The frame is up and the crew is ready to close it in, but the windows are still weeks out. That gap between ordering an item and having it on site is what DADU material lead times describe. When it runs long, every task behind it waits. Here, DADU means detached accessory dwelling unit, a separate home on the same lot as a house.

Delivery times vary by product and supplier, so no one can promise them. What you can control is when each choice gets made.

Details below reflect official Seattle code pages checked in October 2026. Confirm with city staff for your property.

Why Does a Late Item Matter So Much?

Construction follows a sequence. Crews need windows and doors to close in the frame, and finish work needs cabinets, counters and fixtures. A late item can hold up every task that depends on it.

Custom and special order items take the most planning, since a supplier makes them for one project. A unique window shape, built to order cabinets or a specific tile can all need early orders. Standard items are easier to source, but supply can shift, so ask about availability ahead of committing.

Procurement Milestones to Plan Around

One simple method is to tie each order to a milestone:

• Permit submittal: the designer needs window, door and equipment specs.
• Framing start: rough openings and blocking need final sizes.
• Rough plumbing and electrical: fixture and appliance specs set pipe and wire spots.
• Finish stage: cabinets, counters, flooring and trim must be on hand.

Working backward from each milestone shows when each choice must be final. The same exercise shows which items need your input and which the contractor can pick within the specs.

How Energy Specs Tie Orders to the Permit

Some materials affect code compliance. For each energy credit a project claims under the Seattle Energy Code, the permit drawings must name the option selected. Most water heating credits require the drawings to list the equipment type and minimum efficiency.

Windows matter too. SDCI Tip 303 calls for a glazing and opaque door schedule on the plans, with product type, size, count and U-factor. It must say whether each U-factor is NFRC certified or a default value. The SDCI energy code page links the current code.

A default rating brings its own detail. In that case the schedule must describe key features such as frame material and the number of glazing layers. Window and water heater choices often need to be settled by permit submittal, not just by framing.

Do Substitutions Need Approval?

Often, yes. A substitute for a delayed item can seem like an easy fix, but check a few things first:

• Whether it fits the rough opening.
• Its energy rating compared with the original.
• Any change it makes to the approved plans.

SDCI’s building permit revisions page says changes to approved work need SDCI approval first. Agree on a substitution process with your contractor early, including who reviews each proposal and how you approve it in writing.

Supply Links Between Trades

Many items depend on one another. A sink choice affects the cabinet, the counter and the plumbing rough-in. Picking a range sets the hood, the circuit and any gas line.

Utility equipment creates links as well. City Light’s service requirements say the customer must furnish vaults, pads and termination facilities to City Light standards where they apply. Confirm equipment needs with each utility well ahead of trenching.

Building a Selection Schedule

A selection schedule lists each item, who chooses it, when the choice is due and when the order must go in. Ask your contractor to share one at the start.

Finish choices tend to cause the most delays. The post on DADU finish allowances explains how allowances work, and the post on DADU kitchen layout shows how kitchen choices connect to plumbing and power.

Storing Materials on Site

Early delivery solves one problem but can create another, since materials need dry and secure storage. Seattle’s construction stormwater manual has a practice for material delivery, storage and containment that keeps pollutants out of runoff.

On a small lot, staged deliveries may work better than one large drop. Check each delivery against the order right away, because a wrong size is easier to fix early.

A Hypothetical Fremont Window Swap

Picture an invented example: a Fremont owner picks a specific casement window, then learns the supplier has a long backlog. A similar unit from another maker comes up as an option. Its U-factor matches, and the rough opening is the same.

The designer updates the glazing schedule and checks with SDCI whether a revision is needed. Nothing here describes a real property, but it shows how a swap touches the permit as well as the schedule.

Common Lead Time Surprises

• Windows chosen after the permit set needs them.
• A substitute with a different U-factor.
• Cabinets that set the plumbing rough-in late.
• Utility pads or vaults left out of the plan.
• Early deliveries with nowhere dry to sit.

Lead Time FAQ

When should I pick windows for a cottage?

Ideally by permit submittal. Seattle’s energy code and SDCI Tip 303 expect the plans to carry a glazing schedule with U-factors. A later change can mean updating that schedule and checking whether a revision applies.

Can the contractor choose some items for me?

Yes, within the specs. Many owners choose the visible finishes and let the contractor select framing hardware, rough plumbing parts and similar items. Put that split in writing to keep anyone from waiting.

What if a product is discontinued mid project?

Treat it as a substitution. Compare size, energy rating and plan impact, then approve the replacement in writing. Ask the designer whether the approved plans need an update.

Selection Planning Checklist

• List every special order or custom item.
• Mark which items appear on the permit drawings.
• Set a selection deadline for each milestone.
• Agree on a written substitution process.
• Plan dry storage for early deliveries.

Make the permit-linked choices first, then set deadlines for everything else. That order keeps DADU material lead times from setting the pace. The post on the DADU build timeline covers other schedule drivers, and the construction and project management section has related topics.