# Digging basement to add headroom space



## Just Bill (Dec 21, 2008)

I would have the foundation and wall structure checked by an engineer, just for good measure.


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## Scuba_Dave (Jan 16, 2009)

Ecven a foot away can cause a problem if there is enough weight & depending upon the soil


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## jomama45 (Nov 13, 2008)

Realize that you will have a curb inside of your basement when completed, at least 16" high by 24" deep more than likely. This can be a major pain to deal with when trying to make the basement a usable space.

Do to the amount of labor involved, the cost to extend/modify any mechanicals effected, engineering costs, etc... for the very minor gain, this is a very rare kind of prokect. Don't get me wrong, it's do-able, but most look into the cost of adding an at-grade addition on vs. the deeper basement, & the addition is a no-brainer.

Good Luck.


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## walkman (Jan 4, 2009)

Really doesn't sound like it's worth it to gain 6". Rule of thumb is to stay on a 45 slope from the footer, but it's dependent on soil conditions. Especially since who knows what your footer would be like in a house that old. Do you have a walk out basement to wheel out the busted concrete? Are you planning to get the work permitted and inspected? May be hard to sell if you don't. 

Journal of Light construction did an article on this topic about 5-6 months ago that details the entire process (They underpinned and did the curb mentioned above).


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## bernieb (Mar 20, 2010)

I'm a firm believer that hard work builds character, and with that said I'm reminding myself what my long ago deceased boss told me once on a dangerous job , and he told me that there's a solution to every problem, you just have to be smart enough and have the patience to see it through. Now for the basement job consideration........What are the room dimentions now? Do you have a water leakage problem? I'm assuming you have laid up rock walls that the mortor has long ago turned to powder like sand. This is a major project and can be very expensive, but do take into consideration that dampness can be a health issue here, and the cost of running a de-humidifier can be expensive. If you have the room, lay up a 8 inch block wall on a footer with insulation of some type behind, if you drywall use greenboard. This is not the subject but how's the plumbing overall, and does it run under the floor in your project floor?


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## xxPaulCPxx (Dec 2, 2006)

There was an excellent article in the Journal of Light Construction a few months back, and they did exactly what you are wanting to do. Great writeup, illustrations and everything.

Search there for the article.


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## LU'S BASEMENT (May 16, 2010)

thank you for all your comments and suggestions. 

The addition at ground level is not an option because of space. there is no room to the left or right and the backyard is just the perfect size.

I know it sounds like a lot of work to gain only a few inches of space but If i don't do it and then add a celling and a floor that may reduce my head room even more. 

yes it is a walk out basement so taking out the cement is not a real problem. 

The basement is not completely underground only about 40 inches. 

I made a 2 holes in the cement floor and it comes out really easy. it looks like there is only about 1 inch of cement not much gravel and the dirt looks like clay.

needless to say the cement floor is very uneven and full of cracks s it looks like i will have to take it out any way.

yes I am planning to get permits for all the work.

the main idea of this project is to make the first floor apartment into a duplex. Each of the two apartments is about 1300 sq feet, remodeling the basement will almost double the size of the first floor apartment. 

I am planning to make two bedrooms one bathroom and one large family room in the finished basement.

thank you for the information about the article I will look for it in the library.

I like bernieb's bosses philosophy, i kind of live by it. 

I don't have a water leakage problem. Only a little moisture that comes in from the cracks in the cement floor. Not really a moisture problem either. 

The plumbing is great because we changed every single pipe in the house last summer before we moved in. We changed every pipe except the underground pipes that, you guessed it, run under the basement floor. I could take the opportunity and replace those pipes as well or at least the portion that is under the house. that would be beneficial because we have extremely tall trees and their roots get inside the main drainage.

the house walls are made out of a double layer brick above ground. Underground (the 40 inches that I can see) is like you said beautiful stone. I don't know how deep the stone goes but for those 40" of stone in the basement the mortar still is ok. 

A contractor told me that to hire someone to do this project will cost me about 30,000 mostly in labor. I think I can save that money by doing it myself with the help of some friends.

