How Do You Waterproof A New Basement?

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    A basement is a terrific addition to any house since it provides additional room that may be used for a variety of purposes. Yet, the quality of a basement depends on how dry it is. Because of their location below earth, basements are vulnerable to water intrusion from the outside (via leaks and seepage) and the inside (through humidity). The process of waterproofing a basement involves taking an inside-out approach to the issue.

    While professional damp proofers should be called in to fully waterproof a basement, there are various measures you may do to either eliminate the issue entirely or reduce its severity in the meanwhile. Humidity and cold are detrimental to living conditions. If your basement is old or hasn't been maintained, groundwater can leak in and wreak havoc on your foundation.

    If you don't regularly check and repair the waterproofing in your home's basement, crawl space, or other underground areas, mould will grow and spread, causing health problems for you and your family. The tiniest of holes can let this in, thus constant vigilance and repair are required. In reality, waterproofing a basement isn't as complicated as it sounds. Any homeowner with a basic understanding of technology and a few spare hours to devote to a do-it-yourself project may keep their dwelling safe from the weather.

    Waterproofing A Basement From The Outside

    Poor drainage is often to blame for water seepage in unexpected places, such as the basement floor, window frames, and other structural elements. The water table is formed when rainwater percolates through the soil and collects well below the surface. It's possible that your basement is blocking water from drainage away from the ground above it. The water is pushing its way into your basement via hydrostatic pressure. The sole defence against this is a sewage system that diverts rainfall away from the home to prevent it from seep into the ground:

    • Always make sure your gutters and downspouts are in good working order. Kindly clear out the gutters and move the water from the downspouts away from the foundation and walls of the house. If your lot is slanted, redirecting water away from the foundation of the house with a drainage system could solve the issue.
    • Subterranean drainage may be necessary to divert water from a level lot away from the foundation. Instead of trying to do this on your own, choose a professional that specialises in damp proofing.

    how do you waterproof a new basement (1)Building a new house gives you the chance to properly waterproof the basement externally. This process, known as "tanking" because it transforms your basement it in to a watertight tank, along with a proper drainage system, should keep your basement dry even during the heaviest downpours.

    Waterproofing A Basement From The Inside

    Waterproofing a floor from the outside is never a good idea. However, applying specially developed wall coating on the foundation wall will assist prevent the walls of rising damp or "weeping," especially if the coatings are combined with efficient exterior drainage. You can probably get the correct sealers and fillers to prevent water from seeping to your basement at a hardware compatibility store in your area.

    If the issue persist or is particularly serious, have a local damp proofing expert have a look at it and provide a solution. They've got the know-how to get things done properly. You may wish to consider putting in a drier in your cellar as well. As a result of its underground location, basements typically have high relative humidity levels and poor air circulation. Allergens and other contaminants can flourish in such an unhealthy setting. But with the help of waterproofing and a dehumidifier, you'll soon have a basement you can use and even enjoy.

    FAQs About Waterproof Basement

    Firstly, you will have to choose between what kind of waterproofing solution you will be going for. We strongly recommend waterproofing from the outside to stop water at the source. That way, you also protect the building structure. We'll be covering external membrane installation in detail, as the others are mostly stopgap solutions or ways to alleviate excess moisture (but not effective long-term solutions in themselves). If the water has already penetrated your basement, you should think about doing these first steps:

    • Installing a sump pump
      • This is for cases where water has already entered the basement, and installing a sump pump will allow you to remove excess moisture before further waterproofing.
    • Waterproof paint
      • If you're getting a lot of seepage through the walls, you could consider painting your basement walls with waterproof paint. This is a stopgap solution, and while slowing moisture accumulation, it might not necessarily fix the problem.
    • Installing a dehumidifier
      • If you're dealing with a particularly humid basement, one easy solution is to suck the moisture out of the air, storing it in a reservoir that you can empty periodically.
    • Membranes
      • Suppose you're looking for a preventative solution to provide initial defence, as well as bolster any other waterproofing efforts. In that case, your best bet is in PVC (or PVC blend) membrane sheeting installed on the external walls of your basement.


    Next, you'll need to choose which particular waterproofing system type you would like to have installed. Again, we recommend either Wolfin or Cosmofin.

    Wolfin is first-in-class for membrane sheeting and affords extreme protection from the harsh Australian climate. It comes in either Wolfin IB, a standard multi-purpose loose-laid application, and Wolfin GWSK, an adhesive-backed bonded membrane form. However, the installation of Wolfin can only be done by an accredited Wolfin Applicator, making it unsuitable for DIY work unless that person already works in the industry. However, this is still the premium product in its class, so if you desire a truly quality installation that will stand the test of time, it's an excellent choice.

