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Adding basement under existing home

Posted by robinson622 (My Page) on
Tue, Apr 4, 06 at 19:11

In weighing my ideas for adding basement space to my existing home, I was wondering if anyone had their home lifted and added a basement, or you know of someone that did this. I live in a small rancher, and we're thinking of an addition/remodel. I was curious about the cost, etc.


Follow-Up Postings:

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RE: Adding basement under existing home

I don't know about lifting a house. In a previous home it had a partial basement. I once considered have the other part (crawl) escavated. Can't recall the figure, but it was way high.

I would guess putting on and addition (with a basement if desired) would be more economical.


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RE: Adding basement under existing home

Not cheap, and depending on how the slab house was built can get very expensive (ductwork in particular).
It is also relatively risky since the slab was designed for suport by the earth.
A house moving company has the experience to lift.


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RE: Adding basement under existing home

Do you have the room on your land to move the house to a new location. It is still going to be really expensive but it might be easier to dig and install a new foundation with basement and then lift house and move to new location.


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RE: Adding basement under existing home

We have some (not much) space behind the house. We have almost 3/4 acre and most of it is a backyard which we enjoy. We put an inground pool in a few years ago, so there isn't much space. We intentionally set it back from the house incase we wanted to add on to the house. We could put a decent size addition with basement under it, but I'm just weighing the options. We need a pretty large amount of remodeling. Three children, their toys, stuff, etc. and nowhere to store them. I really want them to have a place to play. Right now, my foyer has a fusball table and a treadmill in it. It just doesn't feel like my home with those things everywhere. The basement would solve a lot of problems. We have workout equipment in the garage that we never use except in the spring and summer, because it's too cold most of the time. The house itself is well constructed and was gutted to the studs not very long ago, but the crawlspace is so small you can barely get into it. You should have seen my husband running the line for the ice maker. Thank God he's skinny. We also thought about adding a second floor, but we aren't sure if the foundation can take it. If we put a basement under the house, then we could take care of that problem.

I know we need to talk to a builder, engineer, architect that can tell us what we can do, but we're just getting ideas of what we'd like and can afford to do without being "house poor".


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RE: Adding basement under existing home

robinson622,
just curious to know why you're considering an addition vs. rebuilding?
You mentioned the house had been remodeled once before.
Now you desire a basement and more square footage.

Seems like rebuilding would be more cost effective?


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RE: Adding basement under existing home

I wasn't very clear. We didn't remodel it. It was remodeled about 8 years before we moved in. Our friends lived here then and remodeled it. They moved to a house about 200 yds. away right after it was remodeled. A woman got divorced and wanted to get rid of her home and they got a great deal. We moved in after a few more people owned the house and haven't done anything to the house, only the yard. I thought about demolishing and rebuilding, but I'm not sure we could afford it. With our existing mortgage plus the new construction, but it's still a possibility. I know an addition can be very pricey. If we didn't owe on this mortgage it would be ideal to rebuild. It seems that all my ideas are questionable to me. I could wait and pay down the mortgage a bit, but construction costs only go up in the meantime.

The neighborhood is great. We live close to work and schools. We have tree-covered streets and the river is about a 1/4 mile up the street. We love going for bike rides or walks along the river. The neighbors are friendly, trustworthy and dependable. We considered finding land, but it's tough to leave. The people that sold us the house have told several of our neighbors that they should have stayed and remodeled and wish they never left. We don't want to feel that way, but we definitely need to do something in the next year or two. I just don't want to end up wishing I would have rebuilt instead or regretting the addition.


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RE: Adding basement under existing home

Sounds like a great location and you're happy there.

I know what you mean about having second thoughts. I would define a budget and then decide whats feasible. Good luck with your decision. I'm sure it'll work out.


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RE: Adding basement under existing home

We faced a similar problem (ranch on a slab), and decided to add on the back with an extra deep (9 1/2 ft) basement, which has worked out great.

One of the "interesting" things we found out during the excavation was that the original foundations actually angled up from one end of the house to the other, so if we wanted to add basement under the original section, we would have had to rip out all the old foundations ($$).

Plus there's the issue of after lifting the house, all the old construction would "resettle", with lots of cracked walls, door jamming, and potentially leaky pipes.

Most contractors would rather add on, rather than face the unknowns of trying to dig out a basement.


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RE: Adding basement under existing home