My main concerns are to do it safely and do it right. To get rid of the cement I can get a dumpster that's no problem. The dirt on the other hand can't go in the dumpster so I will need to do some creative landscaping in the front of the house with all that dirt. About 1200 cubic feet of dirt. Some people pay a lot of money to get dirt for landscaping, for me that will be free.

I think getting the supervision of a structural engineer is a must, so I need to look for one. 

I am planning to get some insulation around the every wall but haven't looked into that. 

It looks like a lot of work but I don't mind as long as is manageable and as long as i know what i am doing. 

Neither my wife, my daughter nor I are very tall so I could get away without digging but if i have to take the cement out any way then why not take an extra step to make sure: 1) that i have a tall basement. 2) that i have 2 or 3 inches of gravel that will help control the moist and the radon. 3) that i have enough space for a nice celling 4) that i have enough space for a nice insulated floor. 5) installation of sum-pump and drainage system. 6) free dirt for landscaping ( just kidding) 

Thank you again for all your replies, hope to hear from you soon 
Lu


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## jklingel (Dec 21, 2008)

*footers?*

Sorry, I admit that I just scanned the posts. What about the footers under the basement walls? Will you be getting below them? That would be real ugly. On the "lip" around the perimeter, just shelve it all the way around and you've got it schnockered. 1200 cubic feet of dirt is only 4 to 4.5 truck loads; can you sell it, if need be? Have people come and dig it for free, and save you some digging?? Just thoughts. Good luck. j


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## xxPaulCPxx (Dec 2, 2006)

You are going in the right direction... to say you are only adding 6" of room only proves the poster didn't read what you were REALLY doing. BTW, you may need to dig lower, I think 4" slab is standard.

Here is the article I was takling about (you have to pay for it, but it is worth it):

Lowering a Basement Floor
Gaining an extra foot of headroom isn’t easy, but it can yield valuable living space.

by John Sylvestre (5 Pages)

First 100 Words:
Lowering a Basement Floor Gaining an extra foot of headroom isn’t easy, but it can yield valuable living space John Sylvestre Lowering a basement floor is as difficult as it sounds. First you have to figure out how to support the existing house. Then — after all the finishes have been removed and all the mechanical systems disconnected — comes the fun part: breaking up the slab, excavating dozens of yards of dirt by hand, and underpinning the existing footings. But for clients with a small lot and limited space to expand, it’s sometimes the most practical way to add

View PDF | View HTML


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## bernieb (Mar 20, 2010)

Not to give you something else to "worry about" but I would do a test dig where your main plumbing enters under the concrete floor and see that the lateral pipe is deep enough for the new height. When your house was built a hundred years ago the plumbing code was different than today, and I have seen underground plumbing using "orange burg" clay like pipe 6" diameter "last forever" go house to house then after 3 or four houses go to the main sewer in the street. I doubt if you have a footer under the rock foundation ,but again dig a test ditch. I'd forget about hiring a structural engineer as long as you don't have running mud. Once your confident that the house won't cave in (haha) and I don't think it will ,you can dig down your 16 inches flush with the rock wall, and if a roto-tiller works use it. Once you have your depth you can use the concrete board half inch thick that Low's or Home Depot has to slap up against the exposed dirt wall under the rock wall ,then using 2x4's frame in for a footer of mixed concrete that will jam the base of the concrete board in. Put a small belly in footer next to rock wall, to carry away any water to a designated area to be pumped out if need to be. You can use light weight 4x8x16 core block ,2 rows high to get above dirt wall if there is one that is. You can overhang you studded wall when you build it ,stripping in for the block area. Figure your footer so you have a concrete slab rest for the floor.


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## HooKooDooKu (Jan 7, 2008)

walkman said:


> Really doesn't sound like it's worth it to gain 6".


Yea, but if OP has no where to build an addition, he really doesn't have any other options. 

He already states that its 84" from concrete floor to bottom of floor joists over head. That's 7'. Building codes for habitable space require 7' from floor to ceiling. So technically, he doesn't even have enough space to add drywall for a ceiling and laminated floor directly to the concrete for a floor and stay within code.


