You can cement over a brick chimney easily. The hard part is getting the cement to stick. Most skim coats of concrete will crack and peel off within a few months if you do not know how to properly apply the concrete and care for it while it is curing. The porous nature of the clay brick and the porous concrete skim coat need a little extra help to stay together forever.
Things You'll Need
- Plant mister
- Portland cement
- Magnesium float
- 20mm plastic (if needed)
Fill a plant mister with water and mist the surface of the brick. You don't want to saturate the brick with water, but you do want it to have a layer of moisture on the surface.
Mix portland cement (cement with no aggregate) in a bucket with water in at least a 3 to 1 ratio until it has a batter-like consistency.
Scoop your concrete onto your trowel and trowel the concrete onto the brick surface. Smooth the concrete over the bricks in arc-like sweeps, holding the edge of the trowel at a 45-degree angle, to make sure the coating is consistent.
Cover the entire surface of the brick chimney with concrete, making sure you are misting the brick ahead of applying the concrete so none of it is trowelled onto dry brick.
Smooth the concrete skim coat with a magnesium float. Make sure you dip and wipe the float clean in water often as you go, to prevent any drying concrete from collecting on the float face and ruining the surface you are smoothing.
Continue to mist the entire surface every 20 minutes until the concrete has completely dried and cured. Misting the surface will significantly slow the drying time, which is what you want to ensure that the bond between the brick and concrete is strong.
Tips & Warnings
- If the chimney is in a dry area, cover the concrete with 20mm plastic after misting it, to make sure it does not dry too fast. This heavy plastic will not damage the smoothness of your float finish.
- While in many areas applying a concrete skim coat to a brick fireplace as it is exposed within a house is fine, many areas have specific building code regulations about whether or not it may be applied to the fireplace on the exterior of the building, particularly around the cap. Check your local building codes to make sure before you begin, to avoid any unexpected fines.
How to Cement a Chimney Cap
A chimney cap can refer to a decorative copper or a metal cage-like device placed on top of a chimney to prevent...
How to Install Brick Pavers On Concrete Steps
If you want to refinish concrete steps, you have a few options: You can paint over the steps, you can paint a...
How to Stucco Over Brick Exterior
Stucco can be applied to a variety of materials and surfaces. The great thing about applying stucco to brick is that much...
How to Redo a Brick Fireplace
If you are discontented with your brick fireplace, you may be considering hiring a professional to have it completely removed. Replacing a...
How to Skim Coat a Concrete Slab
Applying a layer of skim coat to an existing concrete slab will cover pitted and hairline-cracked surfaces. The thin layer of concrete...
How to Lay a Brick Walkway Over Concrete
You can dress up the look of concrete walks and patios with brick as long as the concrete is relatively level. Brick...
How to Mix a Parge Coating
Masons use a parge coat to cover walls made of concrete, brick or block. A parge coat is a smooth coat of...
Concrete Block Vs. Brick
Both concrete block and brick masonry are strong, fire-resistant, insect-proof building materials. They have a lot of thermal mass, which helps them...