This is the third part of a multi-part outline of what is involved in buildings a Habitat house. This article covers the steps in raising the roof and drying in the house and a myrid of little details going on at the same time. The first part is Habitat Tutorial – Prepration for Build which covers some of the pre-build steps the Site Project Manger (SPM) and selected volunteers go though just to get ready for the volunteers, and the second is Habitat Tutorial – Part 2 which covers the first day where the walls go up. In addition, there are three sets of pictures with slide shows that have already been published that you may be interested in as they concentrate on people on the job site – volunteers. The first is Habitat for Humanity – 2008 Dinner on the Slab consisting of 25 pictures including our future homeowner Nicole Combs and her son Elijah. The second includes 115 pictures of the first day of the build – Habitat Build 2008 – First Day – Walls Go UP . The third was released earlier yesterday: Habitat Build 2008 Second Day – Roof Goes On which has pictures and blog on the installation of the roof trusses and decking the roof. If you want access to any of the tutorial pictures they are all in one place for all the tutorials to date. Tutorial Slide Show - 146 pictures so far, including many not in this article.
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This is a a drawing I made of a generic roof truss, not too unlike what is actually installed. At least most of the parts are here. Below are pictures of the trusses we actually installed and you may note some minor differences. The major difference is the end trusses which have more vertical 2×4′s in the web so that there are places to nail OSB and siding. None of the ones we put up have a King Post.
The trusses are marked with alignment marks while still on the ground. Each truss is marked 14″ from one end (only), that end being the end that goes on the longest wall, (in our case the back wall). A line is snapped along the back wall exactly 2″ from the back edge of the cap plate. The corresponding 14 inch mark on the roof truss allows for a 12 inch overhang and the 2 inch offset in the snapped line. When the roof truss is slid into place a volunteer aligns the truss mark with the snapped line on the cap plate. If one end is right, then both ends will be right on these manufactured trusses.
I was one of the two marking the trusses. The other was Max, son of our SPM, Jeff Vanderlip. Each truss also receives a mark along the top plate/top rail at 47 1/4 inches and at 9 feet. These marks go on both ends of each truss. The 47 1/4 inch mark is the top edge of the beginning course of the OSB deck (which allows for a 3/4 inch overhang over the end of the truss. 3/4 inch fascia board stretched across the ends of the trusses will take up this overhang. The 9 foot mark is the location of the 1×4 boards used to tie the tops of the trusses together while the trusses are going up. 9 ft is chosen so that two courses of OSB panels can be installed below the 1×4 boards.
To read the rest of this tutorial, click here:
Here I’m showing the first two trusses installed. It should be noted that when we left the site the previous week, the safety pole had an OSB strip mounted along it as shown and we had no roof trusses on site. The Gray Ghosts came in during the week, found the trusses had been delivered and added OSB to the middle of the web area on the two end trusses. They also removed the OSB on the safety pole so that the match up would remain perfectly vertical. In addition they cut OSB panels to fit each end truss, numbered them and the matching truss and left the panels in the front hall for us to find. A real time saver by our friendly Ghosts.
The drawing shows the marking of the trusses on the house at 2 feet apart with the exception of the first one from the starting end. These are 3/4 inch short of 2 feet, e.g. 23 1/4 inches for the first end of cap to truss spacing. The rest are on 24 inch marks from that one. All the trusses are actually on 2 foot spacing. The initial measurement is from the end of the cap plate, but the center of the first truss is 3/4 inch to the right making it centered on the 2 foot mark. The marks are spaced so that the mark can line up with the edge of the truss rather than trying to align to a mark under the truss.
The 1×4 temporary brace boards were also marked on 2 foot marks so that the tops of the trusses could be aligned easily as they go up. The board is marked 3/4 inch in from the first edge, that edge is marked “start” and then the rest marked 24 inch centers from the 3/4 inch mark. This allows the start end to lap the first truss completely and the other marks to align with the centers of the trusses.
Shown in the illustration are special alignment tools made for Cobb Habitat. The first was made by a Gray Ghost from 2×4′s and some of these are still around. I think they still make them.
Aleignment braces being picked up from a wheelbarrow. Note some are a little more refined than others, but all work the same. Drop them over two truss rails and they will be held rigidly at the proper spacing, truss-to-truss.
My drawings are all made with some free software, called “Google Sketchup”. Takes a little getting used to, but I did all four drawings for this article in a couple of hours.
