How To Block Up A Chimney

Whether you're looking to improve energy efficiency, enhance room aesthetics, or simply render an unused chimney redundant, proper chimney blocking is essential.

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We understand that blocking up a chimney can be a daunting task for homeowners. Whether you’re looking to improve energy efficiency, enhance room aesthetics, or simply render an unused chimney redundant, proper chimney blocking is essential. In this blog post, we will provide you with expert advice and step-by-step guidance on how to best block up a chimney in your home.

Assess the chimney’s usage and condition:

Before you begin blocking up a chimney, it’s important to assess its usage and condition. Consider whether you plan to use the chimney in the future or if it will remain unused. Additionally, inspect the chimney for any signs of damage, such as cracks or structural issues. If you suspect any problems, we recommend consulting a professional chimney specialist or surveyor to ensure safety and structural integrity.

Choose the right blocking method:

There are several methods to effectively block up a chimney, each with its own advantages and considerations. Here are three commonly used techniques:

a. Chimney Balloon: A chimney balloon is an inflatable device made of durable materials that is inserted into the chimney flue and inflated to block airflow. This method is relatively simple and reversible, making it a popular choice for temporary blocking.

b. Chimney Cap and Damper: Installing a chimney cap and damper involves fitting a metal cap over the chimney’s top and attaching a damper to control airflow. This method provides better insulation and prevents drafts while still allowing future use of the chimney if desired.

c. Masonry Blocking: This method involves permanently sealing the chimney flue with masonry materials, such as bricks or concrete. Masonry blocking provides a long-lasting solution but may require professional assistance, especially if structural modifications are necessary.

Gather the necessary tools and materials:

Depending on the chosen blocking method, gather the required tools and materials. This may include chimney balloons, chimney caps, dampers, insulation materials, masonry tools (if applicable), safety goggles, gloves, and a ladder.

Prepare the chimney:

Start by cleaning the chimney thoroughly to remove any debris, soot, or creosote buildup. This step ensures a clean surface for effective blocking and minimises potential odours or health hazards.

Implement the chosen blocking method:

Follow the specific instructions for your chosen blocking method, whether it’s installing a chimney balloon, fitting a cap and damper, or undertaking masonry blocking. Ensure you carefully read and understand the manufacturer’s guidelines or seek professional advice if necessary.

Consider ventilation and condensation:

When blocking up a chimney, it’s essential to consider ventilation and condensation. Poor ventilation can lead to dampness and mould growth, so it’s crucial to provide alternative ventilation options in the room, such as air bricks or trickle vents. Additionally, if condensation becomes an issue, consider installing a dehumidifier to maintain optimal humidity levels.

Safety precautions:

While blocking up a chimney may seem like a simple task, it’s important to prioritise safety. Use appropriate personal protective equipment (PPE), such as safety goggles and gloves, and ensure you follow proper ladder safety practices.


Blocking up a chimney can provide various benefits, including improved energy efficiency and enhanced aesthetics. However, it’s crucial to approach the task with caution and follow the recommended techniques and safety measures. If you’re unsure about any aspect of the process, it’s always wise to consult a professional surveyor or chimney specialist who can provide expert advice tailored to your specific needs.

At Winfields Chartered Surveyors, we are committed to helping homeowners make informed decisions about their properties. By following our comprehensive guide, you can confidently embark on the journey, and if you need a survey or advice, please contact us today.

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