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Damp walls or water in your basement? Learn how Thor Protect works, which solution is right for your problem, and what you need to consider during application. Here you’ll find answers to the most frequently asked questions about damp, waterproofing and Thor Protect.
In short: a specially deep-penetrating, plastic-free, non-toxic, purely mineral activator that permanently and effectively binds water, lime, cement and salts together, thereby greatly reducing pore volume long term (petrifies) similar to true barrier render or watertight concrete (WU concrete).
A purely mineral waterproofing system without any kind of plastics.
It reacts with existing moisture and salts, forms capillary-filling crystals (PSH phases), strengthens the masonry and blocks moisture deep within the wall permanently—without drilling, while remaining vapour-permeable.
Thor Protect is a purely mineral system for sealing and protecting buildings and structures of any age or construction period. Thor Protect products are aimed primarily at private users and DIYers who want to treat moisture problems themselves by following instructions. Of course, Thor Protect products have also been used by commercial companies in the building renovation and waterproofing industry for over 30 years, with a guarantee. The systems are used, among other things, for damp masonry, floors, ceilings, walls, basements and mould problems. With proper preparation of the surfaces to be treated, Thor Protect products penetrate the capillary structure of mineral substrates on their own, crystallise there permanently and irreversibly, and thus form an effective barrier against water and capillary moisture penetrating from outside. The range includes impregnations, mineral sealing layers, floor levelling compounds, mortars and special industrial coatings. Thor Protect products contain no silanes, polymers, resins or plastics and are purely mineral.
VOC-free, salt-binding and vapour-permeable.
Thor Protect is a German development. The technology is based on an original formula from the early 1920s at Jena Optik. Under the Thor Protect brand name, the further-developed multi-component system has been sold since 2018 for DIY application. It uses a specialised silica formula with catalysts and crystallisation accelerators that forms a permanently stable crystal structure in the pores of mineral building materials.
Thor Protect, on the other hand, is ideally suited for all types of masonry—brick, stone, mixed masonry and clay—thanks to continuous modification/adaptation of the base activator, the omission of plastic binders, and the use of local minerals such as lime, cement, sand and water glass. The prerequisite is wall surfaces that can absorb moisture and are made of cement or lime.
Lime is the basis for the formation of many different building materials and stones. In geological crystallisation processes, lime hardens into clay, then into sandstone, and into soft to hard stones such as granite, etc. These long natural processes have already been accelerated industrially for a hundred years with Thor Protect systems.
Back then there were no plastic binders; only mineral binding activators were used. When plastic binders (oil industry) emerged in the 1960s, crystallisation technology was increasingly pushed aside. Today, however, there are again a few companies worldwide that successfully use this old, effective technology.
Mineral waterproofing is built to last forever!
Unlike classic waterproofing (e.g. bitumen membranes or injections), Thor Protect works via capillary action, penetrates deep, and remains permanently mineral.
No shrinkage, no loss of plasticisers or solvents—and no drilling required.
Thor Protect also combines waterproofing with strengthening the building fabric.
Thor Protect differs mainly through its mineral mode of action from many conventional waterproofing methods: - Conventional methods often work with bitumen, plastics, foils or visible coatings. - Thor Protect is purely mineral, plastic-free, colourless, odourless and solvent-free. - The agent penetrates the mineral substrate and permanently narrows the pore system there through crystallisation. - Liquid water and capillary moisture are blocked, while the component remains vapour-permeable and therefore breathable. - The look and feel of the surface do not change. - Depending on the application, it can be applied from the inside or outside. - Application is possible without excavation, drilling or chemical injection. However, which type of waterproofing is suitable in a specific case depends on the cause of the moisture, the path of water ingress and the condition of the substrate.
No, Thor Protect is not a horizontal damp-proof course (DPC). The effective Thor Protect impregnation serves as a permanent vertical barrier against moisture and water penetrating capillarily from outside. It prevents this from entering the interior of the building. We deliberately avoid drill-hole injections or other types of horizontal barriers that weaken the masonry structure through perforation or damage. With the Thor Protect system, we offer less invasive interventions in the building’s structural integrity and pursue different solution approaches for vertical sealing. The special properties of Thor Protect not only block water and capillary moisture penetrating from outside, but also permanently strengthen the masonry at the same time.
Thor Protect technology works via capillary action—meaning: moisture is bound by natural crystal growth in the masonry and actively transported towards the surface. This dewaters the wall from the inside out and permanently interrupts water transport.
The key first step is to identify and fix the cause of the moisture. Mould must not simply be painted over.
- Identify the cause (burst pipe, backflow, condensation?)
