Work platform

It's almost time to put up the roof framing. The rafter units are not too heavy to carry, but they're not light, either. And they're long (16'). And we have to put them on top of an 8' wall, which is a long way to reach.

We passed one up today to see how it felt.

I carried it from the storage area to the building, and passed it through a gap in the wall to Julie. Her job was to set one rafter tail on one wall, slide it up, then hook the other rafter tail on the other wall, then center it. She couldn't reach high enough, so I had to run around the building, come in through the door, and help her get it in to place. Too much running back and forth to get all rafter units up like that, and it was hard work. How to make it easier?

• Get a couple helpers for 1/2 an hour.
• Carry the rafter units to the building, as far as I can get them. Then run around, and together we drag them in & hoist them up.
• Rent scaffolding.
• Build scaffolding.

A combination of the above may be the best choice. I decided to build a raised work platform, as a start.

I mostly improvised. The one cool thing I did was to create 4 short, temporary jack studs to attach to existing studs. The building is 10' across, so a pair of extra 2x4 10' sticks rest on these jack studs. 

There are few more sticks here and there to finish the structure. The building, which we've worked hard to make strong and stable, helps the platform be strong and stable, too.

A sheet of plywood rests on top as a nice, large surface to stand on. It's about 3' up, mostly because I had some 3' cut-offs lying around already. Maybe 4' would have been better - 1/2 the height of the walls? Whatever, it works.

Most of the lumber is used full-length.  The plywood plywood deck is only 6' long, but I didn't cut it - it was like that already. Screws hold things together, making it easy to take apart, but the screws carry minimal load  - loads mostly go through wood resting on wood.

Top plates & porch beam

The porch beam holds up the roof over the porch. Over the enclosed building, the studs hold up the rafters, but around the porch, the roof load is carried along porch beams to supports at the end. Here's the plan, with the beam pockets marked.

And the beam pocket as seen in my last post:

First I climbed up the ladder to cut back the sheathing around the beam pockets. I used my grand-father-in-law's jigsaw, since it fit in that small space and was light enough to use up on the ladder.

Hoist the beam in position. One end in the pocket, one end clamped to the porch post. Level & tack in place with a deck screw (3 1/2" #10) at each end.

One end of the beam rests on a jack stud in the wall, which is pretty secure. The other end is next to (not on top of) a porch post. How to carry the load securely in to the post? One option is lag screws or through-bolting, which works pretty well but is bit tedious up on a ladder, with all the predrilling, etc.

I decided to add a "jack stud" to the side of the post. It is attached to the side of the post, running from the underside of the porch beam to the deck beam below. A series of screws through the jack stud in to the post help stabilize things. 

We plumbed the posts (in 2 dimensions) and braced them to each other (at the proper spacing) and diagonally to the deck. Then some 1/4" timber screws through the beam in to post. The timber screws will help with uplift, if the wind tries to steal my roof.

Once the beams were up, we added the double top plates all the way around, including over the porch beam. That ties the porch beam in to the main wall nicely. I'll be adding some tie plates at the joints, as an extra measure.

Fixing a window framing mistake

When framing a window under a load-bearing wall, you need to put in a header to carry the roof load. Typically it's built out of 2x lumber on edge, with plywood sandwiched between to make it the same thickness as the 2x4 wall. (2x6 walls are done a little differently.)

I screwed up and put the header in sideways, with the lumber laying flat. This is far, far weaker.

I tried taking it apart, but it would have meant tearing up the king stud to pull the nails out.

Will it still be strong enough? Here's the math:

The roof design load is 10psf dead load + 25psf snow load = 35psf total. Rafters/studs are 2' O.C., and rafters are 8' long (I designed to use them full length.) Tributary area is 2' x 8' = 16 sq. ft. Design load = 16 sq. ft. x 35 psf = 560 lbs.

