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Waterproofing and Renovation
Frequently Asked Questions
In recent months, we have received a variety of questions about waterproofing and renovation. Whether these queries came from construction groups, forums, or private messages, we provided answers that often turned into technical consultations. We have compiled your questions along with brief answers. Feel free to contact us for additional queries at +48 796 343 313 or a.kaczmarczyk@sanier.pl.
We have also prepared a series of waterproofing and renovation training sessions that we conduct year-round. You can find a list of upcoming sessions in the Courses and Training section.
From the article "Waterproofing and Renovation – Frequently Asked Questions":
- Can we bend roofing felt at a 90-degree angle when insulating foundation corners?
- Is it necessary to insulate monolithic building foundations adjacent to clay soil?
- Is Dysperbit the same as thick-layer bituminous coatings (KMB)?
- Can waterproofing be done year-round?
- Can bituminous materials for waterproofing be stored outdoors during winter to use them in spring?
- Are bituminous masses with polyester beads worse than pure bituminous masses?
- Can construction foil serve as waterproofing between the footing and the wall material?
- Can external and internal waterproofing be applied immediately after building foundation walls?
- Is liquid waterproofing alone sufficient for waterproofing a bathroom? Does it make sense to invest in additional materials?
- Does underfloor heating negatively affect the individual construction layers in bathroom waterproofing?
- Is dimpled membrane considered waterproofing?
- Do installation penetrations require additional sealing?
- Does a wall always need to be plastered for vertical insulation to be watertight, or can KMB be applied directly to hollow blocks?
- Is roofing felt better than EPDM simply because it’s cheaper?
- Are fillets necessary at the junctions between the footing and the wall?
- Is a flat roof really flat?
- Welding EPDM Resitrix SKW membrane: What should be done if there is sloped Styrofoam underneath?
Can Roofing Felt Be Bent at a 90-Degree Angle When Insulating Foundation Corners?
Roofing felt should not be bent sharply. Corners need to be rounded or beveled (45-degree angles). Waterproofing should be done either entirely with roofing felt, KMB (thick-layer bituminous coatings), or other waterproofing materials — never partially with felt and partially with KMB (for corners).
When using KMB, corners also need to be beveled or rounded. Otherwise, fiberglass mesh must be embedded in the KMB at right angles to ensure proper sealing.
Do Monolithic Building Foundations Adjacent to Clay Soil Need to Be Waterproofed?
Yes. Clay is a cohesive soil that does not allow water to pass through. As a result, rainwater will accumulate near the walls and seep into the structure. Therefore, installing waterproofing in this case is essential.
Is Dysperbit the Same as Thick-Layer Bituminous Masses (KMB)?
Dysperbit is a moisture-proof product, meaning it protects against moisture infiltration from wet soil. However, a moisture-proof material does not provide protection against flowing water or water exerting pressure on the wall. It has low UV resistance, limited flexibility, and may crack during drying if applied in thicker layers.
Can Waterproofing Be Done Year-Round?
Yes, but the substrate and ambient temperature must be at least +5°C. The substrate must not be frozen.
Coating waterproofing should not be exposed to rain during curing.
Frozen substrates must be warmed up: use a tent and heaters to heat the area for several hours before applying waterproofing (a minimum of 2-3 days).
Can Bituminous Waterproofing Materials Be Stored Outdoors During Winter for Spring Use?
Membranes can be stored outdoors; however, adhesives or primers for membranes must be stored in heated indoor spaces with a minimum temperature of +5°C.
Water-based or two-component waterproofing materials require storage in rooms where the minimum temperature is +5°C.
Single-component mineral waterproofing materials (powder form) can be stored outdoors but must be protected against mechanical damage and moisture.
Are Bituminous Compounds with Polyester Beads Inferior to Pure Bituminous Compounds?
They are not inferior and can also be used for waterproof insulation. Bituminous compounds with polyester beads are lighter than pure bituminous compounds.
They are used in waterproofing applications where the insulated surfaces cannot be subjected to excessive loads.
Can External and Internal Waterproofing Be Applied Immediately After Constructing Foundation Walls?
It is recommended to wait 2-3 days to allow the mortar to set before applying waterproofing.
Is Liquid Waterproofing Membrane Enough for Bathroom Waterproofing? Should You Invest in Additional Materials?
A liquid waterproofing membrane is sufficient as a coating-based waterproofing solution. However, sealing tapes should be embedded at the junctions of the floor-wall and wall-wall connections to accommodate stress transfer within the waterproofing layer. It is also recommended to use filler-free bathroom-grade silicones or gel-based polyurethane sealants for enhanced protection.
Does Underfloor Heating Negatively Affect the Structural Layers in Bathroom Waterproofing?
It does not have a negative impact.
Is Dimpled Membrane a Waterproofing Layer?
Dimpled membrane is not a waterproofing layer. It serves a protective role as a slip layer and helps drain moisture that condenses on foundation insulation. Proper installation of the membrane is crucial, including the use of mounting strips.
Do Pipe Penetrations Require Additional Sealing?
Pipe penetrations are critical points and require additional sealing.
Does a Wall Always Need to Be Plastered for Vertical Insulation to Be Effective?
The substrate must be even. An even substrate minimizes the use of waterproofing material and ensures the proper performance of the waterproofing layer.
Is Bitumen Felt Better Than EPDM Because It's Cheaper?
EPDM is one of the best waterproofing materials available.
Are Rounded Fillets at the Junctions Between the Footing and the Wall Necessary?
Rounded fillets are essential, with the exception of EPDM waterproofing.
Is a Flat Roof Truly Flat?
In reality, flat roofs are not completely flat. The roof slope should be no less than 3°, typically ranging up to 11°. Slopes can be directed either outward or inward toward the building.
Welding EPDM Resitrix SKW Membrane: What If There's Sloped Styrofoam Below?
Yes, Resitrix SKW should have an overlap of 6–8 cm. Additionally, the EPS should be primed with FG40. This setup prevents the Styrofoam from melting due to hot air exposure during welding.
