Wrimco Waterproofing                              Home  | Specification | Product | Project | Technical data A-Z | Contact us

Adhesive Membrane

Anti-root Membrane

Approved Applicators

Backing Rod

Drainage Cell

Drainage Sheet

Epoxy Adhesive

Epoxy Flooring

Flat Roof Membrane  

Foundation Membrane

Liquid Membrane

Membrane Protection

Product Application

Product Category

Retaining Wall

SBS Sheet Membrane

Torch on Membrane

Under Slab Membrane

Vapour Barriers

Waterproofing Primer


Waterproof Balcony Liquid Membrane Waterproof Bathroom liquid membrane Waterproof Retaining Wall Liquid Rubber Membrane How to waterproof a bathroom Waterproof Internal Wet Area Membrane Waterproof Tiled Balcony Clear Penetrating Sealer Trafficable liquid membrane UV Protection liquid membrane Waterproof Water Feature liquid membrane Hydro Pressure Resistant liquid membrane Waterproof Shower Recess liquid membrane Repair Roof Gutters liquid Membrane Waterproof Planter Box liquid membrane Waterproof Under Tiles Liquid Membrane Waterproof Water Tanks liquid membrane waterproof Flat Roof liquid membrane Waterproof fish pond liquid membrane Waterproof Swimming Pool  How to stop tiled deck leaking waterproof bathroom liquid membrane Waterproof Leaking Shower Tradesman Waterproof Leaking Balcony Liquid Membrane Waterproof Damp Basement Wall Liquid Membrane Crystoflex Max Cementetious waterproofing membrane Waterproof Under Screed Liquid Membrane Waterproof above screed liquid membrane How to waterproof a Planter Box How to waterproof a shower How to waterproof tiled balcony Waterproof Roofs with UV liquid membrane How to waterproof a metal roof Sikalastic 560 - Repair Bitumen membrane Roof How to waterproof a planter box Waterproof Flat roof liquid membrane Below Grade Membrane UV Resistant Polyurethane Membrane Waterproof leaking balcony liquid membrane waterproof damp basement wall liquid membrane Solutions to common waterproofing problems Maxseal Foundation Mapelastic Smart Membrane Polyurethane Membrane MasterSeal M210TIX Latex Rubber Liquid Membrane Waterproof wet basement wall liquid membrane Waterproof leaking Basement Tradesman Waterproof Building Contractors Waterproof Lift Pit Contractors Waterproof leaking Internal Wall tradesman Waterproof leaking deck tradesman waterproof leaking roof, gutters, balcony, car park tradesman Waterproof leaking Box Gutter Tradesmen Waterproof leaking External Wall tradesmen Waterproof Swimming Pool Contractors Waterproof Garage Roof Liquid Membrane Injection Drill Pump Vulkem 350/345/346 Ardex WPM 300 Epoxy - Stop Rising Damp Ardex WPM300 Waterproof Metal Roof Liquid Membrane Waterproof Leaking Under Tiles Liquid Membrane Repair Leaking Balcony, Flat Roof, Planter Box, Bathroom Waterproofer, waterproof Leaking Balcony, Flat Roof, Planter Box, Bathroom tradesman, handyman Waterproof exposed balcony liquid membrane Hydrostatic Pressure resistant Liquid Membrane Waterproof Box gutter liquid