Delivery Methods

Shortly after the hurricane, it became obvious that no single system could be relied upon to rebuild the battered Gulf Coast. In New Orleans alone, 250,000 had been lost. Just before the storm, New Orleans builders were constructing roughly 1,000 homes per year, in part because the city was largely built out. At that rate, it would take 250 years to rebuild. Upon realizing the enormity of the loss, we quickly decided that Katrina Cottages must be produceable by all major systems:


Manufactured housing is houses that are delivered to a jobsite on wheels, either in one piece (single-wide) or two pieces (double-wide). Manufactured housing is regulated by the National Manufactured Housing Construction and Safety Standards Act of 1974, more commonly known as “HUD Code.” Building inspection occurs in the factory so that when a manufactured house arrives onsite, the local building inspector only needs to inspect site-related issues such as utility hookups.


Manufactured housing represents both the worst and the best of the disaster recovery housing world. On the one hand, manufactured housing (often referred to as “mobile homes” or “trailers”) is stigmatized all across America as the cheapest possible housing. Millions of Americans’ perceptions of manufactured housing are something akin to the wretched trailer in this image. As a result, municipalities across the country ban manufactured housing anywhere within their city limits, or otherwise limit it to the “wrong side of the tracks.”

On the other hand, the manufactured housing industry has made huge strides in recent years and builds their units much more substantially than just a few decades ago. Their interiors are often imperceptible from site-built houses in any subdivision in town. And of the countless calls we got from people after Katrina, almost all of them were looking for a house they could buy that was totally complete and which they could set up on their lot quickly. In other words, a manufactured house. The reason for this is clear: when your life has been completely disrupted and you’re trying to survive in a tent or living in your car, the speed with which you can recover some shred of normality is the most important thing to you.


Today’s manufactured housing has only one major flaw: exterior design. The “Manufacturing’s Weakest Link” section on the Lessons page describes in some detail why this is the case. This image is the front porch of Katrina Cottage VII. Obviously, there is no similarity between this cottage and the trailer at the top of this page. But KC VII didn’t start out this way. When it was first built, it was a very poor cartoon of my working drawings. I literally had to go out to the factory and spend days on end with the crew to get it right, getting up on the scaffold again and again to show the workers how to put the parts together. I even spent the night at the factory at the end to help get it out on schedule. And I became good friends with several of the workers in the process, so it wasn’t an adversarial experience. But the most important point is that once they knew what was expected, they could have built 10,000 more just like that one. And communities all over the country that reject manufactured housing like the top image will accept cottages like KC VII. The factory isn’t the problem; design is the problem.


Modular housing is like manufactured housing in that it is built in a factory. Modular housing is delivered to the building site in modules. Like manufactured housing, the module size is limited to a total height of sixteen feet (including the wheels) and a total width of sixteen feet (including eaves, doorknobs, light fixtures and the like) in most states. The length of module has a greater state-to-state variation for both modular and manufactured housing. And transportation costs for both modular and manufactured housing are significant; the general rule is that beyond 500 miles from factory to building site, the transportation cost becomes prohibitive, so customers are limited to manufacturers with factories in their regions.

In most other ways, modular homes are different from manufactured homes. Modular homes are regulated by the International Residential Code, or IRC, in most places, but within the industry it is sometimes referred to as “Mod Code” to distinguish it from HUD Code. Modules arrive with exteriors mostly complete, but without interior wall finishes so that local building inspectors can inspect the structure, electrical, plumbing, and other items before the walls are closed up. There are no inspections within the factory.

Like manufactured housing there is a stigma to modular housing in some parts of the country depending on who the regional manufacturers are, but it tends not to be as great a burden because the modular industry as a whole often does a better job with exterior design. And in both cases, there is no reason that factories cannot turn out perfect architecture to microscopic precision, because computers, smartphones, cameras, cars, and many other items roll off assembly lines to that degree of precision around the world, and have for years.


