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New Effort Underway on Behalf of Barns
Q. My barn has a sag in the roof and the eaves are bulging. What is the problem and what is the repair solution? A. The reason that roofs take on a swayback appearance is that the rafter plates are spreading. One common cause of "saddling" is that the roof structure may have been altered to allow the installation of hay tracks. In some cases, collar beams were removed. In other cases, the entire original gable roof structure may have been removed and replaced with a gambrel structure, a change made to many barns toward the end of the 19th century. The new gambrel roof may not have been designed to take snow loads. Over time, remaining structural elements cannot take up the strain of missing elements and the plates spread. The repair solution is to address the structural inadequacies. Another common reason for saddling is that the tenons, or the pegs in the tenons of the tie beams, have failed, usually from rot or snow loads. Tie beams are the large beams which run from eave to eave and connect pairs of posts. Where there is a long piece of post between the tie beam and the rafter plate, the post can break at the tie beam joint. If the cause of saddling is rot in a joint or a structural member, the cause of the rot should be addressed first. In this case, look at the roof to make sure it is not still leaking. Moisture is the enemy of the timber frame. If there is rot evident in a failed joint, look closely at the nearby plates, rafters, and posts. A perfectly good-looking post or beam may be rotted on the inside leaving only a hollow shell of good wood. Repairs to these rotted members is usually critical. If rafter plates have been repaired or are in good condition, 5/8" allthread can be used to tie the plates together and large decorative washers can be made up to distribute the load of the allthread out on the outside of the plate. I am not a fan of using steel cable in barn repairs. Don't expect to be able to pull the sag out of the roof using the rod. To do this, the roof must be jacked as the rod is tensioned. This issues guest author is Richard Lazarus of Lazarus and Company, House and Barn Rigging, in Spencer, New York. Lazarus has rebuilt, dismantled and restored barns in the Finger Lakes region for the past 24 years. © 2008 New York State Barn Coalition |