Compromise makes a good umbrella, but a poor roof.
James Russell Lowell (1819-1891)
All creatures take shelter from the storm. One of the feral cats who lives behind our house created a nest in the base of a bush near the back yard. Toads burrow snuggly into piles of sand near the walls of the house, and foxes make dens in hollow logs or trees. It is thought that more than 35,000 years ago, Neanderthal man created structural frames from mammoth bones and covered them with animal skins. Since that time, humans have made roofs using everything from “ready made” caves to sod over birch bark, sapling webbing covered with animal hides, and the ever popular thatching. Fired roof tiles were found in Greece as early as the 3rd millennium BC! Over the many years that people have been covering both heads and belongings with something installed over their dwelling places, man has learned to some degree which materials work better than others and also developed new ways to stay safe and dry. I remember hearing as a child, “As long as the roof doesn’t fall in, we’ll be OK,” in response to anything potentially dire. Simply put, it is common knowledge that a roof to call one’s own is both necessary and important.
The decisions about the roof for the new house were made before any other ideas were put in place. The plans for the strength and security of the roof made all other design decisions secondary, much to the frustration of the architects. To decide on the shape and pitch of the roof, Vince read all of the existing FEMA reports and gathered information from other sources like the International Building Code, the Coastal Construction Manual, Miami-Dade and the Texas Department of Insurance. From these sources, he learned that the roof pitch had to be between 4/12 and 6/12 to withstand the wind loading from a big storm. (A roof’s pitch is the measured vertical rise divided by the measured horizontal span, like slope in geometry.) A roof with the wrong shape and slope can literally become a giant wing in heavy winds, lifting itself off the house. If you lose the roof, you lose the house, so this piece of the design was critical. Our roof pitch is 5/12. It is acceptable to have a slightly different ratio, but it is more important to have the roof stay on the house than to have an extra foot of interior width. We had to be careful not to let this number slip too far from the appropriate range when planning the living spaces.
Roofs can be made in many different variations of angles and planes. This house will have a “hip” roof, which means that all sides slope downwards to the walls, usually with a fairly gentle slope. It is a house with no gables or other vertical sides. Since a hip roof is self-bracing, it does not need the same amount of diagonal bracing (wind bracing) that a gable roof requires. Our house is rectangular, so it will have two triangular sides and two that are trapezoidal. On a rectangular plan, a hip roof has four faces that are almost always at the same pitch or slope, which makes them symmetrical about the centerlines. (On a square house, a hip roof is shaped like a pyramid.)
Because they require a more complex system of trusses, hip roofs are somewhat more difficult to construct than a gabled roof. Although the roof itself is harder to construct, the walls that carry the roof are easier to build, being all one level. The triangular faces of the roof are called the hip ends and are bounded by the hips themselves. The hips (where the planes meet) sit on an external corner of the building and rise to the ridge.
One downside to a hip roof is the lack of space within the roof structure to use for other things. There was a recent change in the height allowance by Currituck County, allowing the 35’ maximum height to be measured at mid-roof rather than at the peak of the roof, and that extra footage allowed the ceiling heights to be at 9' with the roof pitch staying where it should be. Once the two main roof decisions (roof shape and roof pitch) were in place, the constraints established by them were concrete. End of discussion. This is why, as mentioned in the earlier, we will have a house that is a beautiful shoebox.
Here is the section of Vince’s specifications for the roof framing:
11) Hips, Valleys, and Ridges – Roof Trusses provided by Universal Forest Products.
12) Roof Sheathing - 5 ply, ¾” CDX pressure-treated (rated for ground contact), exterior-grade APA Structural I rated plywood, glued and screwed using 2 ½” long type 316 stainless steel screws. The first course of plywood is to be ¾” 5 ply, CDX pressure-treated, exterior-grade APA Structural I rated plywood, glued and screwed using 2 ½” long type 316 stainless steel screws, and completely covered by a “peel & stick” rubber membrane sheet (at least 60 mils thick). Provide adhesive fillets on interior of all roof sheathing.
