Decayed Wood Siding

I Just bought a farm house about 100 years old. The exterior hasn't been painted in a very long time. Several of the exterior boards have wood rot and will be replaced. Is there any special treatment for the house before I paint to eliminate any more wood rot from appearing in the future?

Yes, look for patterns of paint peeling to bare wood and exterior wood decay that point to sources of moisture, and then eliminate or reduce the moisture. For example, if you find peeling paint or decayed wood siding in a vertical strip beneath a leaking roof gutter, fix the gutter so it catches the water before it spills down across the wall causing further decay.

Paint Layer Colors

I will be painting the exterior of my 1858 farmhouse. I am not sure of what colors to use. There are ads in the back of magazines to help people choose the best color for their house. Should I try them, or just pick a standard "historic color" from one of the paint manufacturers?

Consider "cratering" for paint evidence. You could begin by checking out what colors your house has actually been at various times in the past. In a small area (perhaps 2" x 2") sand down through the several layers of paint. With 100 grit sandpaper sand in a circular swirling motion creating a very shallow crater, or concave depression. A series of concentric rings of color will be revealed representing the various past layers of paint. The crater's rim at the outer edge shows the existing top layer. Keep sanding away until the wood beneath is revealed at the lower center of the crater. Then smooth the crater's surface by sanding with successively finer grits: 200, 300, 400, perhaps even 600. Wet the surface with water and examine the layers with a magnifying glass. Even if the house has always been white, you may be able to count the layers. Crater for paint color evidence in several locations including siding, trim boards, windows, cornices, etc. Some houses were painted different colors in different locations.

CAUTION: SANDING OLD PAINT CREATES HAZARDOUS LEAD DUST. As you do this sanding, keep the surface damp with a spray bottle containing water and a little detergent and use wet/dry sandpaper. Wipe up residue frequently with a paper towel. For each wipe fold the paper towel over to enclose the soiled paper and to expose fresh paper. Drop paper towels in a plastic bag. Double bag and seal before disposal. Wash up and change your clothes before eating or smoking. Launder clothes separately from other clothes with TSP. Run the rinse cycle with TSP to clean out the washer.