This article will give you a complete material list and cut list for the construction of a 20'x20' wood framed garage, also a complete walk through of the basic framing needed to build your project successfully the first time.
Like with any building project a good material list and blueprint can go a long way, you don't want to be running back to your local lumber store to get your job started and or finished. It can ready be worth the little bit of money you would spent to have a blueprint design and material list make for you by a Freelance Construction Estimator online. For our example we will be building a 20x20 garage with a 16'x8' garage door and a truss framed roof, Why trusses? a regular common truss 20' long the avg. cost is $63.25 (for 2009 prices) that is about what you would spend on rafter framing just a lot less work. This is optional, you can also buy them with modifications to add a attic or loft.(20' $153.00 each) The little added cost can really bring up the value of the finished project, because truss can come pre-build in a way so all you need is floor sheeting and a few nailing backers and its ready for finish trades/work.
Material list, 70' roll of seal-sealer, 5- 16' 2x6 treated lumber,(or green board) The rest is standard lumber, 2- 18' 2x12, 65- 10' 2x4, 16- 16' 2x4, 7- 16' 2x6, 1- 8' 2x6, 47- 1/2 OSB sheeting, 2- Gable trusses, 9- Common trusses, 1 28" door. Next the Cut list, Studs 55- 2x4s at 9'9", door jacks 2- 2x4s at 6'10-1/8, door header 2- 2x6 at 2'9-1/2, garage door header 2- 2x12 at 16'9", fascia blocks 28- 2x6 at 4-1/2". This cut list will set you up so that when you start the framing project, the time it take to finish will be twice as fast, having everything pre-figured and cut goes a long way in this and or any building project.
Getting started, The first thing needed is to run the seal-sealer around the foundation, then add the 2x6 treated lumber on top of the sealer strapping or bolting it on your foundation, (your foundation contractor should add straps or bolts for you to anchor the garage to the foundation) after all the 2x6 is on you will need to chalk out your wall lines square on to the 2x6 treated plate, to be in square all the corner to corner measurements need to be the same. our example garage is 20'x20' to be in square the outside corner to corner measurement of the walls is 28'3-7/16.
Wall framing layout, depending on how many people are giving you a hand at this point makes a big differences on how you should frame it, I will cover the most productive way for a DIY to build a garage. Start with your two side walls, Make to sets of 2- 2x4 top and bottom plates, cut them 8" shorter then the outside measurement of finished garage measurement needed, have them laying in place where they are to be built.(layout goes on the 1-1/2" sides of the 2x4s) Whatever side you start your layout from is the side you start the 1/2 OSB sheeting for each side wall, layout for the side walls would start by measuring out 11-1/4" make a line then put a X to the right of the line if your pulling your measurement from the left and to the left if your measuring from the right,(or people call it "And GO") from that first line. mark down every 16" till you get to the end. Be sure if your adding a door to layout for the door opening, whatever size door you buy you have to add 2-1/2" to the inside opening plus add 3" for header door jacks, our example door is a 28" door, the layout would be two full studs cuts centered over where we want the door 36-1/2" apart, with a 2x6 header to the height of the door and 1 door jack cut under each side. For the corners of the side non-gable walls there will be just 1- 2x4 stud cut on each side, on the corners of the gable walls there will be 3- 2x4 stud cuts on each side. Layout for the front gable wall with garage door, the example door is 16'x8' We would need a double 2x12 with a peace of 1/2" OBS in the center(the 1/2" OSB is the give the header the extra 1/2" needed to be the same size as the walls or the with of the stud 3-1/2) The header for a 16' is 16'9 adding in 3" for the 2x6 soffit that runs on the inside of the finished framed product and 6" for 2- door jacks under each side. (garage door jack sizes can only be figured after you measure you foundation and adjust for concrete height and the 1-1/2 for the 2x6 that runs across that top. Layout for the front and back walls, the first measurement out is 15-1/4" then pull every 16" putting your X's in like stated above. Above any where you cross a header with your layout make a O mark standing for a header jack cut.
Framing, Start by framing the two gable walls complete (every stud needs 2 16-D nails from the plate into the stud on each side) build them without the 1/2" OSB sheeting then stand them up and brace them in place,(note it is sometime easier to put in the garage door header after the wall is built and standing up) next frame the side walls stand them up and nail all the corners in. From the inside start at 1 corner at a time leveling it both ways and bracing it from the top of the corner your leveling across the wall and down to the other side, repeat till all corners are level. Then sheet the the hole outside frame of the garage, on the gable walls you will want to run the sheeting two feet or more above the top plates of the walls, (this helps when its time to set your gables) The non-gable side walls will get sheeted up to 1" below the top plates of the walls. The nails used need to be 8-D and should be placed 6" apart on the seem and 10" apart in the centers where they run on a stud or roof trusses. Note some states and or towns have there own roof and wall nailing requirements, The best thing to do is check with your local city hall before calling the building inspector out to the job.
Roof framing, Normal trusses run 2' on center and your starting measurement is 23-1/4" off the over hangs, our example has a 6" overhang so pulling the layout measurement for the trusses off the sheeting on the wall would be 17-1/4 to the first line then put a X And Go. After layout is complete get both gables set up center on the wall nailed to the sheeting you left hanging above, finish the gables by sheeting the front sides and adding 4-1/2 2x6 blocks along the top sides of the gables 2' apart.(these blocks are for your fascia board to nail to) Next cut the pitch or your roof onto 2- 2x6s (fascia boards) and nail them onto the blocks that was just added to the gables, run the 2x6 long, out past the end from the gable trusses. Bring in one truss at a time upside down you put one side on each side of the wall at a time, flip it up, pull it back and brace it off, repeat till all trusses are up and braced off. Then one truss at a time start moving them over to your layout marks nailing 2 16-D nails into one side and 1 into the other side (6 total per truss) also nailing one 25-1/2" 2x4 brace from the gable truss to the first common truss.(25-1/2" is the outside to outside measurement of two trusses on 24" centers) After all truss are set add 2x6 (fascia) board to the tails of the trusses, first you need to make sure that the top of the truss plains right to the center of the 2x6 fascia, Also start it from the back side of the 2x6 fascia board that was ran long on the gable. If the 2x6 end in the center of your trusses cut it back to the center of the next truss back, last thing to do with the 2x6 is to rap the inside of the garage door opening, keep it flush to the inside of your walls hanging past on the outside. Finish off the framing by leveling your gables and sheeting off your roof per your towns nailing requirements