Caulk is a versatile material that is typically used to fill gaps and cracks around your home’s interior and exterior. The multitude of caulk formulas available means that you can find a caulk to suit your needs, all around your home. Caulking acts as a barrier, keeping air and moisture out, protecting your home from draught and water damage and prohibiting insect infestation. 

The prevention of draught throughout your home also helps to contribute to your energy efficiency. By insulating and waterproofing your space, it will require less energy to make your space warmer and cooler. The reduction in energy required, lowers your electrical power and energy usage, reducing the cost of your energy bill.

Choosing the right caulk

With an abundance of different brands and types of caulk in today’s market, it can be understandably overwhelming to decide which product you should choose to get the best results in your project. 

There are a few main factors to consider when deciding what caulk is right for your needs:

• The temperature range at the application site - Significant fluctuations in temperature can cause the seal to expand and contract, this changing movement can create cracks in the caulk if the formula is not flexible. This weakens the adhesion between the surfaces, which will degrade the caulk, meaning that it will have to be replaced and repaired more frequently.  

• The moisture level at the application site - Higher levels of moisture can reduce the adhesion between the surfaces, which may leave gaps in the seal. It is important in areas of higher moisture, to choose a caulk that contains silicone as opposed to an acrylic-latex formula. By not choosing a water-resistant formula, you are increasing the risk of water damage, insect infestation and mould growth as a weak adhesion between surfaces, means that the seal may not be air or watertight.

Different types of caulk

Acrylic Latex Caulk

• This is the most common type of caulk, a general purpose formula, that is paintable, and easy to clean with soap and water.

• It is best used indoors, in areas of low moisture, so is ideal for filling cracks and gaps around doors and window frames, trims and baseboards.

Butyl Rubber Caulk

• A quick curing formula that has a high degree of elasticity meaning that it is both water and temperature resistant.

• It is ideally used for door frames, skylights, drains and windows.

Polyurethane Caulk

• A multi-purpose product, that is extremely durable and is resistant to moisture, chemicals and corrosion.
• It is frequently used to soil pipes and ductwork, and repairing interior and exterior perimeters of frame openings and expansion joints.

Silicone Caulk

• As opposed to polyurethane caulk, silicone caulk is an inorganic product and so is UV and water resistant. It is valued for its elasticity which enables the caulk to withstand fluctuations in temperature.

• It is best used to seal bathtubs, showers, and other areas prone to high moisture.

Essential caulk tools

Here are some important tools that you will need when using caulk in order to get a neat, professional and long-lasting finish.

• Utility Knife
• Caulk - make sure this is the most suitable formula for your project
• Caulk Gun
• Masking Tape
• Clean Cloths
• Methylated Spirit
• Caulk Smoothing Tool
• Safety gloves
• Wire Brush
• Rubbing Alcohol

Step-by-step caulking guide

Before preparing to use caulk it is important to remove any old, existing caulk from the surfaces.

Removing Old Caulk

Old, existing caulk can be hard and difficult to remove. To make the removal of the caulk easier, you can soften the existing product.

To soften:

Water based formulas (e.g: latex) - Soak a clean cloth in hot water and place the cloth on the caulk for a few minutes to soften the caulk.

Silicone based formulas - Soak a clean cloth in a solvent such as: methylated spirit, white vinegar, acetone or a rubbing alcohol. Place the cloth over the caulk for a few hours, and allow it to soften.

When using solvents and chemicals it is important to always wear safety gloves to protect your skin and to make sure that the area you are working in is properly ventilated.

Removing Soft Caulk

Once the existing caulk has softened, use a utility knife to carefully cut away the existing caulk from the surface, making sure to not scratch the surface underneath. 

Prepare to Caulk

To ensure there is proper adhesion between the surfaces, and that the joints and seams are fully sealed, it is important to clean the surfaces prior to caulk application. 

For Exterior Surfaces -

• Use a wire brush to clean the surface, ridding it of any dirt, rust and mould. 

For Interior Surfaces -

• Use a damp, clean cloth to wash over the surface and remove any dirt and debris. Dry thoroughly.
• Take a mild cleaning detergent or some rubbing alcohol on a clean cloth and go over the area again to make sure it is cleaned properly. This will also work to degrease any non-porous surfaces prior to application.

Make sure all surfaces are thoroughly dry.

