Liner Notes to Put on a Lined-Duct Quote

When a duct line says "lined" and nothing else, the shop still has to ask which liner, how thick, and whether the size on the plan is inside or outside the liner. That slows the quote. This article covers the liner notes a lined-duct request usually needs before it can be priced and fabricated - so you can mark them once and send a cleaner package.

For the full quote checklist (drawings, materials, connections, releases, pickup or delivery), see the Contractor Guide. For lined duct fabrication itself - what the shop builds and how to request an estimate - see Lined Duct. This post stays on the liner notes only.

DuctAxis is a commercial duct fabricator in Clewiston, Florida. We fabricate. We do not install.

Why "lined" by itself is not enough

On a plan, a lined run often looks like any other duct with a note or a hatch. The estimator needs more than that. The liner adds material, labor, and thickness to the piece. If the liner is not named, or the thickness is missing, or nobody says whether the dimension is clear inside or sheet metal outside, the ticket cannot be built without guessing or calling you back.

Common gaps:

"Lined" or "insulated" on the line with no liner product or type from the spec
No liner thickness, or a thickness on the drawings that does not match the spec section
A duct size with no note on whether it is the inside (clear) dimension or the outside sheet metal dimension
Lined runs shown on the plan but no note on where the lining starts and stops
Fittings on a lined run with no note on whether they are lined too
Attachment, edge, or facing requirements in the spec that never make it onto the request

You do not have to rewrite the spec. A clear schedule line plus the spec section that covers duct liner is enough to start estimating. Free estimates and takeoffs are available when the set is thin; clearer liner notes still cut questions.

Start with the spec section

Most liner questions are answered somewhere in the project documents. The fastest way to avoid a callback is to send that part with the request.

Attach or reference the duct liner spec section by number and page, so the estimator reads the same requirement you are working from.
Note any addenda or approved submittals that change the liner, so an older spec page is not priced by mistake.
Flag conflicts between the drawings and the spec instead of picking one. If the plan note and the spec section disagree on liner type or thickness, say so in the request.

Final dimensions, materials, and fabrication follow your approved project requirements and are confirmed during estimating. Do not guess a liner or a thickness to fill a blank - send what the documents state, or flag that it is missing.

Liner type and thickness

These are the two notes the lined duct page asks for first, and the two most often left off.

Liner

The liner product, type, or description exactly as the spec or approved submittal states it
Any facing, coating, or surface requirement the spec calls out for the airstream side
If the spec names a manufacturer or allows an "or equal," include that wording rather than paraphrasing it

Thickness

The liner thickness from the documents, written on the line or referenced to the spec
Separate lines when different systems or areas use different thicknesses, instead of one thickness for the whole job

If the drawings show a lined run but no thickness anywhere, flag it ("liner thickness not shown on M-201 or in spec, need confirmation"). That is faster than a quote built on an assumption.

Inside or outside: say which dimension you mean

This is the note that causes the most rework on lined duct. The liner takes up room inside the sheet metal. A 24 x 12 duct can mean a 24 x 12 clear opening with the metal built larger, or a 24 x 12 sheet metal size with a smaller clear opening once the liner is in.

On every lined line, or once at the top of the schedule:

State whether sizes are inside (clear) dimensions or outside sheet metal dimensions
Use the same convention the drawings use, and say what it is
If the drawings do not say, flag it rather than assuming either way

The same note matters at connections. Where a lined run meets equipment, a bare run, or a fitting from another package, the size that has to match may be the outside metal, not the clear opening. Note which side has to fit.

Where the lining starts and stops

Lined duct is often only part of a system. The plan shows where, but the request should say it plainly so footage is not over- or under-counted.

Lined runs by mark or segment - list which straights and fittings are lined, rather than one total footage
Start and stop points shown on the plan, such as a set distance from equipment or between two marks, written on the request
Mixed runs - when lined and bare duct share a run, put them on separate lines so each is priced correctly
All sides or partial - note it if the documents call for lining on only some sides of the duct

Fittings on a lined run

Elbows, offsets, transitions, and takeoffs on a lined run need the same liner notes as the straights. Do not assume the estimator will carry them over.

Note whether each fitting on the run is lined
Use the same liner, thickness, and inside or outside convention as the straight duct it connects to
Give both end sizes on transitions and reducers, with the inside or outside note applied to both ends
Call out turning vanes, access openings, or other items in a lined fitting when the documents require them

If one fitting is lined and the next is not, mark both so the change is not missed.

Other spec notes worth copying over

Some liner requirements live deeper in the spec and affect how the duct is built. When the documents include them, put them on the request or point to the paragraph:

Attachment method - adhesive, fasteners, or both, as specified
Edge and seam treatment - any requirement for coating, sealing, or protecting cut edges and leading edges
Airstream or velocity notes that the spec ties to liner selection
Any test, rating, or listing the spec requires the liner to meet, quoted as written

Only send what the documents state. Ratings and requirements are confirmed during estimating against the approved project requirements.

Quick checklist before you send the lined duct package

Use this against the lined runs and fittings in the package:

Duct liner spec section attached or referenced by number and page
Addenda or approved submittals that change the liner are included
Liner product or type written as the documents state it
Liner thickness noted, with separate lines where thickness changes
Inside (clear) or outside sheet metal dimension stated for the schedule
Lined runs listed by mark or segment, with start and stop points
Lined and bare duct on separate lines where they share a run
Fittings on lined runs marked lined or not lined
Transition and reducer end sizes follow the same inside or outside convention
Attachment, edge, facing, or rating requirements copied from the spec when present
Conflicts between drawings and spec flagged, not resolved by guessing

If a box is empty, either fill it from the documents or flag it in the request ("liner type not stated for return mains, need confirmation"). That is faster than an incomplete line that looks complete.

How this fits the lined duct package

The lined duct page is where fabrication scope for internally lined work lives - lined duct built to the liner, thickness, and dimensions on your project documents, with the assembly confirmed before fabrication. This article does not replace that page; it only helps the liner notes arrive complete. If the spec calls for double-wall construction instead of internal liner, treat that as a different request and say so, rather than listing it as lined duct.

When you are ready to price the package, use the Contractor Guide for project details, drawings, construction requirements, dates, and pickup or delivery notes. Free shipping applies anywhere in Florida. Delivery details for other states in the service area are confirmed with your project quote - do not assume free shipping outside Florida.

Send the notes with your request

When the liner notes are marked, request a quote. Uploads accept PDF, XLSX, XLS, CSV, DWG, DXF, and ZIP files: up to 8 files, 20 MB each, 50 MB total. For a larger package, call (863) 599-7014 or email office@ductaxis.com.

Quote response time: under 48 hours, excluding weekends. That is how long it takes to get a quote back, not the fabrication lead time.
Shipping: Free shipping anywhere in Florida. Delivery outside Florida is confirmed with your quote.
Shop: 535 E El Paso Avenue, Suite C, Clewiston, FL 33440

Free estimates and takeoffs are available. Send what you have; clearer liner, thickness, and dimension notes still make the first pass cleaner.

Dimensions, material grades, and ratings are confirmed during estimating. This article is general guidance for lined duct quote notes and does not replace your project specifications, drawings, or engineer of record.