Ok, so here’s the deal…..I am remodeling my first home and although I will be the first to admit I do not know how to do a lot of the things I will have to do. I do have a mechanical license and have been in the constrcution world long enough to be dangerous, I realize this, so I also have learned to know what to look out for.
What I have been looking into is the idea of breaking up my current basement slab, diging out about 10-12″ (so I don’t go below the footing) adding crushed gravel, waterproofing, insulation and reporing a 4″ slab. The idea is to have the top of the new slab about level or maybe even 2″ below the top of the footing.
I have checked on the elevation of my footing by digging outside and it appears to be only about 3″ below my current slab. (I am not positive on the footing depth 8-10?? I plan on checking)
So, I understand that I need to findout what elevation my sanitary is at and I know that there are a TON of potential structural concenrs if I dig below or deeper than the footing. I have found some very in-depth forums about foundation underpinning and digging basements out 2′ and more…..I HAVE NO INTENTION OF DOING THAT……but I guess what I really want to know is:
1. Does the basement slab HAVE to be on top of the footing? or can the slab be level with the top of the footing? (are there structural reasons for the slab being on top of the footing?)
2. If I were to digout my basement, do I HAVE to add a drain tile along the inside and outside of my footing? (is it due to disturbing the soil and the potential for adding moisture pockets when I dig?)
3. I am not looking to gain 1-2′ of headroom, I would be happy with 4″.(that way I can have over a 7′ ceiling and so I can put a 80″ door at/under the 6″ support beam in my basement). Can’t I just dig down to about level with the bottom of my footing and build up from there so that my slab is level with the top of the footing? in a traditional “floating slab” , as I thought I had heard them called, that would gain me 4″ (assuming I had a 4″ slab to begin with).
I understand that this would be a HUGE project, and I honestly don’t think this is anything I will do……but I guess I am really just brainstorming possibilties.
Thanks for any knowledge you share!
Replies
That's what I'm talking about!!
Thank you sir!
I appreciate the education junkhound.
haha.....yeah as-far-as the "huge project" goes, I guess I half expected that the responses to my question would be....."what! that will be a huge job, you don't want to do that" so I guess I was just diffusing that from the get-go. I'm 30 and used to working hard.....so most of the projects I consider, everyone I know and all the reasearch I do, people make it sound to be a big deal and I guess I just didn't want those kind of responses.
Thanks for your information, that is very helpful!
questions back your your responses.
1. How do I know if there is internal rebar from the footing to the wall? I don't know of anyway to see that without busting the wall? Is there some way to tell? The house was built in 1954ish and is a walkout Ranch, only about 900sqft/ floor with 83 1/2" from slab to B.O. joist. The slab is perfect right now. No cracks or buckling at all!!! There is one small area near the walkout backyard foundation that has cracked becasue I was replacing the sill plate on the back of the house and was using a column to support the back of the house. As I was wrenching on the column the slab cracked a small amount at the wall. Other than that no cracks and as far as I know, no water problems in the past 2 years.
2. I am in Michigan, so def have a high water table. Also the last couple years we have had a 50 year and 100 year flood, but yet, no water probelms. I live about 200 yards and probably close to 200ft elevation gain from a river (totally guessing on the elevation gain) but, realistically I have a neighbor between me and the river and I am way up from the river.......But I need a drain tile to a sump pump on the interior only...or interior and exterior?
3. The only other possible problem (lets say I have rebar tieing the foundation and footing together).......so, 4" slab, 2" insulation, membrane (not worth counting in measurment), and 4" crushed gravel. that's 10"....if my footing is only 8" tall and I want to be roughly level to the top or, for sake of argument 2" below. That would mean I have to dig down.....possibly about 4" below the footing. From my understanding, the footings most crutial area is just below the footing and on a 45 degree angle outward and down from there. This is how the weight gets dispersed. So, If I have to dig 4" below the footing.......are there concerns I should be aware of?? should I leave a foot of soils inside of the footing and just add gravel and insulation leaving the area below the footing, within a foot, alone? and with that.....how would I then do my drain tile?? do I just start that at a foot inside the footing also??
or do I not need to worry about any of that??
4. The other question I am wondering about and maybe I need ot take this into consideration when repooring the slab....Being that I live in michigan, my frost line is 4' below grade....unless my footing ar close to 4' tall....there is no way my footings are below the frost line. Is that wierd?? do I need a thicker slab at the exterior walls or something liek that? any concerns here??
Thank you Sir!
Walk out basement, perfect slab, no water problems. Raise the house four inches.
I thouht about that...
Thanks for the input Mybuilder.....I appreciate the thinking from all perspectives.
I thought about that....but 2 problems witht that.
1) I have an attached garage, the person that owned the house before me, added 4' of raised floor to extend the livable sqft on the house and then added an attached garage. OR which actually makes more sense, he just added 4' raised floor house into the existing attached garage.....not sure which. But I know the attached garage is newer, because when I replaced the roof last year, the sheeting was newer. (So, I would have to try to disconnect the house from the garage at the original foundation wall, which would cut off a bedroom walk-in closet 4' deep x 10' wide, and then raise the house. I guess I could then do a step down or do it right and add a bump out foundation, which they never did and then connect the new fondation wall to the exisitng house) But honestly......that sounds like a lot more work than digging out the basement.)
2) The other problem is that.......I don't think I could physically jack the house up by myslef....I could dig the baement out myself! I think I would have to hire someone to hook up pneumatic lifts (or whatever they use) all over the house and raise it for me. I am guessing that in and of itself is 10k or more. (not to mention, I would have to disconnect the house from the garage and try to reconnect it.....and with the raised floor bumpout, it just sounds like it would be a lot more than what I want to do.)
Do you agree? or what do you think?
Without plans or pictures, of course, it's hard to confirm. For 4", You could raise the garage too. The big problem isn't raising it. Yes you can do it yourself. Your local rental place should have screw jacks that will lift 10-20 tons 10" or more. The biggest co cern would be any wiring connected to the basement walls. Don't run out and try it based on my two paragraphs, but think how hard pouring new mud in there will be by yourself compared to "turn this screw, turn this screw, turn this screw" until tour house is taller. We do this regularly to fix foundation walls. It's not as hard as it sounds.