How to keep water out of footings

Reply

  #1  
Old 08-16-17, 08:20 PM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,992
Received 2 Votes on 2 Posts
How to keep water out of footings

Any clever ways to keep rain water out of trenches created for footings? Footings have already been poured and there is about 5 feet of water sitting on top. I was thinking of buying a submersible sump pump and lowering it down inside, then once it gets low enough, perhaps digging a hole adjacent to the footing, placing a bucket with the top even with the top of the footing, then placing the pump inside. The walls won't be formed or poured for at least another week and I really want to get this water evacuated.
 
Sponsored Links
  #2  
Old 08-16-17, 08:29 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 26,010
Received 675 Votes on 624 Posts
Yes, a submersible pump would be good, but you need to keep it elevated by sitting it on a clean cement block, brick, or similar... don't just drop it down and sit it in the mud or it will overheat and burn up.
 
  #3  
Old 08-17-17, 04:32 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,992
Received 2 Votes on 2 Posts
I planned on placing it inside a 5 gallon bucket with the lip about even with the surface of the footing
 
  #4  
Old 08-17-17, 05:12 AM
B
Member
Join Date: Oct 2001
Location: USA
Posts: 963
Received 3 Votes on 3 Posts
Once you get the water out, check to be sure the footings weren't undermined
 
  #5  
Old 08-18-17, 07:57 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,992
Received 2 Votes on 2 Posts
That was one of my concerns. I'll be sure to check that. If they were, then what? Tear them out, excavate deeper (how much deeper?), and pour new footings? Or is there some other fix? This is 2,000 psf clay soil, so even more critical that it is done properly.
 
  #6  
Old 08-18-17, 08:29 AM
B
Member
Join Date: Oct 2001
Location: USA
Posts: 963
Received 3 Votes on 3 Posts
Best thing to do is dig out the real soupy stuff in the area it washed out (if any) and fill with a lean (weak) concrete mix. Never seen real good results with packing fill under a footing. If it's just a small area (18" to 24") and the footings have reinforcing in them, you can probably get by with packing fill underneath. because the reinforcing allows the footing to act like a beam and span the soft area. And again, your loads are pretty light.
 
  #7  
Old 08-28-17, 04:44 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,992
Received 2 Votes on 2 Posts
The load was supposed to be light, but they had to dig two feet deeper than anticipated, so now there will be about a 7 foot wall (8" thick) instead of a 5 foot wall. That alone will add significant load and even more of a reason to get the footings perfect, correct?
 
  #8  
Old 08-28-17, 04:50 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,992
Received 2 Votes on 2 Posts
The load was supposed to be light, but they had to dig two feet deeper than anticipated, so now there will be about a 7 foot wall (8" thick) instead of a 4 foot wall. That alone will add significant load and even more of a reason to get the footings perfect, correct?
 
  #9  
Old 08-28-17, 05:42 AM
B
Member
Join Date: Oct 2001
Location: USA
Posts: 963
Received 3 Votes on 3 Posts
In the vast scheme of things, you do have relatively light loads. Standard weight concrete weighs an average of 150#/cf. So: 1' L x .67' (8") thick x 3' extra height x 150# = 302 pounds extra weight per linear foot for the extra concrete depth.

More math!: We always considered 2000#/SF to be a minimum soil bearing capacity before we started looking at alternative foundations. So 2000PSF soil bearing x 1.3' (16") footing width = 2660# per linear foot footing bearing capacity. To save me a lot of typing, the total weight of your 7' wall and a footing is 834# per linear foot. That means the heaviest dead loads on the soil take up about 1/3 of the total bearing capacity. Obviously there are all the above grade live and dead loads, but I have a hard time imagining getting close to the bearing capacity even with a structural slab; and there's a good chance your bearing capacity is even higher. But, again, I'm not an engineer and I know next to nothing about site conditions. Keep after the contractor to get the blessing of a licensed structural engineer.
 
  #10  
Old 08-28-17, 07:18 AM
M
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,992
Received 2 Votes on 2 Posts
I'll be sure that a structural engineer is involved. BTW, with the supplemental footings in place, the overall width is now 30". One of my concerns is whether or not they drilled rebar into the original footing or simply dug down and poured next to it. The latter is more likely because it doesn't appear they dug back enough to even fit a drill in the space. Aside from digging everything out, I don't see how the engineer is going to be able to tell one way or the other. And I suppose xraying them would be costly (https://www.gp-radar.com/concrete.html)
 
  #11  
Old 08-28-17, 07:37 AM
B
Member
Join Date: Oct 2001
Location: USA
Posts: 963
Received 3 Votes on 3 Posts
I've used ground penetrating radar on a couple commercial projects, but I couldn't tell you what the cost was any more. It was a long time ago. It did a great job of locating rebar in a slab and was amazingly accurate!
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: