🪵 Carpentry 101 for this Build

A glossary + technique reference for every "what does that mean?" moment in the cut sheet and framing plan. Read this once before you start; come back to it whenever a term is unfamiliar.

1. Plumb vs. Level vs. Square

Three different orientations, three different words. They get confused all the time.

You can also use a 6' level, a 4' level, and a plumb bob to verify. The 6' level is long enough to span the full 92-⅝" post height with a few inches to spare. The 4' level is the workhorse for beam and rafter work.

2. The Speed Square

The Speed Square (a.k.a. Swanson Speed Square) is a 7" right-triangle tool. Every carpenter has one. It's the single most useful $15 tool in the box. The cut sheet says things like "12" on the tongue, 1" on the blade" — here's what that means and how to actually do it.

How to mark the 4.76° rafter angle (the "12 on tongue, 1 on blade" step)

1. Lay the rafter on a flat surface (sawhorses work). The face you want to mark the angle on is facing up.
2. Hook the fence of the Speed Square over the top edge of the rafter (the 5-½" face, not the 1-½" face). The square now hangs onto the board like a hook.
3. Rotate the square around the pivot (the right-angle corner) until the 12" mark on the tongue edge lines up with a hash mark, and the 1" mark on the blade edge also lines up with a hash mark. The tongue is the short leg (along the hypotenuse), the blade is the long leg (along the fence).
4. Hold the square firmly against the rafter with one hand. With the other hand, drag a pencil along the tongue edge (not the blade). The pencil line is your cut line.
5. The line you just drew is tilted 4.76° from vertical — i.e., the plumb cut for a 1:12 roof slope.

How to mark a 45° miter (for the optional knee braces, or any other angled cut)

1. Set your miter saw to 45°. Or use the Speed Square: the hash marks on the square include 45° and 22.5° reference lines for quick mark-and-cut without a saw setting.
2. For the Speed Square: rotate the square until the hypotenuse aligns with the 45° hash mark on the body. The fence stays hooked to the board edge. Mark along the hypotenuse.

Other Speed Square tricks worth knowing

• Saw guide. You can rest a circular saw on the Speed Square's body and use it as a fence to make a perfectly straight crosscut. Useful for cutting rafter tails to length.
• Protractor. The hash marks on the body cover 0° to 90°. Use the square as a quick angle finder: lay the pivot at the vertex of any angle, read the angle on the scale.
• Marking centers. There's a center-finding scale along the blade edge for finding the center of a board. The hash mark for the board's width (e.g., 5.5" for a 2×6) shows you where the centerline is.

3. Rafter anatomy

Every part of a rafter has a name. Get these straight and the cut sheet will make a lot more sense.

Why the bird's-mouth is shaped the way it is

The bird's-mouth gives the rafter a flat horizontal surface to sit on (the seat) and a vertical surface to push against (the heel). Without it, the rafter would just be a stick balanced on top of the beam, with nothing to keep it from sliding off sideways. The heel cut, butting against the inside of the front 2×8, prevents the rafter from sliding out toward the yard.

The seat cut is sized to be less than the full 5½" width of the 2×6 (typically 3½" wide, so 1" of wood remains uncut outside the seat). This leaves the rafter's bottom edge intact outside the seat so it doesn't split along the grain. Cutting the full width would create a hinge point at the heel that can split under load.

4. Simpson Strong-Tie connectors

Simpson makes the metal connectors that hold timber-frame structures together. The model numbers are SKU-style: the first letter indicates the product family, the rest is a sequential number.

APVB44 — the post base

The APVB44 is a 4×4 nominal post base from the Avant collection (decorative black powder-coat hardware, ZMAX galvanized for corrosion resistance). The 1" standoff between the post bottom and the concrete slab is the critical detail — it keeps the end-grain of the post off the slab where moisture would wick up and rot it. The decorative hex-head SDWS screws through the side flanges are visible from the yard and are part of the "exposed black hardware" aesthetic.

LSSJ26 — the rafter hanger at the high side

The LSSJ26 is a field-slopeable joist hanger. "Field-slopeable" means the seat flange can be bent on-site to match the roof slope — the factory ships it flat and you bend it to the angle you need. This build needs 9 of them, all bent to 1:12 (4.76°). They are ZMAX galvanized (silver, not black) because the Avant collection doesn't have a slopeable hanger equivalent.