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## jomama45 (Nov 13, 2008)

bernieb said:


> Not to give you something else to "worry about" but I would do a test dig where your main plumbing enters under the concrete floor and see that the lateral pipe is deep enough for the new height. When your house was built a hundred years ago the plumbing code was different than today, and I have seen underground plumbing using "orange burg" clay like pipe 6" diameter "last forever" go house to house then after 3 or four houses go to the main sewer in the street. I doubt if you have a footer under the rock foundation ,but again dig a test ditch. *I'd forget about hiring a structural engineer as long as you don't have running mud. Once your confident that the house won't cave in (haha) and I don't think it will *,you can dig down your 16 inches flush with the rock wall, and if a roto-tiller works use it. Once you have your depth you can use the concrete board half inch thick that Low's or Home Depot has to slap up against the exposed dirt wall under the rock wall ,then using 2x4's frame in for a footer of mixed concrete that will jam the base of the concrete board in. Put a small belly in footer next to rock wall, to carry away any water to a designated area to be pumped out if need to be. You can use light weight 4x8x16 core block ,2 rows high to get above dirt wall if there is one that is. You can overhang you studded wall when you build it ,stripping in for the block area. Figure your footer so you have a concrete slab rest for the floor.


 
Seriously, I hope this post was meant to be sarcastic. If not, I certainly wouldn't suggest the OP follow anything highlighted in red especially.

I've yet to meet a 4", freestanding CMU wall that I couldn't defeat with my size 12 boot........


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## stuart45 (Jun 20, 2009)

Extending a home by digging out a new basement has become quite popular here, especially in London where building space for extensions is really limited and land really expensive. Paying 40 grand for a basement can add 100 grand to the value of your home there. 
Most jobs can be done, depending on whether it's cost effective.


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## Scuba_Dave (Jan 16, 2009)

bernieb said:


> I'd forget about hiring a structural engineer as long as you don't have running mud. Once your confident that the house won't cave in (haha) and I don't think it will ,you can dig down your 16 inches flush with the rock wall, and if a roto-tiller works use it. Once you have your depth you can use the concrete board half inch thick that Low's or Home Depot has to slap up against the exposed dirt wall under the rock wall ,then using 2x4's frame in for a footer of mixed concrete that will jam the base of the concrete board in. Put a small belly in footer next to rock wall, to carry away any water to a designated area to be pumped out if need to be. You can use light weight 4x8x16 core block ,2 rows high to get above dirt wall if there is one that is. You can overhang you studded wall when you build it ,stripping in for the block area. Figure your footer so you have a concrete slab rest for the floor.


I'd never dig down flush with the existing wall...and use a ROTO-tiller ???
Excellent way to cave the house in....vibration will cave it in much faster


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## bernieb (Mar 20, 2010)

Really, jomama45: No one knows where the bottom of the rockwall ends, and if there is a footer to begin with. The owner is just busting out thin cracked concrete with a sledge hammer, digging down 16 inches. The main concerns here is the base of the rock wall, and to hire in a structural engineer that will take him to the cleaners, and will go far beyond what is necessary to protect himself is what will happen. The way I see it is the house has been sitting for a hundred years on dirt and digging down 16 inches next to wall won't cause the building to fall in. Now if under the wall is like digging into face powder, we have a different set of rules to go by don't we. So I take you of a man of experience , sop would you share your thoughts and detail explanations on how you would do "the base of the wall area". Not trying to be sarcastic, just trying to help my fellow man thats not afraid of blood sweat and tears.


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## jomama45 (Nov 13, 2008)

bernieb said:


> Really, jomama45: No one knows where the bottom of the rockwall ends, and if there is a footer to begin with. The owner is just busting out thin cracked concrete with a sledge hammer, digging down 16 inches. The main concerns here is the base of the rock wall, and to hire in a structural engineer that will take him to the cleaners, and will go far beyond what is necessary to protect himself is what will happen. The way I see it is the house has been sitting for a hundred years on dirt and digging down 16 inches next to wall won't cause the building to fall in. Now if under the wall is like digging into face powder, we have a different set of rules to go by don't we. So I take you of a man of experience , sop would you share your thoughts and detail explanations on how you would do "the base of the wall area". Not trying to be sarcastic, just trying to help my fellow man thats not afraid of blood sweat and tears.


 
If your original thoughts & suggestions were only meant for very small, exporatory holes, thats one thing. But, if those were recommendations on how to underpin the entire basement, which is how I deciphered them, they are way off base IMPO.

