Modular and Prefab Homes - General Inquiry

mjlbAugust 30, 2012

Shakfu's post prompts me to ask for his/her observations about modular / prefabricated building.

On the one hand, I am amazed at how klugey home construction is, and on the other hand I am so impressed by the fine workmanship and creativity of some tradespeople. I wonder how best to combine modular construction with fine craftsmanship.

Whenever I've been involved with home construction, I've been amazed at how klugey home construction is. It certainly has made me think that assembling building components in a factory would be more efficient, produce a better product, and presumably be less expensive. And a factory would have quality control that would not depend upon the homeowner being continually present on the work site.

But I thoroughly believe that homes should be constructed to suit the site, which often means a custom home. Modular home sites say they can customize a plan, but what kind of parameters must a homeowner work within? And do the modular home builders give you the parameters so that you can do your own custom design, or must you endure lots of back and forth with their designers? Basically, what sorts of limitations must a custom design accommodate in order to build modular?

I've bought a couple of books on prefab homes, which show some very nice end product, but they don't address the design parameters at all. If anyone knows of good websites / books for discussing modular building or comparing modular home companies, I'd love to know about it. Thanks!

(GW has a manufactured home forum, but it's not very active).

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I am by no means an expert in home or modular construction but I am happy to share my experiences.

For the most part, modular homes can be customized to fit just about any design, subject (as always) to budget. General constraints include:

- size of module: most modules can be a maximum of 16ft in width and up to 60ft in length (exterior dimensions). When designing a modular home, one has to be careful as not to have certain structural items in between modules. As an example, while it is possible to have windows/doors/stairs in between two modules, it is not preferred. You would also not want to have bathroom fixtures or kitchen cabinets between two modules
- Because the size of each module is constrained, adding a few feet of dimension in one particular direction may add significant cost. In my design, I have maximized the width of each module. If I wanted to make the foyer bigger, I would have to add a whole new module and incur additional transportation and assembly expenses. However, once you add a module, the incremental expense to make that module larger (up to maximum dimensions) is not significant. Essentially, there are step function costs.
- When you look at my plans, you may be able to figure out that I designed my home to be built with five modules. There are two modules on each floor going "east to west" and one additional module for the kitchen nook

I chose modular for two reasons (1) consistent quality and (2) predictable cost. The quality is consistent because the house is being built in a controlled environment and as a result can be built inside out. Also, the same person does the same thing every day � meaning the person who installs sheetrock does the same thing every day on the factory floor or the person who installs trim does that function every day. Of course workmanship is still predicated on the skill of the individual, however the tasks done in the factory are generally not that difficult. The cost is predictable because buying a modular home is like buying a car. You order the options and design you want and you are provided a fixed price that does not change. I know exactly what my cost will be for construction upfront. Having said that, once you finalize the design, there is no changing. Unlike stick building, it is difficult to make changes mid-process and you don�t have the benefit of seeing how things transform from paper to framing. In stick you can get a feel for the room at the framing stage and make changes at minimal expense (e.g., move a door, or window).

There is still some level of "skill" to completing a modular home. The house is delivered to the site ~80% - 90% complete. In my case, hardwood floors, tile, HVAC will be completed onsite. This gives a homeowner the opportunity to introduce some customization into the process.

I�m happy to answer any specific questions you may have. Overall, I�d say I am very pleased with the process so far. While I have had to compromise on certain design issues, I feel it has forced me to be discipline and stay within a budget.

Lastly, If I were looking to build my dream home that required significant customization or tailoring for a challeninging home site I would still go with custom route.


    Bookmark   August 30, 2012 at 12:48PM
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Thanks for the quick response, Shakeel! A couple more questions:

What was the height limitation on the 16-ft x 60-ft module, and were you limited in ceiling height as a result?

On your HVAC: Was this factored into the design, but simply will be installed on-site? I ask because on my most recent project, the HVAC contractor determined where to place equipment and ductwork, AFTER the framing was complete. The result was an undesired reduced ceiling height in a portion of a bathroom. Similarly, the plumber decided where to run pipes AFTER the framing was complete. The result was an unused plumbing chase, which had it been known, would have improved the bathroom layout.

After my initial posting, I went back and looked at one of my books on prefab, and I do see that there are a variety of construction methods other than stick-built (one example is panelized construction). Did you consider any other non-stick construction? I am guessing that it is easier to "nail down" pricing for modular than for the alternatives.

About pricing: I definitely like your comparison of purchasing a modular home to that of buying a car. But one big concern I would have would be that a modular home builder takes a deposit, but for financial or other reasons, cannot complete the work on time. Does the modular home builder post a bond or does the buyer buy insurance for this risk?

Thanks so much again for your comments.

    Bookmark   August 30, 2012 at 2:30PM
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You can get up to 10ft ceiling heights in modular. However, one constraint I failed to mention is that your particular site needs to be able to accommodate a modular home. Specifically, there needs to be a navigable route to get to your location from the factory as well as enough room on site to use cranes to lift the modules in place. Presence of trees or low hanging wires could prevent you from using modular.

Interior plumbing is done in the factory and included as part of the design consideration. The factory can also install baseboard heating, however, forced air is completed on site. Frankly, we did not consider register placement in our design due to the fact that we will have a full basement and attic. The air handler in the attic will provide service to the 2nd floor via registers in the ceiling which allows for almost infinite placement options. The first floor handler will be in the basement and as such placement of ducts could impact the design. Having said that, there is no reason that one couldn't come up with the design of an HVAC prior to construction.

I did not look at alternative other than pre-fabs.

I will have to review the contract to see what, if any, protection I have from any performance issues. I did not even think about the financial risk you mentioned.

    Bookmark   August 30, 2012 at 2:58PM
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Annie Deighnaugh

We looked at modular housing before we built and chose not to go with it due to the 16' constraint. It would be too difficult given the design we wanted in our house.

Another factor was the fact that we were finishing nearly half the basement which was a full walk out to the south. So that meant that we'd get only about half the benefit of modular as we'd still have to have the same number of trades on site to build the lower half and then have the modular guys build and install the upper it was like building 2 houses instead of one.

The other thing to consider is how fussy you are and how good you are at seeing things in 3 dimensions. (While not an issue for us) very often as the homes and 2x4s are going up, home owners see new views or want changes made based on how the house is evolving, like moving a window or adding a door. There is no making changes on a modular home as you have the plan, order the house, and a few weeks later, it arrives. That's it. Boxes go up, house gets plugged in (electrical, plumbing etc) and it's done.

Still, if I were building a home that wasn't so custom and I wasn't so fussy, I think modular offers a lot of positives to the build process.

    Bookmark   August 31, 2012 at 8:35AM
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