Step by step procedure for a badly rotten stuccoboard area behind some rotten vertical trim: (replacing piece of stuccoboard as well)
Pull out nails with nail puller and/or hammer
scrape off all loose wood and stuccoboard
remove caulk at area to receive saw cut
cut off bad part of trim using a hand saw adjusted properly to exact depth of trim. make sure cut is 90 degrees to edge of trim board
carefully remove bad wood being careful to not rip off caulk along with the outside film surface of your stuccoboard. Use a painters tool to scrape off only the old caulk from the stuccoboard.
Cut out any large sections of bad stuccoboard with the hand saw or an electric cutting tool. Always be careful about generating heat and the potential for starting a fire when using a rotary cutting tool. I always have water close by to cool things down.
Apply two coats of wood hardener to edge of remaining good stuccoboard and trim, also harden, glue and prime area where caulk was removed, exposing masonite
apply two or more coats of glue to stuccoboard edge.
scuff glued areas with sandpaper or steel wool
prime glued area
cut treated plywood to fit area where stuccoboard was removed
nail in plywood and caulk or use flashing tape to seal where plywood meets stuccoboard. (In areas behind trim only)
fabricate an aluminum drip edge that will run down the bottom 2-3 inches of your vertical board (see video)
Make sure edges are rounded in any high-traffic areas. flatten bottom of drip edge by bending it downwards if you want it completely out of the way. I prefer it to stick out a bit if there is no chance of someone bumping into it. That way all water dripping off of the drip edge stays off of the horizontal trim.
Apply flashing tape to top of drip edge and stuccoboard while positioning the drip edge on top of your horizontal board. Rub tape firmly on stuccobard and flashing. Strive for no wrinkles and bubbles in the tape. But once it’s on, it’s not coming off easily.
measure amount of cedar trim “plug” (a spot you require wood for watever reason) or a miratec “plug” to replace removed trim area.
Install plug using deck screws and caulk where top of plug meets existing vertical trim. Make sure you screw into a piece of framing structure. Always drill pilot holes in trim and into the side of house. Also caulk on sides of plug. Do not caulk all the way to rear of trim where vertical trim and plug meet. This will allow water to flow behind trim, if it were to get back there. Do not caulk where plug meets the tray porion of the drip edge. That will keep water from harmlessly dripping out, if the water gets behind trim due to eventual caulk failure.. Use 100% silicone caulk only where Miratec meets stuccoboard. Use polyurethane caulk for all work involving wood trim. Top coat – done !
Step by step procedure for a not so badly rotten stuccoboard or trim area: (fixing stuccoboard or trim with filler)
Instead of cutting out the bad stuccobard or trim, just harden, glue, prime and scuff what you have left, then use exterior spackle to fill rotted area. I use the lightweight spackle. After giving it a few days to cure (feel for stiffness) coat with multiple layers of glue. When it feels like fiberglass, you are done. Scuff and prime glue. Layer 1/8 inch of polyurethane caulk over the primer. Add desired surface texture to caulk by scraping with a pencil-like stick. . Top coat – done!
It is also possible to have decay at the top of a vertical which meets the horizontal board. In that case, you can create a plug or patch, and then top the board with a drip cap. You can see a plug with cap at :26 in this video.
Duration : 0:6:12
[youtube VrP39hIc3sc]