Installing structural beam above basement

5 years ago

My husband and I are doing some research on replacing a load bearing wall with a structural beam on the main floor of our home.

The wall itself is 8 feet wide, but it has openings on each side of it. So the overall opening we will have is a minimum of 14 feet wide. I say minimum because I still need to figure out where there will be a wall below to carry one side of the load from the new beam.

The home does have a basement, so I have questions about whether we may need to change any structure in the basement when we remove the wall on the main floor.

There is no wall or beam directly (parallel) underneath the wall to be removed.
The beam will be between an exterior wall to an interior wall. Will we need to open walls in the basement below the trimmers for the new beam to install additional structure so the weight is carried directly to the basement floor? Or do I just need to be sure the beam and trimmer is directly above a wall in the basement?

Is there anything else we will need to be concerned with?

We will be consulting with someone to help us size the beam and help us with this project, but I want to be sure we are educated. That way we will be sure the job is done correctly.

We live in an area where no building permits are required, so we don't have an inspector or building permit requirement to be sure it is done correctly.

Thank you in advance for anyone who is willing to answer my questions.

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Comments (3)

Bruce in Northern Virginia
5 years ago
I went through this when we opened up walls on our first floor. In general, you need to be able to draw a vertical line through the house and determine how the load will be carried downward, and at the point it hits the ground you must have footings that are deep enough to carry the load.

We removed a load bearing wall that ran from front to back in the middle of the house and we wanted to install a new LVL beam to replace it.
- We installed posts at each end of the house and a couple in between so it split into three spans.
- Then had to show that the new double LVL beams were sufficient to handle each span. The LVL manufacturer had span tables for a two story house that made it very easy to look up.
- Then we showed the engineer the steel I-beam in the basement (original to the house) and that the new 1st floor posts sat on top of the I-beam.
- He then verified that the I-beam was supported by steel posts in the basement, with footings that were poured during original construction.

Ours was simple because the load transferred almost straight down, but you could use the same process to evaluate a more complicated design. Using existing basement walls as supports could be more complicated to evaluate, since they are usually wooden frame on top of a 4-5" thick slab, not footings. I have seen some projects where they cut out part of the basement floor and poured a new footing at the proper depth, and then installed a support post for the structure above.

Bruce
greg_2015
5 years ago
There is no wall or beam directly (parallel) underneath the wall to be removed.

Are you sure it's a load bearing wall that you want to remove then? If there's no support under it, then where is the load being transferred to? Who determined that it's a load bearing wall?
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GN Builders L.L.C
5 years ago
Terri, 14' wide opening is not that big of a span, the size of the beam will depend on the load calculation from above. Done quite a few jobs like this with much bigger spans and every method of doing this type of modification is different.

As the basement support goes, it also depends on the size of the beam you currently have in the basement and what is the column spacing is and the load it designed to carry.

In some cases, if column spacing is too big and it cannot support the additional load adding another column and footing is a must and in some cases, you can get away with solid blocking only in between the beam and the floor if the beam and column spacing can support the load at the bearing point.

Also, as the beam goes you will see in the pictures a flush-mounted header, or you can have a dropped header which requires less work, but if you have 8' ceilings it could be a problem depending on the beam size.

Here is an example to give you an idea...

In pic 1 as you can see the column spacing is much bigger in comparison to the column on the right... Therefore in pic 1 situation, you need an extra column and a footing.

In pic 2 you can get away with just solid blocking and in some cases depending on the load, the foundation cavity needs to be reinforced and it's done by grouting the hollow foundation cavity solid.

Pic 1

Pic 2