53: The Trusses Are Up

Originally I planned to build my own trusses, but then I called a truss company and they quoted me a per truss cost of about $56 and a delivery time of less than a week. So, all of a sudden ordering trusses made a whole lot of sense. I could get the house in the dry a lot quicker if I didn’t have to build trusses first.

The truss company sent out a rep to measure and to discuss options. At my site getting a crane in to set the trusses is impossible, so they absolutely had to be hand raised. The rep said my 30’ trusses (with 16” tails) would run about 130 lbs apiece, not to hard for three people to carry. So, it looked like I was going to order 31 trusses, one gable truss and 30 trusses known as a T64 design.

My workshop has 22’ trusses set on 4’ centers. So, just on a whim I asked the rep what would change if I wanted to set my house trusses on 4’ centers. He said it wouldn’t be any problem, they would just have to beef up the trusses a little, specifically changing the bottom chord from a 2x4 to a 2x6. Oh, and the truss weight would go up about 30 lbs to 160 each. Also I would have to put in 2x4 furring strips on the bottom chord because sheetrock for the ceiling can’t span a 4’ distance. None of those things bothered me. The idea of hand setting 16 trusses that weigh a little more is much more appealing than setting 31 trusses that weigh a little less.

One week later my trusses arrived; total bill $1174 (shipping was free). The next day some guys I eat breakfast with found out they had arrived and offered to come over immediately and help set some trusses. I couldn’t turn that offer down. The gable end truss was on top of the stack so we set that one first. It weighed 180 lbs.

Now, let’s talk a little about method. I knew I couldn’t use a crane; too many trees in the way, and too narrow a lot to get the crane down either side. I had done a lot of research and thought on how to hand-set these trusses safely. Remember, safety was my profession, so usual methods used by some builders might not be acceptable to me. I definitely didn’t want to have a man standing (or sitting) up on top of the exterior wall pulling up trusses. It’s 9.5’ down to the subfloor on the inside and anywhere from 13’ to 18’ to the ground outside of the wall. The last thing I wanted is for someone to fall off the top of that wall. Working off a ladder would be acceptable, but NO one goes up on top of the wall. Believe it or not, I actually did check prices of fall protection harnesses with shock absorbing lanyards. The cheapest one was almost $200. I found a hunter’s fall harness at WalMart for $75, but it looked like it wouldn’t work very well. So, we had to find a way of getting the trusses up on the walls while working preferably from floor level.

Okay, next point. Busting your gut man-handling trusses like this is a one way ticket to a back injury; so mechanical assistance is a must. I still had the block and tackle that I used to raise and sheath the exterior walls. But, even better, one of my friends loaned me a really nice block and tackle with 4 wheels and half inch nylon line. Now that rig was nice. I erected a 4x4 column (12’ tall) and braced it to both the outside wall and to the floor. It looked like we were ready for business.

We carried each truss in and layed them down diagonally across the subfloor. The trusses are a total of 34 feet long, so in a 29’ wide building they have to go diagonal. All three of us would get on one end and lift and rotate up until the truss was vertical with the opposite top chord still flat on the floor. This put the truss heel on our side about 10’ above the floor; perfect height to slide the truss over onto the wall top plate (9.5’ tall). That was a stroke of pure luck, not having to lift the first side up on the wall.

All three guys move down to the other end of the truss and pick it up and walk forward about 10 feet until the truss end is next to the lifting column. As you walk forward the opposite end will slide further up on the top plate. Hook up the block and tackle and up she goes. As you clear the top plate and start lowering again, the other two guys slide the truss forward 6-8 inches so it sits on the top plate too. Yes, the truss is now upside down, but hanging from the tops of the walls. Slide both truss ends along the top plate to the desired position and then rotate it up.

