Cutting Door into Existing Basement

[SarBear]

Hi everyone,

I am an EIT working toward my stamp. I've been working at this company for 1.5 years on mostly small commercial projects. I was given a new project where a homeowner wants to cut a 3' door in his existing basement and build an exterior stairwell to access the basement. My boss said to try coming up with something on my own without her help as a challenge, and I want to do a good job. I've talked to a couple of builders I know, a couple EIT friends, and have consulted Google. So far I have seen 3 options that appear to be used most often for this type of project (see below). Do you have any opinions about what option works best? I am leaning toward Option #2 since it seems like the least amount of cutting that needs to be done, but it still leaves some concrete above the opening (not sure if that matters maybe for shear flow from the framing above?). With Option #2 would I consider the concrete above the opening capable of bearing the loads from the walls above, or should I size the steel angle for the full load and discount the concrete? Should the angle be 8x8 so it fully supports the 8" thick foundation wall? Would Option #3 be better so I can just size a header for the full load?

I'd appreciate any feedback you could give. Thanks!

 

[miningman]

A friend of mine did exactly this a few years ago. I had zero involvement in the project but based on my visual observations these are my
questions. How do you proposes that the contractor deals with the inevitable water and snow that will accumulate for the life of the house?? What system will be in place to prevent pedestrians falling into the stairwell?? Lighting ??

 

[chris3eb]

I don't want to sound too dismissive here, but if your boss is asking you to come up with something on your own, there are two possibilities:
[ol 1]
[li]Your boss wants you to work on identifying the problem and potential solution without help[/li]
[li]Your boss doesn't want to spend the time mentoring you and is hoping someone else will do it[/li]
[/ol]

If it's the first case, it seems to defeat the purpose to ask all of your contacts and internet strangers rather than coming up with your own idea and presenting it to your boss for further discussion. If it's the second case, the internet shouldn't be doing your bosses job for her.

 

[IRstuff]

It seems to me that you should attempt to work out the pros/cons for each option FIRST, then ask for help in finding the things you missed, such as the snow/water accumulation issue, which ostensibly could be dealt with via a grating/drain at the bottom of the steps.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[1503-44]

Depending on the load, you might want to cut that 12" out entirely, as it doubtfully will make a proper lintel beam on its own. No or very few horizontal bars up there. A crack sforming at the corners would render that 12 relatively useless in short order.

Cut the width of the door plus maybe 6-12" additional length each end. Reform with a proper beam with horizontal bars on the bottom and at least 2 on top. and stirrups. I'd do it if it was my house. I guess this is something like option 3?

Do you not have to have a building inspector take a look at your plans first? I'd be surprised if you do not need to have a proper lintel.

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

 

[EcoGen]

First I would verify with the owner that the foundation wall is actually concrete and not CMU block especially since you're saying it's 8 inches thick. Don't take their word for it, visit the site yourself or ask for clear photos showing exposed concrete aggregate faces.

If it's CMU block masonry see below for our typical detail. If it is actually solid concrete, we typically go with concrete lintels above openings to match the existing concrete material already there. The concrete wall above is very stiff and will likely crack at corners as mentioned above before it puts bending into your angle. If you still really want to stick to steel reinforcing, I would go with something stiffer like the second detail I've included below. These details avoid the use of temporary shoring of the area above.

EcoGen Consultants LLC
Structural Engineers
ecogenconsultants.com

 

[XR250]

If it is concrete and only a 3-0 door, you may not need any lintel. Check the capacity of the band spanning across the opening. The angles seem excessive in detail #1. If you need to brace the foundation for out-of-plane, use the new stairwell walls.

 

[Sokka10]

If it's the first case, it seems to defeat the purpose to ask all of your contacts and internet strangers rather than coming up with your own idea and presenting it to your boss for further discussion.

Sarbear, don't pay any mind to this douchy comment from chris3eb. My guess is your boss wants to see if you can find and use any and all resources at your disposal to come up with a solution to a problem instead of just having him tell you what to do. I don't see what the problem is with researching online, reading books, or asking others for advice. You've obviously done a fair amount of study on this, which you otherwise wouldn't have done if your boss just told you what to do.

