Key takeaways
- An early builder estimate is not a price. It is an order of magnitude drawn off incomplete information, and it is allowed to move.
- Three contract structures dominate: fixed price, cost-plus, and cost-plus with a guaranteed maximum. They allocate risk very differently.
- Allowances are where custom home budgets actually break. A bid can be the lowest and the most expensive at the same time.
- Construction runs $400 to $900 per square foot on the Eastside in 2026. A 2,500 sq ft home lands between $1.2M and $2.5M once land, design, permits and site work are in.
- You cannot get a genuine fixed price off an incomplete drawing set. Completeness of documents is what buys you price certainty.
Two builders quote your custom home. One says $1.9M, the other says $2.35M. Most owners read that as a $450,000 difference. Usually it is not. It is two different scopes, two different allowance structures and two different ideas of what happens when something changes.
This page is about reading those numbers. For what a house costs in the first place, the full line-by-line breakdown is in what it costs to build a house in Seattle. Here I am assuming you already have a number and need to know what it actually commits anyone to.
What a builder’s estimate actually is
The word estimate does a lot of work, and it covers three very different things.
A conceptual estimate comes off a sketch or a square footage target. It is a sanity check, nothing more. Treat it as plus or minus 25% and do not build a budget on it.
A design development estimate comes off drawings that show structure, envelope and rough systems. Plus or minus 10% to 15% is realistic. This is the one worth paying attention to, because it is early enough to change things.
A bid comes off a complete permit and construction set, where the builder has priced actual subcontractor quotes against actual drawings. This is the only one that is a price.
The common and expensive mistake is treating the first as though it were the third. If a builder gives you a confident fixed number off a floor plan and an elevation, they have either padded it heavily or they intend to recover the difference through change orders. Both cost you.
The three contract structures
| Fixed price | Cost-plus | Cost-plus with GMP | |
|---|---|---|---|
| How the builder is paid | One agreed sum | Actual cost plus a fee, often 10% to 20% | Actual cost plus a fee, capped |
| Who carries overrun risk | Builder | You | Builder above the cap |
| Price certainty | Highest | Lowest | High, with a ceiling |
| Transparency | Low, you see one number | Highest, open book | High, open book under a cap |
| Needs complete drawings | Yes, absolutely | No | Yes, to set the cap honestly |
| Savings if it goes well | Builder keeps them | You keep them | Usually shared, check the clause |
Fixed price suits an owner who wants certainty and has a complete set of drawings. The builder carries the risk, and prices that risk in. You will pay a premium for the certainty, and you will not see the savings if the job goes smoothly.
Cost-plus suits complex or unusual work where nobody can price the unknowns honestly, and owners who want to see every invoice. The risk sits with you. It requires trust and attention, and it is the structure most likely to end in a dispute when neither is present.
Cost-plus with a guaranteed maximum price is the middle ground most custom homes on the Eastside land on. Open book, but capped. The clause that matters most is what happens to savings under the cap: shared, retained by you, or retained by the builder. Read that clause before you read the number.
Allowances, where budgets actually break
An allowance is a placeholder for something not yet chosen. Appliances, plumbing fixtures, tile, lighting, flooring, cabinetry, landscaping. The builder puts a number in so the bid can be completed.
This is the single biggest reason two bids are not comparable. A builder carrying a $40,000 appliance allowance and a builder carrying a $90,000 one will produce very different totals for exactly the same house, and the lower bid is not cheaper. It is less finished.
What to do about it:
- Ask for the full allowance schedule as a separate list, not buried in the bid.
- Price two or three of the biggest allowances against what you would actually choose. If the allowance is half of that, you have found your real number.
- Check whether the allowance covers supply only, or supply and installation. This catches people constantly.
- Ask what happens to the difference if you spend less than the allowance.
How to compare two bids properly
- Confirm they priced the same drawings. Same set, same revision date. If one priced an earlier revision, the comparison is void.
- Read the exclusions first, before the total. Exclusions are where the difference usually lives: site work, utility connections, permits, landscaping, retaining walls, temporary power.
- Line the allowance schedules up side by side. Normalize them to the same figures, then re-total both bids.
- Compare the contingency. One builder carrying 5% and another carrying nothing are not pricing the same risk.
