Basement waterproofing From the inside: Surface barrier against lateral moisture penetration to protect the masonry from moisture penetrating from the side
Table of contents
- Introduction to basement waterproofing
- What is cross-soaking?
- Causes of damp cellars
- Advantages of basement waterproofing
- Sealing materials and tools
- The Isofin solution
- How does the Isofin surface barrier work?
- Carry out internal sealing with Isofin
- The Isofin calculator
- Costs and duration of waterproofing
- Alternative methods and their weaknesses
- When is Isofin the right choice?
- Holistic approach
- Disadvantages of conventional methods
- Conclusion: Effective solution
Damp basement walls and soaked brickwork not only impair the quality of living, but can also lead to serious structural damage. A surface barrier is the effective solution for transverse moisture penetration when moisture penetrates from the ground into the basement wall. With Isofin, we offer a proven method for internal waterproofing that you can carry out yourself. The correct use of materials is crucial to ensure effective waterproofing.
Introduction to basement waterproofing
What is transverse moisture penetration and how does it occur?
Transverse moisture penetration occurs when water penetrates laterally from the adjacent soil into the basement walls. Unless the sources are identified and rectified, the exterior wall will always be affected by moisture. This typically happens when:
The vertical external seal is missing or damaged
Areas exist that cannot be exposed (under terraces, garages, stairs)
Neighboring buildings or property walls transfer moisture
Stagnant water on the cellar walls
The consequences are serious: wet stains on the wall, crumbling plaster, salt efflorescence, mold growth and musty smells. In addition, the cellar wall loses its natural thermal insulation, which leads to increased heating costs and long-term damage to the building fabric.

Causes of damp cellars
Damp cellars can be caused by a variety of factors. Common causes include damp exterior walls, a high groundwater table or inadequate waterproofing. Soil moisture is one of the most common causes of damp basement walls, along with seepage water and pressing damp. To find the right solution, it is crucial to determine the exact cause of the damp. A specialist can help to identify the cause and select the appropriate waterproofing method. Typical signs of a damp basement wall are damp patches, salt efflorescence or a musty smell. These indicators should be taken seriously in order to avoid major damage to the building fabric.
In order to choose the right waterproofing method, it is important to distinguish between different causes of moisture:
Rising damp: Water rises capillary from the foundation into the wall and is combated by a horizontal barrier
Transverse moisture penetration: Water penetrates laterally from the soil into the basement walls and requires a surface barrier
Condensation: arises due to temperature differences and is remedied by improved ventilation or insulation
Seepage water: A high groundwater table or seepage water can also lead to damp basement walls and often requires professional help for diagnosis and waterproofing. The pressure from the surrounding soil and water-bearing soil layers can be considerable and increase the need for thorough basement waterproofing.
In the case of transverse moisture penetration, the soil transports water to the cellar wall, which then penetrates the masonry due to the capillary effect. Isofin has been specially developed for this type of capillary moisture.
Advantages of basement waterproofing
Effective basement waterproofing offers numerous advantages. It prevents damage to the building fabric, reduces moisture in the basement and significantly improves the indoor climate. This is particularly important for health, as it prevents damp and mold in the basement. In addition, good waterproofing can help to reduce energy costs by preventing warm air from escaping. There are various ways to carry out basement waterproofing, such as the use of waterproofing slurries or bitumen thick coatings. Each method has its specific advantages and should be selected according to the individual circumstances of the cellar.
In many cases, internal sealing is not only sensible, but the only practicable solution:
If external sealing is not structurally possible
For adjoining extensions or closely built-up properties
If the cost of external waterproofing would be disproportionately high. The need for internal waterproofing is often due to structural, spatial or financial reasons.
If the garden or other outdoor facilities are not to be damaged
A specialist can help you choose the right method and materials. An experienced specialist company will ensure that the waterproofing is carried out correctly to achieve optimum results.
With the right method, basement waterproofing from the inside offers an effective long-term solution that significantly improves the usability of the basement rooms.
Sealing materials and tools
Various materials and tools are available for basement waterproofing. Waterproofing slurry and bitumen thick coatings are two of the most popular options. There are several specific products that can be used for waterproofing and it is important to use products from one manufacturer to ensure compatibility. In addition, there are specialized tools such as masonry saws and pile driving checker plates that can be used for the waterproofing work. A professional can help select the right materials and tools and carry out the waterproofing work professionally. Choosing the right materials and tools is crucial to the effectiveness and longevity of the waterproofing.

