Article No: 38

2006-05-01 08:04:27
Building Your Concrete Home, Part 2

(For Part 1 in this series, see the article in the June/July 2002 issue of Concrete Homes.)

Long before many people are ready to build a home, they often come up with ideas for their "dream home" and even go to the point of having an architect draw up plans. These homes are usually designed as wood frame structures, but when that magic time to build finally arrives, some potential builders have become intrigued with insulating concrete forms (ICFs) or concrete masonry block because of their many energy and cost benefits. The question they face then is "Can we still use our dream home plans?"

There are three options for these potential home builders: They can just select one of the hundreds of plans designed specifically for ICF or concrete block; they can try to find a plan close to what they had drawn up; or they can have their dream house plan adapted by an architect experienced with ICF or concrete block design. According to David Shepherd, program manager of Residential Technology for Portland Cement Association (PCA), that is a relatively simple solution.

To help potential home builders make the choice, there are a number of sites on the Internet, starting with PCA's and ICF Association's site, This site lists manufacturers and contractors by state. At a home owner and builder bulletin board is offered where you can post questions. There are also sites for firms that specialize in selling house plans and plan books and magazine sites, such as, that feature plans specifically for ICFs. Typically, plan sites allow visitors to enter the square footage and number of bedrooms and bathrooms, then pull up all the plans matching those choices. Exterior style choices are usually not part of the selections.

Making Changes

If the homeowner decides to have an architect convert his wood frame design to ICFs or masonry block, the main change involves adjusting the plan for thicker walls to accommodate the greater width of blocks compared to wood framing. "If your house is 40 feet long," said Shepherd, "you would be taking a foot out of interior dimension, unless you add to the exterior. As the interior walls are not usually made of concrete, only the exterior walls need the extra thickness. You could take that thickness out of a large room, but not out of a room that is already tight. An exception might be a room that was designed to fit, for example, a large antique cherry sideboard. Sometimes dimensions have a function and sometimes they are just a number somebody pulled out the air."

Where the space adjustment comes from is also affected by the shape of the lot. "If lot dimensions are wide and deep enough, we merely add the extra length and width to the exterior," said Jim Zirkle, president and CEO of Florida-based Home Design Services, "then make the appropriate adjustment on the foundation, floor plan and framing. The interior and overall architecture of the plan can remain almost identical. There are a few areas that might be problematic. You have to get the wood frame wall to line up with the concrete block wall and finish up so there won't be a step. For us to convert plans from wood frame to concrete block is very easy to do.

"If a lot is cramped, some rooms will have to be changed. There are limits to how small you can go, especially with rooms involving plumbing, such as bathrooms, the kitchen and laundry room. Some changes are easy to accommodate and some take actual redesigning based on where they are placed in the floor plan. We look at those first when doing a conversion."

A recent change in code for windows in concrete block houses could also affect a conversion. "Wind pressure on windows and how windows are fastened to concrete block must now meet a standard based on a wind test," Zirkle said. "The architect needs to know modular window dimensions so the mason on the project can give the window installer the correct 1/4-inch tolerance around the window. Masonry openings are no longer allowed to be blocked in. Fortunately, masons in the field are quick studies. They started out using plywood templates cut to standard window sizes. After using them a few times, the mason discarded the templates and created a window chart."

Changing plans from wood frame to ICFs or concrete block also involves connecting details specific to the block chosen. "The architect has to think through what the floor and roof system are going to be, as well," said Al Meek, director of design for Bloodgood, Sharp and Buster, a Des Moines, Iowa firm that specializes in house plans. "There are different details that you have to be aware of. If you want to use a concrete floor, you might use a post-and-beam system. If you want clear span areas, you might use a poured-in-place concrete system or new ICF floor systems.

"On the business side of converting plans, the architect has to watch out for copyright issues. If the client bought plans from a book of plans, we would have to buy reproducibles from that original designer and make changes from there" Meek said. "If an architect has been hired by the client, there is no copyright problem."

Design Elements

Not too long ago, architects and builders tended to stick to a purely rectangular floor plan because they had some doubts about how easily concrete systems could handle the more interesting design elements, such as curved walls, odd angles and arches. This is no longer the case.

