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Post by nicholas on Mar 19, 2014 10:12:58 GMT -5
Hi folks, I know there are many quality carpenters here so I thought I'd throw this question your way.
Has anyone gone through the process of re-doing their basement and foundation to add height? I have a small 1200sqft bungalow and I need to add some extra living space. House was built in 1950 and has a concrete block foundation. Basement ceiling height is only 6'. I'd like it to be 8'. I believe the basement was originally a dirt floor. Concrete has been poured later I think. The floor weeps.
My first plan was to add an addition off the back of the house, but since the foundation needs repair anyway it crossed my mind to see what it took to jack up the house or dig down and start over.
Any and all advice or opinions are very welcomed.
I have no intention of attempting any part of this myself, this does not spell DIY to me
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Post by wrightwoodwork on Mar 19, 2014 16:34:16 GMT -5
Sounds like a job for the specialists. As the floor weeps my guess would be a faulty damp proof membrane or the tanking used to keep the cellar dry is faulty or inadequate. Also as the basement I would guess is below the grounds water table. So if you want to go down you could be looking at water pumps to remove the water. Injecting the ground with brine to freeze the ground and lower the water table. Then foundation will possibly needed lowered. Do you are looking at underpinning. All of these jobs are definitely specialist work. Where to go up it might be a case of hire a crane strap the house, lift up. Then some sort of ring beam to take difference. Obviously there will be a bit more to it than that. It certainly ain't a job I would take on as it is way above my level knowledge. A little bit extreme and slightly unrelated. I know that somewhere in Switzerland, can't remember where. When they built a new railway station across the road. They like the old station so much, so they decided to move the old station with specially built railway tracks. Anyway good luck with the project
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Post by 7 on Mar 20, 2014 0:30:52 GMT -5
Your only real option is to go down. There are two ways that I know of- First go directly under the existing footing- to do this you can only do sections at a time without getting into helical piers or some other costly method. Dig out sections at a time that are short enough for the current foundation concrete to span…maybe 8 or 10 feet…form it up and pour the concrete. You shouldn't need to compact the soil because it should be virgin soil already if you are careful to excavate down to the exact depth you are wanting. It is a good idea to drill rebar up into the current foundation so you fuse the existing with the new. To save money you could talk to an engineer and get a length figure on your concrete's ability to span then remove a section, leave a section, remove a section etc etc around the perimeter…pour several sections at a time so your not mixing by hand or paying a pump truck to come back 15 times. You could also post and beam sections but it is still safer to leave dirt under the footings in several places so the foundation isn't completely suspended with all of its weight pulling down on the connectors which are already going to be insufficient by todays standards. The other option- results not as desirable because you lose significant square footage. Come in a few feet from your current footings then dig down to the depth you want, pour footings & frame up to your existing floor joists. I am not sure where the water table is in your area or exactly where the water is making it in from without seeing your place or knowing about your area. A foundation drain is an effective option for keeping water from getting into the space. I can describe these in more detail if you get serious about moving forward. I hope you have a window down there to get the dirt out through  . The labor part can definitely be a DIY project…if your an ox. If anyone sees any holes in my logic please tune me up I am always ready to learn as well.
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