OK...Here goes. I added a basement under my garage which doubled my storage and workshop. In fact I moved my entire workshop down below.
Here's how I did it.
Since my garage was a 2 car model I decided to run an 8 inch block wall down the center.
I started by making a cut in the floor just on the other side of the center line and removerd all the concrete from one side only. Next I began excavating the dirt down the center line. I did this all by hand by the way. When I got to within 6 feet of the east wall, the garage runs north and south with the door facing south. I dug a 4 foot trench to the east foundation. There I found out there was no foundation, the entryway and family room shared the same slab, so with the help of coworkers we excavated out the dirt and put in an 8 inch conctete block wall running the entire length of the east wall. We did this by laying up a 32 inch wall with a saw tooth and then excavated to the left and laid in the block we moved left to right until the entire wall was done. The tricky part was digging around the footings of the center wall, the house, and the south footing. A friend showed me how to dig out only enough to set in a footing with 2 8 inch block. We stacked these up saw tooth style and poured them full of concrete. Next we dug out next to the block and proceded to add block and footings as we went interlocking the saw tooth block. We made sure we only took out enough dirt to allow for 2 inches of rigid ins. behind the block. The footings along the door and west side as well as the interior wall poised a completely different problem and that was solved by the same process the difference was triming the foundation even with the block and laying up a new wall that when it got even with the foundation and exsiting block we drilled holes and inserted 5/8 rebar which we filled with concrete. This was done in a saw tooth fashion. Adding only a two block type wall each time. First we would do the right hand side and then the left hand side etc. As the basement took form we continued tying the new block to the old block which was 5 block deep into the ground. When we got to the top or the garage floor we laid in a half block so we could pour a 10 inch rebar floor. Since I had a wall running down the length of the barage we poured the floor in 2 pours. The wall had an eight foot opening with double 4 foot steel doors comerical grade. This allowed access between the two rooms that were created. The second pour wasn't as hard as the first because I put in a subterranean car lift that allowed me to store a third auto in the basement. I even excavated 10 feet under my driveway for additional storage and a storm shelter. The entire project took over 18 months. But the good thing about the entire project it was inside work and we only took out that dirt that allowed us to lay in block to support the existing foundation. My friend brought over his Heavy Const. book and showed me how the big boys do it and we followed their examples. The book is called Principles and Practices of Heavy Construction by Ronald Smith. There is a chapter addressing just such problems. Its called underpinning. But instead we decided to lay up a completely new wall and tie the existing wall to it. Once the concrete floor was laid the entire structure was tied together. The work was done during the evening hours with a trailer in the next bay that was filled with dirt. A friend needed the dirt so getting rid of it was easy.
This is NOT a project for the faint hearted. It takes time and patience because you don't get a second chance if it all falls down. But with planning and slow steady work you can do it. My project costs about $13,000 but I had a lot of help and after it was done a few contractors said they wouldn't even consider the project. I did have to move my water line and a sewer line but as luck would have it they fit neatly behind the new block wall.
The only outward appearence of the entire project was the PODS sitting in the driveway storing my STUFF while we worked. We stored the block, sand and mixer in the garage. I only purchased the amounts that would fit into the garage. I looked for sales too. This allowed us, me, to work 24/7 rain or shine.
I now have a dust collecting system for the shop. No more dust in the house and my wife can get her SUV in the garage!!!!!
The footing was 12 inch vee block laid sideways and filled with concrete and rebar with the ends sticking out to accept the next section of footing. This also allowed the new basement floor to be tied to the wall via the rebar.
There are no cracks. YET.


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RE: Adding basement under existing home

Yes, we put a basement under our home this year. We LOVE the extra room, it was worth every penny we've put into it so far.

We had a house mover come and jack up the house, it was put on stilts or cribs while the dirt was being removed and the foundation was being constructed. We had a local mason come in, the one with the best reputation and the longest track history at 45+ years do a concrete block foundation. The foundation was fitted with rerod through several areas horizontally and through all of it vertically. It was tarred and sealed and they stuccoed on the outside. We have a lot of light because of all the windows we had put in and a walk down area with a sliding patio door.

All this fun cost about 36k. I think it was money VERY well spent. This included a new energy efficient furnace and plumbing.


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RE: Adding basement under existing home

blue velvet elvis shows the way to do it.

t-good's project was simpler, as there were only outside walls to worry about.

However, all that tunnelling and burrowing should have been engineered. The moving weight of vehicles and water penetration pose a lot of problems.

I build custom two storey houses with integral 2-3 car garages on tight city lots. Every time I consider making the basement bigger by going under the garage, the costs and complications turn me off. But I have seen basements stretched under patios and drives. Pretty interesting.

Toronto's famous Casa Loma features a 800 ft. tunnel 20 feet down between the castle and the garage and stables.


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RE: Adding basement under existing home

I've seen a house here in FL that was jacked up, and had a story built under it, so the original house was the second floor. No basements in this part of the world! If you go for a basement, be sure to have soil tests done to make sure it is feasible in your area. It would be a shame to go to all the work and expense, only to wind up w/ a damp, musty basement.


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RE: Adding basement under existing home

All I did was to go to the back side od my home that was built on a slab and dig under the foundation and the up to the bottom of the slad then cleared out a 10x15 size space then built in a room put a steel door where I went inder the foundation and braced up the bottom side of the slab with 4x4 for roof and 2x4 for the walls the put on panneling for the wall coverings after I poured a ned slab for the new room. NO TROUBLE at all I have no pipes or anything in the way. Any Questions ask me at shotzie988@aol.com


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RE: Adding basement under existing home

HI,im ron i live in illinois .I am trying too hook some assistance in thinking about a new basement under existing farm house.i understand the pitfalls . i have the eqiupment . i guess im wondering where can i go on the net to get advice on how to tackle such a project.i know people who have done it too there home. but every home is not the same. just by doing it myself i would save big .i have been around concrete poured walls.just want to do it right. pardon the grammer.


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RE: Adding basement under existing home

HI,im ron i live in illinois .I am trying too hook some assistance in thinking about a new basement under existing farm house.i understand the pitfalls . i have the eqiupment . i guess im wondering where can i go on the net to get advice on how to tackle such a project.i know people who have done it too there home. but every home is not the same. just by doing it myself i would save big .i have been around concrete poured walls.just want to do it right. pardon the grammer.


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RE: Adding basement under existing home

Ron, We have done this. We hired someone to do the actual lifting of the home, moved it 16 feet and set back down, but did the digging out and pouring of the new foundation ourselves. DH worked for a concrete business and had access to the forms. It saved us tons this way but there are a lot of things to take into consideration when undertaking such a huge project. I'm not sure we would do it again, but then we added on all four sides of the original home after it was set down, stripped off all the old aluminum siding and gutted the interior and are slowly redoing the interior. We live in the country and were allowed to stay in the home even when it was on the cribbing. That too saved us money not having to rent or move.

You would want to be sure that your insurance will cover your house while you have it 'lifted' as some won't cover it. I can give you many more pointers and talk on the pros on cons, show tons of pictures... but I'm not sure how much rambling you want me to do! lol


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