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Moss, Buckling and missing shingles

Solutions to moisture issues in historic homes-Roofs

mossy shingles
roof leak
Condensation stains

My last article was on the causes of moisture issues in historic houses. On the slim chance that you have not already voraciously devoured this thrilling topic here is a link:

For the most part the concern of occupants of historical homes is for some reasonable thermal comfort in terms of heating in cold weather and ventilation and protection from the sun and warm weather.  In the past people naturally adjusted their clothing and activities to fit the weather. They did not have the expectation of precisely controlled temperature and humidity. They lived within the natural environment with the shelter and technologies available to them.

A house with four occupants generates between one and two gallons of moisture a day from human residents. Moisture from food preparation, showering, or laundry use will produce condensation on the windows in the winter. Frequent condensation on interior window surfaces is an indication that moisture is migrating into exterior walls which can cause long-term damage to historic materials. Moist interior conditions and humid climates can generate mold and fungal growth. It is important to provide adequate ventilation and find a balance between interior temperature, relative humidity, and airflow to avoid interior moisture that can cause damage to historic buildings.

The majority of moisture problems can be mitigated with maintenance, repair, control of ground and roof moisture, and improved ventilation.


Let’s start from the top. The first thing that needs to be checked and repaired, as necessary, is the roof. A roof inspection is one of those preventative maintenance jobs that is easy to overlook. Don’t. Add a once-a-year reminder on your calendar, preferably in spring, to go out on a warm day and fix any problems you find ( Not a bad idea to check your roof after the kind of wind event we had last week. If shingles have blown off that may also indicate that it may be time to have your roof done as the shingles are getting brittle). If you are not comfortable with heights and ladders you do not have to get up close and personal. You can inspect the roof from the ground using binoculars.

Here's what to look for:

Shingles that are buckling, curling, or blistering.
Missing or broken shingles.
Cracked caulk or rust spots on flashing.
Cracked and worn rubber boots around vent pipes.
Masses of moss and lichen which could signal the roof is decaying underneath.

If you find colored grit from asphalt roof tiles in the gutters or on the ground by the drainpipes that's a bad sign. These sand-like granules cover the surface of roof shingles and shield them from the sun’s damaging ultraviolet rays. Check the age of your roof and see if it's nearing the end of its lifecycle. Typically asphalt roofs last 20-30 years depending on the type and grade of shingles. The typical life of a wood shingle roof is 30-40 years. Similarly, a good quality, properly-installed wood shake roof has a life expectancy of 20-40 years. But wood shingle or wood shake roof life expectancy varies considerably depending on the wood shingle or wood shake grade or quality and how it was installed, and exposure.

You may be thinking as I did “What is the difference between a shingle and a shake, and can I get that in chocolate?”

Here is a link defining the differences and similarities: Hint: they do not come in chocolate!

Next week Gutters.. or how to keep your mind in the gutter!

Tom Ayars uses his thirty-plus years of construction experience to help Nantucket homeowners keep their historic (and newer) homes in great condition. Email him at:

[email protected]