The decisions about the roof for the new house were made before any other ideas were put in place. The plans for the strength and security of the roof made all other design decisions secondary, much to the frustration of the architects. To decide on the shape and pitch of the roof, Vince read all of the existing FEMA reports and gathered information from other sources like the International Building Code, the Coastal Construction Manual, Miami-Dade and the Texas Department of Insurance. From these sources, he learned that the roof pitch had to be between 4/12 and 6/12 to withstand the wind loading from a big storm. (A roof’s pitch is the measured vertical rise divided by the measured horizontal span, like slope in geometry.) A roof with the wrong shape and slope can literally become a giant wing in heavy winds, lifting itself off the house. If you lose the roof, you lose the house, so this piece of the design was critical. Our roof pitch is 5/12. It is acceptable to have a slightly different ratio, but it is more important to have the roof stay on the house than to have an extra foot of interior width. We had to be careful not to let this number slip too far from the appropriate range when planning the living spaces.
Roofs can be made in many different variations of angles and planes. This house will have a “hip” roof, which means that all sides slope downwards to the walls, usually with a fairly gentle slope. It is a house with no gables or other vertical sides. Since a hip roof is self-bracing, it does not need the same amount of diagonal bracing (wind bracing) that a gable roof requires. Our house is rectangular, so it will have two triangular sides and two that are trapezoidal. On a rectangular plan, a hip roof has four faces that are almost always at the same pitch or slope, which makes them symmetrical about the centerlines. (On a square house, a hip roof is shaped like a pyramid.)
Because they require a more complex system of trusses, hip roofs are somewhat more difficult to construct than a gabled roof. Although the roof itself is harder to construct, the walls that carry the roof are easier to build, being all one level. The triangular faces of the roof are called the hip ends and are bounded by the hips themselves. The hips (where the planes meet) sit on an external corner of the building and rise to the ridge.
One downside to a hip roof is the lack of space within the roof structure to use for other things. There was a recent change in the height allowance by Currituck County, allowing the 35’ maximum height to be measured at mid-roof rather than at the peak of the roof, and that extra footage allowed the ceiling heights to be at 9' with the roof pitch staying where it should be. Once the two main roof decisions (roof shape and roof pitch) were in place, the constraints established by them were concrete. End of discussion. This is why, as mentioned in the earlier, we will have a house that is a beautiful shoebox.
Here is the section of Vince’s specifications for the roof framing:
8) Ceiling and Collar Joists – Roof trusses provided by Universal Forest Products designed for 150 mph wind loads. End sections (extending beyond the walls) are to be pressure-treaded wood (Forest Products ProWood® Micro).
9) Rafters - Trusses will be anchored to the walls with type 316 stainless steel nailing brackets per engineered plans if there is potential for exposure to exterior moisture. Brackets that are completely internal to the envelope and insulation will be hot-dipped galvanized steel.
10) Sub Fascia - 2" x 6"
11) Hips, Valleys, and Ridges – Roof Trusses provided by Universal Forest Products.
12) Roof Sheathing - 5 ply, ¾” CDX pressure-treated (rated for ground contact), exterior-grade APA Structural I rated plywood, glued and screwed using 2 ½” long type 316 stainless steel screws. The first course of plywood is to be ¾” 5 ply, CDX pressure-treated, exterior-grade APA Structural I rated plywood, glued and screwed using 2 ½” long type 316 stainless steel screws, and completely covered by a “peel & stick” rubber membrane sheet (at least 60 mils thick). Provide adhesive fillets on interior of all roof sheathing.
Vince chose to use engineered and manufactured trusses to be assured that the roof could carry the wind loads. A stick built roof system doesn’t have the same series of checks and balances as those planned by a structural engineer. Johnny Ghee, who also designed the interior trusses, engineered the roof trusses. Johnny has to his credit a unique design feature for roof trusses, based on requests that he was frequently getting for a more authentic 1940’s beach cottage look. In the design of the truss tails, which should be treated for his application because they are exposed, the tail is offset ¾” lower than the actual truss. This leaves enough space for there to be an additional piece of plywood (usually a simulated bead board) to be placed so that the house has a more traditional look. To accomplish that look without Johnny’s innovation, the trusses would have to be stick built, and the roof would not be as strong. It’s a great idea and a way to add an interesting architectural feature within a structurally sound roof. Our house is more contemporary, so we aren’t using that look, but we wanted the treated tails anyway.
