Rafter Tail Rot Repair and Prevention 1) Create a simple but stable temporary cover to shed rain from the rafter. This should be easy to roll up or removed during work and easy to reapply afterwards. There are many impermeable material options as well as not using a cover if dry weather is guaranteed and fabric is away from public access. 2) Remove soft decayed wood, fasteners & any misc. debris. Save the rafter perimeter if possible so it can be used as a form. 3) Decide if wood filler pieces are going to be used in large voids. If so, mill them to fit loosely and document there locations at each rafter. 4) Apply liquid borate preservative such as Bora Care or Board Defense, to any wet or dry decay zones that have been heavily infested with wood decay fungi. Consider treating any wood filler pieces with borates also. Make sure the wood is dry to below 20% moisture prior to any epoxy application. Forced drying may be necessary depending on the schedule and existing weather conditions. 5) Apply 1-5 coats or more of flexible epoxy consolidant 100 over a 2-4 hr. period until the wood fibers in the decay zone are well saturated. Also coat any new wood filler pieces. Focus on saturating end grain and apply at least one coat on face grain of any wood filler that will intersect the epoxy patch/filler 200. 6) Apply flexible Epoxy Patch 200 while the 100 is still wet for the best chemical bond if the day’s schedule allows. Otherwise apply 200 ASAP. The 200 patch will bond well to the 100 whether the 100 is wet, partially cured or fully cured. If wood fillers are used, insert them after filling the voids approx. 1/2 - 3/4 full with epoxy patch. The fillers will be encapsulated in patch after the void is completely filled or you may choose to expose one or more sides of the bare wood filler pieces, depending on individual project specifications. 7) Forms are not usually needed if you thicken the 200 enough and there is some wood to guide your plastic knife or straight edge tool (wood, metal etc.) across the decay span when applying the patch. Forms can be used, but they need a release agent (clear packing tape, butchers wax, clear polyethylene, clear wrap, wax paper etc.) applied on the epoxy side of the form so it can be easily removed after the epoxy cures. 8) When fully cured & tack free, tool the epoxy patch flush with the surrounding fabric. Apply an additional top coat of epoxy patch if there are any voids or low spots that need to be filled. 9) An oversized piece of EPDM (rubber membrane) could be glued to the top of exposed rafters using the 200 epoxy patch as an adhesive. The EPDM is an impermeable membrane that is UV stable. It will help shed water and keep the tails dry if they are going to be permanently exposed to the weather. Once the epoxy cures, cut the EPDM flush to the rafter face if that is the look you prefer or overhang the edges 1/4" or more to achieve a drip line which will help to shed the water from the rafter. 10) Both the consolidant 100 and patch 200 will accept fasteners for sheathing, trim etc. 11) Plane or sand the cured epoxy if paint or stain is required. 12) Document all repairs and monitor the visible fabric for 1-2 years following the repairs. With proper maintenance this type of repair, done properly, will have long lasting results. Variations on the general repair techniques described above should be adjusted according to each project and each individual rafter, but the basics for dealing with wood decay fungus or insect damage remain the same. It is important to understand these are only guidelines and the person performing the repairs should focus on the condition of the fabric and learn why each step of the process is important. Technical support and consulting services are available at conservepoxy or 203-484-4123
Posted on: Sun, 21 Jul 2013 21:02:35 +0000
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