H2.5A — the hurricane tie at the low side

The H2.5A is a small steel strap that wraps over the rafter's bird's-mouth and down both sides of the front 2×8. It locks the rafter down against wind uplift (suction) — without it, a strong wind can lift the rafter off the roof like a wing. Nailed with 8d × 1-½" nails (Simpson N8).

5. Concrete anchors

The post base sits on a concrete slab. The connector between the base and the slab is a mechanical anchor — a steel bolt that's expanded inside a hole drilled in the concrete.

Titen HD vs. wedge anchor

Two common types, both work for this build. The Titen HD is what the cut sheet specifies.

Feature	Titen HD (THD)	Wedge anchor
Brand	Simpson Strong-Tie	Generic (Hillman, Red Head, Powers)
How it works	Threaded screw with a hex head, cuts its own threads into a pre-drilled hole	Bolt with an expansion clip at the bottom; tightening the nut pulls the clip up and expands it against the hole walls
Hole size	½" bit for a ½" Titen HD	Same as the bolt diameter (½" bolt needs a ½" hole)
Tools needed	Hammer drill + ½" masonry bit, impact driver + ¾" socket (or ½" wrench)	Hammer drill + ½" masonry bit, ¾" wrench (or impact driver + socket)
Removable?	Yes — unscrew with impact driver	Difficult — once expanded, you can unscrew the nut but the clip stays in the hole
Cost (1 anchor)	~$4-5	~$1-2
Best for	Post bases, sill plates, anything that might need to come apart later	Permanent installations where you'll never need to remove the bolt

How to install a Titen HD into an existing concrete slab

1. Position the APVB44 post base on the slab. Mark the center of the anchor hole through the base's bottom plate onto the concrete with a pencil or marker.
2. Move the base aside. Drill the hole using a hammer drill with a ½" masonry bit. Drill to a depth of at least ⅝" deeper than the embedment depth of the anchor (typically 3" embedment + ⅝" = 3-⅝" total hole depth for a 3-½" long Titen). Drill straight (perpendicular to the slab), not at an angle.
3. Blow out the concrete dust from the hole. A few puffs from a compressed air can, or tap the side of the slab and let gravity do it. A dust-filled hole reduces anchor grip.
4. Insert the Titen HD through the post base's bottom plate and into the hole. Drive it with an impact driver and a ¾" socket. Tighten until the head is snug against the plate — don't over-torque or you'll strip the threads in the concrete.
5. Verify the post base is rigid. No movement when you push on it. If it moves, the hole may be oversized (drilled too wide) and the anchor won't hold. Drill a new hole 2" away and use a new anchor.

6. Field-bending a hanger

Some Simpson hangers (like the LSSJ26) ship flat and you bend the seat flange to match your slope on-site. "Field-bending" is a controlled bend, not a hack-job.

How to bend an LSSJ26 to 1:12 (4.76°)

1. Stack all 9 LSSJ26 hangers on a flat surface (a piece of plywood on the ground, or a workbench).
2. Mark the bend line on the seat flange of the top hanger. The bend is about ⅔ of the way from the back flange to the front edge of the seat.
3. Clamp the back flange in a vise (or use a hickey bar / pipe wrench on the seat flange) and bend the seat flange down by 4.76°.
4. Use a digital protractor to verify the angle. Or, make a reference gauge: take a 12" piece of scrap 2x4, lay it on a flat surface, place a 1" spacer under one end, and you have a 1:12 slope template. Set the bent hanger's seat against the template and check that the seat matches the slope.
5. Bend all 9 hangers identically. Check all 9 against the reference gauge before going up to the roof.

7. Wood movement

Wood is not stable. It expands and contracts with temperature and humidity. Ignoring this is the #1 cause of failures in outdoor wood structures (cracked panels, split boards, popped screws).

How much does wood move?

• Redwood (this build): ~1/8" per 8' length per 10% change in moisture content. Most redwood at Ashby is already kiln-dried to 12-15% moisture. In use it'll settle to 8-12% over the first year. Expect ~1/8" of seasonal movement on a 14' beam.
• Polycarbonate panels: ~⅛" per 8' panel per 50°F temperature change. A panel can move ¼" between a cool morning and a hot afternoon. This is why the panels need oversized screw holes (pre-drilled 1/8" larger than the screw shank).