The weight limit for a span is normally Fb * b * d * d / (9 * L), where:


Fb = Fiber bending stress of the wood you're using. My 2x4s are Douglas Fir "#1 or BTR". According to WWPA, that wood has a fiber bending stress of 1200. (I have no idea what unit that is!)

b = breadth of the beam, in inches. A 2x4 laid flat (oops) is 3.5" wide.

d = depth of the beam, in inches. A 2x4 laid flat is 1.5" deep. Notice it's squared - this is why lumber on edge is so much stronger.

L = length of the span, in feet. My window rough opening is 2'.

Put it all together: 1200 * 3.5 * 1.5 * 1.5 / (9 * 2) = 525lbs. Not enough.

That formula is for an evenly distributed load across the span, which assumes that the strain on the wood varies linearly with the distance from the point of support. To put it another way, it behaves like a point load on the center of the beam that's 1/2 as large. So, divide my max load by 2.

However, I have 2 pieces of wood here (twice as strong), so multiply my max load by 2. So we're back to 525 lbs. Still not enough.

There's one more factor to consider: there's a double top plate that can carry some of that load, too. If you assume it's just strong as the misplaced header, then I'm fine, but I've never seen that described before, so I was wary of counting on it.

However, we're close. A little more wood could do the trick. And I had the perfect scrap of wood - a piece that was intended to be a window header, but it was 1/4" too short. If I lay it flat across the top, it increases the strength of the header by 50% more - enough to be certain we're strong enough. And I can end-nail the cripple on to this extra header *before* I install it, avoiding the hassle of toe-nailing.

That went together really nicely.

As I've been learning to build, I have asked myself the question: what is the difference between me (a novice) and an experienced pro? There are several obvious answers:

• Pros cost money, I just cost time.
• I'm way slower, because I spend a lot of time figuring out *how* to do this, and because I make mistakes I have to recover from. Also, I get tired because I'm not used to the work.
• I waste material due to mistakes.
• Pros are good at this, and know how to produce high-quality work.
• I care about the outcome far beyond my concerns for reputation and callbacks, so I'll take care when it matters to me.
• Pros cut corners to save money & time (which is also money to them) if they think they can get away with it.

But there's one more point that I have become aware of: pros are really good at hiding their mistakes. A novice can do work that's just good (or just as bad) as a pro, but a pro will make it look like they did a good job, even if they didn't.

Erecting walls

To anyone who has done platform framing before, building walls is the most obvious of activities. For novices, there is a lot of complexity to work through, a lot of learning to be done. I spent most of my time reading, drawing, pondering, conversating. Oh, and resting my hammering arm.

We could frame with either 2x4 or 2x6. 2x6s costs a little more, the lumber is usually a little better, the wall is stronger, and there's more space for in-wall insulation. Stick-built houses around here are usually built with 2x6s, but spaced 24" O.C. (instead of 16" O.C. for 2x4s), to use less wood. That's fine, but then you need stronger sheathing and drywall to span the larger gaps, so the savings are reduced.

Because our building is so small (12' x 10'), losing 4" in each dimension to thicker walls seemed like a lot to lose. Also, heavy insulation isn't important with the use patterns we're expecting in this building. So, we went with 2x4s.

Even though stud spacing for 2x4s is typically 16" in a house, in our little building I chose 24". The main reason is that the 10' dimensions don't work out well with 16" stud spacing. You end up with a couple studs really close together. If I spaced the rafters at 16" to match, I'd have 2 rafters really close together, too. Sheathing ends need to meet right on studs/rafters, and irregularly spaced studs/rafters make that a bit messy. We saw that on the floor, where the middle section of subfloor had to be 6' and 4', not 2' and 8', which would have let me use a full sheet.

It's not a bad idea to make studs and rafters line up. Then the roof load is transferred straight in to the studs, without relying on the top plates to carry that load. In fact, this is a key element of Advanced Framing, allowing a single top plate instead of the traditional double top plate. I'm keeping the double top plate, because it makes joining the walls at the corners easier (as a novice, I need easy).

The building is only a single story, so the wall can be a little weaker, than a 2-story building. So, we picked 2x4s 24" O.C.