Because there are screened porches on either end of the house that are under roof, Vince designed the porch roofs as separate entities, so that the main house roof would not be damaged if the porches broke away during a storm. This means that the main roof will be built and sealed before the porch roofs are added. The trusses for the porches were to be designed as separate from the house. Unfortunately, the trusses and porch roof for the north side of the house were mistakenly designed as being integrated into the main house roof, so we now have had considerable delay while we wait for the new trusses and for the double galvanized truss plates that hold them together. This was much too important a part of the structural strength to let pass: “If you lose the roof, you lose the house.” So far, the two biggest mistakes have been because the trusses were manufactured incorrectly. It’s unfortunate, because even though Universal Forest Products replaces them correctly or helps with the field repairs, it costs us time and effort. Luckily, the mistakes have been caught while they can be fixed, but it definitely isn’t a good thing, and it’s hard to understand why it has happened. The new trusses will be delivered and installed next week (10/7), and then we can finally get the house under roof. Much to his credit, Vince did not “go through the roof” over this error. I could not resist adding that!
When riding along the roads of the Outer Banks, you see that most houses have little square vents all along the sides of the roof. There are also chimneys and skylights and exhaust pipes for one thing or another. Vince has been adamant all along that there be no penetrations in this roof, because wind blown rain can get into even the smallest space and cause a leak. In the end, there may be something that must be vented through the roof, but hopefully that can be avoided. The roof specifications call for 4” of closed cell polyurethane foam (2.2 lb per cubic foot) that is applied directly to the roof deck and covered with 12” of unfaced fiberglass batts, which as a side benefit leaves no room for there to be heat building up between the insulated space and the actual roof. This translates into a nice feature: No need for roof venting!
Once the framing is completed, the roof is tied to the house with tie-downs made of galvanized steel. The tie-downs have an important function, because they carry the load path from the roof of the house all the way to the pilings. When the wind exerts a lift force on the roof, it will in effect be pulling on those very deep pilings. The tie-downs that Vince has chosen are larger and stronger than needed, because…If you lose the roof, you lose the house!
Because there are screened porches on either end of the house that are under roof, Vince designed the porch roofs as separate entities, so that the main house roof would not be damaged if the porches broke away during a storm. This means that the main roof will be built and sealed before the porch roofs are added. The trusses for the porches were to be designed as separate from the house. Unfortunately, the trusses and porch roof for the north side of the house were mistakenly designed as being integrated into the main house roof, so we now have had considerable delay while we wait for the new trusses and for the double galvanized truss plates that hold them together. This was much too important a part of the structural strength to let pass: “If you lose the roof, you lose the house.” So far, the two biggest mistakes have been because the trusses were manufactured incorrectly. It’s unfortunate, because even though Universal Forest Products replaces them correctly or helps with the field repairs, it costs us time and effort. Luckily, the mistakes have been caught while they can be fixed, but it definitely isn’t a good thing, and it’s hard to understand why it has happened. The new trusses will be delivered and installed next week (10/7), and then we can finally get the house under roof. Much to his credit, Vince did not “go through the roof” over this error. I could not resist adding that!
When riding along the roads of the Outer Banks, you see that most houses have little square vents all along the sides of the roof. There are also chimneys and skylights and exhaust pipes for one thing or another. Vince has been adamant all along that there be no penetrations in this roof, because wind blown rain can get into even the smallest space and cause a leak. In the end, there may be something that must be vented through the roof, but hopefully that can be avoided. The roof specifications call for 4” of closed cell polyurethane foam (2.2 lb per cubic foot) that is applied directly to the roof deck and covered with 12” of unfaced fiberglass batts, which as a side benefit leaves no room for there to be heat building up between the insulated space and the actual roof. This translates into a nice feature: No need for roof venting!
Once the framing is completed, the roof is tied to the house with tie-downs made of galvanized steel. The tie-downs have an important function, because they carry the load path from the roof of the house all the way to the pilings. When the wind exerts a lift force on the roof, it will in effect be pulling on those very deep pilings. The tie-downs that Vince has chosen are larger and stronger than needed, because…If you lose the roof, you lose the house!
May you always have walls for the winds, a roof for the rain, tea beside the fire, laughter to cheer you, those you love near you and all your heart might desire
Irish Blessing