Where movement bites you

• Splits at screw holes. Driving a screw into wood without a pilot hole can split the board along the grain, especially near the end of a board. Pre-drill with a bit slightly smaller than the screw's inner shank diameter (not the threads).
• Cracked polycarbonate. Snug holes in polycarbonate panels don't allow the panel to move. A temperature change puts stress on the panel around the screw, and the panel cracks. Pre-drill 1/8" oversized.
• Tight joints binding. If a beam is cut 0.5" too long and you force it into a tight space, the wood will eventually split something (or the fasteners will pop). Always cut slightly short, never slightly long.
• End-grain wicking moisture. The cut end of a board absorbs moisture faster than the sides. This is why the post bottom sits in the APVB44 with a 1" standoff — to keep the end-grain off the slab. If the end touches the slab, the post will rot from the bottom up.

Wet wood vs. kiln-dried wood

The redwood from Ashby is "kiln-dried" or "S-Dry" (surfaced dry) which means the moisture content is below 19% (typically 12-15% for kiln-dried). It's stable enough to use immediately. If you buy "green" lumber (not dried), the wood will shrink noticeably over the first year as it dries. For this build, kiln-dried is fine — and the cut sheet specifies it.

8. Common build practices

These are the things carpenters do as a matter of course but DIYers often skip. Skipping them is the difference between a structure that lasts 5 years and one that lasts 50.

Dry-fit before you commit

"Dry-fitting" means assembling the pieces without glue or fasteners to verify the fit. Cut one rafter, lay it in the LSSJ26 hanger on the 4×12, set the bird's-mouth on the front 2×8, and check that everything sits where it should. If it doesn't fit dry, it won't fit glued. Fix the fit first.

Cut one, use it as a template

For repetitive cuts (9 rafters, 6 knee braces if you add them, 9 LSSJ26 bend angles), cut the first one, verify it's right, and then use it as a physical template to mark and cut the other 8. Stack-and-cut is faster and more consistent than measuring each one from scratch. The first one takes 30 minutes; the next 8 take 5 minutes each.

Gang-cut

"Gang-cutting" means clamping multiple boards together and cutting them all in one pass. This guarantees they're identical. Use this for rafter tails, knee braces, or any other piece where you have 6-9 identical parts.

Pre-drill everything near an end

Any screw or nail within 2" of the end of a board can split the board if driven without a pilot hole. Pre-drill with a bit slightly smaller than the screw's inner shank. For the SDWS screws (5-½" long, ¼" shank), use a 3/16" pilot bit. For the H2.5A nails (8d × 1-½"), use a 1/8" pilot bit.

Plumb, level, square — check at every step

Don't wait until the end of a phase to check the geometry. After every connection, verify the new piece is plumb, level, and square to the pieces it's attached to. A 1° error at the start of a phase becomes a 3" error by the end. Catch errors early, when they're easy to fix.

Snug the joint, then back off

"Snug" means the fasteners are tight enough that the joint doesn't move, but not so tight that the wood compresses visibly. Over-tightening a bolt or screw crushes the wood fibers, which loses grip over time. The joint should feel solid, not stressed.

Read the existing structure before you modify it

The 4×12 you're attaching to has been there for years. Before drilling into it, look at it carefully:

• Where's the existing 4×12 attached to the rest of the pavilion? (Look for bolts, brackets, post locations.) Don't drill into a structural bolt.
• What's behind the 4×12? (Sheathing, siding, weather barrier, electrical, plumbing.) A long LSSJ26 nail going into the 4×12 might hit something behind it. Use a shorter nail if you're not sure.
• Is the 4×12 straight and true? If it's warped, shim the LSSJ26 hanger to match. Don't try to bend the hanger to match a wavy 4×12.

9. Code & permitting

Permit requirements vary by city and county. The Bay Area is generally strict about unpermitted structures, and HOAs (if applicable) are often stricter than the city. Build code (the California Building Code, Title 24) is enforced through the permit process.

Do you need a permit?

Rules of thumb (always verify with your local building department):

• Detached structure over 120 sq ft: Permit required.
• Attached structure (this build): Permit required in most jurisdictions, regardless of size. Even a small attached patio cover needs a permit because it's structurally tied to the house.
• Setback requirements: Many cities have minimum setbacks from property lines. A 14' × 12' structure may not be allowed within 5' of a side yard property line. Check your city's setback rules.
• HOA: If you're in an HOA, submit plans to the architectural review committee before pulling a city permit. HOAs often have their own rules on materials, colors, and visible structures from the street.

