Interior vs Exterior Basement Waterproofing

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Posted by: from Hamilton
12/2/2011 at 10:42:54 AM

My house was built in 1967 and water leaks in a little bit in only 1 corner of the basement.

I've called different basement waterproofing companies and so far everyone suggested the inside method. From what I've heard, the inside method does not work as good as the outside method.

But, these guys explained to me why the outside method does not work 100%. The outside method only replaces the system I already have, which in 40 years so far, has failed.

However, the interior french drain and new weeping pipe is an improvement to what I currently have.

So while the cost is almost doubled, quoted at $90 per linear foot, I still think I want to do the exterior... but when these guys explained to me and how they've fixed hundreds of houses that had been waterproofed from the outside and still failed, it makes me somewhat unsure.

The cost I was quoted to do the inside is $35 per linear foot which includes installation of a sump pump (with sump pit) and the removal of all concrete debris.

My house measures 40' x 27' and it has poured concrete walkways along the outside perimeter of the house of almost 75%. So these would have to all be broken and removed before doing the exterior method.

I need an explanation of why I should prefer the interior or the exterior.

Thank You.

interior vs exterior basement waterproofing
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Date/Time12/2/2011 at 12:15:03 PM

Hi Ben:

From the picture, it looks like the house is leaking at an exterior corner. Firstly, is that a low part of the yard where water can pool? How long has the leak been going on? If not long, what change has occured? Have you called a drain cleaning service as Router Rooter?

An inside sump pump and hole is in case the basement floods. Obviously you have a finished basement and do not want water intrusions of any kind.

Being the age that it is, the outside drainage is the old tiles which have now been replaced with 4 in perf pvc.

Depending on what your budget is I would take the outside route if you want to utilize your basement fully. Keeping the moisture out will keep mould issues from happening as well.

Doing the outside will be messy depending on how far your basement is below ground. Small machines can do the work.

I would get 2 or 3 drainage firms to give you an estimate and then decide what is the best route to go.

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Ben in Hamilton
Date/Time12/2/2011 at 12:30:57 PM

Thank You for the reply.

We just purchased the House in June and previous owner said it only leaked previously in 2009 (I think it's not true).

In October (1st leak), we redirected downspouts at the corner and fixed the concrete to slope away from the house. A couple of days ago with heavy rain fall, it leaked again. So the drainage isn't working properly.

Also the leak is only coming from the very bottom of the basement corner.

An interior back water valve was installed but again, this didn't solve the problem as it only stops sewage from backing up.

When you say drainage firms does this mean basement waterproofing company?

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Date/Time12/2/2011 at 12:51:20 PM

Hi Ben:

There are firms such as Router Rooter that are specialists in this type of application. If they do not do it themselves, they will certainly put you in touch with some REPUTABLE firms. They have the right type of tools, machines and know how.

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Date/Time12/4/2011 at 8:39:57 PM

Although I am an electrician, I am a home owner just like you and have done tons of research for my own home. I agree that the only true method of repair is exterior only. The intent is to keep the water outside the building envelope. You have not done that if you allow the water / moisture inside the envelope and are controlling it from there.

You mentioned that the other contractors said that the previous method failed. They are right to a point...but remember that our basements at the time were "damp proofed" according to code, now we want them "water proofed" which is totally different kettle of fish.

I chose the higher end method for my basement, I have block walls. I dug down to the footings, reparged all the blocks, applied blueskin, installed new weeping tile encased in geotextile material, installed drainage board, installed window wells and vertical weepers where needed, buried my weeping tile and vertical tile in 24 inches of stone (also encased in geotextile material), then backfilled with the native soil.

It has taken almost two years for the backfill to naturally settle. Did not want to mechanically compact the area. It has also taken a full heating season to draw the moisture out of the blocks that has been in there for years...only once I am satisfied that the moisture on the interior is gone, will I attempt to finish my basement.

I am sure there are contractors on this site that will say I went over kill, but to me this is the long term solution, if not the permanent solution.


John Kuehnl-Cadwell

Master Electrician

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Herbert from Bert'll Do It in Mississauga
Date/Time12/29/2011 at 4:03:58 PM

Water in the basement is extremely bad if you intend to develop the area for living and an interior solution will not work in the long run. The only solution is to prevent water from entering the basement and penetrating the foundation walls at all.

If the foundation walls become saturated with water and then freeze the concrete or concrete block will become weakened and cause major structural problems on top of all the mould problems that you may have.

Unfortunately the only solution that I can recommend is the exterior solution. And that solution involves regrading the exterior to drain water away, down spouts to take the water way from the foundation, replacing the drainage tile or weeping tile, applying waterproof coatings and materials to ensure the basement and foundation is waterproof.

Also it appears from the photo that the finished flooring is directly on the concrete floor and the exterior studs are only 2x2 and attached to the block foundation wall. A better method is to utilize a raised floor and 2x3 or 2x4 studs installed an inch from the exterior walls. This method allows for minor water infiltration and drainage.

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