Sikalastic® M 640

• CE Marking and Declaration of Performance to European Technical Assessment (ETA) No 24/0043 based on ETAG 005 Part 6 – Liquid-applied roof waterproofing using kits based on polyurethane.

Elastomeric aromatic polyurethane

12 months from date of production

The Product must be stored in original, unopened and undamaged packaging in dry conditions at temperatures between +5 °C and +25 °C. Higher storage temperatures may reduce shelf life of product. Always refer to packaging. Refer to the current Safety Data Sheet for information on safe handling and storage.

~83 %

Up to +200 °C (short-term)

≤ 80 % r.h.

Beware of condensation. The substrate and uncured material must be at least 3 °C above dew point to reduce the risk of condensation or blooming of the membrane finish. 

≤ 4 % pbw moisture content.

The following test methods can be used:

• Sika®-Tramex meter
• CM - measurement 
• Oven-dry-method

No rising moisture according to ASTM (Polyethylene-sheet).

Note: For the consumption rates and waiting time / overcoating please refer to the PDS of the appropriate primer. Other substrates must be tested for their compatibility. If in doubt, apply a test area first.

~40 min. (at 20 °C)

Fully cured after 7 days

6 hours (at 25 °C & 55 % r.h.)

6 – 24 hours

Appox. 12 hours

Sikalastic® M 640 is applied in min. 2 coats.

Appox. 1.5 - 2.0 kg/m², depending on the system configuration.

For airless application consumption is maximum 0.8 kg/m² per coat.

Note: Do not exceed the maximum recommended consumption per layer 0.8 kg/m² without reinforcement, as this will cause blisters on the surface of the membrane.

Substrate preparation equipment 

• Abrasive blast cleaning / planing / scarifying or grinding equipment
• High pressure power washer

Mixing Equipment 

• Electric single paddle mixer

Application Equipment 

• Brush 
• Roller 
• Airless spray

Concrete substrates must be sound and of sufficient compressive strength (≥ 25 N/mm²) with a minimum pull off strength of 1.5 N/mm²

The surface must be of sufficient structural strength, clean, dry and free of dirt, oil, grease and other contamination. Depending on the material the substrate must be primed and mechanically cleaned. Grinding may be necessary to level the surface. Complete roof system must be designed and secured against wind uplift loadings.

Suitable substrates are such as: concrete, bituminous membrane, metal, unglazed ceramic tiles and wooden substrates.

Prior to application, stir Sikalastic® M 640 gently but thoroughly at least for 1 minute in order to achieve a homogeneous mixture.For mixing, an electric single paddle mixer (300-400 r.p.m.) with a spiral blade can be used. Over mixing must be avoided to minimize air entrainment.

Prior to application, confirm substrate moisture content, r.h. and dew point.

Prior the application of Sikalastic® M 640 the priming coat must have cured, tack-free. For the Waiting Time / Overcoating please refer to the PDS of the appropriate primer.

Non-Reinforced Roof Waterproofing:

Sikalastic® M 640 is applied in two coats. Prior to the application of the 2^nd coat the indicated waiting time of overcoating shall be allowed. Roof coatings may need partial reinforcement over areas of stress or expected movement e.g. joints, overlaps, detailing, crack bridging etc. Use Sika® Joint Tape SA or strips of Sika® Reemat Premium / Sikalastic® Fleece. For joints with moderate movement e.g. Metal Sheet use Sika® Flexitape Heavy incorporating bond-break or Sika® Joint Tape SA.

Reinforced Roof Waterproofing:

Sikalastic® M 640 is applied in combination with Sika® Reemat Premium / Sikalastic® Fleece. Over-coating of bitumen membranes has to be fully reinforced.

1. Apply the first coat, for correct consumption refer to the table of the relevant system of Sikalastic® M 640. Work only as far in advance that the material stays liquid.

2. Roll in the Sika® Reemat Premium /  Sikalastic® Fleece and ensure that there are no bubbles or creases. Overlapping must be a minimum 5 cm and ensure overlaps are sufficiently wet to bond.

3. The roller may require only a little extra material to keep wetted but no further significant material needs to be added at this stage.

4. After the coat is dry enough to walk on, seal the roof area with second coat of Sikalastic® M 640 at a minimum consumption of the revelant system.

Always begin with details prior starting with waterproofing the horizontal surface. For details follow step 1-4.

Note: The applicator must wait 6 - 24 hours between coats. If the overcoating time is exceeded, more than 3 days, Sika® Reactivation Primer, Sika® Concrete Primer or Sikalastic®-1 C Primer PU must be applied at a consumption rate of ~100 g/m².

Clean all tools and application equipment with a suitable thinner (Xylene / MEK / Acetone) immediately after use. Hardened or cured material can only be removed mechanically.