When I bought the lumber to frame the walls, I ordered pre-cut studs. This way they're all the same length - I don't have to count on my ability to cut to length reliably.

My first time framing a window:

Once framed, we tilted up the wall to see how it felt.

Being so big means I have plenty of muscle. Picking up the wall frame was easy. Easy enough that we decided to sheath the wall while it's flat on the ground. That forced some decisions about the sheathing at the gable end and letting the sheathing hang down to tie in to the floor system. To work that out, we had to think about the overhang at the gable end, and I decided we needed lookouts.

Julie really enjoyed the chiseling work.

Once that was taken care of, we proceeded to sheath up the wall. I used 10d galvanized box nails to fasten the sheathing. What a pain in the ass. They bend easily. A knot, or a bad hammer hit, and they'd buckle over. The galvanization meant they stuck in the wood really well, and were hard to pull out. The heads usually folded or pulled off in the process, so there was nothing to grab on to. Often I just flattened the nail in to the sheathing. It looks sloppy, but I had little choice.

After the first piece of sheathing was done, I stepped back to look at the work, and saw that the wall wasn't squared. Arggg! I forgot to square before sheathing! I spent a day figuring out what to do. Keep it as-is? Remove 50 difficult nails? Cut the lumber to square? Cut the wall apart and rebuild? After careful study, I decided that it was close enough to be workable, and continued. I did trim the sheathing on one side so the next piece of sheathing could fit properly.

Finally, the sheathing was done and I picked up the wall. It was very heavy, but I still was able to pick it up alone.

Once up, Julie held it steady while I shifted it back and forth until it was in just the right spot (in 2 dimensions) and plum (measured at both ends) and braced.

Bill helped me tilt up, align, and stabilize the 2nd wall, which will get the door.

The remaining walls continued in a similar vein. I got faster each time. I built the 4th wall and tilted it up in 1 day, which is like 8x slower than a pro. I'm improving!

The 3rd & 4th walls only got 1 piece of sheathing before going up, because the remaining sheathing has to go on the outside of the 1st & 2nd walls, too. Also, we'll use the gap to pass up the rafter units.

The next step is porch beams, then the roof. Here's the pocket where they'll rest on the wall (the plywood needs to be cut away) and the beams themselves. The beams are from trees on our site, full-dimensioned 2x6.

Rafter units

Once the floor was built, you'd think I'd build walls. No. Rafters first!

I started by drawing the roof lines on the deck. Then I used them to mark & cut 1 rafter, including a bird's mouth. The bird's mouth cut didn't go well, and getting them right makes a big difference in how the roof goes together. I decided on a different approach.

It's common to buy pre-made roof trusses, built in a factory. I could have done that, but I wanted to try doing it myself once. But I can do something similar: Rafter units, made of 2 rafters and a ceiling joist.

I built a template on the deck to align all the components, for uniform rafters. There's a placeholder for the ridge board:

This blocking represents the wall, and aligns the ceiling joist:

There's another one on the other side:

Used 1 good rafter as a guide for the plumb cuts on all the others:

I also cut some strips of plywood for later use:

Nailing is loud, especially on a deck, and shards of metal can fly at high speed, so some protection is a good idea:

How to build a rafter unit:

1. Slide rafters in to position:

2. Screw them down to stop them from shifting during assembly:

3. Attach the tops of the rafters to keep them from shifting. The nails were just what I had on hand. Note the plywood isn't really structural (it doesn't need to carry a load), it just holds the rafter unit together until the roof is done. 

4. Place the ceiling joist. There's a little wiggle room, but make sure it doesn't stick out above the rafter.

5. Nail things together. My nails are 3 1/4" long, and the wood is only 3" thick. Driving the nails at this angle actually makes things stronger, while keeping the points from sticking out.

6. 5 nails at each end. Note that they're not *quite* all the way in, so that if I change my mind, I can get a cat's paw in to pull the nails without tearing up the wood.

Completed rafter units:

I built one extra, just in case, but I used screws so I can easily take it apart and repurpose the lumber.

Now, to the walls.