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alexmoen 03-10-2012 08:43 AM

Old basement wall issues
Hi all,

We have an older home (moved to the present location in the 1920's). The basement walls are made from cut fieldstone, and are quite thick (between 18" and 24"). The problem is that the mortar is starting to disintegrate, and it's getting worse as time goes on. You can literally remove it from between the stones with your finger, and it's like sand.

We have lived in this home since 1998, and have only had water issues three times: once, during a very heavy rainstorm, and the downspout extensions weren't put back in place (hmmm... who mowed that day?). The other two times were during spring thaw, after very high snowfall. The snowmelt was coming through the rocks a couple of feet off of the floor (about 6 feet below ground level). There is no sump pump or drain tile in the foundation, and all of these issues have happened in exactly the same spot in the basement (luckily, the lowest spot in the basement, under the coal chute where the coal storage used to be), so everything was very manageable, though still a pain.

I am concerned about the mortar and the future of my foundation, not to mention the cost to repair this. Are there any simple, modern fixes for this problem? Is it a common problem that has an accepted solution?

I have also noticed that the cement floor has started to heave in quite a few places, though, it's covered with carpet, so I can't see the total damage, and frankly, I'm afraid to remove the carpet and face the truth! :)



mudmixer 03-10-2012 02:09 PM

Without seeing a picture or anything, it seems relatively simple. You have an unmanaged water problem. That is the reason for water collecting behind the wall and seeping in as pressures increased and the heaving of the floor as the hydrostatic pressure forced it up and cracked the slab.

Three problems in about 12 years means that the space can never be relied on for finishing unless corrected. The cause could be a weather cycle, changes in exterior drainage or just poor gutters and distribution of the water away from the house. The gutters, downspouts and above ground or buried water distribution can be done if you can drain water well away from the house.

A collector sump and pump in the basement is a minimal solution the reduce the hydrostatic pressure under the slab and on the walls, depending on what soil was used under and around the house.

Obviously, an interior drain tile solution with a sump pump will be ideal since it does not require exterior excavation (disruption of all landscaping) and does a better job in the long term to reduce the hydrostatic pressure. Once you tear up the carpet that cannot hide the heaving, you may see that the removal of concrete for an interior system is not that difficult although the logistics of handling materials out and in can be difficult.

With a thick stone foundation, there is no structural problem if the pressure is reduced. The mortar is probably a lime/sand mortar that has been used for centuries.

How is the fishing up there? - Still as great as usual?


alexmoen 03-12-2012 07:02 AM

Hi Dick, and thanks for the response!

I understand what needs to be done for the water issues... Lord knows we're dealing with that a lot here, and if you are familiar with the area you understand.

The condition of the mortar in the walls is what is concerning me more... The fact that the substance holding my house up is able to be turned into a powder by touching it is kind of disconcerting. But what I am gathering from your comments is that it is normal and natural for the mortar to age this way, and it doesn't affect the integrity of the walls?

The fishing has been good this year, or so I have been told... I don't fish myself, but I talk to lots of fishermen. The ice fishing tournament had lots of fish caught this year, the winning northern was over 9 lbs, so that was quite a change too.


joecaption 03-12-2012 06:30 PM

Regrade the area around the foundation so water runs away from it.
Add a french drain.
Make sure there no mulch piled up againt the foundation.

mudmixer 03-12-2012 09:39 PM

With an excessively wide foundation, it would be difficult to make the foundation weak for lateral loads on a relatively low wall (8' to 9').

As far as vertical loads (especially with compressive strength area) the quality of mortar relating to the vertical capacity of the wall. The wall probably weighs more and is more stable than any wood frame structure (including appliances, furniture and pianos) above. The general rule for high rise (7 to 20 stories) masonry mortar is to use the lowest strength possible and carry the loads.

It is probably more of an appearance problem, except for the water under the floor.


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