Let’s cut to the chase – yes, you absolutely need a building permit for any addition to your home in London. No ifs, ands, or buts. By law, any new construction or structural alteration over 10 m² (108 ft²) – including second-story additions, basement extensions, sunrooms, garage conversions – requires a permit. It’s the homeowner’s responsibility to get that permit before building. This isn’t just red tape; it ensures your project meets the Ontario Building Code and local safety standards. Skip the permit, and you’re asking for trouble with the City later on.

The process is straightforward, but you must be thorough. First, you (or your designer) draw up detailed plans for the addition – floor plans, structural drawings, site plan, etc. London has an online portal where you submit your application and pay the permit fee. City staff will review your plans to ensure they comply with the Ontario Building Code and London’s zoning by-laws. If something’s missing or needs changes, they’ll send it back for corrections. Once everything is in order, the City issues the permit. You’ll get a permit card and approved drawings via email – you must post that permit on-site and keep the plans on hand. Then you’re cleared to start building. Just remember to call in the City inspectors at each required stage (foundation, framing, etc.) as you go – more on that below.

Your addition has to play by the City’s zoning rules. Zoning bylaws control how big your addition can be and where it can sit on your lot. This means setbacks (how far it must be from property lines), lot coverage limits (you can’t cover your entire yard with an addition), height limits, and so on. Every neighborhood and lot may have slightly different rules depending on its zoning designation. The City strongly advises checking these requirements early to avoid costly errors in design. If your proposed addition is too close to the lot line or exceeds something like allowable height or area, you might need to apply for a minor variance from the Committee of Adjustment to get approval. In short: do your homework (or talk to the City’s Planning department) about your property’s zoning before you finalize your addition plans.

The permit approval in London is relatively quick if your application is complete. By provincial law, a building permit for a typical house addition must be reviewed within 10 business days once the City deems the application complete. In other words, you should get an answer in about two weeks for a straightforward addition. (Of course, if you submit incomplete plans or need revisions, that clock pauses – so get your paperwork right the first time to avoid delays.) When it comes to construction, the timeline can vary a lot with the scope of work. As a ballpark, a typical home addition (say, adding a family room or a bedroom) might take around 3 to 6 months of construction. This accounts for site work, the build itself, and finishing. A larger or more complex project – for example, building an entire second story on an existing bungalow – can easily run 6 months to a year by the time it’s fully done. Factors like weather, contractor scheduling, and supply delays can all impact this. The bottom line is: plan for a few months at minimum, and work closely with your contractor on a realistic timeline.

Cost can range widely, but let’s give it to you straight: home additions aren’t cheap. In Ontario (London included), you’re often looking at a few hundred dollars per square foot for a fully finished addition. For example, a basic single-story room addition or sunroom might ballpark around $300–$500+ per square foot once you factor in everything (foundation, structure, interior finishes, etc.). High-end projects or complex builds (like a second-story addition with kitchen/bathroom plumbing involved) can push the cost even higher.

On top of the construction costs, remember you’ll have City fees. The building permit fee in London depends on the size of your project – at minimum you’ll pay about $250 as a base fee for a residential addition. Larger projects pay more, but even then, permit fees are usually a small fraction of the construction budget. (For instance, the average building permit might be around a few hundred bucks, whereas the addition itself could be tens of thousands) You may also need to budget for professional design help – hiring an architect or engineer to draw plans can add a few thousand dollars, but it’s money well spent to do things right. Always plan a contingency in your budget as well – surprises can happen once you open up walls or dig into the ground.

When you have a building permit, the City’s building inspectors will come check the work at key stages – it’s not optional, these inspections are mandatory. Inspections must happen before you cover up certain work, to make sure everything is built to Code and the approved plans. For a typical addition, expect inspections: prior to pouring concrete (for footings/piers), prior to backfilling the foundation (after foundation walls are in), structural framing (after the shell is up, before insulation), HVAC rough-in, plumbing rough-in, insulation (before drywall), and then a final inspection for occupancy. The permit will list all required inspections. It’s your (or your contractor’s) job to call the City to book each inspection when you’re ready. Do not skip this – if you don’t get the required inspections, you could be ordered to stop work or even undo finished work. In fact, the City can refuse to let you occupy or use the new space until it passes a final inspection. So schedule those inspections and get that official sign-off at each stage.

Building without a permit is a huge no-no. We’re talking serious consequences. If you try to sneak in an unpermitted addition, the City can issue a Stop Work Order on the spot. You’ll then have to scramble to get a retroactive permit (with fees and possible penalties), or you might even be forced to tear down the work if it doesn’t meet code. Legally, getting caught building without a permit is an offense under Ontario’s Building Code Act – an individual homeowner can be fined up to $50,000 for a first offense, and up to $100,000 for subsequent offenses. That’s not a typo – they take it that seriously. Beyond the fines, you’re looking at other headaches: the City may require you to open up finished walls so they can inspect, you’ll have zero recourse if the work was done wrong, and when you go to sell the house, an unpermitted addition can derail the sale (buyers or their banks/lawyers will check for permits). You could also be liable if, say, a future accident or injury is traced back to non-permitted construction on your property. Bottom line: don’t even think about it. Get the proper permit and do it right – or risk very expensive lessons later.