    Cosmofin is an industry standard and is best used as a long-term solution as reliable as it is flexible. Cosmofin is used in everything from residential to maritime applications and is easily applicable for home DIY use, especially as it is versatile enough to be applied to almost any external building material, from concrete to timber. Cosmofin comes in both loose-laid, strip-bonded, and fully-bonded applications. The easiest to install is strip-bonded, as it comes with its adhesive as part of the package, while fully-bonded will require the use of traditional adhesives.


    Here are the steps for installing Cosmofin and Wolfin:

    • Saw Cut Termination
      • The first step is to establish where the saw cut terminations are to be positioned and chalk the line base slab and wall terminations. It's important to remember that the wall terminations must be a minimum of 100mm above ground and backfill level. Mix and apply non-shrink grout to all the saw-cut terminations, then whilst still wet, embed the factory bonded membrane profiles into the grout, mechanically fastening the profile with Hilti nips at 150mm centres.
    • Preparing the membrane
      • Measure all the areas of the basement that need to be waterproofed, and cut the membrane to these specific required lengths and dimensions.
    • Installing the membrane
      • The membrane will be hot-air welded directly onto the top and the base terminating profiles, with the membrane having an overlap of 50mm where the sheets are joined together on the verticals.
    • Inspection
      • Inspect all the laps, seams and joints with a screwdriver to ensure waterproofing integrity. There should be no gaps, holes, or areas where the screwdriver can penetrate the membrane system's seam, lap, or joint.
    • Repairs
      • All laps, seams, or joints should be re-welded using the hot air gun to ensure that the membrane system is waterproof without gaps or breaches.
    • Backfilling
      • Before backfilling against the membrane, there are a couple of things to do first. You need to install A44 fabric directly against the membrane and install drainage cells (followed by another layer of fabric). This will protect the membrane and aid the drainage from these areas. The waterproofing contractor normally carries out these works to ensure the total integrity of the membrane system against potential damage.

    Hydrostatic Pressure

    Hydrostatic pressure occurs when water accumulates from rain or garden irrigation systems around your foundation. As gravity pushes down on that water, it will try to 

    escape to relieve that pressure. As a result, the water will force its way through any cracks in your basement walls and floors. The pressure can get so strong that it will cause cracks.


    Cracks in your basement walls, floors, and around windows or doors provide the perfect avenue through which water can flow. Water will always follow the path of least resistance, and these cracks make it easy for water to come inside.


    Basements can be very damp places. When condensation occurs, it can bring mildew, mould, and potential damage along with it, which is a health hazard.

    Methods To Fix Your Moisture Problem

    Exterior Waterproofing

    Exterior waterproofing is one of the biggest undertakings a homeowner can take. This usually means the excavation of the soil surrounding the home's foundation. As you can imagine, this can be a labour-intensive process, requiring heavy tools and machinery. The ideal solution would be to use a polymer-based sealant like our semco liquid membrane during the construction process of your home, and it could last you for the life of the building.

    Interior Waterproofing

    Interior waterproofing is the fastest and most cost-effective way to waterproof your basement. These typically begin with ensuring that any cracks or holes in your basement walls, floors, and around windows and doors are properly sealed and watertight. Water most frequently makes its way into your basement via these cracks. Therefore, properly sealing them is the first step towards ensuring your basement stays dry. Interior waterproofing methods, such as waterproof sealants, also do a good job at keeping humidity levels down, preventing condensation. In addition, these coatings can be put onto basement walls and floors, creating a waterproof barrier. 

    Drainage Systems

    The goal of these drainage systems is to direct water (whether it be groundwater or rainwater) away from the foundation of your home. However, this solution is more costly and time-consuming as it requires installation equipment. The best is to contact a local construction company to do the work. This section will look at the drainage options for new build basements in a bit more detail. With your external waterproofing system, you will need to provide a drainage system to remove water to an internal sump chamber or soak away point.

    Land Drains And French Drains

    To further protect your basement from water ingress, you should install a land drain, sometimes referred to as a French drain. These are laid around the perimeter of the basement at slab level. In essence, you have a trench around the perimeter, which contains a perforated pipe covered with gravel or crushed stone. Water that hits the external surface runs down the membrane through the gravel and is safely removed to a sump chamber, mains drain, or soakaway. This land should be wrapped in a geotextile membrane to stop fine sediments and debris blocking the pipe. Access points and jetting points should also be included for annual maintenance.

    The ultimate goal is a dry internal environment in your basement or cellar. However, any walls in direct contact with the earth may experience hydrostatic water pressure. You, therefore, need to effectively deal with this pressure to stop water from entering the structure. You can tank the basement structure using conventional barrier tanking; however, any slight defect will be exploited if tanking is subjected to sufficient hydrostatic pressure. Also, barrier tanking is generally non-maintainable, increasing the risk of failure over time. A complete external waterproofing system, including an internal cavity membrane, is the best option for mitigating risk. 


