Deck and Addition Engineer Letter — Ledger, Footings, and Guardrails

The most common deck failure mode — ledger pull-out — is also the most preventable. When a ledger is lagged into rim joist with no flashing, inadequate fasteners, or bearing onto siding, the whole deck can come down under design load. It is why ledger attachment is the single most scrutinized inspection point on any deck permit.

When the inspection is missed, or when the deck was built without a permit and is now in the path of a sale or refinance, an engineer letter is the closure tool.

What we verify on site

Ledger attachment. Fastener type (structural screws like SDWS, LedgerLok, or lag screws), size, spacing, and penetration into the house band joist. Flashing against water intrusion. A pattern consistent with IRC Table R507.9.1.3 (or DCA 6 for prescriptive designs).

Lateral load connections. The prescriptive code requires a specific hold-down connection from deck joists to house floor joists — two 1,500 lb hold-downs minimum in most cases. We verify these are present or specify an alternative.

Footings. Type, size, depth below frost line, bearing on undisturbed soil or compacted fill. For concrete piers: geometry, reinforcement if required, and anchor hardware.

Post-to-beam and post-to-footing. Hardware with ICC-ES listings and appropriate uplift and lateral capacity.

Beam and joist sizing. Span verified against span tables or engineered calculation for the applicable load.

Guards and rails. 36” minimum height above walking surface on decks with more than 30” drop. 4” maximum sphere opening. 200 lb concentrated load capacity at the top rail.

Additions: the same analysis scaled up

For additions, we add:

Foundation analysis — either continuation of the existing system or a distinct system that interfaces correctly.

Floor framing sized for the tributary live/dead load.

Roof tie-in, especially where a new roof ties into an existing roof and load paths must be rerouted.

Lateral load continuity — shear walls, hold-downs, and the chain of connections from roof to foundation that resists wind and seismic loads.

The missed-inspection scenario

When a deck was built under a permit but the framing inspection was never approved, the inspector cannot see the ledger attachment through the finish decking boards. Our site visit either accesses the underside (crawlspace, basement, exposed framing) for direct observation or uses a combination of targeted disassembly, contractor photos, and visible evidence to render a sealed finding.

Where the evidence supports certification, we issue the letter. Where it reveals deficiencies, we specify the fix. Either way, the permit path is clear.

If you have an open deck or addition permit, or if you are looking at a property with an unpermitted deck, our missed-inspection service handles these weekly.