How to seal and waterproof construction joints - using polyurethane (PU) sealant and bituminus waterproof tape

Construction Joints are different from plaster cracks in many ways. 

. Joints are usually 2mm to 19mm wide, plaster cracks are usually 0.5-2mm wide.
. Joints usually have movements in them such as structural movements, movement due to unequal expansion of adjoining substrates etc. Plaster cracks are usually static.
. Joints can be sealed using permanently flexible compounds, whereas plaster cracks can be filled using materials that become rigid upon curing.

As a result, joints have to be treated differently from cracks. Here is one of the methods that can be used to seal and waterproof joints.

Materials Required 

. Polyurethane sealant

. 100mm wide Bituminous Tape

. Mason's Kit

Application

. Clean out the joints using a wire brush and remove the dust and debris using a dusting brush.

. Using a gun-grade Polyurethane(PU) Sealant, slowly squeeze out the sealant and move along the joint forming a continuous bead. In case of a break in the bead, overlap the new bead with the old for about an inch and continue. Allow the sealant to cure according to the manufacturer's datasheet.

. After the sealant has completely cured, check and fill any gaps.

. Paste the bituminous sealing tape along the joint sealed using the PU sealant, using a rubber roller giving good pressure. In case a rubber roller is not available, a bundle of cotton waste can also be used to apply pressure. At joints in the tape, ensure overlap of about 50mm. 

. If required, an acrylic topcoat can be applied on the tape by first priming the surface using a latex based primer. The topcoat must be spread about 50mm either side of the tape.

No more leaky joints!

Practical Scenarios

The above method can be used to seal joints such as

 . Parapet wall and terrace slab joints.
 . Joints between walls of adjoining buildings.
 . Skylight joints
 . Window-wall joints etc.

Products Available

. Sikaflex PU Sealant

Sikaflex Construction Sealant is a moisture-cured, 1-component, polyurethane-based,
non-sag elastomeric sealant.

Where to Use 
> Designed for all types of joints where maximum depth of sealant will not exceed 1/2 in.
> Suitable for vertical or horizontal joints; readily placeable at 40°F (4°C). 
> Has many applications as an elastic sealant between materials with dissimilar coefficients of expansion.

Ideal for:
> Weatherproofing of joints between brickwork, blockwork, masonry, wood and concrete
or metal frames.
> Joints in walls, floors, balconies, around window or door frames.
> Expansion joints.
> Roofing.
 
Advantages 
> High elasticity – cures to a tough, durable, flexible consistency with exceptional cut and tear-resistance.
> Stress relaxation.
> Excellent adhesion – bonds to most construction materials without a primer.
> Excellent resistance to aging, weathering.
> Non-staining.
> Urethane-based; suggested by EPA for radon reduction.
> Paintable with water-, oil- and rubber-based paints.
> Capable of ±25% joint movement.
> NSF Certified to NSF/ANSI Standard 61 for potable water contact.

. Sika Multiseal Tape

Self-adhesive, rubber modified, bituminous sealing tape, one side laminated with
aluminium foil.

Sealing and repairing against water ingress and draughts in:

• Roofs including sheet metal work
• Building cracks
• Bituminous felts and other types of roofing sheet
• Joints of wall to wall and floor to wall in sunken slab
• Joints of AC cement sheet with wall
• Around pipe penetrations in walls/concrete

Characteristics / Advantages

• Very easy to apply
• Very economical
• Good adhesion to many substrates
• Weather-proof
• Self-adhesive
• UV-resistant
• Can be over-painted
• Can be applied at low temperatures

In Store now @
Shree Venkateshwara Traders
#712, Modi Hospital Road, WOC,
Mahalaxmipuram, Bangalore 560086

ph: 9036092531
email : venkateshwara.traders@gmail.com