To permanently close a fireplace, you need to seal it at both the top (the chimney) and the bottom (the fireplace opening) to stop drafts, moisture, and pests. It is critical to address both ends to prevent condensation and moisture buildup in the brickwork.
Permanently closing a chimney involves: Installing a chimney cap at the top to prevent water and debris. Sealing the damper and flue with insulation. Boarding up the fireplace or finishing it with drywall or decorative materials.
Sealing a fireplace from the inside can stop expensive drafts and heat loss. The best methods range from quick DIY fixes to sturdy block-offs. Choose the solution that fits your budget and whether you plan to use the fireplace again in the future.
Chimney capping is one of the ways you can deal with the challenges of an unused chimney. You can block the top of your chimney using a flue ventilator or chimney cap with mesh, leaving space for chimney ventilation.
Yes, you can block up a fireplace. However, doing it safely requires careful planning to prevent moisture buildup, dampness, and poor air circulation in your home.
Closing a fireplace correctly depends on whether you are doing it temporarily (between uses) or permanently (for a disused chimney). The most basic method is to fully close the flue damper using the lever or knob, but only after the fire is completely out and no glowing embers remain.
You can fill in the fireplace with thermalite blocks and bricks and then plaster over. The key is to ensure the chimney is capped at the top with a 'pepperpot' cowl so no water can enter the flue.
The absolute cheapest and easiest DIY method is using an old pillow wrapped securely in a heavy-duty trash bag, which you wedge up into the flue. Alternatively, you can buy a dedicated inflatable chimney balloon for about $25 to $40. Both methods stop drafts while leaving enough airflow to prevent moisture buildup.
However, if there is no ventilation in the upper half of the chimney, this should not be done, as internal condensation may occur, leading to dampness and mould.
The "7 Times Rule" is a safety and building code standard stating that the cross-sectional area of a masonry chimney must not exceed 7 times the area of the smallest connected appliance vent pipe (e.g., a gas water heater or furnace draft hood). If the chimney is too large, the exhaust gases cool too quickly, causing draft failure and condensation that damages the masonry.
How to block up a fireplace
Yes, mice frequently go down chimneys. Because they are excellent climbers, they can easily scale the exterior brick or masonry of a house and slip into the flue. Once inside, they may nest in the flue or climb all the way down into your fireplace.
People are getting rid of traditional fireplaces primarily because they are terribly inefficient at heating homes, require constant maintenance and hauling of wood, and pose significant indoor air quality and insurance liability concerns.
To permanently seal a chimney, clean and inspect it first. Then, install a weatherproof chimney cap and use a breathable sealant to close off the flue. Inside, use insulation and a fireplace plug to prevent heat loss and air leaks.
If you recently bought your home, haven't used the fireplace in years, or aren't sure when the last inspection was—do not light a fire. Because: Creosote doesn't disappear. Structural cracks don't fix themselves.
Unused chimneys not only waste a lot of heat, they also pose a potential damp problem as well as being a cause of smoking fireplaces and stoves. You should cap any unused chimneys with a flue ventilator.
Professional roofers possess extensive experience with chimney-related repairs that directly impact roof integrity and weatherproofing systems. Their expertise covers external chimney components including flashing replacement, crown repairs, and addressing problematic areas where the chimney penetrates the roofline.
So if you've got an open chimney, then it is definitely worth draught-proofing it this winter (between fires if you're actively using your fireplaces). If the outlay for a Chimney Sheep® seems like too much of a stretch at the moment, you can use an old pillow or bin bag stuffed with newspaper as an alternative.
Both the Flueblocker and Chimney Balloon are highly effective at stopping drafts and preventing heat from escaping your home through the fireplace. The best choice for your home depends on how much vertical clearance you have in your chimney and your preference for durability versus budget.
A Chimney Sheep® is a chimney draught excluder that stops warm air escaping from a property with an open chimney and prevents cold air coming in, making a home feel more comfortable.
Transform an unused fireplace into a stylish focal point using functional screens, decorative boards, or cozy fillers. Upgrade the space instantly by installing a magnetic cover, a custom-cut painted plywood screen, or simply stacking Birch logs and fairy lights to maintain a warm aesthetic.
To determine if a chimney is load-bearing, look for structural framing ties. Check the attic and basement to see if roof supports, floor joists, or main carrying beams rest on the chimney masonry. A chimney is almost certainly load-bearing if joists frame directly into it or if it supports the building's ridge.
To block up a fireplace from the inside, choose a method based on whether the change is temporary or permanent. For a temporary, seasonal block, use a Magnetic Fireplace Draft Stopper or cut a rigid foam board to fit and seal the edges with fire-rated caulk. For permanent blocking, build a stud frame, cover it with drywall, or lay bricks to seal the opening completely.