Calendar of Events Weather Traffic and Transportation Message Board Directory
for on This Site All the Web Google
 

 

Roger's Home Journal

Roger's Home Journal

A Brand New Basement--Can You Dig It?

By Roger Faris

Oct 18, 2000 -- Excavating for a basement under an existing house was a popular activity during the "Great Depression." Weight lifting machines and exercycles had yet to be invented. There was absolutely nothing on TV. Many homeowners had spare time due to lack of employment. They may have been inspired to create an income-producing apartment, or just build "sweat equity" in their home by adding square feet of usable space.

Some of these projects were reasonably well planned and executed. Digging below the level of an existing foundation can create a real hazard if it's done incorrectly. Most people had the good sense to refrain from digging too close to the perimeter walls. They would excavate to within a few feet of the foundation, build short retaining walls, then pour concrete on the dirt between these short walls and the lower part of the original foundation. This created a sort of oversize bench or concrete shelf around the edge of the new basement, and a pretty good place for storing stuff.

Unfortunately, that era of basement digging also included enthusiasts with less than brilliant minds. Their spectacular mistakes bring to mind the ancient story of a boy who did some truly bone-headed things while running an errand for his mother. At the end of his disastrous day she scolded him with these words: "Epambanondus, you don't have the sense you were born with, you never will have the sense you were born with, and you never did have the sense you were born with!"

Perhaps shovels and wheelbarrows should have been registered, and the operators licensed. I don't know whether to blame bad parenting or weak educational institutions, but the stability of too many foundation walls was compromised by guys who never did have the sense they were born with. The reality that went unrecognized is that one must always leave the soil beneath a load-bearing wall undisturbed. When there's a need to slope the soil away from the bottom of a foundation, engineers calculate a "safe angle of repose" which depends on soil type and presence of water. Asking a house to rest safely on the edge of a vertical cliff of dirt is asking too much.

A much better way to add a basement involves supporting the house with temporary steel beams. These rest on large housejacks and stacks of timbers called "cribbing." This equipment, along with experience in how to use it safely, is usually provided by a house moving or leveling specialty contractor. It adds to the budget, but provides opportunities to do the job the right way.

A great number of our older homes need a completely new foundation. The original ones were often very poorly constructed. They typically lack an adequate spread footing at the base, don't contain reinforcing steel, and have cracked and settled significantly. Quality concrete mixtures, waterproof coatings, gravel backfill, and effective drainage systems were just not part of the way things were done in "the good old days."

If you begin to think seriously about replacing your foundation and basement floor you'll soon realize that expanding the scope of the project a bit could make it even more worthwhile. Seismic safety improvements, spectacular headroom, new windows, additional plumbing fixtures, more living space--it adds up to something quite wonderful.

I don't think you all should wait for a crash in financial markets to get going on this basement work. Way too many people seem to be driving around all of the time, and you're also clogging up the parks, beaches, and boat ramps. Working under your house for the next couple of years could solve a lot of problems. For the good of our region, go home now and start digging.


Roger Faris is the director of the Well Home Program at the Phinney Neighborhood Association. The program provides advice, encouragement, tools, and classes for home improvement and repair. Call (206) 789-4993 for information. For the Earthquake Home Retrofit Program, call (206) 382-2159.

Reader Comments

Discuss this article in the forums!

