When a home is built with an elevated foundation, the first floor is exposed to the outdoors and must be insulated, water-proof and air-tight. Structural floor framing ties the floor to the elevated foundation, supports the walls and protects the home from outside elements.
Typically the structural floor framing attaches to the foundation in several ways:
- Attached to Piers on grade beams – In this type of framing, a 2x treated nailer is bolted to the top of the piers, then a frame consisting of LVL or 2x box frame is built at the edges, with 2x, LVL, or I-Joists are attached to the 2x nailer (See Detail)
- Attached to Standard Concrete Columns on grade beams – In this type of framing, there are two ways the structural floor framing is attached:
- The first is similar to piers on grade, where a 2x treated nailer is bolted to the top of the piers, then a frame consisting of LVL or 2x box frame is built at the edges, with 2x, LVL, or I-Joists are attached to the 2x nailer (See Detail).
- In the second, a metal fastener (I.E. Simpson Column Base) is embedded in the top of the column, LVL sills are attached to the metal fastener, and I-Joists or LVLs are attached with metal fasteners to the sills (See Detail)
- Attached to Piles – In this type of framing, the piles are notched, then LVL sills are bolted to the piles, and I-Joists or LVLs are attached with metal fasteners to the sills (See Detail)
In New Orleans where our homes must be elevated, Make It Right attaches our structural floor system to concrete columns and piles. We have not used the pier / nailer method in an effort to minimize cost and maximize the spacing of columns / piles. After extensive engineering consults, we reduced our foundations by 50% and our structural floor framing by 20%, using a column / pile, sill and I-joist combination.
The grade piles we currently use are larger than needed according to engineering calculations. All piles have a Tip and Butt measurement in inches. The piles we currently use are 8” Tip and a 12” Butt. The Tip is the side that is driven into the ground. The Butt is the end that protrudes from the ground or is cut off a grade when grade beams are poured. Because we currently attach our LVL sills to the piles, alignment is a critical component for the structure. Piles have to be notched to seat sills and cannot be notched more than one half the width of the pile (see detail). Accomplishing this is easier with wider piles since the piles will have some play side to side as they are driven (See detail).
If we used smaller diameter piles, keeping the sills aligned without overcutting would prove a more difficult task.