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Rebuilding old chimneys -- with a European technique

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Steve Vinal is a brickmason by trade who has considerable experience in chimney building and rebuilding. Too many unsafe chimneys in this new age of wood- and coal-burning stoves provided a demand for his services. But the look of dismay that would flood a homeowner's face every time he gave an estimate got to him in the end.

So last year, when he saw an advertisement that offered a less-expensive, yet equally sound solution to the problem of old chimneys, he responded with enthusiasm. Now Mr. Vinal is among a growing number of dealers around the country who renew chimneys structurally by relining them with a poured, high-temperature refractory cement.

If you long for the return of a blazing hearth to your home but question the soundness of your chimney, this relining option might be worth investigating.

In Holland, where the technique was invented more than two decades ago, and in Britain, where it was further developed and refined, the system is known by several names. On this side of the Atlantic it is called PermaFlu.

The name is supposed to represent what the inventors claim the system does: Upgrade on a relatively permanent basis the unlined brick or stone chimneys that predominate in all but the more-recently constructed homes and those modern homes with cracked clay liners.

In simple terms, here is what happens to a chimney that is given the PermaFlu treatment:

The installers come in, clean the chimney, and insert an inflatable form. The form is centered so that there is a minimum one-inch-thick wall of mix all around. This can readily be accomplished even in a serpentine chimney. A slurry of refractory compound is poured around the form. The following day, the form is deflated and removed, leaving a rounded flue that can be 6, 7, 9, or more inches in diameter.

In Britain, the system has been used to line industrial stacks 4 feet in diameter and hundreds of feet high.

The exact composition of the refractory slurry (perfected only after years of trial, according to the manufacturers) is a trade secret. But it does contain certain types of volcanic rock which, while light in weight and incredibly heat-tolerant, also add to the insulating value of the lining.

This has two advantages:

* The flue warms up rapidly, creating a good draft which, in turn, reduces the amount of creosote deposited on the walls.

* In the event of a chimney fire, heat transfer through the chimney to the surrounding wooden floors or walls is dramatically reduced.


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