What's in a permit application

• Site plan (showing the structure's location on the property, setbacks, and distances to the house and property lines)
• Construction drawings (plan, elevations, sections — what's on this site at /renderings/ and /cut-sheet/)
• Material specifications (lumber species/grade, hardware SKUs, fastener schedule — what's on the /shopping-list/)
• Foundation details (slab type, anchor type — what's referenced on the /framing-plan/)
• Engineering calculations (not usually required for a pergola of this size, but if your jurisdiction requires them, hire a structural engineer for a couple hours of stamping)

Inspections

Typical inspection sequence for an attached pergola:

1. Pre-cover inspection (after framing, before roof): an inspector checks the post bases, beam connections, and rafter attachments. They want to see the hardware and the structural connections before they're hidden by the roof.
2. Final inspection (after everything is done): visual inspection, sign-off.

You don't need a separate inspection for the concrete anchors alone — the inspector will check them at the pre-cover inspection.

• Trigger a stop-work order (mid-construction, with the materials on your slab)
• Complicate your home sale (buyers demand permits be closed out or the structure torn down)
• Void your homeowner's insurance for any damage caused by the unpermitted structure
• Result in fines from the city

What the inspector actually looks for

Most residential inspectors are reasonable. They want to verify:

• Anchor type and embedment depth is right (matches the spec)
• Post bases are anchored to sound concrete (not a crumbly old slab)
• Beam-to-post connections use the right fasteners in the right pattern
• Rafter hangers are field-bent to the correct angle and fully nailed
• Hurricane ties are present at every rafter
• Roofing is properly flashed at the house connection

You don't need a perfect install. You need a safe install that meets the structural intent. If something is unclear, ask the inspector before you start — most will tell you over the phone what they need to see.

10. Tool glossary

Tool	What it does	When you need it
Speed Square	7" right-triangle with fence, hash marks for angles, saw guide	Every rafter and brace cut. The single most-used tool.
Framing square	24" × 16" L-shaped square, for laying out stairs and checking larger 90° corners	Optional. The Speed Square handles 90% of what a framing square does for this build.
4' level	4-foot bubble level, accurate to ~0.5°	Verifying beams are level, posts are plumb
6' level	6-foot bubble level, accurate to ~0.5°	Verifying the 92-⅝" post height is plumb across the full length
Laser level or transit	Projects a level line or plane across the jobsite	Setting post heights accurately across a 14' span. The string-line-and-line-level method is a cheaper alternative.
Plumb bob	Weight on a string, gravity defines vertical	Verifying posts are plumb in two directions. Most 4' levels have a plumb-bob mode (rotate 90°).
Circular saw	Handheld power saw, 7-¼" blade typical	Cutting lumber to rough length. Use a fresh 40-tooth carbide blade for clean cuts.
Miter saw	Stationary saw, blade pulls down onto the workpiece, great for repeated identical cuts	Cutting all 9 rafters to length and angle. Highly recommended for this build.
Jigsaw	Handheld power saw with a small reciprocating blade	Cutting curved or detailed cuts like decorative rafter tail shapes
Oscillating multi-tool	Handheld power tool with rapid side-to-side oscillating blade	Flush-cutting, detail sanding, removing old caulk, plunge cuts in tight spaces
Hammer drill	Drill with a hammering action for masonry. Looks like a regular drill but has a "hammer" mode.	Drilling into the existing concrete slab for the post-base Titen HD anchors
½" masonry bit	Carbide-tipped bit for drilling concrete. Use only in hammer mode.	Drilling the ½" anchor holes in the slab. One bit will do all 3 holes; have a spare in case the first one breaks.
Impact driver	Drill with rotational hammer action. Drives screws with much more torque and less wrist strain than a regular drill.	Driving SDWS screws, lag bolts, and any other structural fasteners. Highly recommended.
Socket set (⅜" & ½" drive)	Ratchets, sockets, extensions	Tightening Titen HD anchors (¾" socket), beam hanger nuts, any bolted connections
Caulking gun	Hand-operated dispenser for tubes of caulk or construction adhesive	Sealing around the post bases and any flashing edges
Ratchet straps (2)	Heavy-duty straps with ratchet buckles	Temporarily bracing the posts plumb during installation (Phase 2)
2 sawhorses	Trestles to lay lumber on for cutting	Cutting rafters and other lumber. Worth buying if you don't have them — they make every cut easier.
Extension ladders (2 × 8' minimum)	8' or longer ladders	Working at the 9' post-top and 4×12 connection height. Two ladders so you can brace the structure from both sides.
Fall-protection harness	OSHA-rated full-body harness with lanyard	Required if working above 6' on a ladder. Most jurisdictions require it for any 9'+ work. A $50 harness and a $30 lanyard are cheap insurance.

Carpentry 101 for the Redwood Pergola Extension · last updated July 11, 2026