SikaBond®-T21 is a one-component, moisture-cure polyurethane adhesive that does three jobs at once: wood flooring adhesive, vapour-retarding membrane and sound reduction layer. It bonds directly to concrete with no sleepers or plywood, and its 270 % elongation lets planks move without breaking the glue line.
Used as an all-in-one, it delivers unlimited protection against subfloor moisture vapour: no moisture testing required, a substrate that is dry to the touch is the only condition. It contains no water and therefore will not swell the wood — a decisive advantage on problem species such as beech and bamboo.
- Three functions in one: adhesive, vapour retarder and sound reduction
- Unlimited subfloor moisture protection — no testing required
- 270 % elongation — flooring moves without damaging the bond
- Bridges dormant substrate cracks
- Solid wood up to 19 mm thick × 203 mm wide
- Engineered planks up to 355 mm wide, no length limit
- Contains no water — no wood swelling
- Low odour, low VOC (meets SCAQMD Rule 1168)
- Suitable over radiant floor heating
ACOUSTIC PERFORMANCE
- STC 62 (ASTM E-90) — 168 mm concrete slab, 19 mm suspended gypsum ceiling
- FIIC 52 (ASTM E-989) — 203 mm concrete slab, no ceiling
- Impact sound reduction Δ IIC = 21 (ASTM E-2179)
RESTRICTIONS — READ BEFORE ORDERING
Interior use only, for experienced installers.
Do not use in areas subject to hydrostatic head or a secondary moisture source, on wet, contaminated or friable substrates, over concrete treated with curing compounds or sealers, or on PE, PP, Teflon and certain plasticised synthetics. Not compatible with rubber underlayments containing EPDM.
Do not apply or cure in the presence of uncured silicone, alcohol or solvent cleaners. Solid wood and bamboo are not suitable below grade.
Freeze-sensitive. Store between 10 °C and 25 °C, protected from direct sunlight. Adhesive that has frozen can no longer be used.
SUBSTRATE PREPARATION
Concrete with a minimum compressive strength of 20.6 MPa (3,000 psi), surface profile CSP 1-3, aged 21 to 28 days. Maximum floor variation 4.7 mm over 3 m. Substrate must be clean, dry, sound and free of laitance, oil, grease and sealers. Over ceramic tile, grind the surface and vacuum thoroughly.
COVERAGE BY TROWEL
| All-in-one (adhesive + membrane) | 6.3 × 6.3 mm V-notch — 0.73 to 0.85 m²/L (30 to 35 sq. ft./gal.) |
| Adhesive only | 4.7 × 3 mm V-notch — 1.10 to 1.22 m²/L (45 to 50 sq. ft./gal.) |
| With cork or rubber underlayment | 3 × 3 mm square notch — 1.95 m²/L (80 sq. ft./gal.) |
100 % substrate coverage is required for the vapour-retarder function; 90 % is sufficient for bonding alone. Set the flooring within 20 to 25 minutes of spreading, before a skin forms.
SPECIFICATIONS
| Brand | Sika |
| Range | SikaBond®-T21 |
| Composition | One-component polyurethane, moisture curing |
| Size | 15.14 L (4 US gal.) pail |
| Colour | Light brown |
| Specific gravity | 1.18 kg/L |
| Shore A hardness | 50 (28 days at 23 °C, 50 % RH) |
| Tensile strength | 1.03 MPa (150 psi) |
| Shear strength | 1.03 MPa (150 psi), 1 mm adhesive thickness |
| Elongation at break | ~270 % |
| Water vapour permeability | < 4 g/m²·24 h·mmHg (ASTM E-96) |
| Service temperature | -40 °C to 70 °C |
| Skin / laying time | 45 to 60 minutes (23 °C, 50 % RH) |
| Curing rate | 4.0 mm/24 h (23 °C, 50 % RH) |
| Light foot traffic | 6 to 8 h; sanding after 18 h |
| Ambient temperature | 15 °C to 32 °C |
| Relative humidity | 40 % to 70 % during installation |
| Substrate temperature | > 15 °C (< 20 °C over radiant heating) |
| Storage | 10 °C to 25 °C — freeze-sensitive |
| Shelf life | 12 months |
| Reference | SK-749290 |
| UPC code | 33886152099 |
