Pier/Curtain Wall Modular Sets
In areas of the country where traditional basement and crawlspace foundations may not be found, Pier/Curtain Wall foundations are often used to support structures. These foundations are accepted by the International Residential Code (IRC) as long as they are constructed according to IRC Section R404.4.5.3. This section requires the “curtain” section of such an assembly to be load-bearing where it supports an exterior load-bearing wall of a structure.
If the curtain is not supported by a footer sufficient to make it load-bearing or it is not known if this condition exists, the foundation should be considered a “Pier/Beam” configuration. As such, the exterior rim of a modular box set on such a foundation becomes the “beam”. It must be engineered to carry the load of the exterior walls as well as part of the first-floor load between the piers, which are bearing.
In this situation, floor joists in the modular box perform as if they are suspended between two beams (marriage wall rim/beam and exterior wall “beam”). This can allow for increased floor system vibration. It is highly recommended that “strongback” bridging be installed in OPEN JOIST floor systems to help dampen this vibration.