This shed roof has three basic roof-framing components: standard rafters, a hip on the other side and the valley rafter set you see front and center. The sturdy overhangs are also easy to build. PHOTO and FRAMING BY: Tim Carter

DEAR TIM: Many older homes I have been in have wide-open attics, and the roofs were built without modern trusses. Is it still possible to frame a roof the old-fashioned way? Is it hard? What special tools do you need to frame a roof the way old carpenters did it? What other tips can you offer? Jacob N., New Holland, PA

DEAR JACOB: Oh, you bet it is still possible to build roofs the same way carpenters have done for hundreds, or even thousands, of years. This practice is still alive and well; many carpenters who operate under the radar frame roofs this way each and every day. Trusses are wonderful engineering marvels for modern carpentry and production building. Just about any roof shape or design can be framed using trusses. But often it is just as fast and cost-effective to frame a smaller roof using regular lumber, and a few common tools.

The art of roof framing is indeed a craft. There are many nuances and tricks that can take years to master, but simplistic and basic roof framing can be learned in as little as 30 minutes. The trick to simple roof framing is to ensure the wall system that the roof rests upon is level, plumb and square. Square means that all corners are true 90-degree angles. It is possible to create a square layout for the roof framing on top of walls that are not square, but believe me, it is so much better if the rough carpenters take the time to frame the walls so they are square.

Years ago it was not as critical to have the roof perfectly square. Once the roof framing and rafters were in place, they were covered by individual 6-inch-wide or slightly larger pieces of lumber. It was easy to cut the lumber to fit out-of-square rafters. But today, carpenters use large 4-foot by 8-foot sheets of plywood or oriented-strand board to rapidly cover the roof rafters or trusses. If this framing is out of square, it can be a nightmare to fit these large pieces of lumber along the narrow edge of each rafter.

In reality, you need three very simple tools to cut regular roof rafters, hip and valley rafters and the small jack rafters that intersect hips and valleys: a saw, framing square and tape measure. The only two dimensions you need to know to make all of the necessary cuts are the actual pitch of the roof you desire and the overall width of the span that the roof will cover. Simple geometry takes over at this point.

If you look at a modern high-quality framing square, it has a large number of measurements and tables on the tool. 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.

Roof pitch refers to the angle of the roof or the amount of its slope. It is commonly defined as the number of vertical inches a roof rises per foot of horizontal run. For example, a building plan may call for a 6 / 12 pitch roof. Pitch is defined as the "steepness" of a slope. You can use numbers to communicate this relationship. In this case what the architect is trying to convey is that he wants the slope of the roof to go up six inches for every 12 inches horizontal run.

Mathematicians look at pitch differently. They take the total rise of the roof and compare it to the total span of the roof and determine the actual ratio. For example, a roof that has a total rise above the exterior wall top plate of 6 feet and a total span of 30 feet would be a 1/5 pitch roof.

The overall width of the building is that measurement where the outside surfaces of two parallel exterior walls end. Carpenters often refer to this as the building line. If you go back in time to when you were sitting in your high-school geometry class, you should be able to quickly visualize this overall-width dimension is nothing more than the bottom line of a triangle. The two roof rafters that slope and eventually rest on the exterior walls represent the other two lines of the triangle.

The framing square used by carpenters is nothing more than a right triangle and when you adjust it on the side of a piece of lumber, it produces two accurate cut lines. A right triangle is one that has a 90-degree angle where two of the lines intersect.

This framing square creates the plumb-and-heel-cut lines. Right now it is set for a 6 / 12 pitch cut. The line on the right will be the plumb cut and the longer line on the left is the heel cut that rests on top of the wall. PHOTO CREDIT: Tim Carter

One of these lines is called the plumb cut. The plumb cut creates a line that is perfectly plumb, and is used where the roof rafter contacts the ridge board at the top of the roof. An additional plumb cut is made near the bottom of the rafter in the notch where the rafter passes over the exterior wall. Plumb cuts are also required where a rafter intersects a hip or valley rafter. The framing square also produces a second cut line called the heel cut. This cut line is made on the rafter where the rafter sits flat on top of the exterior wall.

The tables and numbers on a framing square are accurate, but modern construction calculators really are the tool to use to calculate the length of rafters. These very inexpensive tools do all of the mathematics in the blink of an eye. They also need a minimal amount of data entered to produce extremely accurate dimensions for any type of rafter you might cut.