I knew we would have to put a temporary brace up near the peak of each truss and that is 15 feet above the subfloor. I checked out 12’ A-frame ladder prices and they were outrageous (cheapest one I found was $180) so I built myself an A-frame ladder out of four 12’ long 2x4 (total cost $12 plus tax). It’s heavy, but it is stout. I have no problem standing with my feet at the 10’ level and feeling secure while I attach the peak brace. We put a c-clamp on the upper brace 46.5” from the previous truss so that when we rotate the next truss up it would give us something to catch the current truss and keep it from rotating over the top. Once the truss was up and in position, we would nail off the temporary braces, a total of three braces on the top chords and two braces on bottom chords. We had 30-45 mph winds forecast for the first night and I didn’t want any trusses coming back down.

Everything went pretty smooth until the last truss. We were rotating it up and the long push stick slipped off the truss. I was on the short push stick and as the truss swung back down it caught my push stick in the webs and then hit me in the ribs with that same push stick. All it did was knock the wind out of me for a minute, but I was lucky; it missed hitting my head by about a foot. In retrospect now, I’m reminded of a very common accident cause from the many accident investigations I did when working. It’s called over-confidence and getting complacent. We had put 15 other trusses up without a hitch and on the last one our complacency almost got someone (me) hurt. Another cause I have identified was that the truss rotated out of the long push stick because wooden “vee” that we had on the end of the long push stick needed to be bigger. Our vee had maybe 5” sides and it probably needed 7” sides. The last pic is the wooden vee that was too small. I include it because I truly don’t want to see anyone get hurt.
It took three days in all to erect and temporarily brace all the trusses. I’m now attaching all my permanent bracing and starting to put on the 2x4 purlins that the metal roof will screw down too. With any luck I’m in the dry by Christmas.

52: Pour the Front Porch

It’s time to order the trusses. Well actually, the trusses are already up and installed, but let’s try to keep this blog in order. So, I had to pour the front porch concrete first. Why? Because at the corner of the porch sits a column, and on top of that column are two beams. Well, actually they are doubled 2x12’s, but they support two trusses that hold up the roof over the porch. I decided it would be much easier to pour and finish the concrete if the column wasn’t in the way.

Figuring how much concrete I would need wasn’t hard. It’s just length times width times depth. I figured about 20 cubic feet (a cubic yard is 27 cubic feet). I called around to a couple of redi-mix batch plants and they all wanted around $150 for a load this size. Realizing that the concrete truck can’t back up close enough to the porch to pour it directly, I would still have to use a wheelbarrow to get concrete to the porch.

Since I was going to have to use a wheelbarrow anyway, and because I already have a concrete mixer, and because I am pathologically frugal (okay, call it cheap…if you must) and because I like to do things myself, I decided to mix my own concrete. So it was off to buy concrete sand and pea gravel. A yard of each cost me $30 and two bags of Portland cement ran $16. Throw in $5 for gas (gas prices have come back down, now about $2 a gallon…enjoy it while it lasts, cause it ain’t gonna) and all my ingredients for the concrete came out about $50. Humm, one-third the cost of delivered concrete; now you’re talking my language. Or, to put it in terms that women shoppers understand, a 66% off retail sale. Hey guys, there’s bargains out there, but you have to be willing to do a little more than just drive to the store.

Okay, I said I bought two bags of Portland cement. But, it was quite an involved process figuring out how I needed two bags instead of three bags, or four, or even one. There is an old rule of thumb concrete mix out there that I’ve used before. It’s called the 3:2:1 rule; 3 parts gravel, 2 parts sand, 1 part cement. You can use either volume or weight for measuring the 3:2:1 parts, they both work (or are supposed to). To figure how much water you use the water-cement ratio, which should be about 50%, ie half as much water by weight as cement by weight. If you use that ratio you should have some pretty good concrete, but it is going to be very stiff (dry) and pretty hard to work (smooth). Conversely, if you put in enough water to make the concrete easy to work, you end up with weaker concrete. So, you go somewhere in the middle, balancing out workability versus strength. This concrete is for a porch, so it doesn’t have to be as strong as say concrete for a driveway that would have to support the weight of vehicles.