Apply Masking Tape

On interior projects, apply masking tape on either side of the join, leaving around a 3-5mm gap in the middle. It is important that you do not skip this step, as this will be beneficial in the clean-up of your project and the result as it will help you to get as clean, straight lines in your caulk as possible.

Loading the Caulk Gun

Begin by cutting the nozzle of the caulk gun at a 45° angle, it is advisable that you make the opening of the nozzle slightly smaller than the desired width, as this will aid a smoother application.

• Place the caulk cartridge into the caulk gun and squeeze the handle until a bead of caulk reaches the end of the nozzle.

You may want to test the flow of caulk onto a scrap piece of newspaper or a disposable paper towel.

Applying the Caulk

It is best when applying caulk to pull the caulk gun towards you, as pushing the caulk can create an uneven bead and create gaps in the seal.

• Hold the caulk gun at a 45° angle and using a consistent working speed, apply a thin bead of caulk to the joint. 

To stabilise the caulk gun, place one hand close to the nozzle for better control.

Smoothing the Caulk

For this it is best to use a caulk smoothing tool as this will provide you with the neatest finish however, you can also use a wet fingertip to ensure the bead is pushed into the joint.

• Make sure to dip your smoothing tool or fingertip in either rubbing alcohol, or water.
• Run either your finger or the tool over the freshly applied bead of caulk to smooth it and push the caulk between the join in the surfaces.

Cleaning Up

Removing the Masking Tape

The masking tape should be removed before the caulk begins to cure. It is advisable that you remove the tape by pulling the tape away from you at a 45° angle, as to try and not disrupt the freshly applied caulk bead.

Cleaning Up Any Excess Caulk

It is important that any excess caulk is cleaned up rather quickly. 

• Latex-based caulks, if uncured, can be removed with water.
• Silicone-based caulks should be cleaned up with solvents such as: rubbing alcohol or methylated spirit.
• Any caulk that has begun to cure or dry will likely have to be cut away.

Remember to always refer to your product’s manufacturing instructions for the recommended cleaning and removal instructions.

Common Caulk Mistakes to Avoid

• Failing to prepare and clean the surface properly - If any old caulk remains it must be fully removed before trying to lay a new bead, as otherwise it may not adhere properly. It is important that the surface you are applying the caulk to is fully cleaned from any dirt or debris as otherwise the caulk will not be as effective.

• Overcutting the caulk nozzle - The tapered end of the nozzle aids with the control of the application.  By cutting the end of the nozzle, slightly smaller than the opening you are trying to fill, you can use pressure and speed to control the width of the caulk bead. If the nozzle is cut too large, you may end up using excess caulk and making  a mess of the joint.

• Rushing the process - It is important to allow enough time for both caulk application and curing time. Taking time to apply the caulk will prevent you from using too much caulk and making a mess. Once the caulk has been applied, it is essential that you leave a significant period of time for the product to fully dry and cure, as to not disrupt the seal and enable it to set fully. If you require the job to be completed quickly, you should look to invest in a quick-drying formula.

• Not choosing the right caulk - It is essential to evaluate and research which caulk is most suitable for your project. If you are caulking an area exposed to high levels of moisture, you should be looking to use a silicone based product. If you are looking to paint over the caulk, you should make sure that the formula you are using is paintable. If the wrong caulk is used, you may not notice the issue straight away and it may take some time to transpire.

• Filling too large of a gap - If you have a sizable gap (larger than a ¼ inch), you will need to use some backer rods to bridge the gap and stop the caulk from shrinking. By just using caulk, you are at risk of the caulk shrinking and cracking when it cures or distributing unevenly in the drying process.

• Not using a caulking gun - While there are squeezy tubes available, using a caulk gun will not only make the application process easier but it will help you to achieve a much neater finish. 

Expert Advice For Caulk Maintenance 

Caulk maintenance is a fundamental part of home maintenance as caulking plays an essential role in the prevention of leaks and gaps within the home, which can greatly impact energy efficiency. 

Regular Inspections

Regularly inspecting your caulk for signs of damage, mould and discolouration can help to prevent the onset of water damage, airflow and insect infestation. By routinely checking on the condition of the caulk, you can easily fix the problem before it becomes more severe and results in the full removal and replacement of the caulk.

Cleaning the Surface Regularly

It is important to clean the surface both prior to caulk application and regularly afterwards to remove any bacteria, dirt and debris from the joins. Allowing a buildup on the surface of the caulk increases the risk of mould and mildew growth which will degrade the caulk and require you to replace it.