Understanding Chimney Waterproofing

When was the last time you added a waterproof coating to your chimney? If it’s been more than five years, you’re probably overdue. If you’ve never done it, it’s time to start thinking about this, as it can prevent thousands of dollars in damage to your home.

Most homeowners don’t think about their chimney until there’s visible damage. It makes sense, considering how infrequently most people take a close look at their rooftop. Unless you’re climbing up on the roof for some reason, your chimney is likely to get neglected.

Because chimneys sit above the roof line, they’re exposed to harsh conditions all year round, including storms, fallen trees and limbs, snow, rain, and plenty of moisture. Water damage is the primary cause for deterioration, so it’s important to do everything you can to safeguard your chimney.

Waterproofing your chimney now can protect it for many years to come and save you thousands of dollars in repairs later on from would-be damage. If you don’t take the time to protect it now, you’ll have expensive problems down the road. Here’s what you need to know.

How Does Moisture Cause Damage to My Chimney?

The primary (and often invisible) threat to your chimney is moisture that seeps into the brick and mortar joints and accumulates over time. You won’t know there’s a problem until there’s visible damage, but unless you’ve waterproofed your chimney in the last five years, you probably already have a moisture problem.

Here’s how it works. A brick and mortar chimney is designed to be a virtually impenetrable structure, but water will seep in unless you waterproof your brickwork. Brick is porous and will absorb water. When water accumulates, it compromises the integrity of the entire structure because of the freeze/thaw cycle. As the weather changes, the water inside your bricks will expand and contract, causing some bricks to become displaced and weakening the mortar joints.

How Can I Tell If My Chimney Is Already Water Damaged?

To know if water damage is present, there are some telltale signs to watch out for. The first sign of damage is the most obvious—a leak. If your chimney is leaking water, it’s probably coming in through a compromised joint.

Other signs to look for include cracked mortar and broken, missing, or displaced bricks. If any of these signs are present, your best course of action is to contact a professional to inspect your chimney and advise you on your options.

Chimney waterproofing will prevent this type of water damage, but it needs to be done correctly and as soon as possible. If you wait too long, you could experience damage that will limit options until you have your chimney repaired. For example, you might need fireplace tuckpointing before you can apply waterproofing.

A chimney can’t keep out all water, and as it deteriorates, it becomes even more vulnerable to moisture damage. The best way to protect your chimney is to apply a waterproof sealant.

Here’s Why

Chimney Waterproofing Tips & Tricks

When it’s time to protect your chimney from moisture, you can do it yourself or call a pro. It’s easier to hire out the task to a professional, plus it’s less dangerous. However, it’s not hard if you feel comfortable getting up onto the roof.

1. Apply a chimney sealant.

The best way to keep moisture out is to use a chimney sealant. Some types of sealants, like siloxane, will cover up your brickwork, but protecting your chimney is worth more than aesthetic appeal. However, sealant is best for brickwork you know is free from existing water damage. You don’t want to trap any water inside of your brickwork.

Sealing your chimney is fairly simple. First, decide whether you want to use a liquid sealant or something dense, like silane or siloxane. For liquid sealants, choose your product and apply a single coat with a low-pressure pump garden sprayer. Ideally, you want the brick surface to stay wet for at least a few minutes before it all gets absorbed into the brick. In addition to applying a waterproof coating, you’ll need to seal the crown where it meets the brick at the base of the chimney.

If your chimney is made of concrete, use a concrete sealer and follow the manufacturer’s instructions.

2. Use a breathable water repellent for existing damage.

Although waterproofing your chimney with a sealant is great for new chimneys, avoid using a sealant if you already have water damage. Applying a sealant is a preventive measure, not a repair, and it can make existing damage worse.

As your chimney heats up and cools down with the changes in weather, the freeze/thaw cycle will naturally create moisture, but most of it should escape through the bricks on its own. Using a sealer will trap that moisture in your chimney and cause spalling. That’s when the brick faces pop off and if that happens, you’ll need some serious chimney repair.

If you already have damage, don’t seal your chimney completely—you want your chimney to repel additional water but still remain breathable. If you’re going to waterproof a damaged chimney, make sure to use a breathable water repellent. If you want to seal your chimney, have it restored first.

3. Get your chimney repaired first.

It’s possible that your chimney is past the point of simply being waterproofed to be protected. If you already have damage, focus on repairing that first. For example, you might need tuckpointing, brick replacement, or you may require having part of your chimney repaired or rebuilt. These solutions, especially tuckpointing a chimney, are best left to a pro.

If you attempt to waterproof your chimney before making the necessary repairs, you risk sealing in moisture that’s already trapped in the bricks. This subjects your masonry to damage as the weather changes.

4. Hire a professional.

When it’s time to waterproof your chimney, you’ll get the best results by hiring a professional for the job. At Approved Home Improvements, our chimney experts would love to help with all of your waterproofing needs.

St. Louis’s Top Choice for Chimney Waterproofing, Tuckpointing, and More

Whether your chimney is ready for a waterproof coating or you need repairs first, we’ll do it all. We can repair, rebuild, waterproof, and even clean your chimney to help keep it in good shape. Whatever you need, contact us today for a free quote.