membrane Prevent Rising Damp Waterproofing Epoxy Waterproof leaking metal roof tradesman Waterproof Retaining Wall liquid membrane Waterproof Underground Walls liquid membrane Waterproof Internal, External Wall Liquid Membrane Waterproof Concrete Slab Liquid Membrane Waterproof Balcony Liquid Membrane Stop Leaking Shower Liquid Membrane How to repair a leaking fish pond Waterproof Wet Retaining Wall Liquid Membrane Waterproof Aluminium Roof Liquid Membrane How to waterproof a retaining wall How to waterproof a Retaining Wall Waterproof cement screed epoxy Vulkem 360NF Waterproof Car Park Liquid Membrane Waterproof Retaining Wall liquid membrane Waterproof Besser Block Wall Liquid Membrane How to fix leaking fish pond Waterproof Garage Roof Liquid Rubber Membrane Trafficable UV resistant liquid membrane Stop Basement Wall Leaking UV Resistant Polyurethane Liquid Membrane Waterproof water tanks for drinkable water Waterproof Commercial Roof, Balcony Contractors
Commercial Building Sheet Membrane Concrete Roof Sheet Membrane Waterproof Deck Sheet Membrane Entertainment building Waterproofing Membrane Waterproof Government Building Sheet Membrane Waterproof Hospital Building Sheet Membrane Waterproof Landmark Building Bitumen Membrane Waterproofing Planter Box Sheet Membrane Waterproof Plywood Roof Sheet Membrane Waterproof Residential Building Sheet Membrane Waterproof Roof Bitumen Sheet Membrane Waterproof Flat Roof Sheet Membrane Waterproof Retaining Wall Sheet Membrane Terrace waterproofing Sheet Membrane Waterproof University Building Sheet Membrane Wrimco Reference Waterproof Lift Pit Sheet Membrane Waterproof Car Park Roof Sheet Membrane Waterproof Concrete Slab Sheet Membrane Waterproof Concrete Roof Sheet Membrane Tanking Sheet Membrane Systems Vaucluse Waterproofing Project  Mosman Waterproofing Project Waterproofing Palm Beach Waterproofing Dover Height Waterproofing Darling Point Waterproofing Bellevue Hill waterproofing tradesman Under Concrete Slab Waterproofing Knowledge Base FAQ Waterproofing Product Waterproof Leaking Swimming pool tradesman Waterproof Leaking Garage Roof tradesman Repair SBS, APP Sheet Membrane Waterproof Concrete Slab Sheet Membrane Waterproof Leaking Garage Roof Liquid Rubber Membrane Waterproof Leaking Metal Roof Liquid Rubber Membrane Polyurethane Modified Acrylic Liquid Rubber Membrane Waterproof Balustrade Sheet Membrane Waterproof Commercial Building Project Bitumen Sheet Membrane Waterproofing Membrane Protection Drainage Cell Closed Cell Backing Rod Repair Crack Joints Closed cell backer rod Expansion joint backing rod Backing Rod waterproof leaking laundry tradesman Repair Leaking underground basement wall Waterproofer Waterproof leaking planter box tradesman Waterproof Leaking Shower Tradesman Waterproof Planter Box Tradesman Waterproof Leaking Box Gutter Tradesman Waterproof Leaking Balcony Tradesman Waterproof Leaking Fish Pond Tradesman Repair Construction Building Contractors

