of it.

And along the way, we installed the heavy duty LVL headers (Laminated Veneer Lumber) to span the larger openings at the French door and pocket door locations. All of the regular door openings also received new and properly sized headers in the same fashion as those on the 1st floor.

Jack in the bottle – or – bottle jack

One major component of load bearing wall reinforcement is the vertical blocking under each roof joist. The existing blocking was certainly insufficient, but still, it was taking weight from the roof and transferring it down.

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Under those circumstances, do I really want to remove the load bearing wall, or start cutting section out from it? No, certainly not! As a matter of fact, removing or cutting out wall sections would have been next to impossible. Consider the existing roof weight that was poorly but nevertheless still transferred onto the wall.

Our solution rested on two jacks – heavy duty bottle jacks – that allowed us to lift up the roof to the point where the weight was taken off of the load bearing wall.

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We placed the jacks between a header across the roof joists and a header across the floor, both two feet off the load bearing wall, added studs, and lifted 12 foot sections of the roof at a time. When we had about half an inch of clearing between the roof joists and exiting blocks, we removed the blocking and began with the wall reinforcement. Once done, we tightly fitted the new vertical blocking under each roof joist and lowered the roof back back down.

I had some good and essential help with this framing adventure. Thank you to our friend Drew, and also to Dan Rockafield, who lent their expertise and help. A thank you also to Matt who let us use his heavy duty bottle jacks.

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Green roof and blocking – Part 1

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Our work on the green roof dream continues. We recently completed the roof reinforcement over the dining room and the kitchen to accommodate the additional load of the future green roof.

But we still have the reinforcement of the 2nd floor load bearing wall ahead of us. Time to whip out the framing belt and get started towards the south end of the building.

We had recently remove the ceiling joists from the back 1/3 of the building. That gives us enough room between and under the roof joists for the upcoming attic insulation.

With the ceiling joists gone, we decided it would make sense to remove the existing load bearing wall and rebuild it from scratch.

Rebuilding and reinforcing the load bearing wall proceeded with a couple of interesting twists and turns that catapulted us into the classic problem solving mode.

Vertical blocking

We had our structural recommendations and were on the search for a good way of implementing them.

We needed proper vertical blocking under each roof joist … smething we didn’t have.

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On the first floor, we made sure to move and align the studs with the ceiling joists, which allows for direct and safe load transfer. My mind was set on proceeding the same way on the second floor with the roof joists, until it dawned on me that the roof joists are roughly spaced 20 inches on center, while the studs in the load bearing wall are spaced 16 inches on center.

There is no lining up of roof joists with wall studs. Time to hit the reset button.

From plates to headers

Our structural engineer indicated that if wall studs and roof joists don’t line up, we should replace the two by four top plate of the load bearing wall with at two by six header. That header would receive the load transferred from the roof joist through the vertical blocking and safely spread it across the nearest wall studs.

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This got me thinking about the bottom of the wall, which has a typical two by four bottom plate. If the top plate wasn’t good enough, why should the bottom plate be? Well, if the wall studs happen to line up with the floor joist beneath, it wouldn’t matter. I would get a direct, thus safe, load transfer.

But I have no way of telling if they do line up. After my recent snafu I decided to play it safe. The decision to duplicate the two by six header solution at the bottom of the wall came naturally.

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Roof joist reinforcement – kitchen

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I can’t help but to think it appropriate to grow our vegetables above the dining room. Wouldn’t it be even more appropriate to grow them above the kitchen?

First things first: Like with the dining room, we have to address the structural shortcomings and reinforce the existing roof structure above the kitchen.

Unlike with the dining room, we have a slightly shorter roof span and thus only need to sister each existing roof joist on one side. Another big difference, or advantage for that matter, is that we don’t have the ceiling joists to deal with. Their removal earlier spared us from maneuvering through the tight space between the ceiling and roof joists.

How do you attach the sister joists?

I learned about three common methods:

  • Using 16d nails,
  • lag bolts, or
  • carriage bolts.

16d nails were right away eliminated from the list, simply because we didn’t have sufficient space between the existing roof joists to pound them in or use a nail gun. Our structural engineer recommended lag bolts that had a specific structural rating. These worked because we had enough room to drive them into the joists with my small impact driver.

The only problem was cost. Those lag bolts cost more than what I paid for the roof joists we used for the sistering – although I should disclose that we purchased the joist on the salvage and reuse market from The Rebuilding Exchange.

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Roof joist reinforcement – dining room

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An idea that has been sprouting for a while is a vegetable garden on our roof. Finishing the masonry pockets along the roof joists was one component in getting us another step closer to the green roof dream. I now have the privilege to pick up my framing tools again and install the sister joist for the roof reinforcement, starting in the dining room.

The one thing I won’t pick up – at least not on my own – are the 16 foot long roof joists I set aside for the sistering. Too long and too awkward to handle on my own. Our friends Max and Drew, both equipped with excellent carpentry skills, agreed to stop by and help out. Thank you!

The dining room roof joists required sistering on both sides. We worked our way from the outsides toward the middle, maneuvering the joists under the roof. One end got placed into the masonry pocket, while levering the other end snug up against the the roof deck right above the load bearing wall.

We left the most delicious part of the installation for the end – that little pesky header between the dining room center joists.

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That thing had to go to make room for the sister joists. Max carefully cut through all the nails and eventually was able to wiggle the header out.

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We got the missing sister joists into place and connected the short and long piece of the center joist with a 36 inch long simpson strap at the bottom.

That took care of the dining room reinforcement. It’s time to move the operation into the kitchen.

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Pocketing for the green roof

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The masonry repair work in the attic is done. But I have that one more task waiting for me, and it is green roof related. I need to get those pockets punched into the masonry wall for the sistered joists.

The process is similar to the range hood exhaust installation. I use the hammer drill with a masonry bit to drill out the mortar joints and set up a perforation line across the brick. Once that is done, I can grab a hammer and chisel and carve out the joist pocket.

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In the kitchen at the chimney, the two joists stop short of the masonry wall. I placed a sister joist mock up along the roof joist, which allowed me to mark the exact location for the joist pocket. As for all the pockets, it was a tight space to work in. Nevertheless, the pockets turned out all right, and a test placement confirmed that the sistered joists would fit right in.

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