Load Paths
Home Builder’s Guide to Coastal Construction
FEMA 499/June 2005
Technical Fact Sheet No. 10

Purpose: To illustrate the concept of load paths and highlight important
connections in a wind uplift load path.

Key Issues
--Loads acting on a building follow many paths through the building and must
eventually be resisted by the ground, or the building will fail.
--Loads accumulate as they are routed through key connections in a building.
--Member connections are usually the weak link in a load path.
--Failed or missed connections cause loads to be rerouted through unintended
load paths.

Graphic:
Vertical load path from roof to ground on a platform-and-pile-construction
building. Note: Load paths will vary depending on construction type and design.
Adjacent framing members will receive more load if a connection fails.
--Link 1: High winds lift the roof upward. Roofing fasteners link the roof
covering to the sheathing (note: although not a structural connection, the
attachment of the roof covering to the roof sheathing is an essential part of
protecting the building envelope), and sheathing fasteners link the sheathing to
the roof framing members (see Fact Sheet No. 18).
--Link 2: Accumulated roof load is routed through roof-to-wall connections.
Special roof ties connect the roof framing to the bearing walls (see Fact Sheet
No. 17).
--Link 3: Upper walls transfer loads directly to the lower walls. The floor
framing is bypassed by using the metal straps or extended exterior sheathing
that directly connects upper wall studs to the lower wall studs. A similar
connection is used to connect the lower wall to the main floor beam.
--Link 4: The accumulated uplift force is transferred from the main floor beams
to the pile foundation with special brackets or bolts (see Fact Sheet No. 13).
Note: some of this load is offset by the weight of the building.

Note: Horizontal load paths transferring shear from upper stories to the ground
must also be analyzed.

If a connection fails, an alternative load path will form. If the members and
connections in the new load path have inadequate resistance, progressive failure
can occur. Loads must be routed around openings, such as windows and doors.
Accumulated loads on headers are transferred to the studs on the sides of the
openings.

Load path around a window opening.
--Link: an adequate connection must be made between the header and the king stud
in order for the load to continue down the path.
--Link: the bottom of a wall could have points of high uplift due to an
accumulated load from above. Suitable hardware should be installed in the proper
locations.

Load paths can be complex through a connection. It is important that each link
within the connection be strong enough to transfer the full design load.

Load path through a pile connection.
The detail at left shows a typical floor-to-pile connection. Uplift loads are
transferred through the joint in the following order.
1. from upper story to strap
2. from strap to floor beam
3. from floor beam to bolts
4. from bolts to pile
5. from pile to ground