What to know before you start
An addition is new construction attached to an older house. It needs a foundation, framing, a roof that ties into the one you have, and siding, windows and systems that match. It also needs approval from the building department, and often from your HOA, before anyone digs.
DougCO Builds starts with the house and the ground around it. Our estimator measures both, photographs the walls and roof the addition will connect to, and draws the plan. The True Bid lists the foundation, framing, roof tie-in, systems and finishes line by line, so each builder prices the same addition.
What the job includes
- A drawn plan showing the addition and how it connects to the house
- Excavation and an engineered foundation
- Framing, sheathing and a roof tied into the existing roof
- Windows, exterior doors, siding and trim matched to the house
- Heating, cooling, electrical and plumbing extended to the new space
- Insulation, drywall, flooring and interior finishes
- Opening the existing wall and patching where old meets new
- Grading and drainage around the new foundation
What we scope
Bump-out
A small extension of one room, like a bigger kitchen or a bay for a breakfast nook.
Family room
A ground-level addition that adds living space off the kitchen or the back of the house.
Primary suite
A bedroom, bath and closet added on the main floor or over a garage.
Second story
Building up over a single-story house or garage, after an engineer confirms the walls and foundation below can carry it.
Sunroom
A room with lots of glass, built either as insulated, heated living space or as a lighter room for milder months.
What drives the cost
Every project is different, so your True Bid prices yours line by line after the site visit. These are the things that move the price most.
- Size and height
- A bigger footprint means more foundation, roof and wall. Going up adds structural work on the house below.
- Foundation design
- Expansive clay can call for deeper or more heavily engineered foundations, and a soils report often shapes that design.
- Roof tie-in
- Matching the pitch and materials of the existing roof, and keeping water out where old meets new, takes skill and time.
- Plumbing
- An addition with a bathroom or kitchen needs new drains and supply lines, and sometimes a larger water heater.
- Heating and cooling capacity
- Your furnace and air conditioner may not have room to handle the extra space, which can mean a new system or a separate unit.
- Site access
- Tight side yards, slopes and fences can slow excavation and deliveries.
Permits and HOAs in Douglas County
An addition needs a building permit, along with permits for the electrical, plumbing and mechanical work. The permit comes from your town if you live in Castle Rock, Parker, Lone Tree, Castle Pines or Larkspur. In Highlands Ranch and unincorporated areas, it comes from Douglas County's Building Division. Zoning rules set how close you can build to property lines and how tall you can go, so check them before the plan is final.
Permit drawings for an addition usually need more detail than a layout drawing, often including engineered foundation and framing plans. The scope should say who provides them. HOAs are common in Douglas County and often review additions for size, placement, roof lines and materials. Start that review early, since a denial means redrawing the plan.
Built for Douglas County
Foundations are where Douglas County additions get tricky. Expansive clay swells when wet and shrinks when dry, and a new foundation that moves differently from the old one can crack where the two meet. A soils report, an engineered foundation and good drainage around the new walls all help.
Matching the outside takes planning too. Hail, strong sun and dry air age roofs and siding, so brand-new materials can look different from what's on the house even when the product is the same. Some homeowners re-side or reroof the whole house along with the addition. On rural lots with a well and septic system, ask early whether an added bedroom affects what the septic system is approved for.
How DougCO Builds runs your project
- Tell us about itSend the basics through the project form. We call to set up a site visit.
- One site visitOur estimator measures, photographs what's there and talks through what you want.
- Your True BidYou get a written, line-by-line scope and a budget before any contractor sees the job.
- Contractors bid on the same scopeVetted local contractors bid without your contact details. You compare the bids side by side.
- We manage it with youWe check insurance and licensing before work starts, then walk the job at milestones and at the finish.
Questions to ask before you hire
- Who provides the permit drawings and engineering, and is that in your bid?
- How will the new foundation connect to the old one?
- How will you match the roof, siding and windows to the existing house?
- Will my furnace, air conditioner and electrical panel handle the added space?
- How will you protect the house once the wall is opened to connect the addition?
Home Additions questions
Do I need a permit for a home addition in Douglas County?
Yes. Additions need a building permit and inspections, plus permits for electrical, plumbing and mechanical work. The town issues them if you live inside town limits, and Douglas County does everywhere else, including Highlands Ranch.
Should I add on or finish the basement?
If you have an unfinished basement, finishing it is usually simpler, since the foundation and roof already exist. An addition makes sense when you need main-floor space, more daylight or room the basement can't give you. We can scope both.
Does my HOA have to approve an addition?
If you have an HOA, most likely. Douglas County HOAs often review size, setbacks, roof lines, colors and materials. Get approval before you sign a construction contract.
Can I build a second story on my house?
Sometimes. The existing walls and foundation have to carry the new load, which an engineer checks. You also have to move out or live around an open roof for part of the job, and zoning or HOA height limits may apply.
