Rim Joist Remediation – Part 2

In Rim Joist Remediation – Part 1, we discussed the as built conditions of the joist assembly at the main floor. Next we created an air barrier and WRB using VP160.


    Assess the condition of the wall, as well as the assembly components


    Protect the rim joist assembly and foundation below with a WRB


    Create an exterior air barrier to be sealed to the foundation wall and (at minimum) the subfloor (ideally the bottom plate of the stud wall). We will continue the air barrier on the interior wall and seal it to the bottom plate and subfloor


    Repair and replace the siding where required, and recreate the water table detail at the base of the siding, (this was removed during the flood but can be seen in older photographs)


    Finish the exterior foundation wall with parging

Rim Joist Air Barrier and WRB with Henry VP160

We selected Henry VP160 as the air barrier and WRB – it is vapour permeable (important as this will be on the cold side of the assembly), and is fully adhered (simply peel off the back and apply like a sticker). Additionally, spray adhesives and sealants are available if working in particularly challenging areas, but we found we did not need this at all.

The VP 160 was fantastic to work with – it far outperformed our expectations. The night after putting on the initial layers, there was a rainstorm and some edges were unprotected. However, it stayed fully adhered and was extremely flexible and forgiving when we had lumps or gaps to work around. I can’t imagine how easy it would be to use in new construction!

Rim Joist & Water Table

The roll was 4’ high, and we found that the two layers we needed would each be about 16”, so as we cut lengths, we divided them into three (16” x 3 = 48). The first layer went on extremely smoothly. This portion started a little below the top of the 2×8 rim joist and extended several inches below the ladder sill on the foundation wall.

When the building was moved onto its new foundation, it was not quite square, and it looks as though a second rim joist was added, and hangs over the foundation wall by approximately 1/2 to 3/4 of an inch. We simply followed contours with the VP160. Later we will smooth it out with parging.

Drip Edge and Second Layer VP160

Using our water table template below the bottom course of siding (no longer there but measured and marked), we attached an aluminum drip edge. Importantly, since the VP160 is the air barrier, the top of the drip edge is over three inches below the top of the VP160. This allows us well over the minimum 2” overlap recommended to create a good air barrier.

Rim Joist & Water Table

After attaching the drip edge, the second layer of VP160 was installed. In some cases where there was inadequate remaining building paper at the top of our second layer, we added a small third section above (performing as a WRB rather than air barrier here). It was a difficult call though as removing more siding tended to cause further disintegration of the existing paper.

Rim Joist with lapped VP160

Air Barrier and WRB at Corners

Corners were difficult – this work was being done on the east and west elevations only, as further work is required on the front and rear elevations. For this, we tried to go around the corner by approximately 6 inches, leaving the bottom portion of the second layer’s backing on (un-stuck) so that we could add the drip edge at a later point. (In some cases the leading edge was also left with its backing).

In the front elevations, this required us removing portions of the trim, where unfortunately the sheathing behind was completely deteriorated. This is also under the window boxes which were filled with vermiculate that contains asbestos. We patched this with plastic. Each piece removed was carefully labelled. Following asbestos abatement, fixing the front trim (as well as getting the WRB behind it and lapped under the windows) will be one of our first projects.

Rim Joist & Water Table

In part 3, we will discuss the finishes we used and the construction of a historic water table detail.

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