How To Frame A Gabled Dormer

This step by step woodworking project is about how to build a gazebo roof. A rafter is one of a series of sloped structural members (beams) that extend from the ridge or hip to the wall plate , downslope perimeter or eave , and that are designed to support the roof deck and its associated loads. The poles holding up the roof also have to be cemented a small cab like this it wouldn’t take much to take off the snow. Now measure from this point up to the intersection of the ridge board and header to find the length of the valley rafters. Start the next course of sheathing on a different truss to stagger the seams and strengthen the roof and continue sheathing the roof till finished.

As you can see in the image, you need to cut the 3/4″ plywood sheets at the right size before attaching them to the rafters. Your local building codes may also require the use of hurricane ties for each truss member where it rests on the top plate. The author has seen many instances where valleys are constructed on trussed rafters with no internal support to the valley ridge or the valley jack rafters.

As the main roof is a warm roof with the insulation between and down the slope of the rafters, the roofing underlay is a breathable one and there is no need, therefore, to install eaves ventilation. Stretch a string across the top of the rafters, aligned with the inside of the side wall, and make a mark where this line intersects the top of the side rafters. Shingle the roof from the bottom up according to the instructions on the shingle packaging.

The most common flat roof problem relating to rafters is ‘sagging’, which generally occurs in one of two ways; a) Sagging of the rafters themselves due to insufficient strength/rigidity (thickness). Even though conventional framing has been around for centuries, with the advent of trussed roof systems, the demand for pro roof cutter’s has decreased. Roofing battens run across or down a roof (sometimes both) to provide a fixing point for roofing cladding materials such as tiles or shingles. Mansard (image 4) A modified version of the pitched roof that creates a spacious living area in the roof space.

This strategy has the advantage of keeping piping and ductwork within the conditioned volume of the house so these building components don’t require insulation for energy efficiency or protection against freezing. For simplicity, and to prevent error, the first thing I do is deduct the full width of the ridge beam from the building width: in this example 6 ft. 3/4 in. – 1 ½ in. = 5 ft. 11 1/4 in.

Then make good around the walls, using metal fixing strap, long nails, rebar or oak pegs. So if your house is 26 feet wide and the roof ridge beam is centered on the house, you will need a rafter that can span 13 feet. The framing style of the roof refers to the actual components of each roofing truss and the design of the structural foundation of that roof.

No part of a timber roof should ever be cut, modified, remove or the covering of the roof changed (i.e. replacing a slate roof covering by a concrete tile covering) without consulting a structural engineer. The Mansard roof was named after the French 17th-century architect Francois Mansart (1598-1666), who popularized the form. This free farming construction plans and projects information is courtesy of the North Dakota State Univ. The simplest way is to hold the rafter against the ridge and see how far you want the roof rafter to hang over the side of the building. The trusses supported purlins and binders which in turn supported rafters and ceiling joists.

A window frame that is hinged on one vertical side, and which swings open to either the inside or the outside of the building. A small, square cupola that functions as a lookout tower, located at the top of a building. Discipline needs to be exercised in the specification of trussed rafters and particularly in their erection. The size of rafter timbers will depend upon their length from the wall plate to the ridge, the type of roof covering and whether purlins are incorporated in the roof. It’s always good to review the basics in order to avoid accumulated error” which, amongst other things, is what you can get when you step off rafters instead of using a calculator.


As you can see in the image, you need to cut the middle rafters at 45º, using a miter or a circular saw. A prudent builder will therefore measure the distance over the wall plates at the time when the final order for trussed rafters is placed. Placing too big a pile of sheathing on an unbraced truss roof can lead to disaster. That’s because for each foot of horizontal run from the outside of the shed wall, the roof climbs 4 inches, and five times four equals 20.

For him pitch was rise/span, so an 8/12 rafter had a 1/3 pitch.” Never mind that with a shed roof or a salt-box, you were talking about 1/3 of something that didn’t even exist! Basically, you just temporarily prop up the top of the first rafter a little (=radius of central ring: see formulae) off the centre point of the essentially conical roof. I am not a pro carpenter (I am a wood worker), but am considering building a modest-sized house which I call a ‘cabin concept.’ Tremendous article.

In addition, if you’re building a new home or remodeling, make sure any attic decking that provides additional storage space or a platform for a heating and/or cooling unit or hot water tank is raised above the ceiling joists to leave room for adequate insulation. Therefore for their stability and for the stability of the other roof a series of diagonal bracing and longitudinal bracing is required to ensure stability. Roof trusses will hold of most of the load and will ensure the garage’s stability.

Lay the sheets on the rafters and secure them into place with 2” screws, every 8” along the rafters. Most rafters extend down past the edge of the exterior wall, creating an overhang. Rafter ties are always required unless the roof has a structural (self-supporting) ridge, or is built using engineered trusses. By knowing the span of the roof, and the pitch (the pitch is the angle at which the rafters rise) we can work out the length of the rafters. The gambrel roof truss in homes lets you include an upper floor below the roof.

Clerestory trusses are a-symmetrical, with one joist extending beyond the rest of the rafter to allow for a windowed-wall along the roof. The last two roofs we have done were as follows: 1. Drill and nail hundreds of hazel strips to the rafters in a spiral (See pic of hole from underneath). I might recommend using 2×6 16 inches on center if there’s going to be weight on the roof from snow.

Please note that all of the frame was made with the bark left on. Better practice for longevity is to remove the bark. If you familiarize yourself with the components that make up the rafter it should assist you in this roof framing task. You don’t need a central pole, and none of the rafters need be as wide as the building itself. Braced wall gambrel rafters for 20 – 34 ft spans, 2 ft on centers, nailed lumber.

If there are no ceiling joists or if the joists run perpendicular to the rafters, then the code requires rafter ties. The values on the calculator that we use for common roof framing are: Pitch, Rise, Run, and Diagonal. These are magic geometric numbers that were calculated years ago and tell you exactly how long to cut certain rafters if you know the roof pitch and the overall width that the roof spans.

With a symmetrical roof the forces applied to either side of it from the rafters and the weight of the tiles etc should balance, hence there is no need for this to be a particularly substantial timber. Slate has been used to roof buildings in the United States since the colonial era. The next step of the woodworking project is to install the intermediate rafters. You don’t have to understand all the technicalities of rafter cutting to build the dormer roof. If you want to know how to build roof trusses for a garage, you must ask a professional about the right support of the roof as well as its weight.

For a non- henge structure you can mark out the line of the wall with some other method eg rope laid on the ground where the wall will be. The small Charlie will need to be still strong enough to hold up all the rafters.) In the picture the Charlie is a tripod. The vast majority of domestic flat roofs consist of timber rafters and a timber ‘roof deck’. As high up as they are, collar ties have no leverage to prevent the rafters and walls from spreading outward. At the front of the building they were a little different with a section of posts and beams as per walls. But the rafters must resist bending (flexion), where they are relatively weaker.

A pitch of 7/12, for example, would mean that the roof rises 7 inches every foot that it extends. For my default structure of 13 rafters I usually cut about fifteen rafters of 3m (radius of building) plus 1 metre over in the centre plus 1-2 metres over at the eaves. Roof trusses are generally fabricated offsite, reducing price and speeding up the construction of your roof frame.