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Re: Size of Steel Header

From: meganbast@yahoo.com
Category: Structural
Remote Name:
Date: 08 Nov 2005
Time: 12:21 PM


Question [repeated here]: We want to put an opening in a non-bearing masonry wall. It is 12" normal weight block. The wall is 15' wide and 24' high. The opening is to be 10' wide (centered so 3' on either side) and 8' high. What size header is required and much bearing is required (How much should the lintel extend past the opening into the masonry wall?) It would be nice if the header fell in coursing.

Builders Websource® Answer: Structural questions such as this sound easy, but in practice are difficult to answer online without having all the facts and seeing the site first-hand. There is important information missing that would be required in order to make a sound engineering decision. For example:

  • What is width of the wall? Typically CMU's are 7-5/8" wide, however, some are narrower and some are larger.
  • Is the existing wall internally filled solid with cement grout or is it hollow?
  • Assuming the wall is filled solid with cement and assuming the block is approximately 8" wide, the weight of the wall (excluding any rebar or other loads) is probably between 95 to 150 lbs/cubic-foot depending on the type of block and cement. Based on your dimensions noted above, the opening will need to support at least 110 cubic feet of wall weight alone, which translates into somewhere between 11,000 to 16,000 lbs. That's equivalent to four or five vehicles and we haven't even factored in other loads.
  • What is the size and spacing of rebar, both vertically and horizontally. Generally when there is a large opening, added reinforcement is necessary around the opening which is not easy to add retroactively. As a result, an opening this size would likely require a 3-sided steel column and beam reinforcement.
  • You state that the wall is non-bearing. Are there any loads whatsoever bearing on the wall from above, such as roof or ceiling joists? Or is it just a free-standing wall?
  • Do you live in a hazard zone subject to seismic activity, hurricanes, snow loads, or high wind loads? If so, where is it located?

These are just a few of the questions that a structural engineer would ask before determining how best to build an opening in a wall of this size. Furthermore, the proposed opening leaves little shear wall at either end. All live, dead loads and other point or distributed loads (including the weight of the wall iteself) must factor into this analysis. Since this added load must be transferred to either side of the opening, the foundation or wall footing must also be studied to ensure that there is sufficient load-transferring capability to avoid foundation failure.

Depending on the soil type and size of the existing footing, additional reinforcement may be necessary along each side of the opening, particularly if steel columns are used to transfer the load. Proper anchoring and sheer-wall reinforcement is essential to ensure that the wall doesn't come tumbling down when exposed to a stressed condition, such as an earthquake or high wind load. We urge you to contact a licensed structural engineer who can assess all these factors and more so that you can make a safe and educated decision about how to build your wall and what it's going to take to provide an opening of this size. The size of a steel beam or lintel is just one of many questions that need further study before you can attempt this project. We hope this guidance helps.

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