Kenneth Rivet Jan 24, 2003 Centennial Colorado USAF
   How should one search for a buisness that could accomplish, safely, such a project?
kenny Oct 19, 2003 creston iowa 50801 carpenter, investor
   i am going to dig out a basement, using a bobcat, and need to know, how far back from the existing foudation do i need to st up support beams. The beams will be running across the floor joists. i will bi digging down the length of the wall, from under the house, so i want to have as much room as possible for menuevering the cat. The house is aproximately 30'x40'. safety is vital for this project, not only for the people but the house itself. it is not in the budget to hire any others for this job, so please don't refer me or make offers, but thanks, if your were considering it.please respond directly to my email address. this project is scheduled to start tomorow, so i hope to hear from you soon. thanks for your assistance.
Walt Nov 02, 2003 Central,Ohio Bodyman
   Kenny! We are currently thinking of a similar project. I want a partial basement on one end of our house. But I want to go only half way under to the middle structure beam of the floors. At the same time a room addition with the basement area extending under it also leaving us with a 24X20 basement area. and only disturbing one original foundation side. The rear basement foundation wall would be under the center framing of the house adding major strenth to that area.. Does this sound reasonable? Walt
Rob Nov 13, 2003 Newton, IA pilot
   Kenny: Id like to hear how your project is going. It sounds like you intend to replace or extent one or more of the existing foundation walls. Most people keep at least 2' inside the existing foundation and build a retaining wall down to the new floor. My thoughts on supporting the overhead joists would be to dig down leaving 2' or 3' next to the wall then digging a small slot 1' to 2' feet wide all the way to the wall to put a post at each point you want to support the beam. That way your beam can be right next to the foundation. I would like to hear from someone that has done this because building a foundation under a house without it setteling sounds like a trick. My email is Copterrob@yahoo.com
Ryn Adam Jan 13, 2004 Findlay,OH Pastry cook/ Artist
   I have a sm.dirt dug basement w/what looks like 1940-50 laid solid block concrete that the existing house sits on. What would be the best way to make the basement take up the whole or even half of the existing foudation to turn it into a small rec.room without doing any damage to anything important.The way things look it might be impossible not to upset or disturb something important. Is it worth it or should i forget it?
Chris C Jan 14, 2004 Wading River, NY (Long Island) Deisel Mechanic
   I just purchase my first home. It is a small 20x40 summer bungalow. Right now it has a propane heating unit that is too small for the house. I would like to dig out a small basement room to put an oil burner under the house. Access wouuld be by a set of bilco doors at the rear of the house. The house sits on a concrete block foundation and has a crawl space presently. I only need a small room, maybe 10x10 for the heating unit.Could you tell me the best way to go about doing this, As I stated this is my first home and obviously I don't have a ton of money to pay someone else to do this work. Thanks in advance for any help.
BILL PETERS Jan 26, 2004 E. FALMOUTH MA REAL ESTATE SALES
   I CURRENTLY OWN A HOME WITH A PARTIAL BASEMENT. UNDER THE OTHER SECTION OF THE HOUSE IS A CRAWL SPACE WITH A DIRT FLOOR. I WOULD LIKE TO PUT FULL BASEMENT. I WOULD LIKE TO TRY TO DO THIS MYSELF.
remy mcmasters Jan 31, 2004 ks driver
   i live in an older home, approx 100 years. it has a new foundation under the back half, the rest is sandstone. could i dig a basement and replace the whole foundation? could i dig myself then hire out the foundation work?
Matthew Silvers Feb 02, 2004 Boise Nurse, UPS loader
   I am planning on doing this same thing in Boise, Idaho and would love any information & tips. I remember helping my uncle back in the late seventies or early eighties with this same kind of project. It went smoothly for him, but I do not remember the logistics, plus times have changed. Please help. Thanks, Matthew
Mike Mansfield Feb 20, 2004 Greensboro, N.C. Investor
   Project considering: Current basement goes from 8 foot height to probably 2 foot crawl space. Want to dig out basement to allow for minimum 8-9 foot Finished ceiling height, over a just under 30x30 area, lots of dirt needs to be moved (had estimate of around 7-8 dump trucks worth).The main floor of the house, just above the basement is approx. 65x40.Will be excavating dirt from the rear house support walls and center structural supports. Will spiral staircase from main floor to the new intended kids entertainment area (basement).Good idea, risky project? Input would be greatly welcomed
Vijay S. Bajwa Mar 03, 2004 Morganville, NJ Software engineer
