Quick planning overview for home addition cost
Homeowners in Boise, Meridian, Eagle, Kuna, Star, Middleton, Nampa, and Caldwell ask us about home addition cost more than almost any other line item on a remodel budget. This article is part of our Boise Remodeling Cost Guide—the definitive hub for Treasure Valley remodeling costs.
Numbers below are planning ranges from design-build consultations, not advertisements. Your home, layout, and finish level will move you within or beyond these bands.
Use our project estimator for a rough range, then request an in-home visit for written scope.
Room addition cost ranges in the Treasure Valley
Ground-floor additions often run $80,000–$250,000+ including design, permits, foundation, framing, MEP, and finish. Second stories can exceed this when structural retrofits are required.
Foundation and site work
Soils, setbacks, and utility locations in Eagle and Hidden Springs affect foundation type. Rock and drainage add site cost in Foothills lots.
Matching architecture
Roof lines, siding, and window rhythm must match or intentionally contrast per HOA and city design standards.
ADU comparison
ADUs and guest houses overlap addition economics—see ADU services and this guide’s companion articles.
Service areas
Boise additions, Eagle, Kuna, Nampa area.
More planning resources
Explore our Boise Remodeling Cost Guide, Treasure Valley guide, Boise remodeling guide, service areas, Boise kitchen remodels, Meridian bathrooms, Eagle whole-home, Nampa additions, schedule a consultation, and project estimator.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Whole-home programs succeed when structural and MEP decisions precede finish selections. Treasure Valley · Consultation.
Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. Treasure Valley · Consultation.
Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Treasure Valley · Consultation.
Whole-home programs succeed when structural and MEP decisions precede finish selections. Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Treasure Valley · Consultation.
Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Treasure Valley · Consultation.
ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Treasure Valley · Consultation.
Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Treasure Valley · Consultation.
North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley · Consultation.
Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Treasure Valley · Consultation.
Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Treasure Valley · Consultation.
Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Treasure Valley · Consultation.
Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Treasure Valley · Consultation.
Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Treasure Valley · Consultation.
Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Treasure Valley · Consultation.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Whole-home programs succeed when structural and MEP decisions precede finish selections. Treasure Valley · Consultation.
Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. Treasure Valley · Consultation.
Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Treasure Valley · Consultation.
Whole-home programs succeed when structural and MEP decisions precede finish selections. Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Treasure Valley · Consultation.
Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Treasure Valley · Consultation.
ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Treasure Valley · Consultation.
Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Treasure Valley · Consultation.
North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley · Consultation.
Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Treasure Valley · Consultation.
Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Treasure Valley · Consultation.
Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Treasure Valley · Consultation.
Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Treasure Valley · Consultation.
Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Treasure Valley · Consultation.
Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Treasure Valley · Consultation.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Whole-home programs succeed when structural and MEP decisions precede finish selections. Treasure Valley · Consultation.
Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. Treasure Valley · Consultation.
Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Treasure Valley · Consultation.
Whole-home programs succeed when structural and MEP decisions precede finish selections. Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Treasure Valley · Consultation.
Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Treasure Valley · Consultation.
ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Treasure Valley · Consultation.
Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Treasure Valley · Consultation.
North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley · Consultation.
Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Treasure Valley · Consultation.
Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Treasure Valley · Consultation.
Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Treasure Valley · Consultation.
Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Treasure Valley · Consultation.
Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Treasure Valley · Consultation.
Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Treasure Valley · Consultation.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Whole-home programs succeed when structural and MEP decisions precede finish selections. Treasure Valley · Consultation.
Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. Treasure Valley · Consultation.
Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Treasure Valley · Consultation.
Whole-home programs succeed when structural and MEP decisions precede finish selections. Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Treasure Valley · Consultation.
Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Treasure Valley · Consultation.
ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Treasure Valley · Consultation.
Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Treasure Valley · Consultation.
North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley · Consultation.
Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Treasure Valley · Consultation.
Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Treasure Valley · Consultation.
Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Treasure Valley · Consultation.
Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Treasure Valley · Consultation.
Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Treasure Valley · Consultation.
Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Treasure Valley · Consultation.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Whole-home programs succeed when structural and MEP decisions precede finish selections. Treasure Valley · Consultation.
Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. Treasure Valley · Consultation.
Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Treasure Valley · Consultation.
Whole-home programs succeed when structural and MEP decisions precede finish selections. Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Treasure Valley · Consultation.
Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Treasure Valley · Consultation.
ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Treasure Valley · Consultation.
Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Treasure Valley · Consultation.
North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley · Consultation.
Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Treasure Valley · Consultation.
Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Treasure Valley · Consultation.
Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Treasure Valley · Consultation.
Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Treasure Valley · Consultation.
Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Treasure Valley · Consultation.
Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Treasure Valley · Consultation.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Whole-home programs succeed when structural and MEP decisions precede finish selections. Treasure Valley · Consultation.
Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. Treasure Valley · Consultation.
Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Treasure Valley · Consultation.
Whole-home programs succeed when structural and MEP decisions precede finish selections. Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Treasure Valley · Consultation.
Comparing remodel cost to moving should include commissions, moving costs, and emotional disruption—not just sticker price. North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Treasure Valley · Consultation.
ROI-focused updates should match neighborhood comps in Boise and Meridian—avoid over-improving for the street. Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Treasure Valley · Consultation.
Outdoor kitchens need utility planning for gas, electric, and drainage before pavers are installed. Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Treasure Valley · Consultation.
North End bungalows reward creative storage and respectful scale—forced oversized additions can hurt character. Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley · Consultation.
Meridian subdivisions often benefit from open kitchen conversions and mudroom additions at rear entries. Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Treasure Valley · Consultation.
Use room-level budgets: kitchens, baths, and additions sit on different planning curves—see our cost tables. Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Treasure Valley · Consultation.
Hold 10–15% contingency for concealed conditions behind drywall in older Boise and Bench homes. Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Treasure Valley · Consultation.
Ada County plan review often adds weeks when plumbing, electrical, or structural sheets are required—build that into your calendar before ordering demo. Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Treasure Valley · Consultation.
Canyon County projects in Nampa, Middleton, and Caldwell use different portals than Ada; your contractor should submit in the correct jurisdiction from day one. Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Treasure Valley · Consultation.
Treasure Valley ranches and split-levels from the 1970s–1990s frequently need panel and insulation upgrades when walls are opened—budget contingency accordingly. Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Treasure Valley · Consultation.
Eagle and Hidden Springs neighborhoods may require HOA architectural review in addition to county permits—start design early. Written scope with clear allowances beats a low bid that excludes haul-off, protection, or engineering. Treasure Valley · Consultation.
Dry Idaho summers favor exterior concrete and roofing; schedule hardscape and addition work outside winter freeze-thaw cycles when possible. Kitchen appliance rough-in should be locked before drywall close-up—even when appliances are client-supplied. Treasure Valley · Consultation.
Design-build keeps design, permits, and construction under one contract—reducing gaps that cause change orders mid-project. Curbless showers require precise slope and waterproofing—inspection failures delay master bath timelines. Treasure Valley · Consultation.