As for the footing under a stone wall, I'd bet dollars to donuts there is nothing there but dirt.

As for the depth of the wall below the floor, I'd bet there's next to nothing additional buried, except some dirt. Any possible excess wall that could possibly be under the floor is likely so deterierated from moisture, I wouldn't put any faith into it anyways.

Taking a wall that currently has about 40" of unbalanced fill and adding an additional 16" of unbalanced fill at the toe of the wall, & having it last for any kind of duration, is no simple walk in the park.

I've been in this trade long enough to have a healthy dose of repect for the possible issues & risks that are present in a job like this. Afterall, I've been on jobs similar to this, as well as many other underpins, & am luckily still here to talk about it.

I can't give any solid advice on a situation like this over the web, as it would be pure speculation w/o seeing the house firsthand & doing some actual troubleshooting, so why bother?

You may feel that an engineer is overkill on a job like this, but are you willing to put your stamp on this project & assume the liability involved? I know I wouldn't, even if I was contracted to do the work. I've worked far too hard to get to where I am to risk losing it all over a few hundred dollars for an engineer. I'd hope the OP would feel the same, as it is his own property value on the line.


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## Sparky8370 (Jan 7, 2009)

LU'S BASEMENT said:


> I heard that we need to leave about a foot of space undug next to the walls to avoid disturbing the foundation.


That's even more dangerous than "I heard that she can't get pregnant the first time."






bernieb said:


> Not to give you something else to "worry about" but I would do a test dig where your main plumbing enters under the concrete floor and see that the lateral pipe is deep enough for the new height. When your house was built a hundred years ago the plumbing code was different than today, and I have seen underground plumbing using "orange burg" clay like pipe 6" diameter "last forever" go house to house then after 3 or four houses go to the main sewer in the street. I doubt if you have a footer under the rock foundation ,but again dig a test ditch. I'd forget about hiring a structural engineer as long as you don't have running mud. Once your confident that the house won't cave in (haha) and I don't think it will ,you can dig down your 16 inches flush with the rock wall, and if a roto-tiller works use it. Once you have your depth you can use the concrete board half inch thick that Low's or Home Depot has to slap up against the exposed dirt wall under the rock wall ,then using 2x4's frame in for a footer of mixed concrete that will jam the base of the concrete board in. Put a small belly in footer next to rock wall, to carry away any water to a designated area to be pumped out if need to be. You can use light weight 4x8x16 core block ,2 rows high to get above dirt wall if there is one that is. You can overhang you studded wall when you build it ,stripping in for the block area. Figure your footer so you have a concrete slab rest for the floor.


This one started out good but turned into "OMG are you &%%& serious?!?!"

I wouldn't be dumb enough to do that even if I was smart enough to dig holes for column footers near the walls and supported the load that the existing stone foundation supported with a carrying beam on those columns.

Get the engineer. Get it done safely whether or not it means someone else does it. If you can't afford to do it right, you can't afford to do it.


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## xxPaulCPxx (Dec 2, 2006)

stuart45 said:


> Extending a home by digging out a new basement has become quite popular here, especially in London where building space for extensions is really limited and land really expensive.
> Most jobs can be done, depending on whether it's cost effective.


I was wondering, have you heard of adding basements underneath existing slabs? Essentially it's mining operation, but there is considerable mining expertise there!


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## bernieb (Mar 20, 2010)

So, some professional opinions are coming about, and I'm sure Mr home owner is listening. With all that said, and taking into consideration that I have seen in my days three floors high above grade where a gapping round hole of brick was knocked out 12 to 16 feet in diameter and a piece of machinery lowered to the ground. With that said, the set up brick acts as a supporting beam. So why then couldn't an underpin of concrete a foot wide and 90 degrees out from rock wall still keeping the sought after 16 inches of height,and having it for the slab rest also. Doing this 10 feet at a time, but having 8 inches of concrete beam so to speak, going underpin to underpin, poured all at the same time. The 8 inch beam is where the framed interior wall will set and hold back the dirt under the wall. Possibly doing the same on opposite wall ,bracing between with the framing lumber...............you boys are getting me smarter.


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