Quick AnswerA cast-in-place liner is a cementitious mixture poured or troweled into the flue to form a new, smooth, code-compliant liner from within the existing masonry. It's the right call when clay tiles are badly deteriorated or missing altogether, since it also reinforces a weakened chimney structure rather than just adding a new venting sleeve.
What’s Included
Some flues have deteriorated to the point where individual tiles no longer form a stable, continuous liner, and the masonry structure itself needs reinforcement, not just a new venting path. A cast-in-place liner solves both problems at once, bonding to the existing masonry to create a smooth, insulated, structurally reinforced flue from top to bottom.
- A specialized cementitious refractory mix is poured or troweled around a form to create a smooth, seamless liner that bonds directly to the existing masonry, restoring structural integrity along the entire flue length.
- The finished liner is correctly sized for your specific appliance and fuel type, addressing both the deteriorated masonry and any draft or sizing problems in the same job.
- Because the material bonds to and reinforces the surrounding brick and mortar, this method adds real structural strength to a chimney with cracked, loose, or missing tiles, which a sleeve-style liner alone doesn't do.
- The liner is inherently insulated, which improves draft performance and reduces creosote buildup in wood-burning applications.
- We inspect the full flue and surrounding masonry before starting, since obstructions or severe structural damage may need to be addressed before the pour.
- A written, flat-fee estimate is provided covering material and labor before any work begins, given how much this method depends on the specific condition of your flue.
Signs You Need This
- Crumbling, spalling, or missing sections of clay tile inside the flue
- A chimney inspection revealing structural deterioration in the masonry itself
- Repeated liner problems that patch repairs haven't solved
- An older masonry chimney that has never been properly lined
- Visible mortar loss or cracking between flue tile joints
Our Process
Full Flue Inspection
We inspect the entire flue and surrounding masonry to confirm cast-in-place is the right approach versus a sleeve-style liner.
Written Estimate
You receive a flat-fee, written quote reflecting the specific condition of your flue before any work begins.
Forming and Pouring
A form is set to the correct diameter and the refractory mixture is poured or troweled into place, bonding to and reinforcing the existing masonry.
Cure and Verification
The liner is allowed to cure fully, then inspected and tested for proper draft and a smooth, continuous surface top to bottom.
How Much Does It Cost?
Cast-in-place liners typically cost more than a stainless steel sleeve because of the material, labor, and time required to properly form and cure the liner, but they're often the right choice when the masonry itself needs reinforcement rather than just a new venting path. Cost depends on flue length, diameter, and how much prep work the existing masonry needs first. We provide a written, flat-fee estimate after a full inspection, before any work begins.
FAQs
A stainless liner is a separate sleeve installed inside the flue, while cast-in-place material bonds directly to the existing masonry, reinforcing the chimney structure itself in addition to providing a new liner.
Yes, it can be sized and finished appropriately for wood, gas, or oil appliances, similar to a stainless liner, but it's generally chosen specifically when the masonry needs structural repair too.
Installation itself is usually completed in a day, though the material needs time to cure fully before the chimney is put back into regular use. We'll give you a specific timeline during the estimate.