This drawing illustrates the use of the 1×4 braces, the alignment tool, and the placement of angle braces within the underside of the top rails of the roof trusses. With Google Sketchup, once you have made a component (such as the first truss member in the top illustration), you can manipulate it in space and duplicate it anywhere. 2x4s and OSB are drawn in 3D in a matter of seconds and can be rotated and slid into place like real wood. The angle braces started outside of this drawing in free space and then repositioned and rotated in various directions to get it placed in the framing. Everything stays to scale and in perspective as you rotate things around, even look underneath. The angle braces greatly strengthen the house.
Here are pictures of one of the end trusses and of the house with the safety pole stripped of its OSB as we found it Saturday morning. Work of the Gray Ghosts.
Here are the OSB cutouts for the end trusses and the barge rafters already cut by the Gray Ghosts. Thanks guys! OSB is laid on the end trusses along the centers of the web and marked for cutout. The cutouts and the web are both marked so the the OSB can be lifted up to the installed truss and nailed on later. Hoisting a truss with the OSB installed can be done but it is a real strain and adds to the danger. Cutting the OSB from measurements after the truss is up is also possible but a real pain.
The barge rafter is easily cut on the ground using the truss as a pattern. The ends match the truss but so you will know, for a 5/12 roof, the angles are 45 degrees for the top cut and 67 1/2 degrees for the bottom cut. All four were cut in advance by the Gray Ghosts. Otherwise experienced volunteers would have done all of this before the last end truss went up so that they would have a pattern. Barge rafters go on the sloped ends of the roof on the drip line . I’ll have other pictures when I illustrate their installation later in this article.
Here we are installing the fifth truss. Note that multiple alignment spacers are in use and so is the long 1×4 board used for temporary bracing. I’m illustrating the use of the made-on-site forked Y’s to lift and guide the truss onto the frame of the house. The fellow poking his head up is in real danger. He is ready to duck and all the volunteers are told to move the trusses in small increments as he helps them guide it through. He tries to stay visible to everyone on both sides of the wall and that helps them protect him as well.
There are people on the inside guiding the truss with their own poles. The safety beam (often called the “sissy beam”) which bridges across the living room (not in these pictures, partially in the picture below) helps hold the other end of the truss when it bridges that room and also keeps the top end of the “A” from tipping over and dropping down into the house. Jeff calls the people using the Y’s guys – “Wyse Guys”. “Com’on wyse guys pick your end up higher”. The truss tends to catch on the walls and have to be lifted and shoved at the same time to overcome that.
Here the bottom of the truss is held in its approximate final position and the top of the A frame is rotated up to join the others. Notice the extra spacing tools on the right ready to slip over the new truss to hold it at 2 feet from the last one. The sissy beam is the big beam in the bottom left of the picture. The top of the truss was lieing on this and without it could have fallen into the living area. This beam is removed soon after the trusses are up. When the bottoms are right (adjusted to the 14 inch mark on the truss and to the 2 foot mark on the cap beam) and the tops are secured with the braces, the bottoms at each end are nailed with 3 nails in each truss. Two 16d nails on one side and one on the other. More might weaken the truss. The trusses are not nailed to the interior walls. Hurricane straps will be added later.
The technique for the last truss is different. There is little to no space to slide it over and if it slid off, it would be a disaster to a number of people. First a number of step ladders are leaned against the house. The truss is brought around and set up vertically next to the ladders and then hoisted to rest on the tops of the ladders as people with Y’s and others in the rafters keep it from toppling over. Then the volunteers climb the ladders to the third step from the top and, on command from our fearless leader, lift it up as it is guided into place by those on ladders inside. The bottom edge is set against the deadwood and the frame shifted to the proper mark and the top secured with alignment tools. Then the hammers fly, driving nails into the side of the bottom chord into the deadwood on the wall. Job well done! The 14 inch markings on the trusses must have been good as they all lined up perfectly when sighted down the ends!
You can see from the picture above that some volunteers have already started the house-wrap. Actually it is almost done. They were working on this end as the other end was receiving trusses and on the other end as this end was being finished.
This picture was taken about a half hour earlier. One is unrolling and another smoothing. The wrap is nailed in place with roofing nails (don’t use the bottle cap nails!). The rolls are 9′ long. We cut a foot off the roll with a circular saw to get an 8 foot roll. Start 12 inches from one corner and nail it at the top corner at the top of the OSB. Roll it around that corner and nail it along the top edge as you go along. Cover all the windows and doors and X cut them out later. When the next corner is reached, stop and go back and nail the wrap approximately every 3 feet along the center and along the bottom. Keep rolling along the walls corner to corner. Use special tape for all seams.
This is one of the few houses where the wrap is right side up. The tendency is to wrap left to right and that always results in wrap that is upside down. Right to left as shown gets it right side up. It doesn’t matter, I’m just making noise here for the fun of it.