Modular housing has a somewhat more limited application in disaster recovery for two reasons: A modular house can be completed in a few weeks, which is a lot faster than the few months it takes to stick-build a house, but it’s not nearly so fast as the few days it takes to install and finish a manufactured house. The second reason is that because modular houses allow larger houses to be constructed because there is no limit to the number of modules that can be used, its use in disaster recovery tends to be limited to those who are not so financially stressed that they can go ahead and rebuild their entire house rather than just a cottage to get a foothold on their land again.

Katrina Cottage VIII, shown here on temporary display in a parking lot near Washington DC, is one of the smallest modular houses, with only a body module and a roof module. It was the first Mod Code Katrina Cottage built in a factory.


Panelization gives conventional builders a huge edge over their stick-building competitors by allowing a house to go from the foundation to being dried-in in 2-3 days or sometimes less, depending on exactly how the panelization is done. This process often takes several weeks with conventional stick framing. Exterior and interior finish work is performed in the usual manner with most systems.

Wood-frame panelization began with stick-framing; the only difference was that the walls, floors, and roofs were stick-framed in the factory rather than in the field. Stick-Frame Panelization (SFP) is still very popular today because stick-framed walls are very familiar not only to the builders, but to their customers.

The late 1970’s saw the rise of re-conceived panelized construction. The Structural Insulated Panel system, or SIP, for short, was composed of two layers of plywood glued to a core of foam insulation. SIP panels are exceptionally strong and stiff even though they contain no rafters, joists, or studs, and typically have insulating values far in excess of a comparably-sized stick-framed wall or roof that is insulated with fiberglass batts.

Recently, SIP panels themselves have been re-thought, except this time, it is a refinement rather than a reinvention. Fiber-reinforced cementitious siding has been used for years as the exterior cladding of buildings. Some clever inventor realized that not only was the material very strong (it is, after all, made mostly of concrete,) but it is also rot- and termite-proof. So they replaced the plywood skin of SIP panels with Fiber-Reinforced Cementitious sheets, creating a wall panel (the FRC-SIP) that can be dunked in water and will dry out just fine. Katrina Cottage II with built with these panels.

Now, inventors around the world are reinventing panelized construction at such a pace that it is hard to keep up with all the innovations. Some use foam-and-steel panels that are sprayed with concrete to any thickness desired, creating a hardened exterior that can be stuccoed. Because it is sprayed on both sides with quick-drying, gunned-on concrete (gunite,) the foam is encased forever in the center of the wall, insulating the heavy thermal mass of the interior concrete layer. These are generically known as foam sandwich systems (FSS.)

It should be noted that most of the panel systems involving concrete cannot be used on modular or manufactured housing. If not, then why include these systems on a site dedicated to Katrina Cottages, which from the beginning were meant to be deliverable by all major construction methods including manufactured and modular housing? This is because it is feasible to take a Katrina Cottage design which could be manufactured or modularized and simply replace the exterior frame wall with a concrete-based panel system and build it on-site.

Some of the new foam-and-concrete systems reverse the arrangement, building walls quickly of very large foam blocks that create a permanent form into which to pour concrete that creates the structure of the wall. These Insulated Concrete Form, or ICF, Systems are technically not panelized systems because they do not construct walls of full-length panels, but they install almost as quickly as the panelized systems.

Two other distinctions between concrete-in-the-middle (ICF) and concrete-on-the-edges (FSS) systems are: 1) FSS walls are much more resistant to mechanical damage such as being struck by a line drive or by a rock thrown out of a mower, while 2) ICF walls create a straighter finished surface because the stucco installer is finishing over factory-milled foam rather than field-applied gunite. So if you’re looking for a very crisp wall, it’s easier to do with ICF, but if you’re looking for a very relaxed, organic-looking wall that looks as if it may be stuccoed over a natural stone structure, then that comes naturally to FSS.

The Aerated Autoclaved Concrete (AAC) blocks are similar in size to the ICF blocks, except they are made of a concrete mix that is put into an oven (autoclave) and expands dramatically when it is fired, creating air bubbles throughout the block (aerated) that create serious insulation value. AAC blocks are solid; even though there are no cavities like you find in regular concrete blocks, they are both lighter and longer than ordinary block because of the aeration of the concrete. They can be cut with regular hand tools, and need no additional insulation. Some AAC companies now build wall panes as well as blocks, so you can get panels with wall and door openings blocked out shipped to your site.

