Concrete Crack Repair in Basement Walls

Concrete cracks in nearly every wall in a basement. Builders and contractors plan for this cracking by placing steel reinforcing inside the concrete walls. Even though the concrete has cracked, this reinforcement maintains the strength of the wall and it is not a problem for a typical home's foundation.

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Ways Water gets into the Basement

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Unfortunately these concrete cracks allow water to enter the basement. Many homes built today have a waterproofing membrane on the outside of the foundation to control the water and keep it from getting into the basement interior. Older homes are vulnerable to water leaking in because they do not have a waterproofing membrane installed at all. But it is still possible for the crack to be too large for the waterproofing to stretch over the crack and the membrane then tears. Or if the grading is incorrect and slopes toward the house, rainwater will pool next to the home above the level of the waterproofing, enter the concrete crack and flow to the interior. Finally, it is possible for a home's landscaping to be above the protective waterproofing and let water into the concrete crack above the waterproofing membrane.

Repairing the Concrete Crack

Homeowners or professional can fill the crack from the inside of the basement and prevent water from leaking in. Making the repair from the inside is a cost effective and quick method that does not disturb the soil and landscaping on the outside. The repair to the concrete crack is done by injecting an expanding urethane foam into the crack.

Liquid Urethane Foam Injection

The urethane enters the crack as a liquid and when it encounters water, it begins to foam and expand. This expansion forces the foam to completely fill the crack from bottom to top and from front to back. When finished, the foam will keep the water where it belongs, on the outside of the concrete foundation.

The width of the crack does not matter. If water can get through the concrete crack, so can the liquid urethane. This is because the urethane is injected under low pressure with either a standard caulk gun or if done by a professional, by a special dual cartridge gun. A home owner or professional does not have to do any drilling or chiseling to make the crack wider.

While water is required to be present to act as a catalyst to make the urethane to begin to foam, the repair can still be done if the crack is dry. Simply inject 1/2 cup of water into the concrete crack with a spray bottle to make the concrete crack wet inside it.

A Dry Basement

Once the concrete crack is filled with urethane foam water will not be able to leak into the basement. The homeowner can now finish the basement and be sure that the contents will be safe and dry for years to come.

Concrete Crack Repair in Basement Walls

MEMBRANE

Basement Waterproofing Membranes - The Difference Between an Insulated Membrane and Insulating One

I have just come away from a meeting with a major supplier of basement waterproofing membranes.  Like most suppliers in the industry they have always supplied the plastic dimpled membrane for cavity drainage, and condensation has always been a potential hazard with such membranes.  The industry has wrestled with this problem for decades, ever since this generic type of waterproofing became prevalent.

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In the 1970's and '80's it was industry standard practice to recommend that the air space between the membrane and the plasterboard lining be ventilated top and bottom so as to prevent condensation.  During the '90s and early part of the 21st century this advice was generally changed to 'don't ventilate the cavity' as it can actually increase condensation on the membrane by bringing a constant stream of humid air into contact with the cold surface of the membrane itself.  So the advice changed but the problem did not go away.

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Whilst the development of good quality and affordable dehumidifiers which are now readily available in most electrical stores has helped, the potential for condensation on a cold plastic surface is still a real risk.  This risk is made worse by insulating in front of the membrane.  'Why?' you may ask, 'surely if i insulate something I will keep it warmer?'  I t was hearing that very same quote today that inspired me to write this article especially as it came from a major supplier of plastic membranes.

I am not a physicist, I don't even know whether it is the first or second law of Thermodynamics and it doesn't really matter which, but i know that energy cannot be created or destroyed - that much is accepted wisdom.  So... If you are going to make something WARMER by putting in an insulation barrier, then you must also be making something else COLDER by the same amount.  insulation does not generate heat.  It does not make anything warm.  It just stops the transfer of heat from one place to another, or at least slows it down.  So if the room is warm and the ground outside is cold and the membrane is on the outside wall and you then put insulation in-between the warm room and the cold wall you make the wall and anything else on it (the membrane) COLDER and at the same time you keep the room WARMER.  And if, by doing this you make a vapour barrier colder then you increase it's risk of condensation.

Now the difference between insulating a membrane as described above and an 'insulated' membrane is that in an insulated membrane the insulation is an integral part of the membrane, not a separate element in front of it, in fact the insulation is actually BEHIND the vapour barrier, i.e. in-between the cold wall and the vapour barrier itself so that the vapour barrier is actually kept warmer rather than colder.  It is as simple as that.  Insulating in front of a membrane and thinking that you are keeping it warmer, is an easy mistake to make I guess but with a little careful thought also an easy one to avoid.

Read more on thermally insulated membranes and waterproofing basements

Basement Waterproofing Membranes - The Difference Between an Insulated Membrane and Insulating One

MEMBRANE

Basement Waterproofing - New Build

Waterproofing is an essential consideration for anyone who is building a basement which they intend to use for storage or habitable accommodation.

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Too often basement waterproofing is not given high enough priority and as a result a cheap and inappropriate basement waterproofing option is used to try and get inside an unrealistic budget. This often leads to failure and the resultant consequential losses can be disastrous for the owner of the building or property.

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New build basements are often designed and built from well graded and even 'waterproof concrete', concrete block or blocks with concrete infill. A well designed and built structure will generally form the primary resistance to water ingress as the concrete is too dense for water to pass through. However we must always be mindful that where there are construction joints there is risk of failure even if waterbars, hydrophilic/hydrophobic strips are well installed.

With this borne in mind it is always a recommendation that as well as the structure itself, a secondary form of basement waterproofing is adopted even if the structure is new and/or built from 'waterproof concrete'.

