Finished Foundation and Floor Framing Uh-Ohs
Before framing begins, it’s important to check whether the foundation is level and square
[Editor's note: Roger and Lynn Normand are building a Passivhaus in Maine. This is the 24th article in a series that will follow their project from planning through construction.]
The foundation for the main house is complete. It's time to start framing and sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. the main floor deck while we wait for Shawn Woods to excavate the footings for the attached slab-grade garage and three season room.
There’s not a whole lot of “greenness” or “Passivhausness” to talk about in floor framing. But it’s all part of the construction process and hey, we need a main floor to walk on.
The framers — Jason, Travis, Jimmy, and John — began building the main floor deck by applying a capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. break on the top of the concrete in the Logix ICFInsulated concrete form. Hollow insulated forms, usually made from expanded polystyrene (EPS), used for building walls (foundation and above-ground); after stacking and stabilizing the forms, the aligned cores are filled with concrete, which provides the wall structure. foundation to stop any moisture from wicking up into the floor framing.
They then compared the “as is” foundation to the architectural plans. It’s best to start framing the deck on a level and square foundation. That’s especially true for EdgewaterHaus, as the main floor walls and roof trusses are already built in a factory to the specifications of the architectural plans; it’s too late to make any dimensional accommodations to the walls or trusses.
BLOGS BY ROGER NORMAND
A small 1/8-inch gap at the bottom of the wall on a problematic foundation can become a gaping 1/2-inch opening 10 feet higher at the top of the wall, complicating the placement of adjacent wall panels and the trusses. If this were a typical home, such gaps would be shimmed and covered by exterior and interior finishes; no one would know the difference. Not us. Gaps complicate air sealing the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials.. The blower door and thermal imagery will reveal these “thermal holes.” We need an exceptionally tight, well-assembled building envelope to meet the Passivhaus standard.
So if there’s any shimming, it’s best to do it at one place — the bottom plate of the wall. Jason used a laser to methodically check the elevation of the foundation at each point near the wall anchors and measured wall dimensions against the specifications of the plan.
Using the highest point on the foundation as a reference, Jason found two areas with notable variation: the west side of the Bedroom 3 foundation was 1/2 inch low, and the south side of the three-season room foundation was 3/4 inch low.
The foundation was also out of square. Using the south facade as a reference line, the north wing of the building foundation strays from the 60 degree design by up to five degrees. That’s not much, except when the wall extends 50 feet!
The east and west foundation walls of the north wing are not parallel to each other; the foundation is 1 3/4 inch too wide where the garage wall meets the house, expanding to 2 1/2 inch too wide at the far, north side of the garage.
I expected tolerances to be closer
Now some may say that’s just another day in the life of a framer to resolve real-world variation in the foundation.
Perhaps. But I expected better results with the Logix foundation. We had surveyors precisely mark the outside corners of the Logix blocks on the footers. And the snug fit of the many male/female vertical connections points in the Logix block adds confidence. I’m not sure if the vertical and horizontal variance lies in how the blocks were stacked and braced, or the shifting of some block while the concrete was poured into the Logix cavity, or both.
Several areas of Logix did noticeably lift during the pour, then seemed to settle back into place as more concrete was poured. Yet in looking at the completed foundation, there are clearly vertical and horizontal gaps ranging from 1/8 inch to 3/8 inch in many of the Logix blocks.
The worst areas are the top two courses of block, and the very worst is the east section of the wall with the 60 degree angle in the foundation. The vertical supports did not extend to the top two courses of the Logix, and not every course of block was screwed into the vertical supports to prevent uplift.
Concrete exerts enormous pressure when it is being poured. Could better bracing and checking for plumb to the bottom course have improved the results?
Squaring and leveling the foundation
The framers spent several man days adjusting the horizontal and vertical position of the base plates on the foundation to bring the floor framing back to the plan specifications. That meant moving the mudsill inward or outward on the foundation, and shimming it upwards by as much as 3/4 inch. Jason aimed to have dimensions and elevations to a +/- 1/8 inch tolerance across the entire foundation.
The framers next cut, placed, and braced the seven concrete-filled lally columns in the basement, secured two LVLLaminated veneer lumber. Engineered wood product in which wood veneers are glued together in thick sections for use as beams or other structural members. LVL is stronger, straighter, and less prone to warping or shrinkage than conventional lumber and does not require the destruction of mature trees. beams atop several of the lallys, and a delivery truck boomed two beefy steel I-beams into place atop the remaining lally columns.
It looks like we need another lally column
One of the steel I-beams had insufficient bearing on the foundation. That was quickly solved by placing another lally column on the footer where that steel beam meets the foundation.
Our floor was engineered by Coastal Forest Products. The framers started to install the I-beams and floor deck along the main axis of the house.
Another trip to the lumber yard
Coastal delivered the wrong mix of hangers: there were too many 3 1/2-inch-wide hangers and not enough 2 1/2-inch-wide hangers, and there were not enough top-mount hangers for use on the steel beams. We were also short on a section of rim board and some sheathing.
That was solved the next day. Floor framing proceeded along the main axis of the house.
The crew then started the layout for the hangers on the north wing, the one with the 60 degree angle.
Where can I get some 60-degree hangers — fast?
We had received 45 degree hangers instead of the 60 degree hangers called out in the design.
The Coastal rep came on site, confirming the shortage. Sixty degree hangers are a special order item. He promised quick delivery, especially if they had some in stock.
And so we await delivery of the 60 degree hangers to complete the main floor deck.
Meanwhile, the installed deck is rock solid. There’s absolutely no bounce on the floor, even before we pour the 1 1/2-inch concrete. The meticulous care to square and level the foundation bodes well for installing the factory-built panels.
- All photos: Roger Normand
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