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  • Our Most Challenging Chimney Job Ever – Thus Far

    Posted on November 20, 2008 by in Masonry Projects

     

    Original Chimney

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    The chimney as it was before we started the demolition. Note the greenish blue steel band around the chimney just above the roofline. This steel band was keeping the chimney from falling over.

    Boston Brick & Stone has recently completed one of our most challenging jobs ever. We were asked to perform a historical restoration on two magnificent chimneys that were severely damaged by the 1994 Northridge earthquake.

    The property is one of Pasadena’s most treasured residential landmarks. A Paul Williams masterpiece set on over 3 acres overlooking the Arroyo. The entire house is constructed of a classic Ironspot brick which is normally only used as a decorative feature such as a fireplace facing. Trimmed with scaled precast concrete quoins and balustrades the house truly takes your breath away, especially if you are a mason and as fond of bricks and concrete as I am.

    The problem this repair presented was that the chimneys were constructed from the same bricks as the house and although we looked nationwide we were unable to find enough bricks to repair the chimney in the standard adhered thin brick method. Cutting then adhering the existing brick presented several problems in itself, even if we could have found a perfect match brick. Each chimney has 13 courses of decorative corbelling. Imagine 13 layers of bricks that extend out past the brick below it to form a unique decorative design. To complicate it further some of these protruding bricks were the “points” of the brick. See the photo below and I’m sure you will appreciate the magnitude of this problem.


    Concrete Skirt

    Click for Larger Concrete Skirt.
    Here you can see the steel band under the concrete skirt. There were 8 pieces of this concrete skirt, each of which weighed between 500 and 600 pounds.

    Corbel

    Click for Larger Corbelling.
    Each chimney has 13 courses of decorative corbelling. Imagine 13 layers of bricks that extend out past the brick below it to form a unique decorative design.


    Years ago we simply would have had the chimney engineered to repair it with concrete, reinforcing steel and the original brick. We would have constructed a “Bond Beam” which would have been secured to the actual structure of the house so it could not go anywhere in the event of the next earthquake. However building officials have adopted a policy of not allowing this method of repair any longer. Even when the chimney has reinforcing steel in the structure down to the footing we have had problems getting the building officials to issue the permit. The basic ideal is to keep the weight above the roofline down to a minimum. It is a sound idea. With no little weight rising high in the air the chance of bodily harm because of an earthquake is drastically reduced.

    Guardian System

    Click for Larger Guardian System Image. Installing the high tech Guardian System. This treatment of the remaining flues brought the entire chimney up to code with regard to the 2-inch clearance to combustible rule.

    To really make this a challenge the two chimneys had a decorative “skirt” just above the roofline made of solid concrete. Each skirt consisted of eight pieces of solid concrete weighing between 500 and 600 pounds. One of the two chimneys consists of three separate fireplaces and rises almost 60 feet off of the ground. The solid concrete “skirt” was about to fall to the ground and was being held in place by a steel band someone had welded around the chimney just below the skirt. We were wary that the demolition of the chimney would cause the skirt to slip off and we would come down with the chimney and end up in a heap on the ground.

    With those challenges the Technical Department of Boston Brick & Stone set to work with our engineer and we came up with a plan. A “super” scaffold system was designed and erected that would survive the possible collapse of the concrete “skirt”. I fell back upon my experience in the commercial/industrial construction arena and proposed that we use a method known as “Anchored Veneer”. We discussed this with our engineer and decided to incorporate this “skyscraper” technology and employ anchored brick veneer set on a super strong steel frame. This way we could use the original brick and follow the original design almost perfectly. Full bricks can be used and “anchored” directly to the heavy gauge steel studs with specially designed steel ties. I’ve included a photo of the “Anchoring Ties” so you can see how they work.

    Cast-in-Place Flue

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    The new cast-in-place flue. After a thorough camera inspection we continued with the next step.

    The solid concrete “skirt” would be replaced with a lightweight precast concrete skirt that is hollow but looks the same.

    With the plan in place we got to work setting up the “Super” scaffold system built on a wood platform that spanned the set of stairs and the 30 foot drop. After several trips to the Pasadena Permit center we finally had our approved permit.

    The demolishing went perfectly. We succeeded in lowering the solid concrete skirt with a series of ropes and pulleys and 6 large men at the end of the rope on the ground. I can tell you I breathed a tremendous sigh of relief once that skirt was on the ground.

    Bond Beam

    Click for Larger Bond Beam Image
    The chimney down to the roof line. Note the steel straps that hold this large “bond beam” to the structural members of the house.

    Once the demolition was successfully completed to just below the roofline we stopped and re-evaluated the plan to go all the way down to the level of the first floor fire place. We closely examined the condition of the flue from the roofline down with our state-of-the-art camera scanning equipment. We knew there were serious separations in the clay flue liners but they were not caused by any seismic activity. It was obvious that they were placed that way by the original masons who built the chimneys and that the mortar they had set in place simply fell out over time. Because there was no structural damage we were free to employ the latest flue saving technology and save the remaining portion of the chimney. This plan had several advantages. The greatest of which was the option of placing the bond beam at the attic floor level. This allowed us to tie this bond beam into the structure at the attic floor level which is much stronger than tying it to the only the wall.

