I need to cut 5" x 30" out of a basement support beam to accommodate a door and secondary suite height requirements. Would the jack and king posts for the door be enough support for the 5"x30" or do I need to put in 6"x6" posts? footings?

  • Footings are required regardless of post type. Your beam is really 8" thick? – isherwood Mar 18 '16 at 20:38
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    And the only "code approved" way is with the signature of an engineer. – isherwood Mar 18 '16 at 20:38
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    Negative. Do not become a meat popsicle. – Mazura Mar 19 '16 at 0:04
  • A diagram would really help us better understand what you're talking about. – Daniel Griscom Mar 19 '16 at 0:56

If you really have an 8"x10" beam in your basement it is probably supporting a huge amount of weight. Please do not even consider cutting into it without getting an engineer to determine what kind of supporting columns are required. (Cutting away 50% of the depth will reduce the strength by 75%.) I am guessing that in addition to the columns you will need to add footings to avoid punching through the floor, but those kinds of questions depend on exactly how your foundation is built. ("Code requirements" would depend on your location but major structural work like this would almost certainly require a permit and inspection. But frankly the safety ramifications of undermining the house's structure are probably more important.)

In short, this is an enormous project. Is there nowhere else to put the door?

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    Either it's supporting a huge amount of weight, or the house was built at a time when seriously outsized beams were cheap. – Mark Mar 19 '16 at 0:20
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    Keyword: engineer. Upvoted. – Aloysius Defenestrate Mar 19 '16 at 1:54
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    @Mark: Eh. Even if it is oversized I seriously doubt it is unimportant. E.g. I would not even recommend cutting into a double 2x8 beam, which is relatively common. an 8"x10" beam is 5X as strong. That is not an accident. – Hank Mar 19 '16 at 1:55

You need to get an engineer involved to do some calculations.

Options (with an engineer's sign-off) would seem to include pouring some footings and installing steel pipe or I beams for your columns, or building up rebar-reinforced masonry columns. You could face those with brick or stone (or wood) and have something really nice looking.

I wouldn't think standard door framing would be sufficient to replace the load you're transferring to the posts, and I would definitely think you need to pour footings under the columns.

If you notch either edge of that beam anywhere along the length of the beam, whether it's a couple of inches or 30 inches, you really have to consider that you have reduced the effective dimension of the beam by the depth of the cut.

If you cut a 5" notch out of a 10" beam, you have turned the entire open span into a 5" beam. If the beam is 8" wide, I would have to think that the weight of the beam alone would stand a good chance of breaking the beam (without appropriate columnar supports).

One option might be to replace the beam with a steel I beam, which would give you the extra headroom you're looking for without compromising the strength of the beam. Yes, I know how big of a job that sounds like, but that should be a hint about how big a job this actually is and how badly it could go wrong.

  • the beam is made up of 4 - 2"x10"s 30' in length supported by 6"x6" posts every 7' on footings in a concrete floor. it's a 2 story house (plus basement) built in 1955. We would also build a wall along the beam so it will have more support from the studs in the wall. Want to avoid footings as the old concrete is almost impossible to cut. Do you know the dimensions of the I beam I would need? – Wendell Mar 20 '16 at 16:20
  • Maybe you could replace just the span between the two existing posts nearest the opening you want to cut with a smaller pre-fab wood beam or with steel. I would seriously get an engineer/architect looking at it, though. – Craig Mar 20 '16 at 18:51
  • thanks for input. It may be that this project will be cost prohibitive. Will have to figure out another plan. – Wendell Mar 20 '16 at 19:05

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