   Looks like a lot of these messages are about digging a basement under crawl space. I have a novel idea of digging one under a slab. This assumes that the sill plate sits about 1 foot above graded soil. There would be no lifting needed. So here goes: 1. Chop the slab and cart it out 2. Demolish part of a a side wall to let a bobcat in. Go to the farthest wall and dig down. As you dig, knock out the footers, but support the foundations with jacks. 3. Build the basement wall up to meet the foundation of the house. 4. Do all the sides, supporting load-bearing walls as needed 5. Next, lay 2"x6" floor joists on top of sill plate. Because of the limited span length of a 2x6, they will have to be positioned about 16" apart and supported by a steel beam at about 9'out 6. Lay the floor ply (another 3/4"). In total the ceiling height will be reduced by 7". Doors will have to be retrofitted, windows may or may not be.
kathleen Mar 23, 2004 michigan teacher
   we would like to dig out ourcrawlspace into a full basement, any input would be great! this is going to be a do it ourselves kinda project, thanks!
tomrawlings May 16, 2004 newyork self employed
   ive gotten to a very hard compacted dirt- with rocks- anyway, it is very hard to dig into- i tried a chisel and sledge hammer today and it seems to be working- better than a handled tool- is there a tool for this- like a digging bar with a bent end you could strike with sledge and then pull up to dislodge material? how did they do this in the old days before backhoes? tomrawlings@yahoo.com
robert May 30, 2004 australia self employed
   tom - use an electric jack hammer - either hand held drill size or larger with a clay spade. This has allowed me to break up similar hard compacted dirt. Does any one have an easier method of getting soil out of under the house. After 1000 buckets I'm getting tired
Jerone Smith Jul 03, 2004 oxford, ms teacher
   I have a dirt basement with concrete blocks walls. I want to make a small 10 x 12 room. What should I do about the dirt floor? Is it possibe too pour concrete in the area?
charlie Jul 11, 2004 ill maintance worker
   i have a half basement , the house is about 60 some years old i have half a basments and it sets in the middle of the house, blocks are cracking and falling apart and leaks water i need to knock down the 2 walls that are bad but i dont know what to do i cant afford to have someone to do it, is there anyway i can do it my self ,on each side of the basement is a crawl space and the blocks are good it is only the basement walls that are bad ,can anyone please help me with this.
David Jul 17, 2004 Spokane Computer Repair
   Hey, I just bought my first home and it has a 50% partial basement. I am planning on expanding the basement, since the rest is crawlspace, into a full basement. I am trying to figure out what kind of bracing I will need to do so the house does not collapse on me. Everywhere I read, they greatly expressed the need for bracing. My question is, how would I go about bracing the walls while I dug out the dirt. I want the walls of the basement to go entirely to the edge of the house, so the house would rest on the newly created foundation. Or would it be easier to make a sloping wall, something about 35-45 degrees. Any suggestions would be appreciated. Take care.
Bill Aug 27, 2004 Bay City GR
   My wife and I purchased a century-old farm house, with a dirt crawl-space, and supported internally by, literally, logs. Granted, the house is made of true-dimension oak, with 12x12 cross beams. It stood unmoved for a 100 years. Still, for extra space, and, in the event we decide to sell, we wanted to eliminate the perception of a house-on-sticks. We cut an access into the block and footing about 6' wide, and dug a sloping approach - deep enough to get a small Bobcat beneath the floor. The dirt beneath was mostly compacted clay, so the digging left a rather firm bit of ground for the foundation to rest upon. As I dug, I became a bit too aggressive with the floor-space, as it seemed that all of the existing footings were going down almost as deep as I was digging. As I began to dig closer to the footings on the west side, I discovered that their depths were inconsistent. Long story short, I lost 1/2 of one of the smaller walls and footings. Luckily, it was on a wall that was braced to either side by deeper footings. The house remained unaffected. We left 2' of retaining ground in the remainder of the basement, and managed to get to a depth of 7'2", minus the slope for the crock. After laying the tile, spreading the pea-stone, and pouring the floor, we began setting the blocks, and backfilling with pea-gravel between the new inner retaining walls and the existing footings. I went 6 blocks high for a retaining wall. We gained almost 900 additional feet of living space. Instead of refooting the access for the Bobcat, I put in a sliding patio door, and poured a 5' slab outside, and steps to get to ground level. I set a drain in the slab, with tile running beneath the new concrete floor, driving all incoming water to the crock in the new basement. Viola... a walk-out basement. I admit, the process got a bit hairy at times, but the end result was well worth the effort. I supported the 12" beams strategically with posts, and reenforced all of the block walls with rebar and a couple of support posts, concealed within the block. Putting pea-stone between the walls created instant compaction, and drove any moisture down to the tile, and to the crock. Since finishing, we've had several heavy rainfalls, and have yet to see a drop on the new basement floor. We'll see what happens in the winter, with snow. So far, so good.
