Basement waterproofing: Difference between revisions

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{{Short description|Prevention of water infiltration in basements}}

{{Use dmy dates|date=September 2022}}

{{Refimprove|date=April 2017}}

'''Basement waterproofing''' involves techniques and materials used to prevent [[damp (structural)|water]] from penetrating the basement of a house or a building. [[Waterproofing]] a basement that is below ground level can require the application of sealant materials, the installation of drains and [[sump pump]]s, and more.

==Purpose==

Waterproofing is usually required by building codes for structures that are built at or below ground level. Waterproofing and drainage considerations are especially important in cases where [[ground water]] is likely to build up in the soil or where there is a high [[water table]].

Foundation waterproofing is needed in cases where ground water is attempting to reach a level while it moves downward towards the watertable. This leveling causes hydrostatic pressure to be exerted onto foundation walls. This hydrostatic pressure forces water into foundation walls and through the footing-foundation wall joint. Hydrostatic pressure can cause major structural damage to foundation walls and has the ability to mold and decay building materials.

Water in the soil causes [[hydrostatic pressure]] to be exerted underneath basement floors and walls. This hydrostatic pressure can force water in through cracks, which can cause major structural damage as well as mold, decay, and other moisture-related problems.

The three measures developed to prevent this problem differ greatly in ideaology and design. The first being an interior wall sealant is the least effective and will not work. The other two methods are interior and exterior waterproofing.

==Methods==

The other two measures being exterior and interior waterproofing contain much debate. To preface this arguement an explanation of 'waterproofing' must be made. Waterproofing by definition prevents water from entering a structure, this can only be accomplished from the exterior of a structure. Water-diversion is a method in which water is allowed to flow freely into a structure, then usually by some type of submersible pump, the water is removed. This is simple structural engineering.

Several measures exist to prevent water from penetrating a basement foundation or to divert water that has penetrated a foundation:

* [[File:FrenchDrain-04.jpg|alt=French Drain|thumb|French drain]]Interior wall and floor sealers

* Interior water drainage

* Exterior drainage

* Exterior waterproofing coatings

* Box type waterproofing<ref>{{Cite news |last=Waheed |first=M. A. |date=11 July 2014 |title=Top tips to optimally use conventional waterproofing techniques |work=Business Standard India |url=https://www.business-standard.com/article/b2b-connect/top-tips-to-optimally-use-conventional-waterproofing-techniques-114071100665_1.html |access-date=28 May 2021 |archive-date=5 July 2022 |archive-url=https://web.archive.org/web/20220705122802/http://www.business-standard.com/article/b2b-connect/top-tips-to-optimally-use-conventional-waterproofing-techniques-114071100665_1.html |url-status=live }}</ref>

* Foundation crack injections

* French drains

* [[Sump pump]]

==Interior sealants==

Interior water-diversion is acheived by cutting a channel in the concrete slab along the foundation walls, the intruding water is then collected in a perforated pipe and drained to a sump pump. This method alleviates the problem of water seapage onto the basement floor, much like a constantly running shop-vac. This method does not prevent water from entering foundation walls. As hydrostatic pressure forces water into foundation walls, the structural integrity of foundation walls is forced out. Interior systems do not prevent water from being 'wicked' through the damp wall and into dry framing members and living space above. This wicking is what causes molding of building materials.

In poured concrete foundations, cracks and pipe penetrations are the most common entry points for seepage. These openings can be sealed from the interior. [[Epoxy|Epoxies]], which are strong adhesives, or [[Polyurethane|urethanes]] can be pressure injected into the openings, thus penetrating the foundation through to the exterior and cutting off the path of the seepage.

In masonry foundations, interior sealers will not provide permanent protection from water infiltration where hydrostatic pressure is present. However, interior sealers are good for preventing high atmospheric humidity inside the basement from absorbing into the porous masonry and causing [[spalling]]. Spalling is a condition where constant high humidity or moisture breaks down masonry surfaces, causing deterioration and shedding of the concrete surfaces.

Exterior waterproofing prevents water from entering foundation walls henceforth preventing the wicking and molding of building materials. Prior to the 1980's much of the original exterior waterproofing was accually damp-proofing using a degradable asphalt-based covering. Asphalt and tar based compounds are affected by soil p.h. and break down after 10-20 years. Over the past ten years, polymer-based waterproofing products have been developed by Owens Corning. These polymer based products are able to bridge foundation cracks and settling issues while being unaffected by soil p.h. Polymer-based waterproofing will last the life of the structure. New construction, however cannot utilize these materials due to their cost-profit ratio for large tract builders.

Other coatings can be effective where condensation is the main source of wetness. It is also effective if the problem has minor dampness. Usually, interior waterproofing will not stop major leaks.

In conclusion...Interior water-diversion allows water to enter the structure then pumps the water out of the structure. Interior water-diversion does not prevent water from entering the structure where it has the ability to mold and decay building materials. Exterior waterproofing involving polymer-based, not asphalt or tar based, material is the only way to prevent water from entering foundation walls and causing mold and decay. The cost of these systems is always comparative.

==Interior water drainage==

Interior water-diversion systems are usually sold by a salesman, Exterior waterproofing is sold by a qualified builder or engineer.

Although interior water drainage is not technically [[waterproofing]], it is a widely accepted technique in mitigating basement water and is generally referred to as a basement waterproofing solution. Many interior drainage systems are patented and recognized by [[International Building Code|Building Officials and Code Administrators]](BOCA) as being effective in controlling basement water.

A common system for draining water that has penetrated a basement involves creating a channel around the perimeter of the basement alongside the [[Foundation (engineering)|foundation]] footers. A [[French drain]], PVC pipe, or other drainage system is installed in the newly made channel. The installed drain is covered with new cement.

