What Should a Home Addition Estimate Include? A Homeowner's Guide to Comparing Bids

Conceptual image for illustration only; not a completed Stone Fire project.

Three bids for the same home addition can differ by tens of thousands of dollars. That does not automatically mean one contractor is overcharging or another is offering a bargain. The proposals may include different work, materials, allowances, permits, or assumptions about what could be found once construction begins.

The cheapest bid can become the most expensive project if essential work is excluded or allowances are too low. To compare home addition costs fairly, look beyond the total and check whether each estimate describes the same finished project.

What a Complete Home Addition Estimate Should Include

A professional estimate should give you a clear picture of the work, responsibilities, costs, and uncertainties. Before choosing a residential construction company, check that each proposal addresses the following:

Conceptual image for illustration only; not a completed Stone Fire project.

Red Flags That Deserve a Closer Look

A low number alone does not prove a bid is unreliable. However, it is worth asking for a detailed explanation if one proposal is dramatically lower than others. It may reflect a smaller scope, lower-cost materials, or work left out of the estimate.

Be cautious when a bid uses one lump sum with little detail, has allowances that do not fit the selections you discussed, or has no written exclusions. Phrases like “we’ll figure it out as we go” leave important costs and responsibilities uncertain. Pressure to sign immediately is another reason to pause and review the contract carefully.

Ask direct questions and expect clear, written answers. For a deeper bid-review checklist, read our guide to red flags in a contractor’s bid.

How to Compare Bids Side by Side

Give each contractor the same plans, finish expectations, and written project requirements whenever possible. Then create a simple comparison sheet with columns for:

• Scope of work

• Materials and allowances

• Permits, design, and engineering

• Exclusions and assumptions

• Timeline and payment milestones

• Change-order terms and warranty

• Total price

Compare like with like. A proposal with a higher total may include realistic allowances or work that another bid excludes; a lower total may require additional spending later. A higher bid is not automatically better either. What matters is whether the scope is complete, the pricing is specific, and the contractor can explain the numbers.

Conceptual image for illustration only; not a completed Stone Fire project.

Central Oregon Details to Confirm Before You Choose

Home additions in Bend, Redmond, Sisters, Sunriver, La Pine, and nearby communities need site-specific planning. Ask the designer or engineer to identify the applicable snow-load criteria for your property and explain how the addition’s roof, framing, foundation, and connection to the existing home will be addressed. Oregon’s updated structural snow-load requirements make it especially important to confirm the design basis for your project rather than relying on an old assumption. You can review the state’s snow-load technical bulletin.

Wildfire requirements also deserve a specific check. R327 does not automatically apply to every addition. Local rules and project type matter: the City of Bend and Deschutes County identify requirements for certain new dwellings and accessory structures, while additions to existing buildings are not automatically subject to the same provisions. Ask the building department and your design team to confirm whether R327 applies to your project. If it does, the plans and estimate should identify the applicable fire-hardening details, which may include a specified roof fire classification, ignition-resistant materials, ember-resistant vents, and compliant glazing such as tempered glass where required. Our Central Oregon R327 guide explains why confirming applicability early is important.

Finally, permit processes and fees vary by jurisdiction. For projects within Bend city limits, review the City of Bend Building Safety Division. If the property is in unincorporated Deschutes County, use the County’s Oregon ePermitting information. Seasonal site access, material delivery, and inspection scheduling can also affect a realistic timeline. A solid estimate should state what has been checked and what remains subject to confirmation.

Conceptual image for illustration only; not a completed Stone Fire project.

Ask Questions Before You Sign

You do not need to be a construction expert to compare bids well. Ask each contractor to explain the scope, allowances, exclusions, schedule, and assumptions in plain language. Clear answers help you make a decision with confidence and reduce the risk of avoidable surprises.

Stone Fire Construction and Maintenance LLC brings 20 years of combined industry experience, including 10 years serving Central Oregon. We are licensed, bonded, and insured under CCB# 243975. Our approach is straightforward: transparent communication, fair pricing, and a commitment to getting the job done right the first time.

If you have bids or plans for a home addition, bring them to us for a no-pressure walkthrough of what an estimate should cover. Our home renovation services are designed to help you understand your options before you commit.

Scott Bender Stone Fire Construction and Maintenance LLC Phone: 541-948-3775 Email: stonefirebuilders@gmail.com Website: www.stonefirebuilders.com CCB# 243975: Licensed, bonded, and insured