Cut windows out of the house wrap with a utility knife, by cutting diagonally from corner to corner and leave the triangle pieces to be folded and stapled inside. Repeat for the doors but cut out the bottom triangle and discard.
The bottom of window frames get a special treatment after the wrap is installed and stapled back. First the corners receive a window tape that wraps around the window opening and folds down across the bottom window plate. Then a second tape is run across the entire window that laps over as shown to the wall wrap. The cut corners of the tape are completely sealed in this manner. Water that gets between the wrap and the siding near the window has no place to accumulate and keeps on going down the outside.
Here is a wrapped window and door opening. The wrap is folded back and stapled before the window or door goes in. The top flap of the window also receives special treatment. The top flap is trimmed down to fit over the installed window flange and is not stapled inside. The idea is to have the wrap shed any moisture coming from above to the outside of the window flange and not carry it inside. The volunteers doing the wrapping don’t worry about this. They wrap and window installers take care of the top flap as they go along. The important part is not to cut out the entire window opening outline.
Here the top flap has already been trimmed and is being carefully tucked in on top of the outside of the flange above the window being installed. Thus water runs down the wrap and into a channel on the window that keeps it outside.
The window is secured to the wall with screws or nails in the slots. They can be purposely left a little loose so they can move as they expand and contract. The tapes, siding and interior trim will keep them from rattling or moving any noticeable amount inside. It doesn’t seem to matter much either way in this climate. I’m just reporting the recommendations.
The technique is to apply the window wrap foil across the bottom of the window, then the left and right edges and finally across the top of the window. That way all the water flows down like shingles on a house, shedding water all the way.
Here a volunteer is installing deadwood over the interior walls. These serve the purpose of providing a place to nail the drywall ceiling. In this case there are two 2×4 boards nailed to the interior wall cap plate, one on each side. You can just see the ends sticking out above the wall running left to right. The deadwood is needed only on the walls parallel to the rafters.
Meanwhile the decking is going on. Notice the house wrap however. The top flap is sitting above the window waiting for it to be properly placed and taped. Nothing left to chance. The plywood sheets are handed up by strong guys and gals on demand from the crew above. They position the first sheet on the 47 1/4 mark on the truss top rails and center the end on the 4th truss. That is 6 feet from the end (3 each 2′ openings) leaving a 2 foot overhang. That will be trimmed later to 12 inches or whatever the SPM desires.
OSB has a smooth side and a rough side. Always install with the rough side up. Snap a line from the 47 1/4 marks at each end of the roof and use that as a guide for the deck installation. I know we made marks on every truss as asked but the more experienced deck crews always chalk a good line, end to end.
Full 8 foot sheets are installed across the entire front and rear of the house before beginning a second course. The decking crew nails each sheet at the top and bottom of each sheet into the truss, 10 each 8d nails to the sheet. Others come back later and nail the sheets on a pattern of 6″ down the seams and 12″ in the fields. Someone on a ladder can do the bottom edge safely. I did that part.
The second course starts with an OSB sheet cut to be 4′x 4′ square and is offset to the second truss. This offsets this course for the second run and all the subsequent runs are similarly offset. The sheets overhang on each end by two feet.
When a rafter is bowed too much or kinked it is sometimes necessary to add “sister” 2x4s to add a little wood on one side or the other to catch the edges of the plywood properly. Here is a sister board going on for a slightly kinked rafter. Beams are sometimes repaired this way if a worrysome looking crack is found in the wood.
The OSB along the top ridge is left with a 1 1/2 inch gap on each side for installation of a ridge vent later. The gap does not extend all the way across. It should end on the 3d truss from each end. This is an inside view of the gap covered with tarpaper. The tarpaper is not cut out until the ridge vents are reay to install. The roof on the right side has not yet been covered so the H clip gap still shows.
This is an “H clip” (hurricane clip) that must be used between each course of the OSB. This is a view from the inside showing the clip causes a small intentional separation. The clip helps hold the boards together during high winds and big pressure differences from the attic to the outside.
H clip close up.
The decking is snapped with a chalk line at the proper overhang. This house was designed for a 12 inch overhang, but one side was offset to 10.5 inches and the other left at 12 inches. The reasoning seemed to be that one side would match the porch better at the 10.5 setting. Here the excess is trimmed off the 12 inch side with a skill saw moved up the roof in a continuous walk. I think he has done this a few times! A perfect cut. Watch out below! You can see the beginnings of lookouts already installed.
Lookouts are “U” shaped with the uprights extending from the wall to the barge rafter when it is installed. The portion shown is difficult to install (swing a hammer) if the barge rafter is put up first. Thinking ahead. More about them later.
