Replies

1. 
   calvin | Jun 25, 2010 01:44pm | #1

   Jen,

   Did he "mention" 4' deep footings, or is there an addendum on a print?  Interior footings in a basement are already probably 4' below grade.  Besides, they're inside the dwelling.  I assume the new footings are in addition to support on the block wall at either end.

   I wouild cut the concrete floor to the footing size needed, excavate down to undisturbed soil or the bottom of recommended footing thickness and pour new concrete footings to top of slab.  Buy columns (not the cheap 'insert a pin when adjusted to ht.) to fit, install to top of footing (slab ht) and fasten-then fasten to beam.  These columns can be purchased or ordered in approx. 3'' increments with that much adjustment possible.  Note:  If you don't want the column plate on top of your finished floor-you can pour your footing deeper, install the column to it with the bottom below the existing slab, then top off with say 3-1/2" of concrete pinned to the existing slab.  This also would keep any settlement below your slab and the pinned concrete will stay put.  All of this keeping the same elevaton of the existing basement slab.

   If you get to a good base and / or compact whats there, you should not have much if any settlement.

   Depending on what your finished floor will be-be aware that cracks may appear outside the footing (old slab) unless scored away and out from the four corners, though I've never had this happen. 

   He or a good concrete man may advise drilling into the side of the slab b/4 you pour the footings and epoxying rod in that will connect footing to slab.  I have no educated opinion on this (beats the heck outta me).

   Best of luck

1. 
   DanH | Jun 26, 2010 12:03am | #2

   I wouldn't pin the floor to the footing.  Put expansion joint material between the two.  A basement slab that old will want to move, so let it.

   The footing only needs to be thick enough to develop the necessary strength.  I think normally such thickness would work out to be about half the width of the footing, though using rebar would reduce the needed thickness a bit more.  (The width of the footing depends on the weight it carries and the bearing ability of the soil.)  Can't imagine that a 4-foot thick footing would ever be needed in a "inside the envelope" basement.

2. 
   DanH | Jun 26, 2010 08:29am | #3

   With regard to the joints, I was just thinking of some old basements that I've seen where the slab goes up and down seasonally due to soil moisture changes.  Not a universal problem, but since I can't seen the basement in question I'd err on the side of safety, and make it easy for the two pieces of concrete to move independently.

1. 
   TechieTechie | Jun 27, 2010 10:17am | #4

   Old house sag....Help

   All,

   Thanks so much for your help/advice. The pours are only for the 3 new lally columns, not to support the existing envelope...Given that my town has a very high water table (old joke is, there are only 2 kinds of houses...ones that have termites, or ones that don't know have termites), so I'd rather err on the side of caution and add an expansion joint. I'll check with my town's inspectors, see what they require for footing width/depth (particularly in MA, since we seem to be more strictly regulated for most anything).

   So, here's another question (if you don't mind me tapping the brain trust). Do I bother trying to jack up the house, to take out the sag? The sag isn't noticeable to the untrained eye (no vertical wall cracks , expanded corner joints, or runaway marbles), and I'm wondering if I should leave well enough alone. If you do recommend to do so, I know the old maxim (no more than one-eighth an inch a week), and  I'm assuming I'd use the lovely adjustable floor jacks, then once level, put in the permanent columns?

   So much fun!

   Thanks again...Jen

1. 
   DanH | Jun 27, 2010 10:59am | #5

   Depends on how much you want to move things.  If you're only talking a half inch to an inch then it's doable without major pain.  You just need to jack slowly, over a period of a week or two or three. 

   It's amazing how much going from "sorta level" to "level" can do for the "snappiness" of the house -- things that are straight and square just LOOK better, even if the difference isn't consciously visible.

3. 
   k1c | Jun 27, 2010 02:20pm | #6

   basement footing

   I live in north NJ and I had to put in extra columns too.  The inspector wanted 24"x24" by 12" deep footing for the indoor footing.  I cut the square out with diamond dry sawblade (lot of dust and you may want to rent wet saw)  and dug down to 12 inches.  Be careful with digging as you get close to 12" as not to disturb the soil.  It is best to pour the concrete on undisturbed soil.  I dug an inch or so more with garden spade to scrape out the loose soil.  You may come across loose sandy soil or gray organic soil, in which case you should ask the inspector for kind of footing he wants in such cases.

   For leveling, I want to ask are you sure the sagging is due to not enough support?  Is the sagging across the house, following the support beam in question?  Having asked that, if the sagging is not noticeable, you should leave it.  But can you find out just how much it is sagging?  Also, if you look at the ceiling line, the gap between the door and the jamb (and the floor), bathroom floor, looking across the wider expanse of the floor, do you see the sagging?  I don't have experience in jacking up sagging floor, but trying to correct this may at least realign the moldings which you may not want.

   If there are wide openings in the floor above the basement beam, try to see if the jack and king studs (studs that hold the supporting beam for these openings) are supported by a joist or blocks that rest solidly on the basement beam.

   By the way, wait at least a week for the concrete to cure before installing the columns.  Hope it helps.

4. 
   ryagid | Jun 29, 2010 04:20pm | #7

   Hey Jen,

   If you haven't seen it, this article may be of use to you.

   https://www.finehomebuilding.com/how-to/articles/replace-rotten-lally-column.aspx?ac=fp

   Emanuel Silva is a builder in the Boston area, and this is how he goes about solving your problem. He anchored his columns to raised piers, but saw no problem with setting them flush to the slab. Also, his building inspector only required him to dig a footing 1-ft deep that measured 2 ft x 2ft. A previous reply nailed it...you're in the basement, so you're already down quite a ways.

   Emanuel's footing constuction isn't conventional, but he has done a lot of these jobs and hasn't had any problems with cracking.

   Also, I had engineer Rob Munach address the question of whether or not to raise the beam in a sidebar. His advice-- it's tricky and may not be the best idea. You're best bet is likely to stabilize the floor, not raise it. Take a look at the article, I think it will answer a lot of your questions.

   Good Luck,

   Best,

   Rob