"Curved walls are easier to do out of concrete than wood," Shepherd said, "because concrete is fluid when it's wet and the foam forms are so easy to cut. Arches in concrete are done pretty much the same way as in wood — framed out as a square with a buck to accommodate the shape. Odd angles are not a challenge either. In fact, Arxx has an adjustable angle, hinge-style block so plans can use any degree angle customers want. Most ICFs have 30, 45 and 90 degree angle blocks, which are the most typical angles used in house plans."

Plumbing placement does not present a problem when converting plans. "A lot of contractors install conduit, usually, a hollow plastic pipe in the foam that you leave in the wall cavity for through-wall penetration," Shepherd said. "It is bigger than the pipe plumbers are going to put through it.

"For electrical, there is nothing in using concrete that would limit or indicate where you have to put your outlets, which is not the case with wood frame houses. Only a small fraction of wiring (that required by code) goes on exterior walls. Most of the new technology access (jacks, outlets) can be added to interior walls."

Converting plans for two-story homes would require a wider foundation. Also, because of the incredible weight of concrete, walls should line up. According to Shepherd in a Cape Cod house style, for example, you can make exterior walls of ICFs for the first story, and even make the gables of ICFs, but this style usually has two large dormers that are not located directly above the outside wall. If the builder tries to build them out of ICFs, he will have to build an incredible structure underneath them. This is true for anything cantilevered, as well. It can be done, but it would be a luxury item.

"For plans requiring a three-story wall," Shepherd said, "the architect would need to involve a structural engineer. This is something the architect does, rather than the client, for components that he is not comfortable with."

One of the advantages of converting to concrete is the flexibility to do some interesting things with design. Its strength is as much as 400 percent stronger than wood in some applications. The building can carry more span, allowing for bigger windows, for example. One thing that is definitely different in building with concrete systems is making changes while the house is being built. Retro-fitting is prohibitively expensive. So plans need to be final before the pour. Clients often don't think that far ahead, but architects do.

Finding an Architect

"Clients should have an idea of what system they want to use before going to an architect," Meek said, "because he will need to include product-specific details in the converted plan. This means they must find an architect who has experience with the particular system.

"It is the architect's responsibility that the converted plans include everything to enable the house to pass inspection. If there is something that inspectors may not be familiar with, the architect should meet with them and go over the plans and how the system actually works as a precursor to the client applying for the building permit.

Zirkle noted that when a client comes to him with a wood frame plan, it has almost always been designed in a Northern climate, and he is trying to have it adapted to a region that is prone to hurricanes and termites in the South. "We advise clients to find a builder who has built with concrete block before," Zirkle said.

There is about a 50/50 split between clients selecting a different plan or having one redone, according to Zirkle. Concrete block is the first choice in Florida, but generally for the first story only. There is no convenient place to stack block for a second story, so it becomes more expensive in terms of labor to do two stories in block. ICFs are often the choice for multistory projects or of do-it-yourselfers, but Zirkle advises those clients to use a skilled tech rep to oversee construction.

Although private clients can see a variety of plans on Home Design Services' Web site (, and call with questions, Zirkle noted that the company gets most of its business from local builders and national magazines and plan books.

Meek said his company could get more business from its Web site ( if it weren't buried so deep in the search engines. "There are a lot of people who know who we are and they will look for us," Meek said. "Most of our business comes from Internet publishers. We deal with about seven different publishers. Some are magazine sites and some are just house plans sites. We are pushing our publishers to add a concrete home site. There is definitely an interest out there. I get maybe two or three calls a week."

"What is critical to success in finding the right architect," Shepherd said, "is where you look. ICFs are relatively similar in how they function. The biggest difference is not the product, but the people who stand behind the product. I would suggest clients go to a distributor or technical rep for the ICF they select. They can recommend architects who have worked with their product."

Seeing a home built of ICFs or concrete block is also helpful in deciding on whether to convert; however, because concrete systems can accept virtually any finish — siding, brick, stone, stucco or concrete versions of them — the passer-by cannot tell that a house is made of ICFs or concrete masonry merely by looking at the exterior. You may have seen a dream home conversion and not know it.