Masonry Chimney Construction with Round Clay Flue Liners for Mason-Lite Fireplaces - Installation Instructions

Oct 28, 2026

Upload by Đào

Instructions for constructing a masonry chimney using round clay flue liners with Mason-Lite fireplaces (MFP33, MFP39, MFP44, MFP49, MFP63). Specifies recommended materials, required mortar types (refractory mortar for heat-contact joints; standard mortar for block), foundation and structural support, and installation steps for positioning starter and full flue liner sections, building the CMU surround, including weep holes where needed, installing the precast cap with an expansion gap, and sealing the liner-to-cap space using appropriate non-oil caulking. Includes key guidance on flue liner orientation, mortar application limits, expansion airspace, and seismic/foundation considerations.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

Recommended Materials

General Installation Instructions

Foundation and Firebox Requirements

Step-by-Step Chimney Build

Mortar, Sealing, and Expansion Guidance

Orientation and Surface Cleanliness

Seismic and Structural Notes

Masonry Chimney Construction with Round Clay Flue Liners on (for use with MFP33, MFP39, MFP44 MFP491 & MFP631) Read this entire publication before beginning installation of a masonry flue on a Mason-Lite fireplace. It is the installers responsibility to understand and abide by all building code requirements for masonry chimneys. Recommended Materials List for MFP33, MFP39 and MFP44: 12” Round clay flues with male/female end joints (ASTM C315) 12” x 6” Round starter flue with female end 4x8x16 Light weight concrete masonry units (ASTM C90) 4x8x8 Light weight concrete masonry units Refractory mortar non-water soluble (ASTM C24 Cone 10) Standard mortar (ASTM C270) Polysulfide, butyl or urethane rubber caulking other non-oil based sealant/caulking Brick ties (if applicable) Precast concrete cap Facing material Block sealant (if applicable) Chimney pot and rain guard (option) Gap-Fill with sealant Full Flue Liner Section Starter Flue Liner Mason-Lite Fireplace (Side View) Mason-Lite Fireplace (Front View) 1Please note MFP49 and MFP63 comes with a 14” top outlet and requires a 15” Round Clay Flue Liner which when surrounded by 4”CMUs will not fit on the top of the fireplace without additional surrounding structure. 2If using Mason-Lite brick panels, damper block are not needed. A standard masonry flue/chimney system constructed for a Mason-Lite fireplace (Sizes MFP33, MFP39, MFP44, MFP49 and MFP63) should follow these recommended guidelines. A standard masonry chimney may be used on indoor and outdoor installations. It is the responsibility of the installer to understand and follow all building code requirements when constructing a masonry chimney. 1. Install the Mason-Lite fireplace according to instructions. In order for a masonry chimney to be installed with a Mason-Lite fireplace, the unit must be supported by an adequate noncombustible foundation capable of carrying the total weight of the Mason-Lite fireplace, the masonry chimney and facing materials. It is your responsibility to design and provide appropriate foundations and structural reinforcements to insure that the fireplace and foundation can support the weight of the fireplace, chimney and facing materials. IMPORTANT-During fire box construction of the Mason-Lite fireplace, the steel lintel (provided with fireplace as p/n MFP33- 6b, MFP39-6b, MFP44-6b, MFP49-b, MFP63-b) that reinforces the upper dome must be installed. For Indoor installations-a cast iron damper with Mason-Lite damper support blocks (not included with standard firebox kit) must be installed during construction of the firebox2. Please refer to the Mason-Lite Damper installation instructions for the damper and damper blocks required. [http://www.mason-Lite.com/wp-con](http://www.mason-Lite.com/wp-con)tent/uploads/2014/03/Mason-Lite-Damper-Install-Guide_.pdf 2. Place and position starter flue liner, centering it directly over the outlet on top of the fireplace with the straight cut end down. Note starter flue only available for 12” Ø not 15”. Adhere starting flue liner to fireplace dome with refractory mortar. 3. Place the next full 2’ section of flue. Neatly mortar flues together with refractory mortar cleaning up all excess. The male end will be down. Do not use excessive amounts of refractory mortar. 4. Build up the surround with light weight concrete masonry unit (cmu) or other suitable material using standard masonry mortar. Include weep holes as appropriate. Weep holes are important for outdoor installations because of constant weather/moisture exposure. 5. Continue to stack and mortar flue liners and cmu’s to the desired height. Always use refractory mortar for the flue liners and standard mortar for the block. 6. Carefully place and mortar a pre-cast concrete cap to the cmu being sure to center flue liner with the precast cap opening. There must be a uniform gap between the flue liner and cap to allow for expansion. DO NOT MORTAR FLUE LINE

FAQs

What mortar should be used for masonry joints involving heat and combustion by-products?

Use refractory mortar sparingly to seal and adhere masonry materials like a gasket. Refractory mortar is required for masonry joints that contact heat and combustion by-products.

How should the round clay flue liner be oriented during installation?

12” round liners have male/female ends that interlock, and the male end should always be installed down to keep creosote and combustion by-products inside the chase and prevent staining.

Why must there be an expansion gap between the clay flue liner and the chimney cap?

An expansion gap is required to allow the flue liner to expand and contract freely. The document also warns not to mortar the flue liner to the chimney cap (termination).

What sealing materials are recommended for the gap between the flue liner and the cap?

Use polysulfide, butyl, or urethane rubber caulking and avoid silicones. Oil-based sealants are not recommended; if the gap is large, use nonflammable packing and then caulk to prevent water infiltration.

Oct 28, 2026

Upload by Đào