Immature basement repair


  #1  
Old 05-18-00, 07:56 PM
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I am searching for advise on how to go about repairing basement walls. I have very compact clay soil, fairly flat grading except it slopes slightly towards the house starting 10' from the wall, previous "owner" has placed a 3" sump pump discharge into ground and it was freezing in the winter because improper grading. I've add some top soil around the house, covered it with 6 mil plastic and then with traffic bond to keep water away from foundation. Looks like my "improvement" made it worse, because walls used to just bow in during winters and would come back in the summer, now second row of the block has moved against the one that anchored by basement floor about ". I am planning to excavate the walls and backfill with clean gravel, any other suggestions?

Thanks for advise mik-mik
 
  #2  
Old 05-26-00, 01:40 PM
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Think the priorities are out of line.

I have that same situation where the land slopes toward the back of the house, have a stone rubble foundation and used to get water during hard rains after I bought the house. Your typical problem basement.

The solution is too collect as much water, both from downspouts and surface runoff and direct it away before much can penerate the soil close to the foundation.

The general principle is, if the water isn't there it can't do harm.

I excavated a V shaped trench two feet wide, 18 deep and lined it with many layers of heavy mil plastic sheeting.

Put about an inch of small pea gravel at very bottom and 4 inch perf plastic drainpipe to build a drain collection system.

Build a concrete head box at one end to collect one downspout drains directly.

Backfilled the system with 1 - 2" rock. One down spout dumps directly on the rock, runs through and is directed out the drain end to a diversion run off channel.

Works like a charm, 20+ years, hurricanes, big storms, never a drop.

Heavy surface water runs into that system that extends along the full length of the house and is also directly directed away.

Therefore only the perk water in the upper layer of the soil is available to cause problems. The system is pretty foolproof because debris and leaves etc are screened out by the heavy gravel fill and remain on the surface to be cleaned up in routine maintenance.

Somehow you are retaining a lot of water that can perk down and cause problems.

Each site is different in its characteristics but the solution is the same, collect as much water and move it away before absorption.

Each site has different considerations.

Mine, the left side as a run off / drain path could not be used because that took it down the driveway and would cause ice freezing problems in winter.

I have solved many of these problems. Sites are different, principles are always the same.

Survey site, develop a collection and drain plan. Understand special considerations. (freezing, lot of leaves, where screening functions need to built in, etc). Always plan to allow minimum absorption to surrounding soil.

I like gravity to do all the work, never installed a pump in any job. Never dug one out.

That makes the problem worst by disturbing and loosening the soil.

Never had the methods fail to correct a problem. If it will work in built up neighborhoods like Boston with old rubble stone foundations, will work about anywhere.

Am not a fan of the pumped mud method of "sealing" a foundation. Isn't cheap. You are in contest with Mother Nature. Mother Nature always wins, don't fight with Momma Nature.

Soil's characteristics play a role. Different type soils will affect the outcome, clay, sandy, loam, etc.

I have used these methods in sandy soil applications and they probably absorb the most and the projects where successful.

Super tough ones are where a gravity drain route is not possible or difficult to establish.

Fixing the bow is a toughie. Don't know of the feasibility of pushing it back. Might be able using heavy hydraulic jacks if one could design a rig to spread the pushing force and get a sufficient anchor or bracing point.

I am not a big fan of ever digging up the foundation. Think one causes more problems than are solved and it is not cheap.

The gravel drainage idea down along the foundation outside walls is OK for new construction where a proper drainage system is installed at the slab level.

Don't think it is cost or effort effective in retrofit problem situations.

You may be able to live with the bow if the problem causing it can be eliminated.

If you could send me photos might be able to give more specific advise for actual site characteristics. Leave your email here to contact.

 
  #3  
Old 05-26-00, 08:09 PM
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Thanks a lot for your response.
The diversion idea looks very promising, i am just a little concern about the soil that is directly by foundation. If it's not a surface water than ground water could rise to the same level and do the damage?
Could you clarify please about the V shape trench it's 2 feet wide and 18" deep? (they say never assume). I think i can handle this kind of project, can you please tell me what is the minimum drop for the system like this 1/4" per foot or?
I also need help with:
"Build a concrete head box at one end to collect one downspout drains directly.
Backfilled the system with 1 - 2" rock. One down spout dumps directly on the rock, runs
through and is directed out the drain end to a diversion run off channel."
What do you mean by "runs through", water fills the head box to the point where it runs out of the "diversion run off channel" is this channel on the surface or also buried?
Thanks again for all you help, i would include the pictures, just don't have a dig. camera yet
Please e-mail me at mik_mik_pgmr@hotmail.com

 
  #4  
Old 05-27-00, 10:22 AM
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Yes, a 1/4" slope to the pref drainpipe is super. It is not critical. 1/8", 1/16", 1/32" is fine. The system tends to build its own head as the pref pipe fills with water and if the drain path is properly designed it will find its way out. It should be exactly level in the worst case, never slope backwards.

The part about running through the coarse stone/gravel is my right downspout discharges directly on the gravel area and runs down through the voids in the stone to the pref pipe area where it is collected and directed to the drain.

In my case in the fall / winter a lot of leaves tend to build up close to the house and they always seem to be able to find their way into a drainage system and plug it up.

Plus there is always leaf debris in the gutters and it also gets swept down into the collection system. I solved both problems by having the stone / gravel act as a natural screen and filter out all debris before it makes it into the drainage pipe system.

The head box I described in my system had a couple purposes. One I could put a light bulb down in it and go down the other end and look back for an inspection. Two, It gave me a way to getting a good flush if I ever needed too. A sort of case where I over
designed some functions. I haven't really had to do much of that in the life of the system.

Yes, there can be high water tables or excessive ground water. It is a possibility. I never actually found a situation like that.

Probably used more as an excuse by contractors who are unable to get results more than anything.

My gut feel is somehow water runoff from your downspouts and gutters are the main cause of the problems. It is in the vast majority of the cases. In winter the downspouts can plug and the gutters overflow or drip.

The system I described also will collect that because it runs the full length of the house under the gutter. Again the overflow or drips fall onto the stones / gravel run through and are collected by the pref pipe and directed to the drains.

This type system is very tolerant of freezing water as built. In winter it is normal to get a lot of freeze / thaw cycles. The soil in the 1 to 2 foot zone around a foundation remains unfrozen and that is probably the source of your problem.

Drips, intermittent drain run off find their way into that zone, perk down and build up pressure inside the zone.

My drainage path is a simple surface channel between two houses along a row of hedges. Both my neighbor and I share this same path.

Apparently it is far enough away from the house and the soil conditions are so that it works.

Part of it is designing a system, giving things a try and having enough flexibility to adjust if needed. In my case that would mean a lining in the channel or extended prep pipe but experience showed it was not necessary.

There is nothing magic about the system I described. In general I never built two the same the entire time I did these type projects. What is important is to understand the general principles involved.

Many people never understood the concept no matter how many times I would explain it. I even had people who didn't understand after it was done and working. They would change critical parts of it around and cause the problems all over again. Example - Mowing lawns and disconnecting horizontal sections of downspout used to direct water into a yard area. Sometimes it was amazing, folks always wanted to look for strange rare causes. Human creatures can be puzzling.

I am not saying there cannot be rare contributors to the problem, there can. But one should start with the most common causes, eliminate them and work toward the more rare events last, if the conditions are not solved. Hope this clarifies things.


Best of luck


[This message has been edited by Rambler (edited May 27, 2000).]
 
 

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