Author Topic: Repair or Rebuild an old foundation  (Read 10896 times)

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Offline Hamish

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Repair or Rebuild an old foundation
« on: June 05, 2005, 05:27:34 AM »
I recently purchased a 40 year old lake side cabin in the Laurentians.  The cabin is situated on the side of hill.  The cabin foundation is concrete block.  It appears that over the years frost has worked away at the foundation causing cracks and tilting.  My question, "Should I shore up and repair the old foundation or build new?"  If I build new, should I return to the perimeter foundation or use pilings?"

Any thoughts?
Jim

Offline John Raabe

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Re: Repair or Rebuild an old foundation
« Reply #1 on: June 05, 2005, 10:25:13 AM »
The first thing is to find out why the existing foundation is failing. Most likely you are in expansive (clay) soils and the block wall did not have a proper drainage plane and footing drain to carry away the water before it freezes in the soil.

But that's only a guess. Some soils are very nasty - especially heavy clay soils in very cold climates.

Block walls can be reinforced and brought back into alignment. I think it was Journal of Light Construction that had an article a few months ago on just that.

Good footing drains, good waterproofing on the back of the wall and backfilling the wall with clean gravel are not small projects to do after the wall has started to buckle. Of course, if they had been done when the wall was built you probably wouldn't need to be reading this  ;D
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Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #2 on: June 05, 2005, 12:00:41 PM »
Thanks John:

You are right about the soil.  Soil appears to have a high content of fine silt and humus.  I suspect the foundation drainage is limited at best.  

The article you referred to is in the Oct 2004 issue of Journal of Light Construction.  The solution appears to be more than a mere mortal such as I could handle.  The article out lines the use of special hydraulic drivers to sink support piles and anchors.  Although the suggested cost is quite reasonable, in the $3000 range compared to $10's of thousand of which I fear.

If the foundation can not be saved at a reasonably cost is it feasable to use concrete piles and beams to support the cabin.  The storage space created by the foundation is of limited use and could be replaced by building a shed.

Comments
Jim

Offline John Raabe

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Re: Repair or Rebuild an old foundation
« Reply #3 on: June 06, 2005, 10:01:39 AM »
It is possible to use concrete piers and support the house on beams. This would be easier to do in a new location than it would under the existing house. Especially one with what? a failing but existing basement or crawlspace?

On the other hand you could then get the proper drainage of the piers as you will control how they are backfilled.

Yes, the JLC article looked quite involved and expensive. For the life of me I cannot envision a simple solution for your situation either. At least not one that would satisfy a fussy banker or building inspector.
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Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #4 on: June 06, 2005, 05:50:28 PM »
The cottage sits upon the side of a hill.  The Basement / crawl space has an earth floor which slopes from 12 inches at the back of the house to 6 feet at the front over the width of the cabin (16feet).  I believe the foundation is 6 to 7 feet at the back of the cabin.  It would be easier to describe the situation if I send you a couple of pictures of the basement interior and exterior.

Cabin dimensions are 16 feet x 35 feet x 1 story.

So far my first quote from a foundation guy could choke a horse.  The $$$ he is suggesting to rebuild the foundation, I would be better served to dismantle the cabin and start over.

Jim

Jim

Offline John Raabe

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Re: Repair or Rebuild an old foundation
« Reply #5 on: June 07, 2005, 06:59:31 AM »
I would suggest you get a new quote for a drilled pier and beam foundation that the cabin can then be moved onto. It might be less.
« Last Edit: June 07, 2005, 07:00:01 AM by jraabe »
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Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #6 on: June 07, 2005, 07:29:10 PM »
Thanks again.  My first quote is $80k for the rebuild of the foundation.  Builder seems to be reluctant to consider a drilled cement piles and beams.  Excuse is about stability of the piles.  Piles will be pushed or tilted down hill and collapse.

The quote compells me to consider all options.  Have any good sites i should visit to better understand the dynamics of pile and beams on slopes?

Thanks
Jim

Offline Amanda_931

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Re: Repair or Rebuild an old foundation
« Reply #7 on: June 08, 2005, 01:21:11 PM »
I used to be on a list with someone who had a few odd obsessions.  Hydraulic pressure was one of them.

I've lost most if not all my bookmarks since then, but that would be one of the phrases I would use in a search.

Might also look at swales, or "drain to daylight."


Bart_Cubbins

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Re: Repair or Rebuild an old foundation
« Reply #8 on: June 08, 2005, 02:20:35 PM »
Speaking of hydraulic pressure, maybe this type of system would work...



http://permajack.com/index.htm

I have no idea what that would cost. A geotech engineer in your area might know of similar solutions available there.

