Shared Knowledge
"Home Exterior Wood Painting - Latex - My Experiences"
1 August 2011
Summary: exterior home wood painting is certainly a do-it-yourself (DIY) job but if want your paint job to last for many years and I know you do not want to hear it, you have to do preparation work. My experiences: use a Ryobi electric sander; use 180 grit sandpaper; use foam brushes.
Background:
Have 2 story, 3/4 inch thick plywood covered, mostly glass, addition on the back of my home.
Addition painted when built and then once in 20 years and needed a good solid paint job.
Too expensive to pay painter.
Retired, so DIY.
Tools required:
Electric sander.
Extension chords.
18 grit sandpaper.
Glass clean razor scrapper.
Utility knife or box cutter.
Paper towels.
Caulk.
Perhaps MinWax or other brand wood stiffener.
Perhaps Bondo all-purpose putty.
Ladders: perhaps step and longer.
Breather masks.
Foam paint brushes in various widths.
Preparation:
The hard part about painting is not the actual painting although when up a 30 foot ladder you might not think so, but a good solid paint job needs from a little to a lot of preparation work.
(1) The wood must be sound, solid. When I began my paint job, noticed paint discoloration at the corners where 2 plywood panels came together or a plywood panel met a window frame. Upon investigation, found wood rot. Water had gotten into plywood and simply rotted our a large section. Ok what to do about it? And no, I or you simply can not paint over top if it and expect it to last or not eventually leak water into your home or ruin an expensive wooden window frame.
(a Paint is not caulk.
(b) Caulk is not wood putty.
(c) Wood putty is not Bondo.
(d) Bondo is not solid wood.
And what does all the above mean?
If at all possible replace the section of rotted wood. Most times this is possible although you may not want to do it because of the hassle, but if you do not replace, do not simply paint over.
First take a box cutter knife and clean out the wood rot. If the area is very large, you simply must replace the section of wood.
When I have had to replace sections of wood siding, I have either used marine grade exterior plywood or a composite board. If you not a mind to pay for marine grade plywood, at least spring for exterior grade A/C meaning one side has been sanded and suitable for painting.
Composite boards are great in that they are made out of recycled plastic and will not rot or split. Unfortunately, the widest of these boards at this time is only around 9 inches or so.
If replacement is out of the question, do not use wood putty. My experience has been that it just does not hold up outside.
With the wood root cut out, get a can of wood stiffener. MinWax sells a product as do others. Brush this nasty liquid into, onto, the wood left after your removed as much rot as possible. This liquid will help stiffen the remaining wood fibers.
3M sells a product called Bondo. This putty comes in 2 parts and you mix up a batch and then apply to a hole in wood or where you have carved out the wood root. Bondo sets up fairly fast so work quickly. As Bondo begins to harden, you can easily carve it with a putty knife or other. Once Bondo is hard, you have to sand it to get it level, even with the surrounding wood. Bondo can be primed and painted like wood. Bondo is nasty stuff and wear a breather mask when sanding it.
(2) Surface preparation: sanding. Ok, you have solid wood. Now you must prepare the surface for new paint. To do this, I sand using a power sander and 180 grit sandpaper. Now if you have latex paint, the sander you use is actually very important. If the sander has too high a revolution and all sanders actually have revolutions no matter how the actual pad moves, the sander will grab the latex and cause it to "pill" or form small balls and you have a mess on your hands. I use a Ryobi mouse sander. This sander uses loop and hook to hold the sandpaper on and as it is shaped to a point, works great on sanding into corners. The Ryobi also does not "pill" existing latex paint.
(3) Surface preparation: around wooden window frames. On wood framed windows, do not try to sand the edge that comes in contact with window glass. No matter how you try not to, the sander is going to scrape the glass and you will have a permanent mark on the window glass.
(3) Surface preparation: clean, dry surface. Paint is not going to stick to old paint if there is any sort of film to include dust, dirt, etc on old paint. Sanding will removed most but you still should wipe down wood before painting.
(4) Surface preparation: nail holes. Wood is held on with finishing nails. Sometimes these nails are counter-sung below the surface of the wood and sometimes not. All nail should be punched in leaving a small hole that is caulked.
(4) Preparation: caulking. Caulking small and I mean very small, gaps between wood and brick or between 2 pieces of wood or plywood and wood window frames is essential to keeping the exterior weather tight. Use the best exterior silicon-based caulk you can afford. If you plan on painting over the caulk, do not buy the type caulk that can not be painted over. I know, obvious, but things get put in the wrong bin at the big-box home improvement stores all the time and the caulk that clearly says not meant to be painted over will not hold paint for very long.
(5) Preparation: primer. Any wood that is bare because it is new wood or because the sanding process revealed bare wood must be primed before applying latex paint.
Painting:
(1) Brushes. I like foam brushes. Bristle brush leave brush strokes in the paint no matter how you try to avoid them, foam does not. Foam brushes are cheap and come in a variety of widths. Foam brushes allow you to get paint into tight corners that a bristle brush will not handle very well. Since foam brushes are so cheap, you can just throw away rather than clean after use.
(2) Paint. I like latex for the exterior. Latex covers well, forms a nice tight seal and is easy to clean up if you drip some and also brush cleaning is simply washing out the brush with water.
(3) Paint. I know with lots of things there is no correlation between their cost and their quality but with paint, I think there is. So, if you are going to take the time to properly prepare your exterior for painting, go with one of the better quality brands. I use Martin Seymour paint because that is what was put on the house when we renovated 20+ years ago.
(4) Paint. When I am ready to paint, I open the paint can and stir the contents well. When I am done painting for the day, I hammer the lid back down on the paint can tight.
(5) Paint. A full can of paint can be a bit much hauling it up a long ladder to paint high up, so you can user another can and transfer a couple of inches of paint from the original paint can to one you use strictly for ladder use.
(6) Applying. Apply paint in the direction of the wood grain initially and then once covered, use your brush to "finish" going vertically. Any brush strokes you do have in the paint will be less visible if they are vertical rather than horizontal.
(7) Applying. Follow the instructions for applying that are on the outside of your paint can. Do not apply paint when it is either too cold or too hot. Too cold? Below 55 degrees Fahreeight (F). Too hot? About 90 degrees F. Direct sun is ok.