- Carry out moisture and salt diagnostics
- Open up the wall and remove plaster
- Re-plaster the wall with lime-cement plaster approx. 2 cm thick
- Apply Thor Protect impregnation
Then proceed as follows:
1. If there is mould, wear gloves, safety goggles and a mask.
2. Carefully remove affected wallpaper, paste, loose plaster and dense old coatings.
3. If the masonry is heavily soaked, old plaster layers, previous waterproofing and bitumen residues must be completely removed down to bare masonry.
4. Treat existing mould properly. (mould remover/fungicide)
5. Treat the clean, mineral substrate with Thor Protect according to the moisture load.
With condensation moisture or structural thermal bridges, you must also ensure sufficient air circulation. Large furniture should be about 5 to 7 cm away from the wall.
Later paint coats—especially with thermal bridges or condensation (dew point shift)—should be finished afterwards with special antibacterial thermo protective thin coatings from Thor Protect. (see products).^
Thor Protect technology (fungicide) sustainably reduces moisture (fungus blocker) and prevents mould growth, because Thor Protect regulates the moisture balance in the wall so no breeding ground (moisture) for mould develops.
Yes, Thor Protect can help both in basements and living spaces if capillary rising or penetrating moisture in a mineral substrate is the cause.
Before application, existing mould must be removed professionally. Wallpaper, paste, loose plaster and dense coatings such as latex paint must also be removed so Thor Protect can penetrate directly into the mineral substrate.
If the moisture is caused by condensation, incorrect ventilation or structural thermal bridges, that cause must also be addressed. Thor Protect cannot correct structural thermal bridges. In such cases, sufficient air circulation and about 5 to 7 cm distance between large furniture and the wall are important. For thermal bridges or condensation problems that cannot be solved by ventilation, Thor Protect antibacterial thermo thin coating can help.
We’ll be happy to advise you.
No. After the capillary pores in the wall have been gradually closed by permanent crystallisation, the water level in the wall drops and the dew point shifts outward. With correctly applied impregnation, water can no longer penetrate the treated zone. Thor Protect crystallises permanently about 1 to 4 cm deep in the mineral substrate, narrowing pores and capillaries there and acting as a permanent vertical barrier. The outer masonry can still absorb water, and moisture can be present there up to the saturation limit. However, it is prevented from passing through the impregnated area to the inside. The prerequisite is that Thor Protect impregnation has direct contact with the absorbent mineral substrate and has been applied correctly.
If you have a small damp spot, you don’t necessarily have to treat the whole wall. Treat the visible patch plus about 1 metre in all directions around it. (Many of our customers do this very successfully with the 1 m² test pack.) If moisture later appears again next to it, you should treat the entire wall and at least 0.5 metres around the corners (interior walls). Please keep in mind: just because you’ve blocked your wall against penetrating moisture, the cause—and the water outside—hasn’t gone away; it just can’t get into the building at that spot anymore. The cause (it’s always water) can’t be eliminated. So you can’t prevent your building from getting wet from the outside (and it doesn’t harm the building!), you can only effectively and permanently prevent water or moisture from entering the interior from outside. Dry walls, a better indoor climate, less evaporative cooling on the walls. Always remember: you will never find mould on dry walls.
For Thor Protect, the wall must be freely accessible and prepared cleanly (absorbent):
1. Remove wallpaper completely with a scraper. (Also think about paste residue.)
2. Remove mould. Wear a protective mask, safety goggles and gloves.
3. Check the plaster by tapping. Hollow-sounding or loose plaster must be removed. Firm plaster can remain, provided it is not gypsum plaster.
4. All coatings must be removed completely, especially those that are not water-permeable. These include, in particular, enamel paint, oil paint, latex paint, silicone paint, acrylic paint, resins and rubberised coatings, etc.
5. Remove nails, hooks and wall plugs. (Seal holes and cracks larger than 0.3 mm with the sealing powder.)
6. Remove dust, loose paint residue and other deposits with a broom or vacuum so the pores are open.
7. First spray holes and cracks generously with well-shaken Thor Protect primer, then seal them with the supplied sealing powder. A water-permeable emulsion paint coat is less of an issue, as primer and finish can penetrate it.
(Especially in older buildings, make sure this is the original first coat and that there aren’t old water-impermeable coats underneath.) If you’re unsure what type of coating you’re dealing with, use a test pack first to be certain. Thor Protect always works, but you must strictly follow the processing instructions in the application guide.
1. Check the plaster by tapping. Hollow-sounding or loose plaster must be removed. Firm plaster can remain, provided it is not gypsum plaster.
2. All coatings must be removed completely, especially those that are not water-permeable. These include, in particular, enamel paint, oil paint, latex paint, silicone paint, acrylic paint, resins and rubberised coatings, etc.