Bart

Offline Jens

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Re: Repair or Rebuild an old foundation
« Reply #9 on: June 09, 2005, 12:46:54 PM »
A friend of mine bought a house with a solid concrete foundation bowing in.  First he jacked that side of the house up and supported it, then he dug all the dirt out outside.  he then used a screw jack, setting against a lumber frame that went to the opposite wall to move the wall back out.  after some crack repair, he poured large supports extending perpendicular to the wall every 4 ft.  Might be more than you want to do, but could work.  Also, if you get the wall jacked out, you may be able to use surface bonding cement like in many earth sheltered homes.
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Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #10 on: June 09, 2005, 06:08:42 PM »
Hobbiest:

The butress concept was suggested to me the other day.  It sounds like a good idea.

It would appear that the cabin will have to be jacked up in order to make any lasting repairs.

PS, Thanks Amanda 931 and Bart for your suggestions.

Cheers
Jim

Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #11 on: June 12, 2005, 08:25:35 AM »
This is a view of the slope I am dealing with,





Please excuse the junk, but is what the foundation looks like underneath my cabin.





Keep in mind that this cabin does not have road access.  All materials have to be brought in by small boat.


Can the foundation be contructed in sections.  Start with the front wall and work around on wall at a time or must the entire cabin be lifted to construct the new foundation?


Thoughts

Jim

Bart_Cubbins

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Re: Repair or Rebuild an old foundation
« Reply #12 on: June 12, 2005, 11:04:18 AM »
Hamish, is that crack the worst of the damage?? Is the other side the same, with cracking along ground level? Is the damage limited to the end walls?

Does the ground level outside the foundation roughly follow the ground level inside? It looks like the ground under the house was partially dug out for storage, and that the walls did not have adequate reinforcing to resist the one-sided pressure from wet soil and frost. Are the block cores filled with concrete? (You might be able to tell by reaching up between the joists, if the tops aren't completely covered by the sill plate. If not, I guess you could drill a few holes.) If there's no concrete, there's no rebar and therefore no strength to resist lateral pressure.

Given the amount of room for working under the house and the remoteness, I'd try to fix the existing foundation. The damage doesn't appear all that bad in the photos, though it's hard to tell for sure. If the damage is limited to the end walls, then the drainage fixes suggested by John and the  approach suggested by hobbiest should work. I don't think it's necessary to jack up the whole house, but I would put in a temporary beam and posts just to protect yourself while working under the house, just in case.

After the walls are straightened, they should be reinforced. If you can get access from above, you can drop a length of #6 rebar into the cores and then pour in a soupy concrete mix. Normally you'd put one every other block, but given the history of damage I'd put more in the damaged areas. If you can't get access from above, then build buttresses inside.

Bart

Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #13 on: June 12, 2005, 12:47:47 PM »
Bart

Here is the outside wall.  The crack you noticed inside is behind the ladder.  There is another foudation crack right at the corner about where my hand is.



Can't comment on the rebar or concrete in the cavities of the block.  My guess there is no support inside the wall.  Foundation drainage is also unknown.

I will be at the cottage in 2 weeks to review all my options.

Cheers
Jim

Offline JRR

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Re: Repair or Rebuild an old foundation
« Reply #14 on: June 13, 2005, 06:30:02 AM »
I agree with the concept of fixing what you've got.   It doesn't look that bad to me ... I'm not suggesting that some correction isn't needed ... I just think you can do it.

I agree with Bart,  make sure you put supports in place to prevent the thing falling on you ...  the support(s) could be something that you move about to whatever area you are working in ... a system of temporary columns secured to the joists.

My first corrective step would be applying a liberal coating of masonry surface bonding cement ("Surewall", etc) to the inside of the foundation.  This will strengthen the wall and also show if any new cracks develop.

Next I would hand-dig down to the footing around the outside of the foundation.   (I believe I could uncover the whole foundation in two or three days ... assuming the earth is solid enough to support a hole and not to fall in.)  

When the footing is exposed, you can determine what the next steps are.   You want to install a drain system if one is not in place.   A coating of surface cement on the foundation wall exterior may be in order.  You may want to install rigid foam insulation against the exterior of the foundation followed with a stucco-like covering.  You can use the idea of "frost protected footings" found in the following ... http://www.nahbrc.org/Docs/SubsystemNav/Foundations/3808_NAHB_fpsf.pdf?TrackID=&CategoryID=1802&DocumentID=3808

It looks like a pretty nice place you have there,  a number of us wish we had your problem ....
« Last Edit: June 13, 2005, 06:41:30 AM by JRR »

Offline Hamish

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Re: Repair or Rebuild an old foundation
« Reply #15 on: June 13, 2005, 05:03:05 PM »
JRR

Thanks for your input.

The collective knowledge from all who participated has been of great value.  I will be at my cabin again the end of June.  I will report back to all with my solution to the foundation.

Cheers
Jim

Offline glenn kangiser

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Re: Repair or Rebuild an old foundation
« Reply #16 on: June 13, 2005, 06:23:10 PM »
Sorry I haven't had more time to get in on this one and haven't had time to read all posts in detail but I noticed from your picture that your house and pad it sits on is a dam for all the water coming down the hill from above.  I would think you need some good drains above to keep the water from getting under your house - route it around possibly going rather deep with French drains if necessary.
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