Legally, for a house, you might not need an architect – Ontario’s rules allow homeowners to prepare their own plans for a simple addition on a single-family home or duplex. So, if you’re just bumping out a wall for a small extension, you could draw it yourself but you must still meet the Ontario Building Code standards in those plans. In reality, unless you have design and construction experience, doing it DIY is risky. The City of London “strongly recommends” hiring a professional designer or architect to ensure your plans are up to Code and meet all the zoning requirements. Also, certain situations do require professional input: for example, if you’re adding a second story or doing major structural changes, you’ll need an engineer to size beams, footings, and make sure the existing structure can carry the load. At the end of the day, investing in a qualified designer (architect, architectural technologist, or engineer) will save you a ton of headaches – they’ll produce proper drawings, stamp them if needed, and help get your permit approved faster. It’s a no-nonsense move to ensure your addition is safe and compliant.

Absolutely. Big additions = bigger stakes. If you’re adding an entire second floor or a significant extension, you have to consider structural and code implications beyond a basic project. For one, structural support is crucial – you’re putting a lot of new weight on your existing house. An engineer should assess your current foundation and framing to confirm they can support the new level (often you’ll need to reinforce the foundation or add support beams for a second story). You’ll also need to meet all current Building Code requirements for the new construction, which are likely stricter than when your house was originally built. That means things like proper footings, lateral bracing for wind, modern insulation and vapour barriers, up-to-code electrical and plumbing, etc. Also, the Building Code says an addition must not “reduce the performance” of existing systems in the house – for example, if your addition would overwhelm your old furnace or make parts of the house under-ventilated, those systems have to be upgraded to serve the combined space. Fire safety is another big one: if you’re building right near the property line, you can’t just put windows everywhere. In fact, no windows or doors are allowed on a wall that’s closer than 1.2 m (3′-11″) to the property line under the Ontario Building Code (this is to prevent fire from spreading between houses). So, you might have to use blank fire-rated walls or special fire-resistant windows if your addition is tight to the lot boundary. In short, a major addition is not a simple project – you need proper planning and likely professional design work to address structure, code, and integration with your existing home. Don’t worry, we handle this stuff all the time – just know it’s more involved than throwing up some lumber and drywall.

When you build an addition, it’s not just about the new walls and roof – you have to plan for all the guts of the house too (utilities and services). Here are the key things to consider:

Heating/Cooling (HVAC): More square footage means more air to heat in winter and cool in summer. Your existing furnace and AC might not have the capacity to handle the extra space. The Building Code requires that your addition doesn’t cripple your home’s overall heating and ventilation – if the current system becomes inadequate, you’ll need to upgrade or supplement it. In practical terms, that could mean installing a bigger furnace or a second HVAC system, resizing ductwork, etc. An HVAC designer or engineer will typically do a heat loss calculation for the new design (and yes, this often needs to be submitted with the permit application for large additions).

Plumbing: If you’re adding bathrooms or a kitchen in your addition, consider whether your water supply and hot water heater can meet the increased demand. Also, the drain lines need proper sloping and tie-in to your existing sewer line – all of which will be reviewed in your permit plans. Sometimes, the city may require a check on sewer capacity for big additions (usually only if you’re significantly increasing the number of fixtures or adding units). Ensure any plumbing work is done by a licensed plumber under permit – plumbing is inspected as part of your building permit.

Electrical: Any new wiring in the addition has to be inspected by the Electrical Safety Authority (ESA), not the City building department. This means you or your electrician must take out a separate electrical permit with ESA. If you’re adding a bunch of new circuits (for lights, outlets, HVAC equipment, etc.), check if your existing electrical panel can handle it. It’s common to upgrade to a larger amp panel or add a sub-panel when doing a big addition, especially in older homes. Don’t skimp on this – an overloaded electrical system is a major hazard. Hire a ESA-licensed electrician to do the work and coordinate those inspections.

Utilities and Services: Before you even dig, call Ontario One Call to mark underground utilities (gas, water, sewer, hydro lines, etc.) on your property. Hitting a buried gas line or hydro cable will ruin your day (and your wallet). It’s the law to call before you dig, and it’s free – so there’s no excuse. Also, take note of any overhead power lines around your house. If you’re adding a second story or extending near where lines connect, you must maintain safe clearances. In Ontario, generally you need to keep structures at least 3 metres away from distribution lines – Hydro One actually specifies a 4.8 m minimum horizontal setback from overhead power lines up to 44kV. You cannot build over or directly under a power line either. So, in some cases, you might have to get the utility company to relocate lines or make them underground if they conflict with your planned addition. Always plan for these utility moves before construction – it can take time to coordinate with hydro, gas, or telecom companies.

In summary, think of your home’s utilities as part of the addition project. Budget for potential upgrades to HVAC, electrical, or water heaters. Get the necessary permits (building permit covers plumbing/HVAC, and an ESA permit covers electrical). And follow all safety protocols for utility locates and clearances. It’s all part of doing the job right and ensuring your new space functions seamlessly with the old.