Garage and Basement Tanking: The Complete Guide to Perfect Waterproofing
Is your garage or basement suffering from water infiltration? Tanking is a proven technique for waterproofing underground rooms from the inside. Find out how it works, which products to use and the current prices in 2026.
Tanking (or internal waterproofing) consists of creating a waterproof barrier on the interior walls of an underground room: cellar, basement, semi-buried garage or crawl space. This technique blocks water infiltration from the inside, without having to perform heavy excavation work on the outside.
According to DTU 14.1, tanking is suitable for rooms subject to moderate to medium water pressure. For high pressure (shallow water table), it may be necessary to combine tanking with peripheral drainage.
When to opt for tanking?
- • Water infiltration through the basement walls or floor
- • Seepage and persistent signs of humidity
- • Project to convert a cellar into a living space
- • Exterior access impossible or too costly
- • Protection of a semi-buried garage
Different Tanking Techniques
Waterproofing mortar tanking
The most common technique. A special mortar based on cement, resins, and water-repellent additives is applied in 2 to 3 layers on the walls and floor. It crystallizes in the concrete pores to create a waterproof barrier.
Resin injection tanking
Holes are drilled into the walls, then a polyurethane or acrylic resin is injected under pressure. The resin spreads into cracks and pores to block the water.
Membrane tanking (lining)
A waterproof membrane (PVC, EPDM or bitumen) is glued or mechanically fixed to the walls. This solution is often used in large commercial or industrial areas.
The 6 Steps to Successful Tanking
Well-executed tanking can last for more than 30 years. Here are the key steps to guarantee effective and durable waterproofing for your garage or basement.
Diagnosis and preparation
Identify the source of infiltration, empty and clean the room, let the walls dry for 2 to 4 weeks if necessary.
Substrate preparation
Chip off defective plaster, fill cracks and holes with a suitable mortar, create a fillet at the wall base.
Application of the first coat
Apply the waterproofing mortar in a thick layer (5 to 10 mm) on all surfaces to be treated.
Installation of reinforcement strips
Embed glass fiber reinforcement strips into corners, floor/wall junctions, and over cracks.
Application of the second coat
After the first coat has dried (24 to 48 hours), apply a second cross-coat of waterproofing mortar.
Finishing and protection
Allow to dry completely (7 to 14 days), then apply a finish paint or decorative coating if desired.
Recommended Tanking Products
Ready-to-use mortars
- • Weber.tec Superflex: versatile, easy application
- • Sika Top Seal 107: very good pressure resistance
- • Arcacim S2: economical, ideal for large areas
Injection resins
- • Polyurethane resin: expansive, fills voids
- • Acrylic resin: flexible, follows micro-movements
- • Acrylate gel: deep penetration into the substrate
Beware of "miracle" products
Beware of anti-humidity paints sold in general stores. They may temporarily hide symptoms but do not constitute true tanking. For durable waterproofing, use DTU 14.1 certified products.
Tanking Prices in 2026
| Service | Price per m² | For 30 m² |
|---|---|---|
| Mortar tanking (2 coats) | €80 to €150 | €2,400 to €4,500 |
| Tanking + floor treatment | €120 to €180 | €3,600 to €5,400 |
| Injection tanking | €100 to €200 | €3,000 to €6,000 |
| Membrane tanking + finishing | €150 to €250 | €4,500 to €7,500 |
* Included VAT price including labor and materials. Indicative rates may vary according to the state of the substrate, accessibility and region.
Advantages and Limitations of Tanking
Points forts
- Effective solution against pressure infiltration
- Work can be carried out from the inside (no excavation)
- Lower cost than peripheral drainage
- Allows for the conversion of the basement or cellar
- Durability of at least 20 to 30 years
Points faibles
- Does not treat the external cause of humidity
- Slight reduction in interior space (2-3 cm)
- Requires an empty room during the work
- Significant drying time before use
- Less effective if water pressure is very high
Tanking or Drainage: Which Solution to Choose?
The choice between tanking and drainage depends on several factors: the origin of humidity, water pressure, the accessibility of the land and the available budget.
| Criterion | Tanking | Drainage |
|---|---|---|
| Interior work | ✓ Yes | ✗ No |
| Treats external cause | ✗ No | ✓ Yes |
| High water pressure | ◐ Limited | ✓ Suitable |
| Average cost (30 m²) | €3,000 to €5,000 | €8,000 to €12,000 |
| Duration of work | 3 to 5 days | 1 to 2 weeks |
Our advice: For moderate infiltration in a basement or garage, tanking is often the most economical and fastest solution. If your ground has a high water table or general drainage problems, combine both techniques for optimal protection.
Frequently Asked Questions about Tanking
Is tanking definitive?
A well-executed tanking with quality products can last 20 to 30 years, or even more. However, ground movement or structural cracks may require localized repairs over time.
Can you do tanking yourself?
Technically yes, if you are an experienced DIY enthusiast. Ready-to-use mortars are accessible to the general public. However, ground preparation and execution details (corners, joints) are crucial for the effectiveness of the treatment.
How long before using the room?
After application, allow 7 to 14 days of complete drying before you can paint or refurbish the room. This delay can be longer in humid or cold conditions.
Does tanking also block rising damp?
Partially. Tanking creates a barrier against liquid water, but rising damp can bypass the treatment if they are not specifically treated. For a complete solution, consider resin injection at the base of the wall.
Sources et références
Cet article s'appuie sur des sources officielles et vérifiées pour garantir la fiabilité des informations.
- [1]DTU 14.1 - Tanking works— AFNOR
- [2]
- [3]
Sophie Durand
Expert vérifiéCivil Engineer
18 years of experience in waterproofing underground structures