Sunday, January 28, 2007

Rafters - The Three Most Common Types

For any carpenter in residential construction that cuts roofs for a living, day in and day out, there are three types of rafters that he will constantly see. These are the common rafter, the hip/valley rafter, and the jack rafter.

The common rafter is the main rafter in any roof. The common rafter sits on top of the wall, its length meets the ridgeboard at the center of the building, making up half the span. The best example of this type of rafter is the gable roof. The gable roof is made up of nothing but common rafters. A gable roof is the easiest roof to cut and frame of any other type of roof. All common rafters are the same length from the plumb cut to the birdsmouth, and usually all have the same length tail.

The second most framed roof is the hip roof. The hip roof uses all three types of rafters mentioned here. The hip roof has no gable end to frame, but instead, has a roof that slopes to all 4 sides of the house. The main element in a hip roof is the common rafter. The amount of common rafters in a hip roof varies with the length and width of the building. For example, if a building has four equal sides (20x20, 24x24, etc.) the hip roof would resemble a pyramid and has four common rafters, one on each wall. The longer the length of the building the more common rafters there will be and the longer the ridgeboard will be.

What makes a hip roof? The hip rafter. If a building is square or rectangular there will be four hip rafters. The birdsmouth of a hip rafter sits right on the corner of the building. Its length slopes up at a 45 degree angle to where two commons meet the ridgeboard and make a 90 degree angle. The size of a hip rafter is determined by the size of the common rafter. If the common rafter is a 2x8, rule of thumb and most building codes call for the hip to be the next size up, in this case a 2x10.

A valley rafter has the same characteristics as a hip rafter except instead of originating at an outside corner, its birdsmouth sits where two walls create an inside corner. This situation is created when roofs run perpendicular to one another. These roofs slope to the valley rafter which bisects these roofs at a 45 degree angle.

Where there are hip or valley rafters, there are jack rafters. Jack rafters complete the framing on a hip roof from the hip to the top plate, starting a the common rafter down to the top plate or tail of the hip rafter. The tails of the jack rafter are cut the same as a common rafter. The plumb cut is the same pitch as a common rafter but cut at a 45 degree angle (compound angle) to match up with the angle of the hip.

With valley rafters, jack rafters usually start at a ridge and terminate at the valley. The cut at the ridge is a normal plumb cut. The cut at the valley is a plumb cut but the long point is at the bottom of the rafter and cut at a 45 degree angle (compound angle) to match the valley angle.

Mike Merisko (C) 2007

Monday, January 15, 2007

Building By The Square Foot

How much material is it going to take to do the job? What is the labor cost for the project? These are questions a contractor asks himself when bidding a job. In most cases a contractor will use the square foot method to determine the answer to those questions.

This method of take off is particularly handy in figuring sheet good type materials such as wall sheathing, plywood decking, roof sheathing and drywall. To find the square footage for one of these areas, multiply the height or width times(x) the length. For example if you have an eight foot high wall by 40 feet long the square footage for the wall would be 320 square feet. Most sheet goods are 4 feet by 8 feet or 32 square feet. The square footage of the wall is divided by 32. It will take 10 sheets of plywood or insulated sheathing to cover this wall.

This same method can be used to figure the plywood or OSB for the house deck and roof. To figure the deck simply multiply the width of the deck by the length to get the square footage and divide by 32. Figuring the square footage of a roof is similar but with a twist. For the roof multiply the length of the rafters by the length of the roof. Take the result times 2 for the total square footage for both sides of a gable roof, then divide by 32 to get the amount of plywood to sheet the roof. The square footage of a hip roof is figured the same way.

Drywall is also figured by the square foot. This can be an involved process. It can be broken down into two parts. First the square footage for the ceilings can be figured. Like the deck this is figured length times width. Then the lineal feet of all the walls is taken times the height. Interior walls will be added in twice because they have drywall on both sides. Labor to hang, tape, and paint the drywall is also figured this way.

Besides drywall and painting, many other labor costs are figured by the square foot. Roofing and siding are figured by the square. A square is 100 square feet. For example if a roof is 1200 square feet, it will take 12 squares of shingles to cover it. The same unit of measurement goes for vinyl, wood, alumimnum, steel and cement sidings.

Carpentry makes use of this measurement also. The cost to frame a house is usually figured by the square foot. Costs to build a whole house are estimated this way to help people determine if a house or its house plans are affordable for them to build.

Flooring is also among one of those things that use the square foot method to figure labor and materials. This includes ceramic and quarry tiles, hardwood, laminate, and vinyl flooring, and carpeting. Most contractors and installers use a price per square foot for their labor when calculating their costs for installation.

This information will help you understand contractor estimates and help you do your own calculations for projects.

Mike Merisko(c) 2007

Wednesday, January 03, 2007

Vinyl Siding: The Misunderstood Finish

For the last 20 years vinyl siding has been the exterior finish of choice, ahead of wood, aluminum, and steel. Besides being virtually maintenance free, it is also chosen for its colors, style choices and durability.

Many of the myths about vinyl siding stem from its early years when cracking, fading, and buckling were part of its characteristics. Technology quickly caught up with these faults and made it a more viable product for an exterior finish.

Another false read that people may have gotten about vinyl siding is seeing a poor installation on a new or re-sided house. Installers not knowledgable or not following the manufacturers recommended installation instructions could produce a poor job making one think its typical of all vinyl siding jobs.

One of the most common mistakes made when installing vinyl siding is not allowing room for expansion. During warm weather a 12 foot panel can expand up to 1/2 inch. Because of this, the siding is installed 1/4 to 3/8 of an inch short of J-channels and corners depending on the temperature its installed in.

Another no-no is nailing the sidng tight to the wall. Vinyl siding has a slotted nailing strip along its top edge. When nailing the siding on, one must drive the nails as close to the center of the slot as possible and leave the nail heads no closer than an 1/8 inch away from the strip. This will allow the siding panel to slide left to right and expand without buckling.

Another complaint is not being able to match and replace a damaged panel. If one installs or has installed a reputable brand name vinyl siding chances are it will be available should the need arise. After installation its a good idea to keep a small piece of the siding and to write the color and brand name on the back with permanent marker.

Whether installing or having vinyl siding installed, do your homework. Research some of the different makers of vinyl siding and their products they have available. If you are installing the siding yourself, follow the manufacturers installation instructions. If you hire a contractor to do the job, ask for addresses of jobs he's done so you can see his work.

Mike Merisko (c) 2007