Sikasil WS-305 CN Silicone:  


Sikasil WS-305 CN is a neutral-curing silicone sealant with a high movement capability and excellent adhesion to a wide range of substrates.

Sikasil WS-305 CN is manufactured in accordance with ISO 9001 quality assurance system and the responsible care program.


Product Benefits


Meets requirements of ISO 11600 25 LM F & G, ASTM C 920 (class 50), TT-S00230C, TT-S001543A

Outstanding UV and weathering resistance

Adheres well to many substrates including glass, metals, coated and painted metals, plastics and wood


Areas of Application


Sikasil WS-305 CN can be used for weatherproofing and sealing applications where durability under severe conditions is required.

Sikasil WS-305 CN is particularly suited as a weather seal for curtain walling and windows.

This product is suitable for professional experienced users only. Tests with actual substrates and conditions have to be performed to ensure adhesion and material compatibility.


Cure Mechanism


Sikasil WS-305 CN cures by reaction with atmospheric moisture. The reaction thus starts at the surface and proceeds to the core of the joint. The curing speed depends on the relative humidity and the temperature (see diagram 1 below). Heating above 50 C to speed up the vulcanization is not advisable as it may lead to bubble formation. At low temperatures the water content of the air is lower and the curing reaction proceeds more slowly.

Diagram 1:Curing speed 1C-Sikasil


Application Limits


Most Sikasil WS, FS, SG, IG, WT, AS and other engineering silicone sealants manufactured by Sika are compatible with each other.Sikasil WS and FS sealants are compatible with SikaGlaze IG sealants. All other sealants have to be approved by Sika before using them in combination with Sikasil WS-305 CN. Where two or more different reactive sealants are used, allow the first to cure completely before applying the next.

Do not use Sikasil WS-305 CN on pre-stressed polyacrylate and polycarbonate elements as it may cause environmental stress cracking (crazing).

The compatibility of gaskets, backer rods and other accessory materials with Sikasil WS-305 CN must be tested in advance.

Joints deeper than 15 mm should be avoided.

The above information is offered for general guidance only. Advice on specific applications will be given on request.


Method of Application


Surface preparation


Surfaces must be clean, dry and free from oil, grease and dust.

Advice on specific applications and surface pretreatment methods is available from the Technical Service Department.




After suitable joint and substrate preparation, Sikasil WS-305 CN is gunned into place. Joints must be properly dimensioned as changes are no longer possible after construction. For optimum performance the joint width should be designed according to the movement capability of the sealant based on the actual expected movement. The minimum joint depth is 6 mm and a width / depth ratio of 2:1 must be respected. For backfilling it is recommended to use closed cell, sealant compatible foam backer rods e.g. high resilience polyethylene foam rod. If joints are too shallow for backing material to be employed, we recommend using a polyethylene tape. This acts as a release film (bond breaker), allowing the joint to move and the silicone to stretch freely.

For more information please contact our Technical Department.


Tooling and finishing


Tooling and finishing must be carried out within the skin time of the adhesive.

When tooling freshly applied Sikasil WS-305 CN press the adhesive to the joint flanks to get a good wetting of the bonding surface.




Uncured Sikasil WS-305 CN may be removed from tools and equipment with Sika Remover-208 or another suitable solvent. Once cured, the material can only be removed mechanically.

Hands and exposed skin should be washed immediately using Sika Handclean Towel or a suitable industrial hand cleaner and water. Do not use solvents.




Sikasil WS-305 CN cannot be overpainted.


Further Information


Copies of the following publications are available on request:

Material Safety Data Sheet


Packaging Information


300 ml


600 ml


Chemical base

1-C silicone

Colour (CQP1 001-1)

300 ml cartridge: Black, Grey, Transparent, White

600 ml sausage: Black

Cure mechanism


Cure type


Density (uncured) (CQP 006-4) transparent

all other colours

1.03 kg/l approx.

1.49 kg/l approx.

Non-sag properties (CQP 061-4 / ISO 7390)

< 2 mm approx.

Application temperature

5 - 40 C

Skin time2 (CQP 019-2)

35 min. approx.

Tack-free time2 (CQP 019-1)

180 min. approx.

Curing speed (CQP 049-1)

See diagram 1

Shore A-hardness (CQP 023-1/ISO 868)

15 approx.

Tensile strength (CQP 036-1/ISO 37)

1.0 N/mm2 approx.

Elongation at break (CQP 036-1/ISO 37)

900% approx.

Tear propagation resistance (CQP 045-1/ISO 34)

4 N/mm approx.

100% modulus (CQP 036-1/ISO 37)

0.4 N/mm2 approx.

Movement accommodation capability (ASTM C 719)

+/- 50%

Thermal resistance (CQP 513-1)
Short term
4 hours
1 hour


180 C approx.

200 C approx.

220 C approx.

Service temperature

-40 to 150 C approx.

Shelf life (storage below 25 C) (CQP 016-1)

12 months


1) CQP = Corporate Quality Procedure               2) 23 C (73 F) / 50% r.h.



Waterproofing FAQ

Membrane Protection Board

Waterproofing Coating

Waterproof Drainage Sheet

Waterproofing Primer

Repair and Maintenance