The trick to becoming comfortable with roof framing is to frame a very small roof at first. For example, just try a simple roof that would sit on a box that measures 2 feet wide by 32 inches long. You will be shocked how simple it is to make perfect cuts so the rafters meet at the top, with no gap whatsoever.

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DEAR TIM: I am going to frame some exterior wood walls and don't have a clue where to start. As with anything, I am sure there are some pitfalls to avoid and labor-saving tips that will allow my walls to be perfect or nearly so. Can you give me a quick run down of what I need to know to ensure the job will go smoothly? Patrick G., Racine, WI

DEAR PATRICK: Your question brings back a vivid memory. Years ago I was building a room addition on a house and immediately next door the neighbor started to build his own room addition. He framed his exterior walls in the air and had all sorts of clamps and devices to hold the pieces of wood together as he tried to nail them. It was a comedy of errors and it took him five times longer to do it his way than if he had just mimicked what I was doing with my crew.

The first thing you need to know is that you should use Mother Nature's gravity to your advantage. Frame all of your walls on the ground or the floor surface and then tilt them up once they are finished. Some carpenters go so far as to completely apply the exterior finish siding and trim on the walls before they are tilted up. You need to be a highly-skilled craftsman to make this work, so don't try it for a few years.

The wall on the floor is square and ready for OSB sheathing. The bottom and top plate are exactly the same length. The king studs in the wall are also the same height. Doing this ensures the wall will be square when the diagonal measurements from corner to corner are the same. PHOTO BY: Tim Carter

The walls themselves and the floor plan shape they create must be square if you want the next story and / or the roof to go on with no problems. The building term square means that a rectangular or square shape of an object is made up of four 90 degree angles. If you remember your high school geometry, you may recall you can have at least two other objects that also have four sides to them; a rhombus and a trapezoid. You want to avoid these shapes at all costs.

The first thing to do is to create a layout on the ground where the walls will go. Make sure the layout is square. You can use an inexpensive construction calculator to do the math or you can make your own 90 degree angles with common, known math solutions. For example, you can use the tried and tested method of the 3, 4, 5 right-triangle solution. A triangle that has three sides where one is 3 feet long, another is 4 feet and the final leg is 5 feet long creates a right triangle. The intersection of the 3 foot and 4 foot leg create a perfect 90 degree angle.

Any multiples of these dimensions also work; 6, 8, 10 or 12, 16, and 20 are also combinations that yield a perfect 90 degree angle.

When you start to frame your walls, the height of all of the main studs must be exactly the same. Check them as mill-cut studs are by no means always perfect. Recently, I ordered 100 2x4 by 8 feet studs and quickly learned that some in the pile were exactly 8 feet long while others where 96 and 5/16ths long. That is a significant difference.

The top and bottom plates of the walls also need to be the exact same length. After you nail the studs to the plates, you have created a parallelogram that you must now nudge into a perfect square or rectangle with four 90 degree angles at each corner.

To square up the wall once all parts are nailed together, make sure the bottom plate is in a straight line. You can do this by snapping a chalk line on the floor and tapping the bottom plate so that its edge is along this line for its entire length. If the floor is wood, tack the bottom plate to the floor to ensure it stays put along the chalk line.

The last step is to check the diagonal measurements across the wall. Use a helper with this task. If you both attach a tape measure to a corner and then pull across the wall to the opposite diagonal corner, your tapes will create a giant X on the wall. Measure accurately from corner to corner.

At first, each of you will likely have different measurements. Whoever has the longer of the two measurements should take a hammer and tap the end of the top plate towards the other person. This will shorten the long diagonal measurement and make the other measurement start to grow. When both measurements are identical, the wall is perfectly square.

Once the wall is perfectly square, it is time to apply the sheathing. This material comes in 4 x 8 foot sheets and is usually one-half inch thick. You want to apply either OSB, plywood or some other structural material at each corner of the wall. Once this material is nailed in place to the wall studs, the wall will remain square and will not rack under wind or seismic loads. This bracing is a critical framing requirement.

It is far easier to apply this sheathing while the wall is flat on the ground. Resist the temptation to stand the wall up without the sheathing. The wall will be heavier with the sheathing in place, but you can get some help from friends or neighbors to help you tilt the walls into position.

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