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WATER ENTRY IN BUILDINGS
AGE of MOLD - Old is the Mold?
BASEMENT CEILING VAPOR BARRIER
BASEMENT MOLD WATER IMPACT
BRICK WALL DRAINAGE WEEP HOLES
BUCKLED FOUNDATIONS due to INSULATION?
BUILDING DAMAGE ASSESSMENT & REPAIR
CONDENSATION on WINDOWS & SKYLIGHTS
DEW POINT TABLE - CONDENSATION POINT GUIDE
EFFLORESCENCE, Salts & White / Brown Deposits
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOD DAMAGED FOUNDATIONS
FLOOD VENTS & FLOOD PORTS
FLOODS IN BUILDINGS-mold
FLOOR DAMAGE DIAGNOSIS
FOOTING & FOUNDATION DRAINS
FOUNDATION BULGE or LEAN MEASUREMENTS
FOUNDATION CRACKS & DAMAGE GUIDE
FREEZE-PROOF A BUILDING
FROST HEAVES, FOUNDATION, SLAB
HUMIDITY LEVEL TARGET
ROOF ICE DAM LEAKS
MOISTURE CONTROL in BUILDINGS
MOLD INFORMATION CENTER
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
SEWAGE BACKUP, WHAT TO DO
SEWAGE BACKUP TEST & CLEANUP
SEWAGE BACKUP PREVENTION
SEWAGE PUMP CLOG DAMAGE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
TRAPS on PLUMBING FIXTURES
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in BUILDINGS
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
Basement perimeter drains, French Drains, or B-Dri/Beaver Basement type basement de-watering systems: this article series discusses types of interior perimeter drain or what some call a "french drain" for stopping foundation leaks or preventing wet basements and crawl spaces. We describe the basic types of exterior and interior foundation drainage and de-watering systems for homes.
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Readers should see WET BASEMENT PREVENTION and also see BASEMENT WATERPROOFING. Readers needing more extensive guidance on preventing or fixing basement leaks and moisture should see BASEMENT LEAKS, INSPECT FOR, or if your building includes areas over crawl spaces, see CRAWL SPACE DRYOUT - home. If your building has been flooded, see FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. Our page top drawing of types of indoor foundation and basement drainage systems is provided courtesy of Carson Dunlop Associates.
A perimeter drain, as we explain in this article, is an indoor drain cut into the floor around the perimeter of a basement or crawl space to intercept and remove water from the building interior. We illustrate perimeter drains and we comment on their effectiveness and installation details below.
Interior foundation perimeter drains typically intercept water leaking through a foundation wall or around the building wall/floor slab intersection. The intercepted water is conducted to a sump pit and sump pump for disposal, or it may be conducted to a location from which it can drain by gravity.
Some people call an interior perimeter drain used for basement or crawl space de-watering a "French Drain". Whatever you want to call it, an interior perimeter drainage system cut into the basement or crawl space floor can effectively stop basement or crawl space flooding - or can it?
What are the Definitions of a French Drain, Footing Drain, & Perimeter Drain?
So what is the difference between a french drain, a footing drain, and a perimeter drain. A French drain is shown above, and a footing drain is shown in our two sketches below.
A footing drain, that is an exterior foundation drainage system placed outside the foundation wall near the wall footing, at the level we show, covered with gravel, and if the footing drain going to do anything, it is piped to daylight or to a catch basin that is in turn pumped to daylight or to a storm drain.
Details about footing drains - exterior foundation drainage systems - are at FOOTING & FOUNDATION DRAINS
Are Indoor Perimeter Drains a Foolproof Cure for Wet Basements ?
Photos of Basement De-Watering Systems: B-Dri™ and Beaver Basement™ types
Below we show two implementations of the type of basement perimeter drain de-watering system sketched above. At below left you can see that a trench was cut into the floor and something was buried there, along the foundation wall: typically perforated pipe in a gravel-filled trench that slopes around the floor to end at either a sump pump pit or if you are lucky, a spot where you can drain water out of the building to daylight using just gravity.
The installer left a 1/4-inch gap to encourage water that runs down the wall to flow into the drainage trench. This system will usually keep water off of the basement floor quite successfully but it does little to keep moisture out of the area as water evaporates from the wall surface as well as flowing into the trench.
A second common basement de-watering system shown at above-right is also an indoor foundation perimeter drain system like the one we described above. But this installation includes heavy plastic that extends a few inches up the wall, perhaps to encourage water to run behind the plastic and into the gravel trench. This approach also covers up an ugly wet water stained row of concrete blocks at the bottom of the foundation wall. Early B-Dry™ type basement drainage systems used this approach.
At contemporary B-Dry™ and similar installations that we have inspected the installers have shifted to running this heavy plastic barrier up the entire face of the foundation wall, right up to the sill plate. We like that improvement as it should dramatically reduce moisture movement into the room itself as water runs down the wall and into the drainage trench.
In that system one is, of course, unable to see the foundation wall to gain any understanding of just when and where water is entering the structure.
Trenchless Basement Water Interception Systems
Green link shows where you are in this article series.
Our home page for diagnosing and curing foundation leaks and wet basements or crawl spaces is WATER ENTRY in buildings. If your building has been flooded, see FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
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