This is the first barge rafter going up. This is the other end of the house from the previous picture and the far edge has not yet been trimmed. The rafter is patterned to the truss while it is on the ground. As mentioned earlier, it was cut by the Gray Ghosts during the week. The technique is to lift it up on one end and let the roof crew pull it up and position it. They have clamps ready. The rafter is lowered over the edge, pulled up to the OSB and carefully positioned, then clamped in place. This is the “long” one and fits at the top end to the OSB on the other side and aligns 3/4 inch above the bottom edge of the OSB at the bottom. The fascia along the bottom edge will lap this piece and make everything right. The “short barge rafter” fits against the bottom edge of the long one. Once clamped, they are nailed into place from the top on both sides of the roof using 8d nails. The barge rafters go on before the tar paper when possible.
Here is the same end of the house showing details of the installation. Notice the first (long) one is installed flush up against the overhanging roof on the other side and the second is butted against it. Notice that they are numbered and marked for each end of the house and where located.
This picture, taken earlier in the day, illustrates the installation of the panels pre-cut by the Gray Ghosts. Each panel had been laid out and cut to fit the truss while it was on the ground. Terry is crew-chiefing the installation on one end of the house and carefully fitting the panel into place.
Before the last end is closed up there are some things that must be done to ensure that nothing is left out of the attic. Terry is shoving long 2×4 boards to be used as catwalks and to stabilize the bottoms of the trusses which “float” above the interior walls. Installing these boards will stabilize the bottoms of the trusses so that they remain on 2′ centers for ease in drywall ceiling installation. Extra lumber also goes in for use by the heating and air guy to build an attic floor for his system. He will be happy to find sheets of OSB and lumber for his HVAC platform waiting for him. Sometimes the roof truss design includes a couple of trusses that have some of the web relocated to make a pocket for the HVAC unit.
Here one of the boards Terry shoved in earlier is being nailed down to the bottom rails of the trusses. Notice that she is using the spacers to maintain uniform and exact spacing, essential to those installing drywall ceilings later. Without these boards in place the rafters can move back and forth and could make ceiling installation a pain.
This photo illustrates two items of interest. The first is the drip edge applied to the lower edge of the roof. It typically goes on before the tar paper and the tar paper laps over it (bottom horizontal edges only). The second is the ladder hold-off positioned on blocks and secured by bent nails so that the ladder will not contact the drip edge or the roof as it is being installed.
Once the barge rafters are in place (or if rain threatens) the felt (tarpaper) can be applied. The felt is installed with the bottom edge even with the bottom edge of the roof. It should not overlap the roof edge. Overlap the higher courses by locating the bottom edge on a line on the felt, typically 4 inches. It must be installed as flat as possible. Larger wrinkles will show through the shingles. Nail tightly with plastic-cap roofing nails 3 across the felt and about 3 feet apart across the roof. Note: after doing this, we were told to go back and put more nails in the edges. We ended up with about 1 foot apart. We will install the shingles on our next work day.
Here the drip edge is applied over the tarpaper and against the new barge rafter. The drip edge has a wide and a narrow edge. I had a closeup picture of the drip edge ends, but somehow it got lost – sorry folks.
Install the wide edge on the roof and the narrow edge drops down over the fascia or barge rafter. Once again, the drip edge goes under the tar paper on the horizontal (bottom) edge of the house and on top of the tar paper along the sloping edge over the barge rafters. Attach the drip edge with 7/8 roofing nails every 24 inches. Overlap the joint where the downhill run meets the horizontal run at the corners. Overlap the drip edge at joints by 1/2 inch. This requires cutting away one of the webs with a metal shear.
This is a hurricane strap of the kind used to attach the top wall to the roof trusses. One end of each goes on the top wall cap and the other ends connect to a truss. This is in addition to the 3 nails already holding the truss in place at each end. The hurricane strap helps keep the roof on in high winds. Each strap is rated for holding down under more than 500 pounds of uplift and about 150 pounds of lateral load. Use 5 each 8d nails in each end of the strap. If a different style strap is furnished, a nail goes in every hole. Do not drill holes or use oversize or undersize nails. Different nails may be required for larger size straps. Use what you are told to use.
The first strap is properly installed. The second one had to be removed and replaced because the web extended down onto the cap plate and would interfere with the drywall on both the ceiling and the wall.
Now here is a Handy little device for where hammers are hard to swing. It is a palm hammer aka palm nailer. Pneumatically operated, it tap-tap-taps a nail in a matter of a couple of seconds. You insert the nail head into the working end, it grips it with a magnet and as soon as you touch the nail to the wood with a small amount of pressure, it drives it in. It will drive nails in very tight places and is easy to use.