There undoubtedly will be new panelized systems developed in the near future; please let us know if you are aware of some. In particular, we want to know about systems that are able to be submerged every 25-30 years and dry out without damage.

Panel Systems


This Panelized Housing system was developed by the Center for Applied Transect Studies in Miami by Andrés Duany and Matt Lambert. It includes both a panelization system, a set of cottage plans that work with the system, and an architectural code that allows for customization of the character within appropriate ranges.

The following are companies that produce panelized systems in the categories above.

SFP - Stick-Framed Panels

Manufacturing plants across the country make SFP panels; they are so numerous that it is not feasible to list them all here. Builders should know the best local SFP fabricators.

SIP - Structural Insulated Panel

SIP manufacturing plants are almost as numerous, and will not be listed here, either. Rather, check with the Structural Insulated Panel Association website, which lists all of the manufacturers and builders in your area.

FRC-SIP - Fiber-Reinforced Concrete Structural Insulated Panel

One of the pioneers of the FRC-SIP is Homefront, which is the company that supplied the panels for Katrina Cottage II, Katrina Cottage V, and Katrina Cottage VI.

FSS - Foam Sandwich System

FSS has been under development for several years, but early systems had the troublesome little detail of panels that must be cut to fit on the jobsite, creating veritable snowstorms of styrofoam debris for as long as houses are being framed. Needless to say, the required cleanup was an issue, as was the fact that the sales team was always battling the repeated question of “are you building this place out of drinking cups?” Shortly after Katrina, Green Sandwich Technologies solved the problem with several improvements, including manufacturing all of the panels off-site so that they need only be assembled very quickly onsite before being shot with gunite. They have unfortunately gone out of business in the years since, but another manufacturer should pick up where they left off because the system held great promise on several counts.

ICF - Insulated Concrete Forms

As with SFP and SIP systems, there are numerous ICF manufacturers. The industry trade organization is the Insulating Concrete Form Association. One word of caution: in a hurricane zone, be careful to ensure that the finish applied to the surface is strong enough to resist impact from wind-borne debris.

AAC - Autoclaved Aerated Concrete

Until a few years ago, there were only two principal AAC manufacturers in the USA. Today, there are several. Their trade organization is the Autoclaved Aerated Concrete Products Association. Originally, AAC manufacturers in the US produced only AAC blocks, meant to be laid similar to concrete blocks. Now, however, some have expanded to custom-built wall panels, significantly speeding construction.



Remember the old Sears houses from a century ago? You could order them out of the Sears Catalog and the entire package of materials needed to construct the entire house would arrive on your site a few days later. The idea of kit houses surfaced again in the wake of Hurricane Katrina. It makes sense because it speeds up the reconstruction process by avoiding the inevitable material shortages that will only get worse as the recovery construction gets into full swing. Lowe’s ran a Katrina Cottage program for a few years after Katrina that wasn’t strictly a kit house program. Instead, after a homeowner selected one of the approved cottage plans, a Lowe’s associate would take them through the store selecting the exact numbers of each item needed to build their cottage. There were other businesses which considered bringing back a full kit program, but that did not materialize post-Katrina. It is still, however, a viable option that should be considered.



Stick-framed construction needs little introduction, as it has been the predominant construction system in the US for well over a century. Chances are, you grew up in a stick-framed house. Balloon framing was popular in the 19th Century, but platform framing moved to the forefront in the 20th Century. Stick-framed walls are usually built of 2x4 or 2x6 wood studs, floor joists are usually 2x10 or 2x12, and rafters or trusses vary according to the span of the roof.

There are both advantages and disadvantages to stick-framed construction for disaster recovery housing. On the one hand, it’s the slowest method available, only slightly slower than kit houses because the homebuilder doesn’t get the complete kit of materials at the beginning but rather has to buy them as needed during construction. On the other hand, far more people can stick-frame houses than can build by any other means. A few million US residents have framed their own houses, and more would be likely to do so in the construction trades crunch that inevitably follows a major disaster.

© New Urban Guild 2017