I live in a house that was built around 1865 with a stone foundation. There are a few spots that water seeps in and onto the floor when we get heavy rains or rain over several days. I've had two waterproofing companies out and one wants $14,000 to excavate outside, down along the foundation to install a drainage system. Replacing the patio and driveway that would be destroyed would be additional costs. The other wants over $10,000 to dig up the basement floor to install piping and two sump pumps. Is there something like a sealant or other effective repair that can be done at a lower cost?
The proposed work that you describe is what I call water collection systems. These systems may be the final solution for collecting water around foundations built with modern materials and methods, but they may be detrimental to old buildings. In my experience, many have been found to be damaging to old stone or brick foundations. Waterproofing contractors often offer a lifetime warranty for water intrusion, but can they guarantee against possible foundation failures in the coming decades?
The installation of the most common of these water collection systems involves digging a trench around the inside of the foundation walls. If there is a concrete floor, it gets cut open around the perimeter. The trench is then filled with crushed stone and perforated drainage pipe. Some type of water collector is then installed at the base of the walls, similar to a baseboard molding. This molding however allows water collected from the base of the walls to enter the drain pipe system. One or more sump pits with pumps then discharge the collected water to the exterior.
Old stone and brick foundations rarely have any footings at the base of the walls. The basement floor is often at the maximum depth of the foundation. Excavating at the base of an old foundation is risky and best left to those that are experienced with old structural masonry techniques.
Another problem with this type of installation involves the drainage system. Since the drainage pipe is usually installed at the soil level below old foundations, I have often found serious soil erosion. Each time water enters the drain system, some fine soil can be carried with it. This continues until a structural problem arises from the undermining or the expensive drainage system becomes clogged with silt.
Correct the Source
Too often folks tell me that the waterproofing contractor they hired only offered a single option for correcting a water penetration issue. That option just happens to be the most intrusive and costly. If I were considering hiring a contractor to fix my wet basement, I would hope that the causes of the water were evaluated and remedies suggested. Here are some of the most common sources of water entry:
- Inadequate or clogged gutters and downspouts not extended. There's a significant amount of water that falls on a roof during heavy rains. This needs to be collected in a maintained system that discharges the water well away from old house foundations.
- Improper grading. The soil near the foundation should slope away from the house. Current standards require that the ground should slope down at least 6 inches within 10 feet of the foundation. Many homes with basement water issues have been corrected by simply adding soil around the perimeter and grading it to shed the water away. Care should be taken if adding soil. Dirt should be kept well away from siding, trim, or basement window frames.
- Foundation maintenance. Old stone and brick foundations typically need some re-pointing, when the old mortar has worked its way out of the joints. Many stone foundations also need the interior mortar coating restored.
I don't know of any sealers or other miracle cures for wet basements in old houses. Without addressing the source of the water, there's not much any "waterproofing" system can correct. An expensive waterproofing treatment might just be necessary for the most chronic wet basement problems, but I would personally consider it a last resort. Just keep in mind that collecting the water after it seeps through your basement walls isn't really a waterproof foundation.
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