When the concrete construction itself is considered to be integrally waterproof this is described as type B form of basement waterproofing.

Where the structure is not considered to be integrally waterproofing then we have 2 options for dealing with the potential for water ingress. One is to Tank it and the other is to waterproof it with a Cavity Drain Membrane.

Tanking a basement means that a product is applied internally or externally and is designed to physically stop and hold back the water. This is referred to as Type A basement waterproofing.

A Cavity Drain Membrane system is applied to the internal face of the earth retaining structure where it can accept the ingress of water depressurise it and manage it to a safe evacuation point. This is referred to as type C form of basement waterproofing.

Tanking as a form of basement waterproofing to new structures has inherent risks. Whether you apply it internally or externally to the structure tanking systems need to be applied 100% defect free to be affective, if water is delivered under pressure against the structure. As dispute and High Court case between two companies Outwing Construction and Thomas Weatherald has set a precedent in the basement waterproofing industry and UK law. The ruling in the High Court of Justice was that it is not reasonable for a tanking or waterproofing system to be applied 100% defect free. What this means is that if you design for or apply a basement waterproofing system to the structure which needs to be 100% free of defects to work and it fails you can be liable for the consequences of that failure. By their very nature all tanking systems need to be 100% defect free to work when tested by water under pressure from the ground.

Most new build basement waterproofing designs that incorporate an external tanking system also include a land drain the purpose of which is to help de-water the surrounding ground areas and reduce the level of water which is delivered against the structure. There are often many associated problems with land drains used in basement waterproofing. A land drain should be positioned on the outside of the structure below the level of the internal slab so that it helps to relieve the volume of water to the full depth of the retained soil. Many times the position of the land drain is shown on a drawing or installed above the internal slab level and therefore could only ever be partially effective.

'The form and feasibility of remedial treatment' is a buzz phrase in the basement waterproofing industry. It means if there is a problem having the ability to get back to something to identify where and what the problem is and then rectify it. This is a problem with both external tanking and land drains as they are often buried under tonnes of earth. The size of the land drain is another issue as who can accurately predict the volume of water which could be expected to come to have at any time in the future? Also as stated the tanking system may rely heavily on the land drain and how can anyone guarantee it against defect or blockage in the future - again the form and feasibility of remedial treatment comes into question.

The BS8102:2009 (British Standard code of practice for protection of below ground structures against water from the ground) recommends a maintainable basement waterproofing system. A buried external tanking system and land drain are not easily often maintainable.

Building a strong basement structure to form the primary resistance against water is a good idea but where there are construction joints we must expect that water ingress could occur at some point. Therefore a more reliable form of secondary waterproofing other than the structure itself is a cavity drain membrane system or Type C basement waterproofing.

Before the recent revision of the BS8102:2009 the previous code of practice BS8102:1990 stated that Type C form of construction and waterproofing was the most 'trouble free and effective'. Now the BS8102 says that Type A, B and C together is the most effective which probably goes without saying but as a stand alone basement waterproofing system type C cavity drain membrane is still more reliable that the others.

Cavity drain membrane basement waterproofing systems take into consideration the following points:

• Where earth is retained against a structure we must consider that water will enter the fabric of the building at some time in that structures life.

• When water enters a structure and finds an air gap it depressurises and looses its potency.

So the way a cavity drain membrane basement waterproofing systems like System 500 works is to provide air gaps and therefore depressurisation zones on the inside of the structure which relieve the water pressure. This is done firstly with an 8mm studded membrane applied to the walls. The stud profile serves to hold the product slightly away from the structure to which it is applied. Any water entering through the walls is depressurised within the air gap provided by the studs of membrane, losses its potency and falls to the wall/floor junction. A perforated drainage conduit is situated at the base of the wall either in a recessed channel in the slab or on the slab with a layer of closed cell insulation. The drainage conduit serves 3 main functions. The first is that it collects and delivers water to an appropriate drainage outlet to be evacuated from the structure. The second is that it acts as a form work at the wall/floor junction which serves to maintain an air gap and therefore depressurisation zone at the point where water enters or ends up in most structures i.e. the wall/floor junction. Thirdly it allows future maintenance and testing of the system via rodding/inspection ports situated in the ring main of conduit and this in turn conforms to the recommendations in BS8102. Another feature of some suppliers drainage conduit is a separated fin design on the back face of each section. In some basement waterproofing designs where it is applicable this deals with the risk of condensation forming on the dry side of the membrane and also with the risk of imperfections (small tears/holes/rips in the membrane) by maintaining an open wall/floor junction.

The drainage conduit is connected to either passive or powered means of evacuating the water. Passive means drained naturally by gravity to an existing drainage outlet, open elevation or designed in drainage. Powered is where none of the aforementioned options is available or feasible and a sump and pump is used.

A floor membrane is applied across the floor area as a vapour barrier and linked to the drainage conduit or wall membrane to complete the basement waterproofing system.

Almost any wall and floor finish required can be achieved on top of a Cavity Drain Membrane System.

The advantages of using a cavity membrane system are:-

• There is often little or no preparation
• They are flexible and can move with the structure.
• They are not vapour permeable.
• They are considered to be sympathetic to the structure and reversible
• They can cater for less than adequate workmanship and interstitial condensation.
• They can be maintainable.
• They can be applied in less than ideal site conditions so will not hold up a project programme.
• They can be tested prior to installing fixtures and fittings.
• 10 year insured guarantee's can be obtained when installed by a suitable specialist.
• Full design liability can taken by certain specialist basement waterproofing contractors

Basement Waterproofing - New Build

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