    Bond Beam

    Click for Larger Bond Beam Image.
    The bond beam ready to pour.

    Once approved by the city and the General Contractor in charge of the entire remodel we got to work on installing the new “Guardian Cast In Place Flue Liner” by Firesafe Industries. This is a simple idea combined with a superior cementous material that when correctly installs removes the 2-inch clearance to combustible code requirement.

    This cementous material has to be only ¾-inch thick to add structural strength to the chimney structure and remove this code requirement. The cementous material expands when heated so it closes any small cracks within the application as soon as a fire is started. Because it only has to be ¾-inch thick it does not reduce the flue area too much. So although these chimneys were right up against the wood structure of the house, the Guardian system not only made these chimneys safe – it brought them into code compliance.


    Heat Retardant

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    Installing a product which protects the regular concrete from suffering heat damage.

    Angle Iron Brace Support

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    The angle iron brace support which we installed on both chimneys. This is the appliance chimney. The 3-inch diameter heavy wall pipe will connect to the bolts that run through the chimney and will be supported by the 1/4-inch angle iron.


    With the remaining original chimney system made safe and brought up to code we proceeded with the new construction. We used heavy gauge metal studs set with “X-Bracing”, the same basic idea that essential structures such as hospitals are constructed with.

    X Bracing

    Click for Larger X Bracing Image. The elaborate “X” bracing, we used a thicker gauge steel stud for extra strength.

    Waterproof Membrane

    Click for Larger Waterproof Membrane Image. The waterproof membrane we installed over the 1/2-inch structural plywood. Note the bolts protruding through. These will hold;the precast concrete skirts up.


    The “X-Bracing” provides incredible strength and stability. “Structural One” plywood was attached then we used Modified Bituthene for a waterproof barrier instead of the standard black paper. This provided us with a rubberized waterproof membrane that had elastic properties. We did not want any leaks! We used Sonotubes to form the flues through the bond beam.

    Once the concrete was poured we coated it with “Fire Guard”.

    Copper flashings were installed with the bricks and then they were soldered in place, attached to the copper we had installed within the masonry structure. No way could this flashing ever pull out on us now – not in 1000 years!


    Simpson Hold

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    A Simpson hold connected to a 3/4-inch bolt that goes 3-feet down into the bond beam.

    Copper Flashing

    Click for Larger Copper Flashing Image.
    The copper flashing actually embedded into the concrete.


    Next, the actual brick and anchoring system. Our master masons cleaned and reused the original brick and constructed the new portion of the chimney to match the original perfectly. The new owners of the property commented to me that they could not tell that the chimney had been repaired or even where the old chimney ended and the new portion began. No greater compliment could have been paid to me. The property has two other chimneys which were repaired after the 1994 earthquake but the contractor was not true to Paul William’s design and it is painfully obvious.

    Anchoring System

    Click for Larger Image. The anchoring system we used to attach the bricks to the chimney. The steel connectors were attached to the metal studs.

    Precast Concrete Skirts

    Click for Larger Image. The above shows how we attached the lightweight precast concrete skirts to the chimney using the bolts shown in other photo.


    The bracing system was installed next. This consisted of 3-inch diameter steel pipe which we had powder coated to withstand the weather. Two pipe braces on each chimney attached to 1/4-inch 3 x 3-inch angle iron within the chimney structure, bolted to the steel studs with 1/2-inch bolts. Inside the house we designed a steel rack which spanned the entire attic floor area and was bolted to the structural members of the house.

    Pipe Braces

    Click for Larger Image. The two pipe braces attached to an angle iron frame installed in the attic. Not the welded in place copper flashings.

    Clay Pots

    Click for Larger Image. The appliance chimney completed just before the final wash.


    With the braces, the bricks and the custom made precast concrete skirt in place we were faced with the final challenge. The top of the chimney had to support three clay decorative pots to keep rainwater out of the hollow chase and allow heated air to escape — all without violating any code requirements or altering the finished look from the original.

    I sat up on that scaffold for several hours before I finally came up with a plan. I don’t want to give away any of our trade secrets here so I won’t elaborate on the design but I will say that it accomplished all of the above.


    Clay Pots

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    The photo shows the top I designed. The “clay” pots are actually metal coated with specially designed stucco. This top is not visible from the ground, keeps the water out and allows heat to escape the chase.

    Appliance Chimney

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    The Appliance Chimney almost completed.


    The customer and the General Contractor were delighted with our work and our service.
    They promptly contracted Boston Brick & Stone to design and construct a Full Masonry chimney system to match the existing chimneys. This new chimney is to service the newly designed kitchen. In addition Boston Brick & Stone is restoring all of the brickwork on the house and on the guesthouse at the bottom of the property.

    Living Room Chimney

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    The Living Room Chimney completed.

    Completion

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    Completed Chimney


    Several other projects are pending which include a pool, pool house and landscaping that we have submitted bids on and are awaiting final approval.

    Still Standing

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    Our Chimneys are still standing after the fire.

    Still Standing

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    Our Chimneys are still standing after the fire.


    Tragically this beautiful house burned down on October 5th, 2008. See “A Historical Loss in Pasadena” another Boston Brick & Stone newsletter article that tells the whole story.

    Our chimneys are still standing.