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Re: Repair Decayed Lower Jamb Joint

Posted: March 19th, 2012, 6:40 pm
by johnleeke
OK, that's good. Thanks.

Re: Repair Decayed Lower Jamb Joint

Posted: March 21st, 2012, 10:16 pm
by Paul Marlowe
Method #4
Wood-epoxy repair, contemporary type.

Whenever repairing vulnerable wood fabric such as window jamb bottoms and sills, I usually apply liquid borates after removing most or all of the wood decay. This is because the fungus is likely to be hidden deep into the surrounding area. Drying out the water from the borates will have to be accomplished prior to applying epoxy. The moisture needs to be below 20% to get a good bond with most epoxy products. It is fine to get it drier. Check the Manufacturers recommendations. When possible it is best to prepare the adjacent area as you would for painting prior to applying borates or epoxy. This allows better migrations of the liquids into the surrounding wood cells.

At this phase or before, it is important to create a cover for weather protection and to help keep the Public from touching your work. If the weather or the Public is not a problem you may decide not to cover the window. When using epoxies it is the Applicators responsibility to inform all workers they are not to touch the epoxy. This is easier said than done. I even found experienced Tradesmen to be tempted enough to poke wet epoxy and then have to be taught how best to clean up their hands. I often flag wet areas with blue tape labeled "WET EPOXY DO NOT TOUCH".

Sometimes certain small sections of wood that are decayed can be left in place. This is sometimes done when an outside form of the original substrate will be beneficial for maintaining accuracy, such as a round bead or even a flat section of the jamb that helps to achieve the accurate finished plane. You may even choose to leave paint on the face until later to help keep this so called form in place. When these face forms are thin and fragile, extra care and attention needs to be given to applying multiple coats of consolidant to the decayed backside.

Once the wood is dry a flexible slow curing epoxy consolidant needs to be applied. This is usually done with a small natural bristle chip brush. The more epoxy the substrate absorbs the better. Make sure the epoxy is staying in the visible wood and not seeping into a stud bay etc. Space out the coats allowing the glossy sheen to become flat. If you can get to the point that you maintain a gloss for about 30 min. you are probably near fiber saturation.

Moving on to the patch, paste or filler epoxy. This should also be flexible and compatible with the consolidant/primer. The system I use allows you to apply this wet on wet with the consolidant (best bond) or onto a tacky or cured consolidant. I prefer applying this flush to the surface because the jamb intersects the sill and tooling this area is somewhat challenging. Also, flush filling at least the first coat minimizes damage created to the surrounding wood while tooling. The first coat of patch shouldn't be allowed to cure to fast because that can promote overheating which can compromise the quality of the epoxy molecules to properly link together. This is normally only a concern when the void is large or there is excess heat from sunlight or some other source of heat. Choose an extra slow curing Summer formula if very hot temperature is present, or try to shade the area. Always tool after each coat cures, waiting at least long enough so it is tack free and cuts, sands or planes well. If paint has been left on any thin form faces, this should be prepared at this time.

If a second coat of patch is needed you normally have smaller voids and therefore can use a faster curing patch formula without a need for the consolidant. You can overfill this coat if you choose, depending on how stable the area is and how difficult the tooling might be. In very detailed areas you may find the need for a third touch-up coat if the specifications require it. With this process you can blend in the repair so it will be unnoticeable once painted. After the primer coat check for any flaws and fill as needed with epoxy patch or a quick dry filler of your choice. Sand when cured, spot prime and paint.