Room additions is one of the most popular trade in the construction/remodeling industry.

when ever you're looking to expend your house square footage you'll need the right guidelines 

how to approach room additions category.

Home additions can be sometimes very easy to build if the conditions will allow it. for example: Adding a room to a house on hill side is much harder and cost effective to build and to get approved plans compare to Adding a Room to a house on a flat zone.

Home additions on hill side if the addition is on the hill will must have grading of the dirt, retaining wall with deep footing and maybe caissons if the bedroom addition is on the air to support the new weight that was calculated by the structure engineer. 

also to build second floor addition on existing first floor or adding room above garage cost more because it takes more engineering details and reinforcement of the existing structure to be able to carry the weight of the new addition. 

On the other hand, First floor addition on flat area will be the easiest to build and to get plans approved by the city.

Average cost of room addition is varied, depend on the conditions and the approved plans details. the minimum to build an addition today will start from $150 to $200 per square foot not including finish materials such as flooring, light fixtures, painting, etc.

For Example: 20x20 room addition cost between $60,000 to $80,000 usd on a flat zone area and depends on plans details.

10x20 room addition cost between $40,000 usd to $50,000 usd because it's a small room addition and the process is the same as the large room addition. Home owners must know that small living room addition will cost more then large living room addition per square foot, so if you have the space you better go with larger living room addition.

Bathroom addition cost more then just bedroom addition just because of the fact that there is a lot more work and details in the project, For Example: Bathroom addition has plumbing installation, electrical installation, tile installation and much more details involved.

Bathroom addition cost will be at list 20% - 30% additional cost from just bedroom addition or family room addition.

The Process To Build Room Addition:

First step before anything else is to hire a General Contractor who has an architect and engineer to help you to get the plans approved. don't get any estimates before that because they will not be real or accurate.

After getting the plans approved (usually take 3 to 6 month) depends in the city,

(Los Angeles can take 2 to 4 weeks).

First step is to create footing per design and per plans. usually on a flat area you'll need to dig minimum 24 inch deep and 12 inch wide on raised foundation house unless it show different details on the plans.

then you'll need to build forming inside the footing with plywood and supporting wood sticks.

the forming must be leveled with the existing house floor joists.

after creating the footing you'll need to install rebars inside the footing (Usually number 4 Rebars in two sections. two at the bottom and two at the top.

you'll need to install hold downs every few feet and sometimes anchor bolts to support sheer wall. 

The next step is to pass inspection and to pour concrete (minimum 2,500 PSI)

Framing will be the next step according to plans. Exterior walls, Windows, Doors, Roof framing, floor joist and sub floor but not before installing insulation in the floor joist and pass inspection. All materials type should be listed in the plans details.

if there is bathroom addition or kitchen addition there will be plumbing process according to plans and must meet all codes required. it's always better to hire a license GC that will take the full responsibility for each trade.

Electrical progress will be the next step and all outlets, switches, light fixtures and recessed lights should be installed up to code and plans.

When this is all done there will be an inspection for rough pluming, electrical and framing. Inspector should sign the permit card and GC must move to the next step.

If the exterior wall is stucco finish there will be another inspection for exterior lath (Black paper and chicken wire) if the exterior finish is wood siding or cement siding there will be inspection for black paper or other insulation material as it appear in the plans. 

Insulation is required on all exterior walls, roof rafters and floor joists. there is different insulation grades and usually on exterior walls we install R13 or R15 and on Roof rafters we install R30 (Details should be on the plans and must be followed).

After passing insulation inspection, next step is covering the walls with drywall (Drywall type will show on plans details).

Inspection for drywall nailing is required and after it pass the next inspection will be on final when all the work will be done and completed.