The Isofin solution: Innovative technology for dry cellar walls
The Isofin system offers an effective way of remediating damp masonry. Unlike conventional methods, you don't have to dig up the entire outside area - a key benefit for built-up properties. The Isofin system offers a product specifically designed for basement wall waterproofing and includes a variety of materials ranging from simple lime renders to specialized remedial render systems.
Isofin technology is based on the principle of hydrophobization: the pore walls of the building materials are given a water-repellent finish without closing the pores. This offers the following advantages:
Effective barrier against moisture penetrating from the side
Restoration of natural thermal insulation after drying out
Maintaining the diffusion openness of the wall ("breathability")
Long-term protection of the building fabric

How does the Isofin surface barrier work?
With the Isofin surface barrier, the special water repellent is applied to the masonry through drilled holes. There it displaces the existing pore water and forms a wafer-thin water-repellent layer on the pore walls, which prevents capillary water transport and thus prevents moisture penetration. In addition, waterproof concrete can serve as an effective barrier against penetrating water by filling the basement without joints.
The special thing about Isofin is its ability to penetrate even water-saturated masonry and distribute itself optimally there. After treatment, the pores can dry out and refill with air instead of water. The wall thus regains its natural thermal insulation capacity, while at the same time the diffusion openness (breathability) of the building fabric is maintained.

How to carry out interior sealing with Isofin yourself
Thanks to the sophisticated system, the creation of an Isofin surface barrier is also possible for ambitious DIY enthusiasts, especially when waterproofing basements:
Drill: Drill holes (10-12 mm diameter) in a checkerboard pattern with horizontal and vertical spacing of 25 cm. The holes should penetrate about two thirds of the wall thickness and run downwards at an angle of 30-45°.
Inject: Insert the Isofin injection bottles with the special cap screwed on into the drill holes. The masonry absorbs the Isofin automatically.
Sealing: Once the isofin has been completely absorbed (1-10 days depending on the masonry and moisture), remove the empty bottles and seal the drill holes with a little mortar.
The right amount of Isofin depends on the wall thickness. Our special dosing bottle has an integrated scale that shows you the correct quantity depending on the wall thickness. For a basement wall approx. 36 cm thick, you need one bottle of Isofin (500 ml) per drill hole.



