Between holidays, travel and weather delays this update has been delayed far longer than i would have anticipated . However work has continued as well as can be achieved given the weather that we’ve had in north Georgia this winter.
The next major milestone after beginning panel installation was the initial inspection by the structural engineers, Baku Patel and his assistant Srikanth Bajaj, of Palmer Engineering. Since the construction method is new to the area the local planning department required us to contract with the structural engineering firm for onsite inspections of the panel installation.
Before the discussion of the inspection a little background on the house is in order. The basic plan of the house is a rectangle, with two bump-outs on the south side, a porch on the west, a mudroom on the east and a jog in the north wall. The bump-outs on the south wall and the mudroom on the east lend strength to the walls; this meant that additional structure was needed on the west and north. We ended up adding two shear walls, one on each side. The north wall has eight feet of unbalanced backfill and the south is at grade.
The first inspection was set for December 15. By then the contractor had completed the following:
• Dowels inserted and epoxied for all installed walls panels
• Shear wall on west side - 11-foot panel
• West wall from the shear wall to the north corner - 18-foot panels
• North wall - 18-foot panels
• East wall from the north corner to the intersection with the mudroom - 18-foot panels
• Basement window in the north bedroom - opening cut, mesh and rebar in place and ready for mortar
The engineers were able to review the following structural elements:
• FastFoot footing
• Dowel spacing & length
• Dowel to rebar connection in pilaster
• Available depth for mortar behind rebar in pilasters
• Application of RG1 mesh at interior and exterior corners
• Application of RG2 mesh where necessary
• RG3 mesh and rebar at top and bottom of window opening
• RG2 mesh at corner of window columns
There are a number of structural issues involved in building our plan using SCIPS. The first issue was how to build the below-grade SCIPS walls. To the best of my knowledge most houses built using GCT panels have not involved significant panel area below grade; most are cast concrete walls below grade with SCIPS panels above. We wanted the added R-value of having the EPS below grade so additional strength was required. The solution was to build pilasters - mortar and rebar columns - into the below-grade portions of the wall on the exterior surface. These were at 16” OC. The rebar was placed inside the galvanized wire and the foam burned out to allow sufficient room for the structural mortar. The wall rebar was tied to the dowels to meet code.
The second issue was how to support the floors. Both the main floor and the loft floor (approximately half of the area of the main floor) will be concrete, placed over steel floor joists. That’s a lot of weight so we needed additional strength. The solution was pilasters on the inside, also 16” OC, but offset 8” from the outside pilasters to preserve as much R-value as possible.
The pilasters and rebar can be seen here: note that the final burnout of foam and positioning of rebar had not been done when this was taken.
The third structural issue was how design the window openings for maximum strength and minimum thermal bridging. The solution, which was implemented and ready to inspect on the first window opening, involved burning out the foam to allow for the installation of horizontal rebar above and below the window, on the inside and outside wythes of mortar.
The window opening, with rebar above and below, can be seen in the following picture:
We had quite a crew assembled for the inspection. In addition to the Baku and Sri from Palmer Engineering we were joined by Joe Martin of the architectural team, plus Victor Camacho and Scott Miller of Gulf Concrete. Victor is VP of sales and operations as well as being an engineer, while Scott is the sales and technical advisor.
The video of the day of the inspection is here .
Results of the day’s review are below.
The Fast-Foot footings met with general approval. Placement of the dowels was quick. Larry’s recommendation that we use epoxied dowels instead of rebar wired in place before the pour proved to be successful - it would have been quite difficult to keep the rebar in position during the pour.
However, the dowel placement itself could have used a little more thought prior to installation. Our original plan was to place the dowels so that they fit just inside the wire of the GCT panels. However, after placing the panels and reviewing the situation prior to mortar application it was clear that the dowels should have been 1/2” inside the wire, in order to guarantee adequate mortar coverage. We ended up using spacers to move the rebar 1/2’ inside the wire. Since the rebar was already placed and could not be bent where it came out of the concrete we ended up adding mortar for the bottom 18” in order to get the proper coverage.
The application of the additional mesh is relatively straight-forward and no problems were identified.
The plan for the windows underwent significant revision. Instead of using rebar and burning out the foam the engineers agreed that an additional layer of mesh would be sufficient. This would preserve the full foam for insulation and simplify installation.
All in all it was a successful day. Now, on to mortar placement!
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