In the past, Insulated Concrete Forms (ICF) were primarily used for residential construction and low-rise commercial projects. Today, as developers, architects and builders strive to build green, energy efficient and sustainable buildings at an affordable cost, ICF has become a viable and cost effective building solution for hi-rise applications as well.
It is no longer uncommon to see ICF structures in excess of 10 stories. While the industry celebrates this success, it opens up new challenges for the building and design communities. There are several unique considerations that require special attention which are discussed below.
When selecting an ICF for hi-rise construction, product features such as interlock, foam density, block size, form capacity, web design and web spacing should be evaluated. These elements can make a considerable difference in the efficiency and successful completion of a hi-rise project. It is also essential to consider the manufacturer’s training materials, technical assistance and engineering support when reviewing a product’s compatibility for a project. It is worth the small additional cost for a reliable brand since the objective is often to enable occupancy as quickly as possible.
Engineering is an extremely important factor for hi-rise construction. Walls can be designed either as non-load bearing or load bearing using a variety of different concrete core thicknesses. A wall with a large number of openings typically requires structural column designs between the openings up the entire building. This can lead to the requirement of considerably more reinforcing steel and wider concrete core thicknesses. Connections to floor slabs, internal walls, stair wells and elevator shafts must all be reviewed carefully as there are numerous alternatives to these design elements.
ICF walls are typically supported on the inside of the building footprint only. On lower buildings it is easy to add additional bracing to the exterior if required, as it can be easily installed and removed. The taller a building is, the more difficult it is to install exterior support due to safety concerns for workers, added labor hours and increased material costs. Areas that often require additional form support are at floor connections where the ICF has to be cut to accommodate the floor system. It is important to work closely with the ICF manufacturer to develop creative ways to solve these issues from the interior side of the wall.
Due to the increased heights in hi-rise construction, safety and liability are much greater concerns. Scaffolding systems must meet the proper engineering and safety requirements for hi-rise structures and should be equipped to provide both front and back safety rail applications. Fasteners used to secure to the ICF wall and floor slab must be engineered for the application. Additional use of safety lines etc. might also be necessary.
Pouring ICF walls is more challenging for hi-rise applications than low-rise applications. As building height increases, wind and precipitation are usually intensified which can increase the difficulty of a concrete pour. Special attention must be paid to concrete mix design, slump, aggregate, admixtures, lift rates, consolidation and pump flow to prevent forms from bulging or failing. Attention to detail when installing the forms and following proper pouring techniques are necessary to ensure straight, plumb walls, limit liability and reduce the risk of job-site injury. In addition, an experienced crew, pump operator and a high quality ICF should be combined to ensure a successful, safe pour.
Tell us about your hi-rise ICF experiences, tips and tricks!