Sikalastic®-641

Polyurethane low odour liquid applied membrane for roof waterproofing

Sikalastic®-641 is a 1-part polyurethane, reinforced, low odour, cold-applied liquid membrane. It provides a UV-stable, seamless, elastic, low maintenance, durable, smooth waterproof finish using Sika's unique i-Cure technology. The product is suitable for hot and cold climates.

1-part, no mixing, easy and ready to use
Thickness: ~1.50–2.2 mm
Resistant to UV exposure
Highly reflective (~RAL 9016, available on indent)
Resistant to yellowing
Cold applied – requires no heat or flame
Low odour - suitable for odour sensitive projects
High solids content
Seamless
Easy to detail with Sika^® Reemat Premium
Easily recoated - no removal required
Vapour permeable
Applied by brush / roller
Elastic and crack bridging
Retains flexibility at low temperatures
Good adhesion to most construction substrates
Fast curing
Resistant to common atmospheric conditions

Product Data Sheet Show all documents

Usage

Top coat for SikaRoof® i-Cure-15/18/22 systems in both new construction and refurbishment projects
Top coat for the ETA approved, low odour SikaRoof iCure-15/18/22 systems.
Waterproofing structures with numerous details such as penetrations, drains, roof lights and complex geometry
Cost efficient service life extension of failing roofs
As a reflective top coat (traffic white ~RAL 9016, available on indent) providing cool roof characteristics and solar efficient roofs
For odour sensitive areas
Only for exterior use

Advantages

1-part, no mixing, easy and ready to use
Thickness: ~1.50–2.2 mm
Resistant to UV exposure
Highly reflective (~RAL 9016, available on indent)
Resistant to yellowing
Cold applied – requires no heat or flame
Low odour - suitable for odour sensitive projects
High solids content
Seamless
Easy to detail with Sika^® Reemat Premium
Easily recoated - no removal required
Vapour permeable
Applied by brush / roller
Elastic and crack bridging
Retains flexibility at low temperatures
Good adhesion to most construction substrates
Fast curing
Resistant to common atmospheric conditions

Packaging

15 litre containers.

Colour

Slate grey (~RAL 7015)

Product Details

Sustainability / Certifications / Approvals

ENVIRONMENTAL INFORMATION

Conformity with LEED v4 MRc 4 (Option 2): Building Product Disclosure and Optimization - Material Ingredients
BRE Environmental Product Declaration (EPD)

APPROVALS / STANDARDS

CE Marking and Declaration of Performance to ETA 14/0177
European Technical Assessment ETA 14/0177 based on ETAG 005 Part 1 and 6 - Liquid-applied roof waterproofing using kits based on polyurethane
External Fire Exposure to Roofs - 10 Year System BS 476 Part 3: 2004, Sikalastic®-641, Exova, Test report No. 336139
External Fire Exposure to Roofs - 10 Year System DD CEN/TS 1187:2012 Test 1, Sikalastic®-641, Exova, Test report No. 336143
External Fire Exposure to Roofs - 25 Year System BS 476 Part 3, Sikalastic®-641, Exova, Test report No. 336140
External Fire Exposure to Roofs - 25 Year System DD CEN/TS 1187:2012 Test 1, Sikalastic®-641, Exova, Test report No. 336141
Fire Testing with Burning Brands, Wind and Radiant Heat- 10 Year System DD CEN/TS 1187:2012 Test 4, Sikalastic®-641, Exova, Test report No. 336142
Fire Testing with Burning Brands, Wind and Radiant Heat- 25 Year System DD CEN/TS 1187:2012 Test 4, Sikalastic®-641, Exova, Test report No. 336141
Odour comparison Sikalastic®-641, Odournet, Report No. 456-2014-17
Odour comparison Sikalastic®-641, Odournet, Report No. 456-2014-19
Reaction to Fire - 25 Year System EN 13501-5: 2007 + A1: 2009, Sikalastic®-641, Exova, Classification report No. WF 336207
Roof Coverings Exposed to External Fire - 10 Year System EN 13501-1: 2005 + A1: 2009 Test 4, Sikalastic®-641, Exova, Classification report No. WF 336203
Roof Coverings Exposed to External Fire - 10 Year System EN 13501-1: 2005 + A1: 2009, Sikalastic®-641, Exova, Classification report No. WF 336206
Roof Coverings Exposed to External Fire - 10 Year System EN 13501-5: 2005 + A1: 2009, Sikalastic®-641, Exova, Classification report No. WF 336204
Roof Coverings Exposed to External Fire - 25 Year System EN 13501-1: 2005 + A1: 2009 Test 4, Sikalastic®-641, Exova, Classification report No. WF 336202
Roof Coverings Exposed to External Fire - 25 Year System EN 13501-5: 2005 + A1: 2009, Sikalastic®-641, Exova, Classification report No. WF 336205

Product Information

Chemical Base

Aliphatic polyurethane

Shelf Life

9 months from date of production

Storage Conditions

The product must be stored in original, unopened and undamaged sealed packaging in dry conditions at temperatures between +0 °C and +25 °C. Always refer to packaging.

Density

~1.42 kg/l

(EN ISO 2811-1)

Value +23°C

Solid content by weight

~88.0 % (+23 °C / 50 % r.h.)