Anyway, I'm inclined to agree with XR250. Others have suggested the installation of a new concrete beam over the window. That sounds like a good solution, but it's not typically done in my neck of the woods so I can't speak to that idea.

 

[SarBear]

Thanks everyone! I really appreciate your thoughts.

you may not need any lintel

I thought about this, but wouldn't there need to be a minimum amount of reinforcement in the concrete header? Since I don't know what's in there as far as rebar, I didn't think this would be allowed.

we typically go with concrete lintels above openings to match the existing concrete material already there

Reform with a proper beam with horizontal bars on the bottom and at least 2 on top. and stirrups.

Thank you for the details, EcoGen. Yes, this wall is concrete, not CMU for sure. I've seen some pictures online where they cut the opening like 1503-44 says, but I can't figure out how the new beam is attached to the remaining concrete?

I saw a YouTube video where an engineer explained that you can't just put in a steel angle or wood header for a basement cutout, but doesn't say what you should do instead.

https://www.youtube.com/watch?v=9tavRVkdz_w

 

[chris3eb]

To Sokka:

don't pay any mind to this douchy comment

I stand by my comment - and this really isn't the forum to give those kinds of insults.

Here is how OP described the situation:

My boss said to try coming up with something on my own without her help as a challenge

If the boss is giving OP an "open book test" so to speak, then OP doing research is one thing, but wouldn't OP asking other engineers for help cross the line?

instead of just having *her* tell you what to do

I also don't agree that this is the boss's only way of helping. Couldn't the boss be giving the same general guidance that Eng-Tips is giving?

your boss wants to see if you can find and use any and all resources at your disposal

Would that include going to the boss's boss and asking for help? How about another engineer at the firm? Is this different because we're on the internet?

 

[Sokka10]

Yeah sorry, I shouldn't have said that. It's just that I'm having flashbacks to when I first started out and my boss always acted super annoyed when I asked for help. He'd tell me to come up with something that I thought would work, so I'd sit in my cubicle for 3 hours sweating it out, doing everything I could to find something that would look reasonable. Then I'd present it to my boss who would tell me that A) You took way too long to do that and B) Here's why your solution sucks.

In my mind I was thinking, "Well thanks dude, I just barely graduated, I've never heard of a cantilevered HSS column in my entire life, and we don't have a single reference book in this entire office to point me in the right direction."

It is highly likely that SarBear's boss is like my old boss. In that case, I take pity on him/her and want to help. No one gets anything in return for trying to help out a fellow engineer on this site, but on the other hand no one is required to help either so to me there's no point in commenting on someone's post unless it's to help.

In the case that SarBear's boss wants him/her to come up with a solution on his/her own with no direction and without being able to consult anybody else...I think that's terrible management. SarBear won't learn anything from that exercise and the boss will end up having to tell her what to do anyway. That was basically my entire experience at the first place I worked.

So yeah...you're probably right, one of the two things you think is happening is probably happening. But in either case, I empathize with SarBear because we were all there at one time.

 

[chris3eb]

Sokka - no worries. Giving the boss the benefit of the doubt, they may be honestly trying to see what OP would come up with so the boss can have a better sense of where OP is at. If that's the case, it doesn't let the boss get a clear view of OP's abilities if OP is asking for help from outside sources rather than synthesizing the knowledge on their own.

Maybe OP is in a situation like you described and is sugarcoating the situation by describing it as a purposeful challenge, but we don't know that. If that's the case, I wonder if it's truly helping OP by playing along, or if it would help OP more to suggest that they should brave the discomfort and push their boss for more information.

 

[Flotsam7018]

I'd start with XR250's suggestion - treat the remaining concrete above the opening as an unreinforced concrete beam per Chapter 14. Also ensure that the shear demand is less than 1/2 the unreinforced shear capacity per 9.6.3.1.