Roof Leak Repair Sealant Guide

Many consumers who are faced with roof leaks will turn to purchase some form of roof sealant product from their local hardware retailer, as the first line of defense to get some relief from their peril.

Although the long-term leak repair result is often best administered by a licensed and qualified roofing contractor; there are particular sealant products which can provide temporary relief, and or are used as components of a comprehensive repair by professionals.

There are a multitude of brands of products, and an array of sealant products themselves. This no doubt can create confusion for the purchaser of such items.

What Are The Different Types Of Roof Sealant?

First to understand is that where caulking is concerned; there are essentially five major types of caulking. Acrylic based caulking and latex based caulking. The third variety is asphalt based caulking. The remaining caulking varieties include silicone and butyl caulking.

All caulking varieties are designed for particular applications. In some instances, different compositions of caulking may be used for the same purpose.

Silicone Based Caulking

As an example; silicone caulk is traditionally used for bathroom applications, and where water contact may be an issue. Silicone can also be used around windows and doors, and is commonly used for sealing joints of aluminum gutters.

Acrylic Based Caulking

For caulking or re-caulking of metal flashing details on roofs; it is suggested to use an acrylic based caulking, for a variety of reasons. The product remains flexible over time, and is available in a variety of colours, and is proven to weather well in light of temperature change; from hot to cold weather variations. Historically, asphalt based caulking has been used to seal metal flashings. Such caulking is prone to dry out more quickly than acrylic based caulks however.

Acrylic caulking can be tougher to work with however, as attempting to tool a neat bead, similar to working with silicone; can be easy to smear when using a finger or caulking tool.

Latex Based Caulking

Latex based caulking  (typically used for sealing gaps in base boards or mouldings); is easier to work with, as wetting down a finger or caulking tool, provides one the ability to provide a smooth clean bead along a given surface.

How to Caulk?

When attempting any type of caulking work, it can be helpful to practice on a piece of cardboard or scrap wood piece to become comfortable with the feel of the caulking gun. The most important first step is to insure that surfaces to be caulked are clean and free of debris and dirt. For gaps that are more than a quarter of an inch; it is best to install a foam backer rod, which serves to fill voids, and provides a proper base for the caulking to be properly adhered.

When using a caulking gun, apply even pressure, and cut the tip of the caulking tube on an angle to make it easier to apply a neat contour to the application.

Also be sure that metal flashings are properly secured to the underlying surface, before attempting any caulking work.

A helpful tip is to use painters tape along both sides of the intended caulking line; before applying sealant. Once the applied caulk has tacked up or cured; one can carefully remove the tape, resulting in a neater finished appearance.

Flat Roof Leaks

For leaks which present themselves on flat roofs; there are several coating products which can be applied as temporary patch materials. Some products are even suitable to be applied on a wet roof surface.

Beware that certain solvent based products such as those found in most asphalt based caulking or coatings; will actually serve to damage some forms of flat roofing material; such as modified bitumen membranes.

Common failure points on modified bitumen membrane flat roofs, include seams between the rolls, and protrusions through the roof like pipes, stacks, conduits, etc. Roof appliances such as chimneys, skylights, drains, and transition details like doorways, are common leak areas.

Step one is to examine the area carefully by first removing any excess water. Check that roof drains or associated gutters are not blocked. If there is a large volume of water on a flat roof and it has an internal drain ( like a bath tub); it is often a good idea to put a broom shaft or pipe into the drain bowl, so that any exiting water does not overwhelm the drain; resulting in a burst pipe below the roof grade. Obviously, ensure that what is inserted in the drain cannot wash down into the drain itself. A corn broom is a handy tool for such purposes.

Once excess water has been removed; sweep the areas clean of debris. Examine any seams in the material carefully to spot any breaches in the seams or “fish mouths” which can be representative of water entry points.

Roofer’s Tape

As a temporary measure; one can purchase roofer’s tape (usually about 6” wide), coming in the form of a roll. Primer the surface using modified bitumen liquid coating, applied with a brush, and then apply the roofing tape over the affected seam.

Peel And Stick Modified Bitumen Rolls

For larger areas or splits in the membrane such as in the field of the roof; there are peel and stick modified bitumen rolls which can be purchased from most building suppliers. Cut an appropriate sized piece of the self adhering membrane, then using tin snips; cut rounded edges on all four corners of the patch material (sharp corners may be prone to lift with ice and snow), and rounded corners will help divert water. Using the bitumen primer liquid, coat the area to be repaired and allow to tack up.

Next, apply the mod-bit membrane patch over the damaged area. Be sure to broom out the membrane patch so that it adheres properly.

Perimeters of the patch may also be caulked using bituminous caulk available in tubes.

On tar and gravel flat roofs; finding leak origins can be trickier for the novice. Particularly if the roof is very large; it can feel like trying to find a needle in a haystack.

If one can identify an obvious split or blister on the surface of the roof; such items can be easily patched.

The key to a successful patch is in preparing the surface by scraping back all loose gravel well away from the repair area. Using a hammer; bang the repair area to loosen further gravel which may be embedded in the tar, and clean away. Next, take a wire brush and scrub the area to further loosen debris dirt and gravel. A spade can be useful to scrape back and forth to remove as much embedded gravel as possible. Cutaway any loose felts using a utility knife, and or split open any blisters protruding from the roof.

Clean, and clean again the repair area until you can be confident that the tar surface is exposed as best as possible. It is important to get the area as clean as possible, to allow repair materials to adhere to the existing roof.

Coat the cleaned repair area(s) using a bituminous primer, which can be brush or roller applied. Allow such material to tack up. Using mesh tape, cover over the split seam area. The next step is to apply two liberal coatings of liquid rubber coating. Allow each coating to cure up somewhat, before applying a secondary coating. Many liquid rubber products can be applied on damp surfaced roofs and will stick. It is important to look for this quality when purchasing any such products.

For minor repairs, this technique may hold one until such time as comprehensive repairs may be completed by a qualified roofing contractor. If a flat roof is not too large; it may be useful to coat the whole roof surface in liquid rubber using a roller; which may help insure that the actual leak source gets caught.

Elastomeric Coating

Elastomeric coatings are also used on flat roofs to help extend the life-cycle of flat roof assemblies and to provide a measure of UV resistance; as many of the coatings are white or silver to reflect the sun’s rays. Such products are fluid coatings which can be applied by roller or sprayer. Such coatings are often used on low slope metal roofs to help extend the life or rejuvenate rusting panels. It is important to follow manufacturer instructions with regard to preparing the roof surface for a coating material.

Note that in spite of certain product manufacturer claims; a coating product may not be a solution that is equivalent to having a proper water-proofing job completed by a qualified roofing contractor.

Such products as dymonic and dymeric caulks (acrylic based) are used for metal to glass transitions; such as with glass curtain walls or solariums, and windows that have aluminum frames meeting an alternative surface like concrete or wood.

Such caulk is also commonly specified for use in control joints, for concrete panels, found on certain commercial and highrise buildings. Usually, every ten years or so; such buildings require restoration of exterior sealants.

The process usually involves cleaning out any existing deficient caulking, cleaning the adjacent surfaces using appropriate cleaners; then installing a new backer rod of an appropriate thickness, Finally the new caulking can be applied and tooled to a neat finish. On highrise structures, much of the work must be carried out using swing stages or sending technicians down the sides of a building on a bosun’s chair.

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