What's the Best Way to Install Cedar-Shingle Siding on an Old House?comments (4) June 20th, 2012 in Blogs
As part of a city lead-abatement program, Erik Neave's 1865 Wisconsin house is being re-shingled. New white cedar shingles will cover up a layer of painted shingles, which given the age of the house no doubt are contaminated with lead-based paint.
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The facelift will certainly brighten the appearance of the house while entombing the paint, but it's the installation that has Neave concerned. The contractor who successfully bid for the job has installed a layer of 1/4-in. fanfold insulation over the old shingles and is busy stapling up the new ones even as Neave writes to Fine Homebuilding's Breaktime forum for advice.
"I was on my honeymoon when they started and they are about halfway done with the house now," he writes. "I have never installed shingles before but on the things I've seen online, I am a bit concerned about the installation."
Neave's worry? Because the singles are being installed directly over the fanfold insulation, there will be no air circulation behind them, and everything he's read on the subject suggests there should be.
"When asked about this, the contractor said that the fanfold insulation achieves this purpose," Neave says. "It sounds a bit fishy to me because I thought insulation would do the opposite...I want to trust that they know what they are doing, but it is stressing me out that I won't really know if this type of installation is quality till a few years down the road when problems show up."
Here's how it should be done
Mike Smith, a builder from Rhode Island, lays out for Neave how the job should be approached, beginning with stripping all of the old shingles off the house.
Then, Smith says, replace the flashing at doors and windows, wrap the house with 15-lb. or 30-lb. felt, scrape the lead paint off the existing trim (following EPA lead-abatement procedures), repaint the trim and re-shingle.
"If this contractor does what he's saying...he is going to bury all your trim..." Smith says. "He's a hack. Who wrote your specs? Where did you get this guy from? Or perhaps I'm being too harsh. It doesn't sound like you are going to get a very good job."
But the windows the contractor has installed look good, Neave replies, and the exterior trim has been built out and capped with aluminum. The real issue here is whether the installation method the contractor has chosen will trap moisture on the back of the shingles and raise the potential for problems down the road.
On that question, Smith is confident the fanfold will not act as a vapor barrier because it should allow the passage of water vapor. Its purpose, he adds, is to level the existing layer of shingles to make a good nail base for the new ones.
"Realistically," Smith adds. "I don't know what other choices you have other than choosing a different siding...like fiber cement, or vinyl...or red cedar, etc."
DanH agrees with Smith.
"About the fanfold," he writes. "Fanfold siding backer (it's not really 'insulation' to any degree worth mentioning) is almost always perforated so that moisture can pass through to a moderate degree.
"Far from ideal, but it's not a solid, impervious piece of plastic/foil. How well the shingles will work out on the fanfold is hard to say. Certainly far from ideal, but ideal would cost a lot more money."
But Piffin does not buy in.
"They should start by tearing off the old shingles," Piffin says. "The fanfold is OK but requires a breather between it and cedars."
In these circumstances, the new shingles will hold up only if the climate is dry, there are large roof overhangs and plenty of trees to shelter the house from wind-driven rain, Piffin adds.
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