mike Oct 05, 2004 reno,nv J O A T
   could someone please tell me where i can buy the screw type jacks that go under the floor joists--i need a few more to finish leveling my floors. mike
Richard Fernandez Nov 03, 2004 Denver, Co. USA I.T. / Telecom Tech.
   I see a lot of people asking about making 1/2 basement into Full basement or converting crawl space into workroom/storage area. This is what I want to know. Where are the replies at on how to do these things?
Harry Jan 01, 2005 Michigan engineer
   I see a lot of questions here. Where are the answers?
SPOL Editor Jan 02, 2005
   Richart, Harry, now's your chance at fame and fortune. Care to tackle some of the questions? This is an open forum.
Bob G Jan 16, 2005 Sedalia, MO Comuputer tech
   I have an exising basement that is "I" shaped and does not have enought head room to make it usefull for anything except storage. I want to did it deeper and have an idea. I thought about digging 1 1/2' to 2' holes next to the current foundation a few feet down. These holes would be for to support a engineered beam that would support the floor joists. I would leave all this in place once everthing was supported I could dig out the rest of the basement to a depth that would allow 9' finished ceilings. The beam and support I put in would stay and a new foundation wall would be poured next to the existing wall. Does anyone see any problem with my idea.
Hunter S. Thompson Jan 20, 2005 Las Vegas Author
   Some friends of mine did something similar at a house they owned out in the California desert. They drilled holes about ten feet deep, threw in some rebar, then filled them with concrete. They used these columns to support the house, then dug out the dirt between the columns under the house. Install a few grow lights and..ta da...secret underground pot farm. Unfortunately somebody ratted them out, the cops raided the joint, and eventually they tore the whole place down and filled up the hole. Maybe if you leave out the pot farm this would work.
Bernadette Beaman Feb 09, 2005 Indianapolis, IN
   We have a partial basement and would like to dig out the crawl space to add a full basement? Not sure where to begin, any answers?
Troy George Feb 26, 2005 pataskala, ohio
   I have a 60yr old block house there are no sump pumps,or yard drainage,the basement is cracked everywhere. The outside walls show signs of cracking, the doors and windows are off when it rains and the walls leak and the drain goes to god knows where and backs up in heavy rain. should I plug drain?
mike Mar 04, 2005 il retired
   i have a two story addition on the back of my house on the orginal part of the house i have a full basement with poured walls no leak under the addition i have a 3 foot crawl. i would like to connect this to my existing basement and dig it to about 7 feet any ideas on how to do this myself?
Rachel Mar 29, 2005 seattle cook
   goodbye Hunter
Thomas Crossan Aug 23, 2005 Waldwick, NJ Postal Carrier
   Would like to know if we can turn crawl space into new basement (25'x30')? Split Level House. Crawlspace has full concrete floor and about four feet from floor to ceiling under Dining Room, Living Room and Kitchen Floor. I don't know how deep foundation below concrete floor. Is it worth to dig out or what? Can we do it ourselves or hire someone to do this job and how much would it be? Thanks.
Mike Olson Oct 01, 2005 Edmonton, AB Surveyor
   I am looking at adding a basement under my house. I am trying to find the best and safest way to accomplish this. Either a new foundation or a retaining wall a couple of feet in from the existing foundation. Any help would be greatly appreciated. mike_ole@hotmail.com
Lena Dec 10, 2005 Flint, MI USA Autoworker
   I'm having a home built. I live in Flint Michigan ... when is the latest time to get a basement poured without the worry of future cracks and leaks from the harsh cold? THe builder tells me he can pour a basment anytime ... It was 17 degrees yesterday. Just seems too cold to me. Is there a frost law that builders need to go by, or do they just hope for the best?
Michael Grunden Jan 01, 2006 Findlay factory
   I have a older 2 story farm house with a 4 foot crawl space, the footer is just below freeze line. I want to add on a new 1 story addition with a basement to the existing house.The wall and foundation that I want to attach to is NOT a load-bearing wall. How close to that wall can I safely dig to put on a new addition with a basement? I'd prefer not to disturb the existing wall and foundation as the starting wall for the basement. Can I lay a new basement wall next to it?
Sandra Correa-Tiernan Jan 14, 2006 Lindenhurst, NY Respiratory Therapist
   I am having difficulty finding a company that will do a basement excavation in my area. I own a 100 yr house with a 6 1/2ft ht basement and an abandon water well tank. With the sky rocketing cost of real estate, I would like to finish my basement.