    It is important to consider your environment when installing a new-build basement. This will require a professional who can analyse the soil type, ground drainage, the presence of any potential contaminants (PermaSEAL Geodrain cavity drain membrane is resistant to all chemicals normally found in the ground), and the height of the water table. These should be considered in light of the intended use of your basement.

    External Waterproofing Systems

    With external waterproofing systems, we recommend combining a primary and secondary waterproofing system along with a priming stage.


    The first step in external waterproofing in most cases is priming. Priming involves applying a specially-designed spray such as Kiesel Waterproofing Primer or Kiesol MB Primer to the external structure. This forces the masonry pores to narrow, creating a water-repellent surface. Primers are also designed to bond with the waterproof coating used in the primary waterproofing stage.

    Primary Waterproofing 

    Primary waterproofing involves applying a waterproof material directly to the external wall. It would be best to waterproof the substrate with a waterproofing compound such as Multi Tight. These specially-designed coatings have a high compression strength and are watertight even under aggressive pressure.  

    For 3 to 5 years, exterior waterproofing materials wear off caused by the ebb and flow of groundwater. Depending on the soil type, location, and landscape slope (grade); a basement can have longer-lasting exterior waterproofing. Regardless, all homes become vulnerable at some point.

    During a home's construction, walls, floors, and foundations must be waterproofed with a sealant to avoid water leakage and flooding. But over time, sealants deteriorate and leaks can sneak through the cracks. If your basement floods during most rainstorms, this might be a good time for a waterproofing upgrade.

    Secondary Waterproofing – External Membranes 

    It is recommended that a waterproof membrane be applied to the outside. It drains water out from the structure quickly, reducing hydrostatic pressure. Moreover, the membrane acts as a barrier to protect the primary waterproofing from damage, especially during backfilling phase. As the backfill settles, it also functions as a slip membrane. Membrane that separates an internal space from the exterior

    Many studs are used to make a hollow in these membranes. Because of this, water may easily drain down the cavity and into a land sink or French drain. The following is further data pertaining to drains. The water is sent by the drain to the main drain, a sump with a pump, or a soak away. The membrane itself acts as a filter, screening out any impurities in the water.

    This keeps microscopic debris out of the sewers, where it could cause clogs. By using the aforementioned exterior waterproofing method, you'll have not one, but two layers of protection against water. You can considerably reduce the potential for errors by combining these approaches. Both approaches are highly adaptable, assuring you that the external stone waterproofing will continue to do its job even if the structure shifts or settles in the future.

    Sump And Pumpsump And Pump Piping

    how do you waterproof a new basement (3)As shown above, cavity drain barrier systems can have groundwater removed using a Sump and Dual Pump system. Commonly, they have a pump and a sump in one unit, and sometimes even two pumps in case one breaks. You should be able to turn off the system and service the pumps without disrupting the flow of water. The same logic applies to a battery backup in case the power goes out.


    The usefulness of a basement depends on the level of humidity it maintains. It can easily let water in from the outside (via leaks and seepage) or the inside (through condensation) (through humidity). It can be mitigated in several ways, the most obvious of which is by inspecting and fixing the waterproofing in your home's basement, crawl space, or other underground regions. Whole basement waterproofing requires the assistance of professional damp proofers, but DIY basement waterproofing is possible for any homeowner with a basic understanding of technology and a few spare hours to devote to the endeavour. It is crucial to externally waterproof the basement while constructing a new home.

    Tanking is used to prevent water from entering a basement during even the most severe rainstorms. Applying a specifically formulated wall coating to the foundation wall can help prevent rising moisture or "weeping," which can be caused by improperly waterproofing a floor from the outside. If the problem persists or is severe, you should call in a local damp proofing professional for advice. Furthermore, exterior hydrostatic pressure can be mitigated by applying a waterproof membrane. The membrane serves as both a protective barrier for the primary waterproofing and a separating slip membrane between an interior and outside area.

    The membrane itself performs the role of a filter, preventing even the tiniest particles of trash from entering the wastewater treatment system. Groundwater can be drained with the use of a pump and a sump in a single unit, or even two pumps in the event that the first fails. Each method is flexible and can be used as a backup in the event of a blackout.

    Content Summary

    • But, a damp basement isn't a good basement.
    • Waterproofing a basement requires turning the problem upside down.
    • When constructing a new home, you can take the opportunity to externally waterproof the basement.
    • You should also think about installing a dryer in your cellar.
    • In addition, the membrane serves as a shield to safeguard the primary waterproofing from harm, particularly throughout the backfilling process.
    • The water flows to the main sewer line, a sump with a pump, or a soak away.
    • If you use the external waterproofing approach described above, you'll have double the protection against moisture.
    • Septic Tank and Pump
    • It has been demonstrated above that a Sump and Dual Pump system can be used to drain groundwater from cavity drain barrier systems.
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