Frozen water in a wet crawl space (C) Daniel FriedmanHow to Stop Ongoing or Recurrent Crawl Space Water Entry

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Stop crawl space water entry:

How to stop water from entering a building crawl space. Here we explain the three basic approaches to stopping crawl space leaks & water entry. This article series describes the steps needed to get into, inspect, clean, and then dry out a building crawl space.

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How to Stop Ongoing Crawl Space Water Entry

Wet crawl space unsafe to enter (C) Daniel FriedmanStop water from entering the crawl space from outside sources

This means attend to roof gutters and downspouts - the most common cause of crawl space water entry or high moisture in most areas.

[Click to enlarge any image]

Our page top photo shows frozen water in a wet and cold crawl space below a condominium in Poughkeepsie, New York. The very wet masonry blocks along the rear wall of the crawl area and water stains higher on these walls tell us where the water is coming from.

The photo at left shows another crawl space with standing water.

If a building site is unusually wet or springs are adjacent to the building foundation, additional steps such as the installation of a drainage system and sump pump inside or exterior foundation drainage and waterproofing could be necessary.

But before pursuing those costly measures, be absolutely certain that roof runoff and surface runoff have been directed well away from the building.

Inspect the building exterior, from roof to ground, for sources of water that need to be directed away from the structure.

Watch out: by far the most common source of crawl space water entry is improper handling of roof runoff. Spilling water along the building foundation wall because gutters are clogged, leaky, or absent, concentrates water in that location, ultimately overwhelming any foundation drain system.

Don't assume that just because gutters and downspouts are installed that they are working properly. Look more closely for signs of gutter overflow, clogged or leaky downspouts, drip lines under the roof eaves and similar clues.
At GUTTERS & DOWNSPOUTS we include roof drainage system inspection & diagnosis details.

If you see water stains high on the crawl space foundation wall it's a good guess that water is entering from either roof spillage by the foundation or by in-slope grade directing surface water against the building.


see FOUNDATION WATERPROOFING that discuss various methods used to keep water and excessive moisture out of buildings or to get rid of water that has leaked into a building.

Stop water from entering the crawl space from inside sources

foam insulation on water pipes (C) Daniel Friedmanthis means:

  • Inspect the building interior, attic to basement and crawl spaces, also looking for sources of leaks, moisture, improper venting, that could affect the structure. In the basement and crawl spaces, look for visual evidence of the pattern of water entry - where has water been entering the building?

    Trace that water to its source and cause.
  • Inspect the crawl space itself for clues pointing to water entry sources. We list a number of these below, including actual wet conditions, condensation on pipes, under flooring, on foundation walls; foundation wall stains, presence of sump pumps or other drainage systems, odors, visible mold.

    Watch out: as we detail at CRAWL SPACE SAFETY ADVICE, entering a wet crawl area is dangerous, involving shock hazards and possible chemical or sewage contaminants.
  • Repair any leaks in building drains over or in the crawl space.

    Check below bathrooms, kitchens, and also check hot water heating lines or steam condensate return lines in the crawl space.

    Watch out: sewage-contaminated crawl areas are unsafe to enter without protective gear unless the space has been properly cleaned and disinfected.
  • Repair any leaks in supply piping in the crawl space.
  • Insulate cold water pipes in the crawl space to stop dripping of condensation that forms on the cold water lines in humid weather. It's a good idea to do this in the basement too.


Should you ventilate the crawl space ?

Crawl space vent shown from inside the crawl area (C) Daniel FriedmanCrawl space venting – this is a debated topic as in humid weather venting outside air into a cool crawl space might increase crawl space moisture.

We no longer recommend simple passive venting nor humidistat-controlled venting except in special circumstances.

When our onsite inspection indicates a long-standing moisture problem in such an area the best current advice is to stop venting the crawl space and to convert the crawl space to a dry, conditioned space.

That means we close off crawl space vents, dry out the area, and add some heat to it.

At CRAWL SPACE DEHUMIDIFICATION we explain the use of heat, dehumidifiers, or crawl space exhaust vents to try to improve the humidity level in crawlspaces.

Crawl space venting practices and building codes specifying crawl space vent areas also discussed

Watch out: in some conditions, dust containment, negative air, and more protective gear or help from professionals may be needed.

This article series describes the steps needed to get into, inspect, clean, and then dry out a building crawl space. We give a step by step crawl space entry, inspection, cleanout, dryout and keep dry guide explains how to get into or inspect a crawl space even if there is no ready access, how to assess crawl space conditions, how to stop water that is entering the crawl area, how to dry out the space, how to clean up and if necessary disinfect or sanitize the crawl space, and how to keep out crawl space water and moisture in the future.


Continue reading at CRAWL SPACE WATERPROOFING or select a topic from the More Reading links shown below.


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CRAWL SPACE WATER ENTRY STOP at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Frequently Asked Questions (FAQs)

Question: how much will it cost me to dry out my crawl space?

hey first off great site, very informative.
I have a 450 sq.ft. crawl space accessed directly from a living space basement. It is clean and dry with gravel and stuff all over the place. I just bought the place and I was thinking maybe I should just have someone put french drain system around the perimeter there and put a 20 mill poly, a sump pump and just pour concrete all over (saw that online and thought is a good idea)and last spray foam the walls and joists. My question is how much roughly would all that cost me and do you think it is a great idea to do so.
thank you so much for your advise. - Walden 11/1/2012



The cost to install an interior perimeter drain in your crawl space depends mostly on

- the area covered
- the ease of access - entry and headroom
- the condition of the surface - e.g. if it is not level or doesn't slope to a drain location
- ease of disposition - to where water has to be pumped
- extent of wiring done
- need for backup power

Figure anywhere from $500 to $5000 for an area I know nothing about

I think I would first look for the history of water entry, signs of moisture trouble, ease of fixing outside sources of water entry, and other crawl space moisture sources and weigh those against the cost for this insurance..


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