Contact your insurance company before construction starts
The fastest way to add a new addition to your home insurance is to call your current insurer and tell them what you are building. Most insurers will not automatically cover new structures — a garage, sunroom, deck, or bedroom addition — until you report them and they update your policy. If you wait until after construction is done, you may find that damage to the new space is not covered.
Your insurer will ask for basic details: what you are building, the square footage, the materials (wood frame, brick, etc.), and when construction will be finished. Some companies can add the coverage over the phone and email you a policy update the same day. Others may send an adjuster to inspect the work before finalizing the addition to your policy.
The timing matters because your coverage date is the date the addition is added to your policy, not the date you finish building. If a fire damages your new garage on the day before you call your insurer, that damage will not be covered.
Key Takeaways
- Call your insurer as soon as you know you are building an addition, before construction begins, so coverage starts on the date you add it to your policy.
- Your insurer will ask for the size, materials, and expected completion date of the addition, and may send an adjuster to inspect once it is finished.
- The cost to add coverage depends on the size and type of addition, and your insurer will calculate a new premium based on the increased home value.
- If you do not report the addition, damage to it will not be covered under your existing homeowners policy.
- Some additions like decks or pools may require separate coverage or higher limits than standard homeowners policies provide.
What information your insurer will need
When you call, have the following details ready: the type of structure (attached garage, bedroom, sunroom, deck, pool, etc.), the square footage or dimensions, the construction materials, whether it is attached to the house or detached, and the expected completion date. If you have construction plans or a contractor's estimate, your insurer may ask to see those.
Some insurers also ask whether the addition will have utilities (electrical, plumbing, heating) and whether it will be used for living space or storage. A heated bedroom addition costs more to insure than an unheated storage shed, because the replacement cost is higher.
If you are still in the planning stage, you do not need exact measurements — an estimate is fine. You can update the information later once construction is underway or finished.
How the cost of adding coverage is calculated
Your premium increase depends on the size of the addition and what it is made of. A 200-square-foot attached garage will cost less to add than a 400-square-foot bedroom addition, because the bedroom has higher replacement value. Materials matter too: a wood-frame addition costs less per square foot to insure than a brick addition, because brick is more expensive to rebuild.
Your insurer calculates the replacement cost of the addition — what it would cost to rebuild it from scratch if it burned down or was destroyed — and uses that to set the premium. They may also factor in your location (areas with higher labor costs pay more), your home's age and condition, and your claims history.
The increase is usually modest for small additions. A typical 200-square-foot garage might add $15 to $40 per year to your premium, though this varies widely by insurer, location, and your existing coverage limits. Ask your insurer for a quote before you commit to the addition.
When an adjuster will inspect the addition
Many insurers send an adjuster to inspect the finished addition before finalizing the coverage. This is not a pass-or-fail inspection — the adjuster is confirming that the addition matches what you described and was built to code. They measure the space, check the materials, and verify that utilities are installed correctly if the addition includes them.
Schedule the inspection after construction is substantially complete but before you move furniture in or start using the space heavily. The adjuster will take photos and notes, and your insurer will use this information to finalize your policy update. The inspection usually takes 30 minutes to an hour.
If the addition is significantly different from what you described — for example, you said it would be 200 square feet but it is actually 300 — your insurer may adjust the premium or ask you to clarify before coverage takes effect.
Additions that may need separate or higher coverage
Some additions fall outside standard homeowners coverage or require higher limits than your current policy provides. Swimming pools, hot tubs, and trampolines usually need a separate rider or endorsement because they increase liability risk. If someone is injured in your pool, your standard homeowners liability coverage may not be enough.
Detached structures like guest houses, studios, or workshops may also need separate coverage if they are large or used for business. A detached garage for storage is usually covered under your standard policy, but a detached studio you rent out or use for a home business may not be.
Ask your insurer whether your addition needs a rider, endorsement, or separate policy. These add to your premium but are often cheaper than buying a separate policy for the structure.
What happens if you do not report the addition
If you build an addition and do not tell your insurer, damage to that addition will not be covered. If a fire destroys your new garage, your insurer will deny the claim because the garage was not on your policy. You will also be underinsured on your home's total value, which can affect how much your insurer pays out on other claims.
Some insurers discover unreported additions during a claim or when they inspect your home for renewal. If they find an addition you did not report, they may refuse to cover it, charge you back-dated premiums, or cancel your policy for misrepresentation. It is much simpler to report the addition upfront.
How to update your policy after the addition is complete
Once the addition is finished and inspected, your insurer will send you an updated declarations page showing the new coverage and premium. Review this carefully to make sure the square footage, materials, and coverage limits are correct. If anything is wrong, call your insurer to correct it before the update takes effect.
Keep a copy of the updated declarations page with your insurance documents. If you ever need to file a claim on the addition, you will need proof that it was covered on the date of the loss.
Frequently Asked Questions
Can I add coverage for an addition I already built?
Yes, but coverage will start on the date you add it to your policy, not the date you finished building. Any damage that occurred before you reported it will not be covered. Call your insurer as soon as possible to minimize the gap.
Will adding an addition increase my homeowners insurance premium?
Yes, because the addition increases your home's replacement value. The amount depends on the size and type of addition. A small deck might add $10 to $20 per year, while a large bedroom addition could add $50 to $100 or more. Ask your insurer for a quote.
Do I need a building permit for the addition to be covered?
Most insurers do not require a permit to add coverage, but they may ask whether the work was permitted. Building without a permit can affect coverage if the addition is damaged and the insurer discovers it was unpermitted. Check your local building code requirements before starting construction.
What if my contractor's insurance covers the addition during construction?
Your contractor's insurance covers damage during the building process, but once construction is done, you need to add the addition to your homeowners policy. Do not assume the contractor's coverage extends after the work is finished.
Can I add coverage for a deck or pool the same way as a room addition?
Decks are usually added the same way as room additions. Pools and hot tubs typically need a separate rider or endorsement because of liability concerns. Call your insurer to ask what coverage is available for the specific structure you are building.