Solid content by volume

~84.0 % (+23 °C / 50 % r.h.)

System information

System Structure

Refer to System Data Sheet:

SikaRoof® i-Cure-15
SikaRoof® i-Cure-18
SikaRoof® i-Cure-22

Technical Information

Tensile Strength

Unreinforced

6.0 N/mm²

External Fire Performance

B_Roof (t1) + (t4) over Build up roofing system

(ENV 1187)

Reaction to Fire

Euroclass E

Solar Reflectance Index

≥ 108^*

(ASTM 1980)

* All values refer to the initial (properly cured, non-weathered) status of Sikalastic®-641 white (RAL 9016, available on indent).

Service Temperature

-30 °C to +90 °C

Dry film thickness

Roofing system	Thickness
SikaRoof® i-Cure-15	1.5 mm
SikaRoof® i-Cure-18	1.8 mm
SikaRoof® i-Cure-22	2.2 mm

Application

Application Information

Product Temperature

It is recommended the product is stored under warm conditions (+20 °C) prior to application at temperatures below +10 °C.

Ambient Air Temperature

+5 °C min / +40 °C max

Relative Air Humidity

20 % r.h. min / 85 % r.h. max

Substrate Temperature

+5 °C min. / +60 °C max.

Dew Point

Beware of condensation.
The substrate and uncured applied product must be at least +3 °C above dew point to reduce the risk of condensation or blooming on the surface of the applied product.

Substrate Moisture Content

≤4 % parts by weight.
Test method: Sika®-Tramex meter
No rising moisture according to ASTM (Polyethylene-sheet).

Substrate Pre-Treatment

Refer to System Data Sheets: SikaRoof® systems.

Pot Life

~1 hour (+20 °C / 50 % r.h.)

Times are approximate and will be affected by changing ambient conditions particularly temperature and relative humidity.

Material in opened containers must be applied immediately. In opened containers, the material will form a film after ~1 hour.

Waiting Time / Overcoating

Ambient conditions	Minimum waiting time¹
+5 °C / 50 % r.h.	~18 hours
+10 °C / 50 % r.h.	~8–10 hours
+20 °C / 50 % r.h.	~4–6 hours
+30 °C / 50 % r.h.	~4 hours

1 After four days, the surface must be cleaned and primed with Sika® Reactivation Primer before continuing.

Times are approximate and will be affected by changing ambient conditions particularly temperature and relative humidity.

Applied Product Ready for Use

Ambient conditions	Rain resistant¹	Touch dry	Full cure²
+5 °C / 50 % r.h.	1 hour	10–12 hours	24 hours
+10 °C / 50 % r.h.	1 hour	6–8 hours	18–24 hours
+20 °C / 50 % r.h.	1 hour	4–6 hours	12–18 hours
+30 °C / 50 % r.h	1 hour	3–5 hours	8–12 hours

1 Be aware that the impact of heavy rain or rain showers can physically mark or damage the still liquid membrane.

2 Application at higher than recommended film thicknesses may result in a prolonged “soft” feel to the coating. This will eventually cure.

Note: Times are approximate and will be affected by changing ambient conditions, particularly temperature and relative humidity.

Application steps

SUBSTRATE PREPARATION

General

Refer to System Data Sheet or System Method Statement for information on preparing substrates to receive the base coat application of Sikalastic-631.

Apply Sikalastic®-641 to the fully cured Sikalastic-631 within four days after the base coat application. If more than four days has passed, the base coat surface must be prepared with Sika Reactivation Primer prior to top coat application. Refer to the PDS for Sika Reactivation Primer for further information.

Existing Sikalastic®-641 system

Clean the membrane surface using a power wash at ~14 N/mm² (2000 psi) including detergent then rinse thoroughly and allow to dry. Existing Sikalastic®-641 systems older than four days must be prepared with Sika Reactivation Primer as outlined above.

MIXING

Sikalastic®-641 is supplied ready for use. Before application, stir for a minimum of 1 minute using mixing paddle and drill or other suitable equipment to mix the liquid and all the coloured pigment until a uniform colour has been achieved. Over-stirring must be avoided to minimise air entrainment.

APPLICATION

Reference must be made to further documentation where applicable, such as relevant method statement, application manual and installation or working instructions.

General

Always begin application with detailing before installation of the main horizontal surfaces.

Primer

Pour the appropriate mixed primer onto the prepared substrate and apply by brush or appropriate roller. Ensure a continuous, pore free coat covers the substrate. Confirm primer waiting / overcoating time has been achieved before applying successive products. Refer to individual primer Product Data Sheet.

Base coat

Refer to the System Data Sheet or the System Method Statement.

Reinforcement

Refer to the System Data Sheet or the System Method Statement.

Top coat

Pour stirred Sikalastic®-641 onto the fully cured, reinforced base coat layer, and apply evenly by brush or short piled roller at the required consumption rate in 2 directions at right angles to each other. Confirm overcoating times before application. Refer to the System Data Sheet or the System Method Statement.

Ensure each application / coat is clean and dry before applying next coat.

Note: Material will dry on the surface in around 30 minutes depending on temperature and humidity conditions. Always maintain a wet edge and finish surface as work proceeds. Returning to re-work areas that are partially dried may damage the surface.