Okay, so you go buy a bag (or two) of Portland cement. It weighs 92.4 lbs (yes, that’s kinda heavy) and you want to know how much concrete that bag will make using the 3:2:1 rule. Well, let’s see. If I go by “weight” I’ll have 92 lbs of cement, twice that much weight in sand (184 lbs) and three times that much weight of gravel (276 lbs) and about 46 lbs of water. So far I have 598 lbs of ingredients, but does that make 598 lbs of concrete, and how many cubic feet of concrete is that (because in the end I still need 20 cubic feet). From my civil engineering days I remember that concrete weighs about 150 lbs per cubic foot, so 598 divided by 150 means this mix “should” yield me just under 4 cubic feet of concrete. At this rate I will need 5 bags of Portland to make 20 cubic feet.

Now this 3:2:1 rule is supposed to work both for weight of ingredients, AND for volume of ingredients. So, let’s do the same exercise with volume. Since the cement comes in a paper bag with rounded corners, it’s kinda hard to figure the volume of Portland we have in one bag. We could empty the cement out and then use the same bag over again for sand and rock (2 bags of sand, 3 bags of rock). But, the bag would never last long enough to do that. So, I dumped the cement into a box and then measured length, width and height of boxed cement to determine how many cubic feet were in one bag. So, you don’t have to do this for yourself, one 92.4 lb bag of Portland is 0.85 cubic feet. Okay, so 0.85 cubic feet plus twice that in sand (1.7 cubic feet) and three times that in rock (2.55 cubic feet) and 0.42 cubic feet of water adds up to 5.52 cubic feet of concrete out of one bag of Portland.

Okay, so by “weight”, one bag of Portland makes about 4 cubic feet, and by “volume” one bag makes 5.5 cubic feet, NOT the same number. This 3:2:1 method was supposed to work for both weight and volume. But, which one is right because they both can’t be. Here was my dilemma. I put the question up on a house building forum I am a member of, and one of the responses was, call a batch plant and ask them how much weight of ingredients they would use to make 20 cubic feet (3/4 of a yard) of concrete. I thought that was a prudent suggestion, so I called my favorite batch plant and they gave me the following: 1490 lbs of rock, 1009 lbs of sand, 285 lbs of Portland cement and 133 lbs of water. That reduces down to 0.6 yards of rock, 0.4 yards of sand, 3 bags of Portland and 16 gallons of water; and from that I should get 20 cubic feet of concrete.

Just adding up the volume of rock and sand you get 1 yard (I need ¾ yard, 20 cubic feet). This bothered me, thinking somehow they gave me the wrong numbers, or I misunderstood what they gave me. So, I called several other local batch plants; and it got even more interesting because they all gave me different numbers. While everyone quoted about the same numbers for rock and sand they were widely different in the amount of Portland cement I would need. I got numbers ranging from a low of 285 lbs, to a high of 500, with several numbers in between. Now, I’m really worried. Needing to make a decision I went with the 285 lb number because I have bought plenty of concrete from these guys and it’s always been good.

I already had the gravel and sand; so I bought a third bag of Portland cement and the girlfriend and I got started. I ran the mixer, and shoveled the wet concrete into the 5’ x 8’ work area and she worked it into a flat slab. It took about 3 hours to get all 11 or so mixer loads of concrete into place and then I took over with final smoothing of the slab. Thirty minutes later I was through with smoothing, so we misted it with water and covered it with visqueen. I left the visqueen on for a whole week while I worked on other things. After maybe four days I could see the slab edges were beginning to turn from the color of wet cement (dark gray) to the color of dried cement (light gray). After a week maybe 1/3 of the middle of the slab still looked wet, so I removed the visqueen and let it finish drying.

I’m happy with the slab. It didn’t turn out quite as smooth or uniform as it would have if I’d hired it done, or if I had been able to bring all the concrete in at once (in a truck). But it still looks pretty good. So, now it’s on to putting up roof trusses.

A note to future builders - If you try to mix your own, either limit yourself to a slab no bigger than this (5 x 8), or get a second concrete mixer going (with an extra person to run that mixer). You need to be able to keep a “wet edge” to ease the working (smoothing) of the slab. And to keep a wet edge you need to keep that concrete coming pretty continuously. Additionally, after three hours of concrete work, even though we both are in pretty good shape (work outs at the gym four days a week), we were still pretty tired. Any bigger slab and this project would have become real tough.