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Pre-fab basement for modular

Discussion in 'Main Forum' started by paula miller, Aug 7, 2016.

  1. paula miller

    paula miller New Member

    Aug 7, 2016
    we are in the process of building our systems built (modular) home. We want a full basement and our site would allow full walkout on one side. We would like to use a poured concrete basement wall, or perhaps a product like Superior Walls brand Xi plus. Our builder says that this type of foundation wall would not work with modular homes, and he wants us to use his concrete block "man". I have reviewed Modular Council's Builder's guide to modular home set up & completion, & cannot find any mention of pre-cast foundations, or see any reason why they cannot be used.
    Can you enlighten me?
  2. jake

    jake Owner Staff Member

    Apr 21, 2014
    Hi Paula,

    Welcome to the community! Foundations are a funny thing. They're one of the few steps to homebuilding that are pretty much the same between modular and on-site building, but they're not 100% the same. For example, a modular home must be placed on a crawl space or full basement, not on a concrete slab.

    Going with pre-cast foundation walls for a modular home seems like a logical leap - if you're building your home off-site, why not the foundation as well? In practice though there can be plenty of reasons why your builder may not want to go that direction. Not being familiar with your exact situation, I can't say for sure why, but here are some possibilities.

    • It may be that the builder hasn't used pre-cast foundations before and so isn't confident that they can build the home to as high a standard using that method.
    • The grade that the house is set on may be too extreme to allow for pre-cast foundations. This is a likely culprit because your home is on a slope that allows you to walk out of the basement. Pouring concrete would give your builder the flexibility they need to make sure the foundation is the correct height all the way around.
    • Perhaps there is a problem with the soil which would prevent them from being used safely.
    • There are disadvantages to using pre-cast foundations which may not out-weigh the advantages in your case. For example, one major advantage is that insulation can be built in to pre-case foundations, making them more energy efficient. If you live in a region where you don't spend a lot on heating and cooling, this advantage is greatly diminished, while you still have to deal with disadvantages like needing to do maintenance by reapplying sealant and surface protection.
    • Perhaps builder already has a relationship with the foundation guys he normally uses and wants to keep that relationship in good standing.
    • It could also be as simple as your builder feeling that in your specific situation, a poured foundation would be superior over the lifetime of your home.
    Whether or not I'm totally off the mark with my guesses, you should feel free to ask your builder to elaborate on why pre-cast foundations can't be used for your modular home. One word of advice though - before you do, ask yourself whether you feel strongly about using pre-cast over poured.
  3. Mary Holcomb

    Mary Holcomb New Member

    Sep 20, 2016
    Hey, thank you, for the question and sharing information. All the best!

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