Relining a Masonry Chimney
Introduction to the Basics
Chimney relining is often the best way to assure safety and proper performance with solid fuel (wood, coal, pellet) appliances. In fact, chimney lining has become almost mandatory in order to bring existing chimneys up to present codes.
Reasons for lining or relining your chimney include:
1. Properly sizing (by reducing) the chimney flue. Proper sizing assures better draft, less creosote and other advantages
2. Upgrading the safety quotient - having a liner inside your chimney assures that the fire will stay in a tightly sealed tube - and also transfer less heat through the wall of the chimney to nearby framing and combustible material.
3. Some older chimneys were built of brick with no liner - and some newer chimneys have cracked and deteriorated clay liners. Either of these pose safety hazards.
There are three basic material types used in masonry chimney lining:
1. Stainless Steel rigid pipe - is often the best material to use when the chimney run is straight. Rigid pipe is quite a bit thicker than flex pipe and the smoother interior wall will help with draft and cut down on soot and creosote formation.
2. Stainless Steel Flexible pipe - is available in various grades and thicknesses and can make relining relatively easy since it is often pulled down in one piece. It is easy to snake around bends and can even be slightly flattened (ovalized) to fit through difficult spots like dampers, etc.
3. Cast in Place liners - are made of a cement slurry which is poured down the chimney around a round bladder - after the cement has hardened, the bladder is deflated and removed, leaving a round flue of your specified size. Another method uses a nose cone which is pulled up through the wet cement to form the flue passage. Cast in place liners can help strengthen older chimneys because the cement fills in gaps from the inside-out. One popular vendor of cast in place chimney liners is AHRENS (http://www.ahrenschimney.com/).
NOTE: Poured in place liners should only be done by certified professionals - it is not a DIY or GC (general contractor/handyman) type of job.
To summarize the above, most masonry chimney do need lining or relining in preparation for a modern stove or insert. Stainless is used most often as the lining material, but if your chimney has structural issues you may want to look into the poured cement systems. The remainder of this article will relate only to chimney lining with stainless steel.
Lining a Masonry Fireplace Chimney for a wood or coal insert or hearth stove
Most of the same materials and techniques will be used whether you line a masonry fireplace or a chimney serving a freestanding stoves. Follow most of the advice below, but first read our article on installing a Fireplace insert .
Inspecting and Preparing the Chimney
As with most other projects, planning and preparation are the key to a successful relining job. The first step is to inspect, or have inspected, the chimney in it’s current condition. Note the following:
1. Does the chimney have flue tiles installed already?
2. What are in the inside measurements (ID) of the chimney?
3. Does there appear to be turns in the chimney - or areas where the chimney ID changes?
4. How dirty is the chimney?
5. What is the condition of the mortar and interior of the chimney?
6. If possible, inspect the chimney structure inside the attic of your home and confirm thickness of the exterior walls, condition of the masonry and other criteria.
7. Measure or estimate the total height of the chimney which will be lined. Chimneys do not need to be lined to the very bottom, just to the place where they pass through the wall to connect to your appliance.
Armed with this information you will be ready to make a few key decisions.
Flex or stainless?
wall pass though options?
Whether you are installing the liner yourself or having a pro do it, the above will give you some background and overview of the relining process.
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