The Isofin calculator for the perfect material quantity
We have developed our Isofin calculator so that you know exactly how much material you need. Simply enter the dimensions of the surface to be treated and our tool will calculate precisely:
The required number of drill holes
The required quantity of Isofin injection bottles
The optimum drill hole distribution
This will help you avoid unnecessary additional costs due to overestimation or frustrating repeat orders if the material requirements are underestimated. Also take into account the ingress of groundwater to ensure professional waterproofing. It is important to have the specific reason for the moisture determined by a specialist in order to take targeted action against ground moisture, seepage water and pressing groundwater.
To the calculatorCosts and duration of waterproofing
The costs and duration of the waterproofing work depend on the specific conditions in the basement. Waterproofing from the inside can usually be carried out more quickly and cost-effectively than waterproofing from the outside. However, it is important that the waterproofing work is carried out by a professional to ensure that it is correct and durable. Costs can vary depending on the method and extent of the work, but should be seen as an investment in the future of the building. Effective waterproofing protects the building fabric and improves the usability of the basement rooms in the long term. It also prevents dangerous damage to the building fabric of the house caused by damp in the basement.
Alternative methods and their weaknesses
It is often recommended to work with bitumen. However, this method has considerable disadvantages:
Bitumen is primarily suitable for external waterproofing
Bitumen prevents wall breathing when used indoors in cellars
The trapped moisture can no longer evaporate
The risk of mold forming behind the bitumen layer increases
Adhesion to damp surfaces is problematic
In contrast, Isofin hydrophobizes the pore walls without closing the pores. This allows the wall to continue to breathe and the existing water to evaporate, which offers practical advantages. Tip: Make sure you choose the right materials and specialist companies to make the most of these benefits.
In which cases is a surface barrier with Isofin the right choice?
An Isofin surface barrier is particularly recommended:
In the event of missing or defective vertical external waterproofing, also known as a vertical barrier. Reliable waterproofing on the exterior basement wall is crucial to prevent the ingress of water from the sides and thus avoid water damage.
In areas that are not accessible from the outside (under terraces, garages)
In the event of interlocking moisture from adjacent components or neighboring buildings
For height offsets in the cellar floor that allow water to enter from the side
As an alternative to costly external sealing
Important to know: Isofin has been specially developed for capillary moisture and works optimally in the case of transverse moisture penetration and rising damp.
Holistic approach to moisture remediation
Moisture can pose a risk to the building fabric not only in the cellar, but throughout the entire building. With Isofin, we offer an efficient solution that offers practical benefits thanks to its simple self-assembly. Basement waterproofing is an essential part of our holistic approach to moisture remediation.
The remediation of damp masonry with Isofin includes:
Analyzing the sources of moisture. A precise determination of the cause is essential in order to select the appropriate sealing method.
Targeted treatment with Isofin surface barriers
If required, combination with horizontal barriers against rising damp
Sufficient drying time for the masonry
After creating an Isofin surface barrier, the masonry needs time to dry out. This time varies depending on the degree of moisture, wall thickness and room climate. Please note the following tips for optimum drying:
Ensure that the treated rooms are well ventilated
If possible, set up a fan that directs the air along the wall
Wait until the walls are completely dry before plastering or painting so as not to jeopardize the structural integrity of the building
Only use diffusion-open wall coatings later on
The first drying effects are usually visible after 2-3 months. Complete drying can take 5-7 months depending on the circumstances.
Disadvantages of conventional interior seals and how Isofin overcomes them
The following disadvantages are often cited with conventional methods:
The cause is not remedied: Conventional methods only combat the symptoms. Isofin solution: The hydrophobic pore walls actually stop the transport of water.
Trapped moisture: Sealing slurries and barrier plasters trap the water in the masonry. Isofin solution: Diffusion-open sealing allows the existing water to evaporate.
Reduced living space: facing shells make the rooms smaller. Isofin solution: No change to the room geometry as it is injected directly into the existing wall.
Insufficient effect: Conventional interior sealants often only combat moisture on the surface. Isofin solution: Deeply effective hydrophobization across the entire wall cross-section.
Thanks to its innovative technology, Isofin overcomes the typical disadvantages of conventional interior waterproofing and offers an effective long-term solution. You can find information on application and further tips on basement waterproofing in our detailed instructions. The combination of horizontal and vertical barriers is particularly effective in sustainably combating moisture problems in old buildings.
When waterproofing basements, there are some common sources of error that should be avoided to ensure successful and long-lasting waterproofing. Some of these sources of error are:
Inadequate preparation of the substrate: The substrate must be carefully prepared before the waterproofing is applied. This includes the removal of dirt, oils and other substances that could impair the waterproofing. A clean and sound substrate is crucial for the adhesion of the waterproofing materials.
Incorrect choice of waterproofing method: The choice of the correct waterproofing method depends on the specific conditions in the basement. The wrong choice can lead to inadequate waterproofing. It is important to accurately identify the cause of the moisture and select the appropriate method, be it a surface barrier, a horizontal barrier or a combination of both.
Insufficient thickness of the waterproofing layer: The waterproofing layer must have a certain thickness to be effective. A layer that is too thin can lead to inadequate waterproofing. Make sure you follow the manufacturer's instructions exactly and apply the recommended layer thickness.
Failure to seal properly: Sealing must be done properly to ensure that it is effective. This includes using the correct materials and following the manufacturer's instructions. Errors in application can significantly reduce the effectiveness of the seal.
Insufficient drying of the basement: Before waterproofing is carried out, the basement must be sufficiently dried. Insufficient drying can lead to inadequate waterproofing. If necessary, use construction dryers or fans to speed up the drying process.
Ignoring the basement waterproofing: The basement waterproofing should be checked and maintained regularly to ensure that it remains effective. Small cracks or damage can quickly lead to major problems if they are not repaired in time.
By avoiding these sources of error, successful and durable basement waterproofing can be guaranteed. It is advisable to consult a professional to ensure that the waterproofing is carried out properly. An experienced specialist company can help you choose the right method and materials and carry out the waterproofing work professionally.
Conclusion: Effective solution for dry cellars
With an Isofin surface barrier, we offer a proven, self-applicable solution for waterproofing basements from the inside. It permanently protects your basement walls and screed from moisture penetrating from the side and restores the natural thermal insulation properties of the masonry.
Calculate your individual material requirements now with our Isofin calculator or contact us for a personal consultation. Contacting our experts is crucial in order to precisely identify the causes of damp in the cellar and initiate suitable measures for cellar renovation. With Isofin, you are opting for a sustainable solution that will protect your home from the damaging effects of damp.
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