Sealants - Build Your Skills Leaflet 205

Sealants do two different jobs, depending on whether they're a liquid or a paste (sometimes known as a mastic). Liquid sealants are used mainly to waterproof surfaces, while mastics make waterproof or weatherproof joints between adjacent - and often different - materials or surfaces.
Liquid sealants include waterproofers for flat roofs, liquid dampproof membranes for walls and floors, interior damp sealants and waterproofers for external walls, drives and patios.

Sealants may be based on traditional ingredients such as bitumen, or may contain manmade chemicals such as water-repelling silicones.
Mastic sealants and putties are sold in tubs, or in cartridges to fit a standard trigger-operated cartridge gun. Different product types are used for jobs as diverse as waterproofing gutter joints, sealing around door and window frames or making waterproof joints between baths or shower trays and adjacent walls.

Wickes Good Idea Leaflet - Sealants is packed with DIY help & advice on using liquid sealants and mastics including waterproofer for roofs.

Wickes Good Idea Leaflet - Sealants is packed with DIY help & advice on using liquid sealants, mastics and applying with cartridge guns

Using Sealants

Liquid Sealants

Liquid sealants for roofs and masonry are usually brushed on, although some masonry sealants can be sprayed so long as you can avoid overspray by masking or shielding adjacent surfaces. [PIC 1]
Surfaces to be treated should be clean, free from loose surface material and dry, unless the manufacturer's instructions say otherwise. If liquid sealants are being used indoors, make sure there is adequate ventilation.
If you are applying bituminous paints or waterproofers, it is a good idea to use old brushes that can be thrown away once the job is completed. It is very difficult to remove these products from brushes satisfactorily.

Mastic Sealants

Mastic sealants are usually applied as a toothpaste-like bead along a joint between adjacent surfaces. The surfaces should be clean, dry and free from dust and loose material.
Cartridge sealants have remarkable gap-filling properties, but cannot do the impossible. Deep gaps may need packing with inert material such as aerosol foam filler or glass fibre loft insulation blanket before the gap is filled with sealant. [PIC 2]
Silicone sealants can irritate the skin, and care should be taken when using them not to transfer traces of sealant to the eyes.
Remember to remove the nozzle and cut off the seal on a new cartridge tube before starting to use the sealant.
Decide what size of sealant bead you want, then use a sharp knife to make a 45° cut through the nozzle at the required diameter.
Fit the cartridge into the gun and squeeze the trigger to force the piston up inside the tube. To stop the flow of sealant, release the small metal tab through which the piston shaft passes. [PIC 3]
Store part-used cartridges horizontally in a frost-free environment.

Types of Sealants

There is now a wide range of liquid and mastic sealants available for all sorts of waterproofing and repair jobs. Make sure you select the correct type of product for the job in hand, and always read the manufacturer's instructions and safety advice carefully before using it.

Liquid Sealants

Flat roofs don't last for ever, and can eventually develop porous patches that are difficult to detect. They are also prone to localised blistering and cracking. You can tackle porous felt by giving it a coat or two of Wickes' liquid bitumen-based Waterproofer for Roofs, and repair blisters and cracks with Roof & Gutter Sealant, a tub mastic which you simply trowel into place.

If rising or penetrating damp is your problem, Wickes has two damp sealants you can turn to. The first is Liquid Dampproof Membrane, a heavy-duty coating for floors and basement walls. The second is Interior Damp Sealant, which will stop problems such as condensation in disused flues from affecting your decorations.

When it comes to keeping masonry dry, choose the product to match the application. Water Seal will waterproof walls, Drive Seal will keep block paver drives looking good and Paving & Patio Seal will do the same for light-traffic surfaces.

With all these products, check the coverage on the container before buying, to ensure that you have enough to complete the job.

Cartridge Sealants

There's an ever-increasing range of different sealants available in cartridge form. Indoors, two of the most useful are Decorator's Filler and Bath & Kitchen Seal. The former is an acrylic-based filler that's ideal for filling persistent gaps and cracks - along skirting boards, round door architraves and into wall/ceiling angles. The latter is a white or clear silicone sealant that's perfect for waterproofing around sinks, baths and shower trays. Its flexibility makes it ideal for use along the rear edge of kitchen worktops too, where any slight movement of the units below can open up a gap between the worktop and tiled walls.

Outdoors, the most widely used product is probably Outdoor Frame Sealant, which as its name implies seals the joint between door and window frames and the surrounding masonry. It's available in white, brown and natural shades to match your colour scheme. There's also a special version formulated for use with PVCu windows. And for high performance in exposed areas, Wickes' Ultimate Sealant is the answer. It can also be used as an adhesive, and can be overpainted once it has skinned over.

When it comes to glazing, you can choose between Glazier's Putty for installing single panes and Double Glazing Sealant for new glazing units (note that this product is not recommended for use with PVCu windows, however).

Up on the roof, Roof & Gutter sealant will tackle cracks and tears in roofing felt, and deal with cracked or leaking gutters and joints too.

Lastly, there's a clear All Weather Sealant that is ideal for many other general purpose sealing tasks - waterproofing around the base of outside light fittings, for example.

Using Masking Tape

Outdoors, applying sealant neatly is not a high priority. So long as the bead is continuous and is well bonded to both surfaces, it will do its job perfectly. But indoors you'll want sealant beads to look neat and unobtrusive, especially around bathroom fittings and along the rear edge of kitchen worktops. The secret of success is to use masking tape. Stick it to both surfaces, 2 to 3mm from the internal angle. Then cut the cartridge nozzle at a 45° angle to give a bead that's just wide enough to fill the angle between the two tape edges.

To start the flow of sealant, apply gentle pressure by squeezing the trigger. As soon as the sealant appears at the tip of the nozzle, place it in the angle with the nozzle held at 45° to the wall. Push it along the angle, allowing the nozzle to shape the sealant bead into a neat concave curve. Leave it to skin over for a while, then peel off the masking tape.

Wickes Good Idea Leaflet - Sealants is packed with DIY help & advice on using liquid sealants, mastics and using masking tape to apply.

1. Stick masking tape along both sides of the angle you want to seal.

Wickes Good Idea Leaflet - Sealants is packed with DIY help & advice on using liquid sealants, mastics and using masking tape and cartridge guns to apply.

2. Push the nozzle along the join so its underside forms the sealant bead into a concave shape.

3. When the sealant has skinned over, peel off the tape to leave a perfectly formed bead.

Problem Solver

Problem The inside of a garage wall becomes very damp in wet weather: Wickes Solution Treat the outside of the brickwork with a couple of coats of Wickes Water Seal to prevent further water penetration.
Problem Rainwater drips from several joints on an old cast iron rainwater system.: Wickes Solution Clean the area of the gutter around the joints with a wire brush. Then use Wickes Roof & Gutter Sealant to waterproof the joints.
Problem It's very hard to extrude the sealant from a newly-bought cartridge.: Wickes Solution If the cartridge is very cold, the sealant will not be fluid enough to extrude. Store cartridges at room temperature before use, and thaw out cold cartridges by immersing them in warm water for a short while.
Problem The sealant flow is difficult to control, and carries on even when the gun trigger is released.: Wickes Solution Apply steady and even pressure to the trigger to keep the sealant flowing steadily from the nozzle. To stop the flow, release the small metal tab through which the piston shaft passes, and set the gun down where any slight seepage of sealant that may occur will not mark surfaces.
Problem The sealant has set hard in the nozzle of a partly-used cartridge.: Wickes Solution Unscrew the nozzle and insert a small screwdriver or similar tool into the narrow end to push out the hardened plug of sealant.