In a house exterior of say 70 or 80 years of age, there are moments where power washing is approached very cautiously. If it is an all wood exterior there are definitely moments where pointing water at 3,000 per square inch pressure is Not a good idea. Water can infiltrate into the tiniest crevices at that pressure and do interior damage later on(just ask our neighbors who have used other contractors in the past- entire interior ceilings, gone and falling in-be very careful). For wood exteriors it’s important to stay in the 1,500-2,000 psi range while power washing, and it’s even more important to have your contractor up in the air shooting Down at the exterior. This keep water from forcing up into the bottom edge of lap siding and entering the home.
Siding is a tricky issue as well. When aluminum siding looks like it could use a good cleaning, that may actually be the point at which the homeowner might choose to go ahead and paint the siding after washing. It’s rare that aluminum siding holds up well after a wash. MAny times it can look even more worn out after a wash due to it’s already chalking up from age. This doesn’t just apply to siding that is now 40 years old. Newer siding only 10-15 years old can lose its factory enamel depending on which side of the home it rests on. A recent home we toured had almost 2 different colors apparent-and mainly due to the western exposures being bleached and chalked out. Time then to probably paint it. If so, make sure the contractor uses a blended, self-priming exterior coating such as Porter PPG Permanizer or Sherwin Williams Duration. Both are rated excellent for double coating of aluminum.