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  1. #1
    Join Date
    Feb 2014

    Default Questions about adding an exterior crawl space door in block foundation?

    I need to make a secondary crawl space access door in the foundation of my house. It is a block foundation with a sill sitting on top. Do I need to be concerned with the locations and potential weakening of the building structure and outside walls? Would I be okay with just a 2 x 4 header turned upright nailed together supporting the sill, transferring the weight to two 2x8s joined together on each side? Thinking about tackling this project myself? Any recommendations?

  2. #2
    Join Date
    Jul 2010

    Default Re: Questions about adding an exterior crawl space door in block foundation?

    1. Every time you disturb a wall, to put in a door for example, you have to re-frame the wall to compensate. Even when the wall is not a load bearing one. Your situation is no different.

    2. 2x4 is not enough for a header. For 2x8 supporters you need 2-2x8 or a 4x8 header, to support the seal plate.

    3. Degree of difficulty: 7 out of 10. You need experience in carpentry, masonry and others. There will be block cutting, chiseling, cementing and a few other trades.

    Send photos.

  3. #3
    Join Date
    Jan 2008

    Default Re: Questions about adding an exterior crawl space door in block foundation?

    This may be do-able as you describe. What was done at the original crawl-space access door? If you follow the same procedures here for a similar or lesser width span you should be OK.

    If possible you'll want to cut the block with a diamond blade in a skilsaw along the edge of a whole block on both sides; this will leave you with less to fill in where the half blocks are, and if you're lucky those may have a center web meaning you don't have to replace them with cut halves. You'll have to cut from both sides and chisel out where the saw blade didn't reach. On a conventional one-story frame house with a 8" doubled rim joist, you can safely create a 32" opening without needing any extra reinforcement beyond making sure the doubled rim joist is well nailed together. Wider openings may need additional support as will a two-story house. Your local codes department can tell you what the maximum unsupported span can be in your area- that's where to start this project. Armed with knowledge this may not be a tough job for DIY; about the worst I can see is some block-work if you've got 3-hole block without a center web, and even that isn't too bad to deal with.


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