When your basement was built the foundation contractor installed a perimeter drain system and waterproofed the walls, correct? Well, maybe. Way too often home builders will only use damp proofing methods instead of waterproofing methods. This spray on material looks like true waterproofing emulsion, but is watered down and not nearly as thick. The next thing that many home builders do poorly is their installation of the perimeter drain. Way too often they will use corrugated pipe as a perimeter drain because the excavation is not graded for proper drainage.
This corrugated pipe runs up and down the peaks and valleys along the bottom of the excavation and then cover this piping with extra plumber rock. Plumbers rock is too small and there generally is not enough to properly cover the drainage system. Finally it is time to backfill. As everyone knows, that have been is to a new construction site, there is trash, building waste and un-compacted soil used for backfill. All of these things contribute to an exterior waterproofing system that does not last for more than about 7-10 years.
The number one thing needed to properly waterproofing the exterior of a structure is – care. Yes, you must care. You must use proper materials, take your time and have pride in the workmanship. Without these things your home will not be waterproofed correctly.
Moisture is transferred from the outside of the building to the basement interior by four primary mechanisms. First, water flow. Water takes the path of least resistance, if this is into your basement, then that is where the water will flow. Second, capillary action. Concrete is a porous material, it is very hard yet porous. Think of capillary action being like a wick. As concrete sets in water, this water is absorbed by the concrete until it becomes complete saturated and then disperses moisture and water vapor to the inside of the home.
Next is vapor diffusion. Vapor diffusion is much like capillary suction, except with water vapor. Water vapor only needs the smallest of openings to penetrate a structure and raise humidity levels. Lastly, air movement. Any time that a door or window is opened not only are you bringing air in to the home but you are pulling air from the basement to the upper living levels. This is known as stack effect. Your home acts like a chimney drawing air from the bottom toward the top. 40% of the air we breathe in our homes comes from the basement.
If exterior water is making its way into your basement or crawlspace you are in the need of proper exterior waterproofing. To properly waterproof your home it will need to be excavated. The footing will need to be exposed and all exterior issues will need to be dealt with.
Foundation walls will need to be cleaned and then a spray or roll on polymer waterproofing product will need to be applied. Once dry, this coating will need to be covered with a dimple board product that protects your newly sealed surface and also allows better water flow downward. The next step is to install a drain pipe system that is properly sloped for continuous drainage. This slope can be to a sump pit or to daylight, depending on the site layout. The drain pipe is then covered with a ¾” clean rock. This rock backfill can be from 1’ up to 60% of the wall height, depending on the soil conditions. On top of the rock a non-woven geo-textile material is wrapped to help filter soil without clogging. After the geo-textile material installation soil backfill can begin. This soil needs to be native clayey soils that resist water intrusion. Backfilling with loose soils creates a highway for the water opposed to clay soils that force water away.
Proper exterior waterproofing is no small chore and should not be attempted by unqualified people. You are protecting your home and the job should be done correctly and provide a permanent solution to your home. Remember though, exterior wall waterproofing cannot prevent water from moving deeply below your foundation walls. This water can move through your basement or crawlspace floor. In these cases an interior drainage system will complement your exterior efforts, not replace them. An interior drainage system is not waterproofing. Interior drain systems are water management agents that relieve excess water from around and under your foundation.
Also, keep in mind that if your are moving the exterior water to a sump pump system, this system must be up to the task. Modern sump pumps, battery backup sump pumps and high quality sump basins are available to remove this collected water away from your home.
Foundation drain tile systems are the means by which groundwater can be transported away from your basements foundation and floor. If you want a dry basement and a sound foundation, you must have an adequate foundation drainage system.
For more information, contact your local basement waterproofing expert today!