Green roof and blocking – Part 1

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.


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.


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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About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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