When looking for design inspiration for our tiny house we didn’t see many tiny homes that were using asphalt shingles. Cedar shingles or shakes and metal roofs seemed to be the most common choice and there were even some fairly obscure roofing products being used.
At first we thought we would go with cedar shingles. They look great and are lighter than asphalt. There were a few problems with cedar shingles, however. The roof on our tiny house was a 2:12 slope; what this means is that for every 2 feet the roof raises vertically it will go 12 feet horizontally. This works out to a 9° slope. Cedar shingles and shakes are not recommended on slopes less then 4:12 or 18° slope. A waterproof membrane could be installed under the cedar shingles to prevent leaks but this would add weight and the shingles may not drain properly which puts them at risk to rot quicker. Cedar shingles are light when bone dry but since they absorb a fair bit of moisture from rain and snow they would lose most, if not all, of their weight savings. They also lay thicker so we would lose almost an inch of interior head space; the maximum height of the trailer needed to be under 13′ 6″ so thicker roofing material would translate to more space lost inside. Cedar shingles are almost three times as expensive as asphalt shingles and more time consuming to install. The final straw was that the low slope makes it hard to see the roof from the ground anyway so there wasn’t really much aesthetic value to be gained.
Metal roofs are also popular. They they are fairly affordable, last a long time and are the best choice for water collection. One drawback to consider is that metal roofs can be noisy, especially in heavy rainfall and hail. The noise alone would have been acceptable to us but the big drawback for metal roofs is the height they require to install. They take up a great deal of vertical space. There needs to be strapping on the roof to help with airflow, which adds ¾”. Then the metal itself is corrugated to add rigidity, usually making the sheets about 1 ½” thick. Those two factors would have reduced our head space by about 2″ in our lofts which for us meant that metal was no longer an option.
We knew the asphalt would perform well on the slope of our roof and was the thinnest roofing option. It was also affordable. The only drawback was the weight difference but this really didn’t amount to much, only about 200 lbs more than cedar when it is completely dry. This weight gain was acceptable considering we saved much more than that by using LP SmartSiding and eliminated the need for OSB sheathing altogether.
Note that the ice and water shield overlaps the trim board at the top of the wall. The roof needed to be finished last because there are no overhangs to prevent water from getting behind the siding.