- Look at general conditions and the fee. Supervision, site facilities, insurance and overhead. On a custom home this is a meaningful percentage, and it varies widely.
- Ask both for their change order rate in writing, as a percentage, before you choose.
Once those six are normalized, the gap between two bids is usually far smaller than it first appeared, and occasionally it reverses.
If you are borrowing, the leveled bid does a second job. A construction lender wants a signed contract and a fixed budget before it will close, and typically measures the loan against the lower of cost and appraised value, so a weak or incomplete bid shows up directly in the construction loan.
Change orders
Change orders are not a sign something went wrong. On a custom home they are inevitable: you will change your mind, and the ground will surprise everybody at least once.
What matters is how they are priced and approved. Agree in writing, before construction starts, that no change order proceeds without written approval, that each one states its cost and its schedule impact, and that the markup percentage is fixed in the contract rather than decided in the moment. An owner who approves changes verbally on site, one at a time, arrives at the end of the job with a number nobody recognizes.
Where the architect fits
Three specific places, and it is worth being concrete rather than promotional about them.
Before the bid. A complete, coordinated drawing set is what makes a fixed price possible at all. Incomplete documents do not save money, they move the cost to change orders where you have no leverage and no competition.
During the bid. Putting one identical set out to two or three builders is the only reliable way to learn what the work is worth. We level the bids, which means normalizing exclusions and allowances so you are comparing like with like, and we flag where a number looks too low to be real.
During construction. Construction administration is the phase where somebody who is not paid by the builder confirms what is built matches what was approved, reviews change orders before you sign them, and holds the punch list at the end.
I quote a fixed fee for design and permit, set by the project budget and location; most fall between $10,000 and $200,000 depending on scope. How fees are structured is set out in the fee guide. To be clear about our position: we design and administer, and we do not build. We are not paid by the builder, and that independence is the entire point of the role during bidding.
On the Eastside specifically
Construction runs $400 to $900 per square foot in 2026, and a 2,500 sq ft home lands between $1.2M and $2.5M once land, design, permits and site work are counted. Site work is the line that varies most and the one most often excluded from an early estimate: a sloped lot, a critical area, a long utility run or a retaining wall can move the number by six figures before anyone has framed a wall.
Sequence and duration are covered in the custom home timeline. If you are choosing an architect first, start at custom home architect Seattle, or the city pages for Bellevue and Kirkland.
Questions
What is the difference between a builder’s estimate and a bid?
An estimate is an order of magnitude drawn off incomplete drawings and is allowed to move. A bid is a price drawn off a complete permit and construction set, where the builder has priced real subcontractor quotes against real drawings. A confident fixed number given off a floor plan is either padded or will be recovered later through change orders.
Is fixed price or cost-plus better for a custom home?
Fixed price gives certainty and requires complete drawings, and the builder prices the risk in. Cost-plus is open book and suits unusual work where the unknowns cannot be priced honestly, but you carry the overrun. Most Eastside custom homes land on cost-plus with a guaranteed maximum price, which is open book under a cap. Check what the contract does with savings under that cap before you read the number.
Why are two builder bids for the same house so different?
Usually they are not pricing the same thing. The difference is normally in exclusions, allowance levels and contingency rather than in the cost of the work. Level both bids by confirming they priced the same drawing revision, reading the exclusions first, normalizing the allowance schedules to identical figures, then re-totalling. The gap typically shrinks and occasionally reverses.
What is an allowance and why does it matter?
An allowance is a placeholder for something not yet selected, such as appliances, tile or lighting. It is the main reason two bids are not comparable: a builder carrying a $40,000 appliance allowance and one carrying $90,000 produce different totals for the same house, and the lower one is not cheaper, it is less finished. Always ask whether an allowance covers supply only or supply and installation.
What does it cost to build a custom home on the Seattle Eastside in 2026?
Construction runs $400 to $900 per square foot. A 2,500 sq ft custom home lands between $1.2M and $2.5M once land, design, permits and site work are included. Site work is the most variable line and the one most often excluded from early estimates.
Does Piper Cole Architects build custom homes?
No. We are an architecture firm. We design the home, take it through permitting, put the drawing set out to competitive bid, level the bids so you are comparing like with like, and administer construction once a builder is appointed. We do not hold the construction contract.