3. Remove nails, hooks and wall plugs. (Seal holes and cracks larger than 0.3 mm with the sealing powder.)
4. Remove dust, loose paint residue and other deposits with a broom or vacuum so the pores are open.
Of course, Thor Protect can also be applied directly to damp surfaces. Pre-drying is therefore not necessary. On the contrary—the moisture in the wall makes it easier for Thor Protect to penetrate.
You can apply Thor Protect directly to the damp wall. Pre-drying is not required. What matters is that the surface is clean, open-pored and accessible. Loose plaster, non-water-permeable coatings, dust and loose paint residue must be removed beforehand.
The Thor Protect crystallisation process works at any time. It is influenced by porosity and capillary structure, as well as salt and mineral content in the building material.
The ideal time is as soon as the mineral substrate has been fully prepared, cleaned and made open-pored according to the application guide. The wall may be damp and does not need to dry out completely before application.
Important:
- Remove loose plaster, paint and water-impermeable coatings.
- Seal cracks and holes over 0.3 mm with mineral materials.
- If there is heavy salt efflorescence, remove it mechanically beforehand.
- Apply primer and process the finisher wet-on-wet after about 60 to 90 minutes.
- Then allow about 14 to 28 days for crystallisation. For indoor application, processing is weather-independent and possible even in rain or winter.
If you use too little primer or finisher, the wall may not seal completely. As long as the finisher is still damp, you can re-treat the affected areas. With the primer, a bit more is fine.
Too much finisher, however, can cause white marks. Therefore, wipe off excess liquid with a cloth about an hour after application. If the finisher has already hardened, the treated surface will no longer absorb primer. If you’re unsure, call us and get free, no-obligation help with your application.
Thor Protect is suitable for permanent waterproofing and impregnation of absorbent, mineral substrates indoors and outdoors.
Suitable substrates include, among others:
- Concrete and screed
- Mortar and cement
- Lime and cement plaster
- Brick and natural stone
- Terracotta and mineral roof tiles
- Paving and mineral masonry
Typical areas of use include:
- Damp basements and vaulted cellars
- Living rooms, bedrooms and children’s rooms
- Bathrooms and kitchens
- Walls, floors and ceilings
- Facades, roofs, garages and window sills
- Foundations and floor slabs
- Stables and other agricultural areas
- Listed building conservation
- Plinth waterproofing
- Remediation of persistent mould damage
- Drinking water and rainwater cisterns
- Underground car parks, lift shafts and tunnels
- Areas where external waterproofing is not possible or is too complex
Thor Protect can be used both externally (facade) as protection against penetrating water and weathering, and internally against moisture and water coming through from outside. It also protects against freeze-thaw damage, efflorescence, and algae, moss, lichen and fungi.
A prerequisite is an absorbent, mineral substrate. Cracks and holes over 0.3 millimetres must be sealed or narrowed with mineral materials before impregnation. Outdoors, Thor Protect must not be applied below 5°C and not during the winter months.
The effective, long-lasting Thor Protect impregnation can be used on both interior and exterior walls (facade). Especially in difficult or tight conditions, internal waterproofing is often the more practical and cost-effective solution—without any excavation.
In most cases, waterproofing with Thor Protect is done from the inside—no excavation, no heavy machinery and no intervention in the foundation. Ideal for occupied buildings and hard-to-access areas.
As a rule, the house does not need to be excavated all the way around for renovation with Thor Protect. Thor Protect can be applied as internal waterproofing directly onto the prepared mineral substrate, without drilling or chiselling.
This blocks water from passing through to the inside. However, the outside of the masonry can still remain damp. Whether internal waterproofing is sufficient for your specific damage pattern depends on the cause of the moisture and the condition of the substrate.
Yes, Thor Protect can be used successfully on historic buildings and structures in heritage conservation and restoration, provided there are absorbent, mineral substrates such as brick, natural stone, terracotta, old plaster or old paving.
The impregnation works inside the material and preserves its breathability. It forms no visible film, no glossy layer and causes no colour change. This preserves the original character of the historic material.
In addition, Thor Protect can protect the substrate from moisture, weathering, frost and freeze-thaw stress, microorganisms and salt efflorescence.
Especially in historic buildings, the Thor Protect system is used without drilling, without plastics and without damaging the structure. The building fabric is not only preserved, but also strengthened mineralically.
Thor Protect impregnation fully seals the wall through crystallisation within 2 to 4 weeks, depending on geometry, salt load and ambient climate. Shortly after application, it displaces water from the wall down to the penetration depth of the impregnation, so it may temporarily appear even damper than before. Increased emergence of salts and other efflorescence one to two days after Thor Protect impregnation is completely normal. However, these salts and efflorescence must be swept off.
