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Relining Old Chimneys, continued

Setting Up

Safety is a key consideration in our chimney restoration projects. We've learned that taking a little extra time during setup to provide solid scaffolding and good access allows us to work in a more relaxed manner, helping us to concentrate on the tasks at hand. During the restoration process, a lot of effort goes into gaining safe access to roofs and chimney tops. We try not to nail anything into the roof itself; instead, we hang the majority of our scaffolding from ridges and peaks using systems like the Ultimate Ridge Hooks (Deer Hill Enterprises, 800/588-9660) and Vanguard Chimney Brackets (Lynn Ladder & Scaffolding, 800/225-2510). If necessary, we will build up beams to span valleys, anchor them to lumber or ladders hung from ridge hooks, and bolt our scaffolding to the beams (Figure 3).

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Figure 3.Solid, well-thought-out scaffolding provides a sense of security as well as a safe place to work. The chimney has been wrapped with plastic stretch wrap to help it resist the pressure of the fluid mortar that will be pumped around the inflatable formers.

Dust control. Most of our projects take place in occupied houses, so we also take care to protect both the house and its contents with well-placed runners and drop cloths. To control dust, we screen off our work areas with poly Zip Walls (800/718-2255, www.zipwall.com) and use powerful dust-collection vacuums while doing demolition or other dusty work. We've had very good results with the August West Sootsweeper II (available from Copperfield Chimney Supply, 800/247-3305, www.copperfield.com), which is a high-powered vacuum manufactured for chimney sweeps. Although it isn't listed as a HEPA system, the manufacturer claims that it will filter out particles as small as .5 microns and move 350 cfm. We use it by putting the hose inside the fireplace so it sucks up the dust laden air before it has a chance to spread. To reduce indoor noise, as well as to prevent any dust particles that may make it past the filter from being exhausted in the house, we keep the vacuum itself outdoors whenever possible, running a 3-inch or larger flexible hose to the work area. To protect ourselves during chimney sweeping and demolition, we wear full-face respirators and disposable coveralls (Figure 4).

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Figure 4.Tyvek coveralls and full-face respirators protect workers from potentially carcinogenic dust.

Demolition and Temporary Reinforcing

Many of the older, unlined chimneys in our area were built in the early 1900s and are separated into multiple flues with freestanding brick wythes that aren't keyed into the chimney walls in any way. Weathering and erosion of the mortar leave them very unstable. Homeowners often realize they have a problem when they start finding loose bricks from a collapsing wythe in their fireplaces. These deteriorated wythes must be removed before any liners can be installed.

Take it from the top. We remove as much of the wythes as we can from above. This is easy at first, because the topmost courses can be reached by hand. Once we get beyond arm's length, we use a variety of hand tools that can be mounted on bull-float handles. We also use the Chamber Chipper tool from Golden Manufacturing (800/446-5354, www.chimneys.com/goldenflue), which is an inline air hammer mounted on a shaft of 3/4-inch galvanized pipe. The piston is lowered into the chimney, and the control stays at the top (see photo at top of page 1). The chipper can be extended as long as 40 feet, although we find it difficult to control when it's asked to reach beyond 20 feet or so.

The deteriorated bricks that are chipped loose simply fall to the bottom of the chimney into the fireplace firebox, which is padded with plywood, temporarily closed at the front, and fitted with a vacuum hose to control dust (Figure 5).

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Figure 5.A plywood covering over the front of the fireplace contains broken masonry that falls from the chimney during demolition, and an efficient vacuum filters out dust before it can infiltrate the living space (top). The accumulated brick and mortar fragments are removed once the demo phase is complete (bottom).

In a two- or three-story house, it can be difficult to get all the way from the roof to the ground floor. If the firebox in an upstairs chimney is deteriorated, we'll often remove it and work our way down through the fireplace opening. When the demolition phase is done, we build a solid new firebox.

Ho, ho, ho. If the chimney is large enough, it's often easiest to climb into the chimney from the rooftop by extending the scaffolding out over the chimney and then hanging a steel fire escape ladder from it (Figure 6). Workers entering the chimney wear respirators, hard hats, and safety harnesses. A vacuum in the fireplace below pulls fresh air down the chimney around the worker and removes dust to allow better visibility.

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Figure 6.If the size of the chimney permits, a worker can climb into it from above to dislodge deteriorated wythes, providing the space needed for the new poured liner (top). A metal fire escape ladder fastened to the rooftop scaffolding provides safe and convenient access (bottom). Openings in the chimney wall, like the unused stovepipe thimble visible in the photo at left, must be bricked up before the liner is poured, or a disastrous blowout can result.

During this part of the job, we also keep an eye out for hidden openings in the chimney. Occasionally, for example, we'll find an old stovepipe thimble that was never bricked up but got covered with wallpaper. Such problem areas have to be repaired before the liner mix is poured, or it will blow out into wall cavities or living spaces.

Strapping and wrapping. During the pour, the chimney is subject to a great deal of hydraulic pressure from the wet liner mix. Unless that's taken into account, the result can be a disastrous blowout. Because the upper portion of a chimney is exposed to the weather, it's often much weaker than the lower portion. We frequently tear deteriorated old chimneys down to the roofline and rebuild them in the original style. Where weakened sections are accessible from inside the house, we reinforce them with sheets of plywood cut to the dimensions of the chimney and secured with ratcheting cargo straps (Figure 7).

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Figure 7.The freshly poured liner mix exerts considerable pressure on the surrounding brick, so tender old masonry is compressively reinforced with plywood and ratcheting cargo straps. Plywood and straps will be removed once the new poured liner has set up.

Another method we often use is to wrap the chimney with several layers of stretch-wrap film -- the same material used for securing material to shipping pallets. We buy this from a safety products supplier in 18-inch-wide rolls. When tightly wound around the chimney, it provides enough compression to resist the outward pressure of the wet liner mix.