How to Write Construction Specifications for a Custom Home
If you want to know how to write specifications for a construction project, here’s the short version: go through the house in the order it gets built, and for every item write down the product, the quality level, the quantity or location, who supplies it, and who installs it. Anything not yet decided becomes a dollar allowance. Anything you aren’t providing goes on a written exclusions list. The plans show where things go. The specifications say exactly what those things are.
Most budget blowups and client fights I see trace back to a spec that said “standard” or “builder grade” or nothing at all. A vague spec is a blank check, and you’re the one who signed it.
What are construction specifications, and why do they matter?
Construction specifications are the written description of the materials, products, and workmanship that go into the house. They sit next to the drawings and the contract, and together those three documents define what the client is buying.
They do three jobs for a builder:
They make the price real. You can’t price “nice windows.” You can price a specific line, material, color, and glass package.
They make bids comparable. When every trade prices the same written scope, the low number means something.
They settle arguments before they start. When a client says “I assumed that was included,” you open the document instead of opening negotiations.
Specs and the budget are two halves of the same system. I covered how they fit together in Construction Budget and Specifications.
How do you write specifications for a construction project, step by step?
Start from the plans and a standard list. Use the same category list on every house, in construction order. A blank page guarantees you’ll forget something.
Walk the house on paper. Site work, foundation, framing, exterior, mechanicals, insulation, drywall, interior finishes, exterior flatwork, landscaping. Then go room by room for finishes.
Describe each item fully. Manufacturer or product line, model or series, size, material, finish, color, and where it goes. If you allow substitutions, write “or approved equal” and say who approves.
Assign responsibility. Who furnishes it and who installs it. Owner-supplied items are a classic gap, so call them out.
Convert the undecided into allowances. State the dollar amount and precisely what it covers: material only, or material and labor, with or without tax and delivery.
Write the exclusions. Window coverings, landscaping beyond a set scope, utility fees, rock excavation, whatever applies. If it isn’t in the house price, say so in ink.
Tie it to the budget. Every spec line should map to a budget line. If a spec has no number behind it, you either forgot to price it or forgot to exclude it.
Review it with the client and get initials. Read it together, line by line, before the contract is signed.
What does a construction specifications example look like?
Here’s a weak spec, the kind I see all the time: “Hardwood floors in main living areas.”
Here’s the same line written properly. This is an illustration, so plug in your own products:
Product: engineered white oak, 7-inch wide plank, site-finished, matte clear coat
Locations: entry, living, dining, kitchen, hallways, and primary bedroom, per the finish plan
Not included: closets and secondary bedrooms, which receive carpet under a separate line
Installation: glue-down over slab, furnished and installed by the builder’s flooring trade
Allowance: none, since the product is selected. A change in species, width, or finish is a change order
The first version can mean five different floors at five different prices. The second one means one floor.
What goes on a construction specifications list?
Your list should cover every category of cost in the house. A typical custom home construction specifications list includes:
General conditions: permits, supervision, temporary utilities, cleanup, insurance
Site work: clearing, excavation, utilities, drainage, driveway
Structure: foundation, framing, trusses, sheathing
Exterior shell: roofing, windows, exterior doors, siding or masonry, waterproofing
Mechanical systems: plumbing, electrical, HVAC, low voltage
Insulation and drywall: types, R-values, texture or finish level
Interior finishes: cabinets, countertops, tile, flooring, trim, interior doors, paint, hardware
Fixtures and appliances: plumbing fixtures, lighting, appliances, mirrors, shower glass
Exterior improvements: flatwork, decks, fencing, landscaping, irrigation
Allowances and exclusions: each one listed separately with its dollar amount or its boundary
If you’d rather start from a list that’s already built out, our Budget and Specifications Template pairs the two documents so they stay in sync.
What construction specification format should you use?
Use whatever format you’ll actually keep consistent from house to house. Commercial projects are usually organized around the Construction Specifications Institute’s MasterFormat, a standard numbered division system. Most custom home builders don’t need that level of formality. A simple outline organized by phase or cost code, matching your budget categories, works well for residential.
The rules that matter more than the numbering scheme:
Same order as the budget. One list of categories, used in both documents.
One item per line. Paragraphs hide things.
Dated and versioned. Every revision gets a new date, and the contract references the specific version.
Plain English. Your client has to understand it, and so does a judge if it ever comes to that.
Performance vs prescriptive specs: which should you use?
Use prescriptive specs for almost everything in a custom home, and performance specs where the result matters more than the brand. A prescriptive spec names the product and method: this faucet, this finish. A performance spec names the outcome: an HVAC system designed to hold a stated indoor temperature at design conditions, or a slab engineered for the soils report.
Prescriptive is easier to price and easier to verify. Performance leaves your trade room to solve the problem, but it’s harder to compare bids, and you’d better define how the result gets measured. Many builders mix them: prescriptive for finishes, performance for engineered systems.
What are the most common specification mistakes?
Weasel words. “Standard,” “typical,” “high quality,” and “as needed” mean whatever the reader wants them to mean.
Allowances that are too low. A lowball number wins the job and loses the client. See how construction allowances work.
Specs that conflict with the plans. State in the contract which document governs when they disagree.
No exclusions list. Silence gets read in the client’s favor.
Never updating them. When a selection or change order alters the house, the spec gets revised. Your selections process should feed right back into it.
Frequently asked questions
Who writes the construction specifications, the architect or the builder?
On custom homes it’s often the builder, sometimes working from an architect’s outline spec. Whoever writes them, the builder has to own them, because the builder is the one pricing and building to them.
How detailed should construction specifications be?
Detailed enough that a stranger could price the house and land within a few percent of your number. If two reasonable people could read a line and picture different products, it needs more detail.
Is there a standard construction specification format for houses?
Not a required one. Commercial work commonly follows MasterFormat, while residential builders usually use a simpler phase-based or cost-code outline that matches their budget.
Are specifications part of the contract?
They should be, attached as an exhibit and referenced by date. How your contract incorporates them is a legal question, so have your attorney review the language.
BTW, if you’d rather not build your spec sheet and budget from a blank page, grab our Budget and Specifications Template over at the Building Optimal Shop, where you can check out the rest of our swag to build a better business. Proceeds go to benefit, Exponencialistas, my non-profit investing in entrepreneurs transforming their communities in Latin America.