The drainage system collects any water entering the basement and drains it to an internally placed [[sump pump]] system, which will then pump the water out of the basement. The [[Federal Emergency Management Agency]] (FEMA) recommends basement waterproofing with a water alarm and "battery-operated backup pump" as a preventive measure against the high cost of flooding.<ref>{{Cite web|url=https://www.floodsmart.gov/flood/first-prepare-for-flooding|title=FloodSmart &#124; How to Prepare for a Flood and Minimize Losses|access-date=20 March 2020|archive-date=9 May 2020|archive-url=https://web.archive.org/web/20200509204644/https://www.floodsmart.gov/flood/first-prepare-for-flooding|url-status=live}}</ref> Wall conduits (such as [[dimple board]]s or other membranes) are fastened to the foundation wall and extend over the new drainage to guide any moisture down into the system.

==Exterior waterproofing==

Waterproofing a structure from the exterior is the only method the U.S. [[International Building Code]] (IBC) recognizes as adequate to prevent structural damage caused by water intrusion.

Waterproofing an existing basement begins with excavating to the bottom sides of the [[Shallow foundation|footings]]. Once excavated, the walls are then power washed and allowed to dry. The dry walls are sealed with a waterproofing membrane,<ref>{{cite news|last1=Carter|first1=Tim|title=How to redirect water around a damp garage|url=https://www.washingtonpost.com/news/where-we-live/wp/2015/09/01/how-to-redirect-water-around-a-damp-garage/|newspaper=The Washington Post|accessdate=2 November 2015|archive-date=15 August 2016|archive-url=https://web.archive.org/web/20160815233130/https://www.washingtonpost.com/news/where-we-live/wp/2015/09/01/how-to-redirect-water-around-a-damp-garage/|url-status=live}}</ref> and new drainage tiles (weeping tiles) are placed at the side of the footing.

A [[French drain]], PVC pipe, or other drainage system is installed and water is led further from the basement.

=== Polymer ===

Over the past ten years, [[polymer]]-based waterproofing products have been developed. Polymer-based products last for the lifetime of the building and are not affected by [[soil pH]]. Polymer-based waterproofing materials can be sprayed directly onto a wall, are very fast curing, and are semi-flexible, allowing for some movement of the [[:wikt:substrate|substrate]].

==Causes of water seepage and leaks==

Water seepage in basement and crawl spaces usually occurs over long periods of time and can be caused by numerous factors.

* [[Concrete]] is one of the most commonly used materials in home construction. When pockets of air are not removed during construction, or the mixture is not allowed to cure properly, the concrete can crack, which allows water to force its way through the wall.

* Foundations (footings) are horizontal pads that define the perimeter of foundation walls. When footings are too narrow or are not laid deep enough, they are susceptible to movement caused by soil [[erosion]].

* Gutters and [[downspout]]s are used to catch rain water as it falls and to discharge it away from houses and buildings. When gutters are clogged or downspouts are broken, rainwater is absorbed by the soil near the foundation, increasing [[Fluid statics#Hydrostatic pressure|hydrostatic pressure]].

* [[Weeping tile]] is a porous plastic drain pipe installed around the perimeter of the house. The main purpose of external weeping tile is preventing water from getting into a basement. However, these pipes can become clogged or damaged, which causes excess water to put pressure on internal walls and basement floors.

* Water build up inside window wells, after heavy rain or snow, can lead to leaks through basement window seams. Window well covers can be used to prevent water from accumulating in the window well.

* Ground saturation is another common form of basement leaks. When the footing drain fails the ground around the basement can contain too much water and when the saturation point is met flooding can occur.

==Warning signs of water damage==

Signs that water is seeping into a basement or crawlspace often take years to develop and may not be easily visible. Over time, multiple signs of damage may become evident and could lead to [[Structural integrity and failure|structural failure]].

* Cracked walls: Cracks may be horizontal, vertical, diagonal or stair-stepped. Severe pressure or structural damage is evident by widening cracks.

* Buckling walls: Usually caused by hydrostatic pressure. Walls appear to be bowed inward.

* Peeling paint: Water seeping through walls may lead to bubbling or peeling paint along basement walls.<ref>{{cite news|last1=Chodorov|first1=Jill|title=Basement flooding may put a damper on your home sale|url=https://www.washingtonpost.com/news/where-we-live/wp/2015/07/08/basement-flooding-may-put-a-damper-on-your-home-sale/|newspaper=The Washington Post|accessdate=2 November 2015|archive-date=18 May 2018|archive-url=https://web.archive.org/web/20180518045102/https://www.washingtonpost.com/news/where-we-live/wp/2015/07/08/basement-flooding-may-put-a-damper-on-your-home-sale/|url-status=live}}</ref>

* [[Efflorescence]]: White, powdery residue found on basement walls near the floor.

* [[Mold (fungus)|Mold]]: Fungi that usually grow in damp, dark areas and can cause respiratory problems after prolonged exposure.

==Foundation crack injections==

Foundation crack injections are used when poured concrete foundations crack, either from settlement or the expansion and contraction of the concrete. Epoxy crack injections are typically used for structural purposes while hydrophobic or hydrophilic polyurethane injections are used to seal cracks to prevent penetration of moisture or water. Concrete is both strong and inexpensive, making it an ideal product in construction. However, concrete is not waterproof.

==References==

{{Reflist|30em}}

[[Category:Construction]]

[[Category:Foundations (buildings and structures)]]

[[Category:Moisture protection]]

[[Category:Stormwater management]]