I found this one on the Dewalt Factory Outlet web site for $89.00. It weighs 2.6 pounds, drives 6d to 16d nails. Stick a nail head into the opening at the bottom, press it to a board and it goes right in in about a second. Sears has a different brand for $215 made by Jet, claims 1000 blows per minute. I have no idea what the difference is between all these. Porter Cable has one about $119.00 to $130.00 They come with various attachements. Drives nails from 3d to 70d ???. Surely that is a typo. It did say it drives “stakes”. Home Depot did not list any.
Another safety feature is a the T shaped horizontal boards nailed across the end trusses at each end of the house. This consists of 3 2×4′s nailed with one of the 2×4′s trapped edgewise between the other two. This very strong structure was attached to the end trusses to reinforce them. It was made on site.
Here a caulk seal is being applied rather thickly to the outside walls to discourage wind, water and insects. The drywall that goes up later will cover this no matter how thick. Also the floor covering and base cove will catch anything that might show. Most of our caulk is donated. In the case of plumbing walls on the outside wall such as in the laundry, the caulk seal goes to the outter of the two walls. It is not needed on interior walls.
Here a window and door caulk is applied to the concrete in an exterior doorway just before the door is dropped in. A larger dollop is in the cut-nail hole. This is the first of several passes to make sure that it is well caulked. The door has already been checked for fit.
Here the door is being nailed in. The door was fitted, caulked, then carefully adjusted for vertical in all directions using the long level. This header and frame were a good fit. If the header is more than an inch above the door, then a 1×4 would be nailed in to the bottom of the header. Either side can be raised to make the gap at the top of the door even all the way across, meaning the gap you see above the swinging part of the door, not the frame vs door. The hinge side must be set vertical and then nailed with a single 16d galvanized finish nail through the brick mold on the outside top. This nail is left partially out so it can be removed if necessary. Check the door and then nail the center and bottom of the hinge-side brick mold. Then adjust the gap on each edge of the door making sure the the top and latch sides are even.
Drive shims into the gap between the door frame and the rough opening at each hinge and at the lock side jamb, and drive 16d galvanized finish nails to lock the frame into position. Once certain of the fit, use 16d galvanized finish nails every 16 inches around the door brick molding.
Shims installed and cut off.
6 inch fascia boards are shown here installed to the ends of the trusses. These will be covered with an aluminum fascia later. The aluminum fascia will be installed with the top edge behind the drip edge and will lap under the soffit that will also be installed later.
Here we are looking at the blocking installed earlier. We are looking from the inside but the blocking is installed from the outside between the trusses. OSB boards are cut to just fit between the rafters and tall enough to fit from the bottom of the cap plate to within 2 inches of the roof. The blocking is nailed to the cap plate and serve the purpose of holding back insulation from getting into the soffit while holding open a a gap for cooling air to enter the attic from the soffit. They are typically 9×22 inch boards cut from OSB or blue board where blue board is used on a house. This one is OSB all the way, no blue board. This picture happens to have two hurricane straps and the header of the master bedroom picture window. This is a well-built house Nicole!
Here the lookouts are being finished by Terry using the palm hammer. It was a very useful tool on the short boards running from the wall to the barge rafter and for reaching up one-handed to drive in the nails in the exterior of the barge rafter. It would be difficult to both hold and drive a nail without turning loose in a potentially overbalanced position on a tall ladder. Yes, there is a pneumatic tube there but it happens to be well hidden behind his arm.
In the past the barge rafters were built completely on the ground after measuring the gap. This resulted in a problem in driving the nails into the long board with the barge rafter in place. The solution was to first put up the running boards and cut the short ones to fit later. The palm hammer could have done the total job but it is still fairly heavy. We are still experimenting on where to use it. I can say that the ladies particularly like it as it gets the nails in quickly every time.
Lookouts are installed 4 to a roof edge. The top and bottom ones are installed with the outer ends about 18 inches from the top and bottom of the run and the other two are placed about evenly between them. The longer lookout block is 21 inches long. The shorter ones are cut to match the overhang. Lookouts serve to strengthen the overhang and barge rafter connection to the roof.
The day is done! Well except for the cleanup of course. Terry and Travis admire their finishing touches while most of the crew have moved on and/or toting things to the storage container. When I got home I sat down thinking I would take off my shoes in preparation for a shower. I woke up 4 1/2 hours later.
It was a busy day for all of us, but everybody did have fun! Look for more to come. This is only the second day of a 10 day run to build a house for Nicole.
PS all the pictures and many more for this tutorial are available here: Tutorial Slide Show