Woodshop: 4 Ways to Hold Up Your Roof

Beneath every roof is a structural system to support its weight, plus the force of all the snow, wind, and people that might stand atop it. Here are four support possibilities, along with lots of reasons to use them (or not).

1. Simple rafters. Dimensional lumber is easy to buy, cut, and erect. It might not be the cheapest way to span a given distance, and it’s not even an option for long spans: 2×12 is the maximum depth you can get, and anything longer than 16 feet requires a special order. But the convenience makes simple rafters a great choice when you need to build it NOW.

2. Built-up rafters. This category includes more sophisticated types of lumber, like glulam and LVLs. Another example is an open-web beam, which looks like a cross between an I-beam and a truss. This stuff is more expensive than dimensional lumber, and might require a longer lead time. But you can get a longer span with built-up rafters, as well as greater structural depth for placing insulation if that’s where you choose to insulate.

Triforce built-up rafters. (from https://www2.buildinggreen.com)

Triforce built-up rafters. (from https://www2.buildinggreen.com)

3. Trusses. Prefabricated and delivered in one piece, trusses are usually the most economical way to span a distance. They save you the trouble of cutting a bird’s mouth and a precise peak angle, assuming you order them correctly and the factory gets the order right. And they’re easy to work with, although hoisting them into place might require some mechanical help. The main disadvantage of trusses is that they chew into your headroom, making the attic strictly a storage space.

Trusses make the attic uninhabitable... no harm done if you planned to insulate at floor level.

Trusses make the attic uninhabitable… no harm done if you planned to insulate at floor level.

4. Sister beams. If you want to retrofit a roof without demolishing the existing structure, you can make the existing structure stronger instead. Cut dimensional lumber as you would for simple rafters and nail them to one or both sides of the rafters you already have. The advantage here is you get to keep your old rafters, and the sister beams can be shallow (say, 2×8 rather than 2×12) since they don’t do all the work themselves.

Bob's roof: old timbers, new sisters.

Bob’s roof: old timbers, new sisters.

Woodshop: Installing Drywall

Drywall is a magical material. It covers walls, it hides plumbing and electricals and HVAC, it accepts any kind of paint job, it provides enough strength for a variety of wall hangings, and it’s easily patched and repaired. And all that in a lightweight, easy-to-cut package. But while drywall is easy to work with, its goal – perfectly plumb finish walls free of bumps and visible joints – is not at all easy to achieve.

The best advice I can give you about installing drywall, if you want it to look good, is to hire a professional. And not just any old building professional, but a drywall specialist. Nobody else has the experience and skill to cut the sheets right, align them right, screw them in the right distance, and give you that perfect finish.

Still want to install drywall yourself? OK. Start with the ceiling, then do the walls from top to bottom. It’s fine to leave an inch gap between the bottommost sheet and the floor, because later you’ll install baseboard to cover the gap. Make sure all your joints are factory edge to factory edge – they might taper to make space for the tape and mud that will eventually obscure the seams. Your outer sheets are the ones you’ll cut to fit the shape of your wall.

Scoring a line with a utility knife and straightedge.

Scoring a line with a utility knife and straightedge.

Straight cuts are quite literally a snap. Measure and draw on your sheet the line you want to cut. Then, using a utility knife, score the gypsum board’s paper coating. (You only need to score one side.) Now imagine the drywall is a book and your score line is the spine, and apply force to close the book. Your sheet will break along the score line with a very satisfying SNAP. Just slice through the paper coating on the other side, and your cut is complete. Repeat as often as necessary to get the shape you need… and remember, once you snap a piece off, you can’t put it back.

Drywall sheets are usually screwed into the studs, not nailed, because the impact of a hammered nail can crack the gypsum. Drywall screws hold great, but a screw head can easily penetrate the outer paper coating, making the connection useless. You’ll need a special drill bit with a gauge that stops the drill as it reaches the wall surface. You’ll also want to run a straightedge across the studs to confirm they’re all in the same plane.

Screwing a drywall sheet to the studs behind it.

Screwing a drywall sheet to the studs behind it.

Here we go. Hold up your cut (or whole) sheet of drywall so the seams are flush with all the seams surrounding it, tack-screw it in a couple places, check alignment, and finish screwing. Don’t leave any part of any screw head sticking out beyond the wall surface, or you’ll be cursing when you go to paint. Also, make sure every screw catches on a stud behind, or it’ll get stuck partway embedded. Any mistake, you’ll need to pull out a screw and then fill in the hole later when you tape and mud.

I told you it wasn’t easy.

Woodshop: Moving Cabinets

Previously in Woodshop we discussed how to install a cabinet, a crucial skill for new construction. Today we’ll explore the remodeling counterpart: how to remove a cabinet from the wall intact and then (maybe) re-hang it in a new location.

Start by taking everything out of the cabinet. Think of it as a good opportunity to reorganize the contents! Also remove drawers and non-fixed shelves, and unscrew the door hinges from the cabinet frame. These steps reduce the weight and keep moving elements out of the way while you handle the frame.

Assess how the cabinet is currently attached to the wall. This unit in Bob’s house had four screws spaced equally along the top edge of the frame. First, remove any fasteners along the bottom or at mid-height, since it’s the top edge that supports the cabinet’s weight. Then, grab a strong friend and have him or her support the cabinet while you remove the top fasteners. Slowly pull the cabinet from the wall – you might have to run a utility knife blade around the edge so you don’t peel paint – and set it down on a drop cloth.

We removed this cabinet from Bob's doomed kitchen wall and hung it in the dining room.

We removed this cabinet from Bob’s doomed kitchen wall and hung it in the dining room.

Next, determine the new position of your cabinet and pre-drill screw holes. At Bob’s house we had the benefit of full barnboard walls, meaning we could attach our screws anywhere and get a solid structural connection. But if the finish is drywall then you’ll be well advised to locate the studs.

Run a level along the wall, too. Bob’s target wall was shockingly out of plumb, requiring us to install a cleat behind the cabinet bottom for spacing, plus trim to fill the wedge-shaped gaps between the wall and the cabinet back. You definitely don’t want your shelves to slope.

The wedge-shaped trim detail that makes Bob's cabinet plumb.

The wedge-shaped trim detail that makes Bob’s cabinet plumb.

Finally, have your friend hold the cabinet steady in its new location until you’ve drilled in two screws for support. Thank your friend. Drill in the remaining screws, reinstall the shelves/drawers/doors, and fill ‘er up.