Thomas Loader Jan 15, 2006 Newfoundland Geologist
   I have a 80 year old two story home, currently it has no foundation, it was build on logs and rocks. The floor has sunk in some places and several load bearing walls have been removed by previous owners. I plan to dig a basment and pour foundation walls and perhaps lift the house a foot or two to get the sill up away from the ground. I hope The basement and foundation will give me something solid that I can stand some 6x6 columns on that I will use to supprot a beam there the lead bering walls were removed. To get under the house I plan to dig a 8 foot hole with a mini digger under the front door then proceed from there with pick and shovel. I figure I have anout 200 truck loads of dirt to move - it will take a while. If anyone has comments of suggestions for this project I'd be interested in what you have to say. Cheers.
Leon Bourassa Jan 22, 2006 Edmonton, AB, Canada Plumber
   Howdy. I have a 50 year old house with a half basement and 2 separate crawlspaces - one has a dirt floor, and one has a poured slab floor, both are about 3-4 feet high. I want to dig these out to make my basement the full size of my existing home. Can someone please tell me the best method of doing this myslef? The two crawl spaces are under 2 separate additions onto the original house, and I worry about the stability of either of the addidions.
Joe Mueller Feb 27, 2006 Milwaukee, Wi Tool & Die maker
   Hi, I've read alot of these and have not seen any answers yet. I hope you e-mail me or post it thanks. I have a 140 year old 2 story brick house with a half stone basement and 2 separate crawlspaces - Both were dug in the 70' I think for forced air heat. I want to dig these out to make my basement the full size of my existing home. Can someone please tell me the best method of doing this myslef? I could dig by hand or take down the addition and dig down and over from there. I worry about the stability of the house and what about the plumming?
Jim Spaulding Mar 17, 2006 Arvada, CO
   Here is how I was told by a structural engineer to add a cellar in my crawl space. Step one, dig out the crawl space all the way up to the footer (as deep as you are going to need it). Pour a new footer for the additional walls that will be needed. Either build frames and pour new concrete walls (at least 6" thick) or use concrete block and mortar. Bring the new wall up along side the exisiting footers, then drill through the new block wall, into the footer and insert rebar. The rebar is then "cemented" into place with a special caulk (presumably sold at home improvement stores). Obviously if you are pouring the new cellar walls, rebar can be left sticking out of the footers and into the space that will be filled with the new concrete. A slab floor can them be added, probably with some kind of sump pump installed to take care of any water seepage. My crawlspace is fairly deep (50") so I'm going to go ahead and dig down about 30 to 36" to get enough head space to actually stad up down there. This will be my new cellar for storing my bottled homebrew and my new stainless steel conical fermenters. It will be a BIG job (especiallly hauling out the dirt). But it will be well worth it when it's done!
Deryck Schwartz Mar 27, 2006 New Hamburg, Ont, Canada Insurance Broker
   Well after reading all these comments and how to do it's. Here is what we are doing. Our house was built in 1880,s poured basement, only 6' feet high. You all heard of Blood Sweat and tears. Well thats what its all about. We are going to lower are basement by 4ft. there is a proces called underpinng, what you do is dig under your footing ( foundation) every 4 feet one section at a time to the depth you need plus 8" inches. Once you dig under the 4ft section to your depth, drill up into the foundation and insert rebar and pour. after 24 hour remove and move 8ft over and dig a 4ft section and repeat go two feet in each direction. Keep this up untill you have the intire foundation underpined.Then you must dig the entire basement out to the depth you need. The whole basement outer egde will be flush with your foundation. Once that is done run weepping tile around the walls pour 4inches of A gravel then 4 inch of cemment. Have fun fun this is the easiest way to end up in devorce court if you involve your spouse. Get a bunch of buddies and go nuts untill you have it done every week from May to July, Then you have too dry wall electric, oh ya do not forget to move your furnace and water heater, have FUN
John Mar 30, 2006 New Richland, MN driver
   I have a 100 year old house on a fieldstone foundation with a crawl space and a root cellar in one corner. that corner has not settled as much as the rest and the oposite corner is breaking apart. I am coming into a small inheritance soon and its now or never with the foundation issue. Don't want to spend too much but something has to be done. It would be nice to have a full basement where I could have my heating equipment and a warm main floor, and flat floor to boot. anyone know a most reasonable contractor in my area?

You may discuss this article in the forums!


 

© 2008 Seattle Press on Line.

Powered by JournalMaker.