As a rule, Thor Protect is fully crystallised and hardened after about 14 days. Depending on the substrate, however, it can take up to 6 weeks until the wall is fully closed to liquid water and feels dry. Ventilation supports drying. A dehumidifier is usually not required. You should only paint or wallpaper once the wall feels dry. (Finger test)
The actual waterproofing is completed within a few days.
Drying then takes place purely mineral, without heating rods.
Initial results are noticeable after 3–7 days.
Full drying of the wall capillaries usually takes place within 2–4 weeks, depending on wall cross-section, salt accumulation and climate.
A dehumidifier is usually not required. You should only paint or wallpaper once the wall feels dry. (Finger test)
If the wall is still damp after application, be patient at first. Thor Protect is usually hardened after about 14 days. Depending on the substrate, however, it can take up to 6 weeks for the solutions to fully react and for the wall to be sealed against liquid water. Let the wall dry naturally and ventilate regularly. A dehumidifier is not required and should not be used. You can wipe up any water that emerges with a cloth. You can simply sweep off salt crystals on the surface. If the wall remains damp even after 6 weeks, in rare cases a follow-up treatment may be necessary. Then a colleague will take care of an individual assessment.
To reassure you: Thor Protect always works. In very rare cases, a follow-up treatment is necessary despite correct application. But it has never happened that a wall wasn't sealed at all.
You can usually re-plaster as early as one day after treatment. If the wall is very wet, wait until no visible water is coming out. A primer may be required for subsequent plastering. You should only paint or wallpaper once the wall feels dry (finger test) and no new salts are emerging. The crystallisation process usually takes two to four weeks, longer in exceptional cases. If in doubt, wait an extra week. For further finishing, use vapour-permeable, mineral materials, for example lime plaster, lime-cement plaster or silicate paint. Some paints and most wallpapers (especially the paste) don’t like it when moisture is still coming out of the wall. For mould, condensation and thermal bridges, use Thor Protect special coatings as a finish coat for a proper, long-lasting result. Standard emulsion paints and plastic paints are unsuitable. You’re also welcome to tile the Thor Protect-treated surfaces again. But don’t use tile adhesive (contains plastics); instead, bed the new tiles flush and void-free in cement, as master builders did centuries ago. Those tiles are still hanging today!
After sealing with Thor Protect products, the now dry surfaces should be finished with vapour-permeable materials such as lime plaster, lime-cement plaster or silicate paint. For mould problems, condensation areas and thermal bridges, a Thor Protect anti-mould thermo thin coating should then be applied. We’ll be happy to advise you on this. Emulsion or plastic paints are unsuitable. With screed, insulation or plaster, make sure to use mineral products as well.
The costs naturally depend on the area to be sealed. For guidance, as of August 2026:
- 1 m² test set: €99 - Small-area set for 2.5 m²: €230 - Basic set for 5 m²: €399 up to a basic set for 100 m²: €2,549
i.e., depending on the size of the area, from €99 per m² down to €25.49 per m²
If you later purchase from 15 m², the price of the test set is fully refunded.
Prices subject to change.
When applied correctly, Thor Protect waterproofing is permanent. Through crystallisation, the impregnation becomes part of the mineral substrate and can generally only be destroyed by mechanical intervention such as drilling, chiselling or breaking.
The full effect is usually achieved after 2 to 4 weeks. In individual cases, the reaction can take up to 6 weeks. The prerequisite for a permanent effect is a suitable, open-pored mineral substrate and application according to the instructions.
Unlike other products on the waterproofing market, Thor Protect is purely mineral (without organic binders), highly alkaline, active in the treated mineral substrate, and turns treated mineral surfaces into water-resistant, breathable stone. (watertight petrification) This technology has been used successfully in hydraulic engineering for a hundred years. Thor Protect stops not only water, but also alkalis and acids. It is also UV-resistant and environmentally friendly.
Thor Protect is 100% purely mineral, contains no plastics or solvents and is therefore emission-free, non-allergenic and sustainable.
All components are recyclable and harmless to health.
Thor Protect is colourless, odourless, solvent-free, UV-resistant and non-toxic.
Ideal even for highly sensitive rooms.
Yes, safety data sheets are of course available; you can conveniently download them as PDF files under "Safety data sheets" on our website.
Thor Protect has been used for over 100 years in commercial and industrial settings—e.g. for large housing companies, tunnel construction, hydraulic engineering, agriculture, etc. Now it is also available for private use. For data protection reasons, please ask us personally for specific references, or take a look at our website for references from thousands of satisfied customers with moisture problems—not only in basements. Verified customer reviews are also available on Trusted Shops, Google Reviews, Trustpilot, Erfahrungen.de, Facebook, Instagram, etc., and on our website.
Try Thor Protect first on a small area. The test pack contains the products you need to waterproof 1 m² of basement wall or basement floor.
Talk to one of our trained technicians about your moisture damage:
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