Three common renovation myths that can cost you big time

During my years in the renovation industry, I’ve seen countless homeowners make the same mistakes. They start with the best of intentions but fall victim to common misconceptions that derail their projects and inflate their budgets. Let me address three of the most prevalent myths that I encounter when speaking with prospective clients.
Myth 1: You’ll get an accurate cost estimate from architectural drawings and permit plans
One of the biggest misconceptions is that architectural drawings and building permit plans will give you everything you need for accurate renovation pricing. Unfortunately, that’s not how it works.
Permit plans are designed to meet the basic requirements for approval. They don’t provide the detailed information necessary to properly cost a project. Without comprehensive plans—including a Designated Substance Survey, structural specifications, a soil survey, an HVAC design, a reflected ceiling plan and a schedule for finishes — you’re left with massive gaps. These gaps lead to misinterpretations, change orders (budget amendments) and subsequently – skyrocketing costs. I’ll delve into change orders under Myth 3.
Here’s a summary of what is required to help builders accurately supply a cost estimate for your home renovation.
A Designated Substance Survey – or DSS – is legally required by the Ontario Ministry of Labour and is the homeowner’s responsibility. Contractors must have the DSS posted on-site for inspection. This survey identifies hazardous materials like asbestos—commonly found in stucco, plaster, and duct wraps in most pre-1980s homes— lead paint and mold. Without a DSS, demolition quotes won’t account for mitigation costs, leading to unexpected and costly change orders.

Structural and steel drawings are needed when structural changes, such as additions, are required. Created and stamped by a structural engineer, these drawings provide the essential framework and details for the project, including crucial explanations of how different components are welded, assembled and fit together.
Soil plans. While permits and architectural plans may outline what’s possible, they don’t confirm whether existing foundations can support added weight. A soil engineer must evaluate the footings, and a structural engineer may identify the need for costly measures like underpinning, which can add $60,000–$80,000 or more to the budget. Without these evaluations, clients risk unexpected change orders and significant delays.
HVAC designs, developed by an HVAC engineer, are essential to evaluate existing heating and cooling systems and to ensure accurate planning. Replacing an HVAC system often involves more than swapping out a furnace or adding a heat pump. When renovating, especially for a high efficiency home, you’ll need an HRV or ERV system alongside proper ductwork. Existing ducts may not be compatible due to sizing issues.
A reflected ceiling plan (RCP) details all electrical components of a home. It specifies the number and placement of lights, switches, and plugs, along with upgrades like moving from a 100-amp to a 200-amp panel. Without an RCP, quotes are based on code minimums, which – in my 18 years in this business – never match client expectations.
A Schedule of Finishes specifies all finish details, from cabinet handles and doorknobs to tiles, flooring, and fixtures. Without it, builders typically provide basic allowances, often leading to costly upgrades. For example, a toilet might be budgeted at $300, but higher-end options add hundreds per unit.
As you can see, developing a precise estimate isn’t simple or quick. At Greening Homes, we typically spend about 40 to 60 hours over several weeks to create a thorough, accurate and competitively-bid estimate. This work costs money but it’s well worth it. I often see homeowners shopping around for the lowest bid without understanding what’s really included. When you don’t provide enough information up front, you’re not comparing apples to apples, and you’re leaving yourself open to surprises later.
Myth 2: Finishes are the biggest expense in a renovation
Many homeowners fixate on the cost of finishes, assuming that choosing less expensive options will significantly reduce their budget. While finishes do affect the total cost, they’re not the main driver of your project’s price.
The scope of work truly determines your budget. For instance, if your renovation has a $1 million scope, downgrading your finishes might save you $25,000 to $50,000 – not an insignificant amount, but hardly transformative. You won’t turn a $1 million project into a $600,000 one just by economizing on finishes.
Myth 3: All builders can’t be trusted
There’s a lingering perception that all builders are out to take advantage of homeowners. Sadly, the industry hasn’t always helped itself here. Some contractors win jobs by offering lowball bids, only to make up the difference with change orders and other means, which serve as a major profit driver.
This practice has contributed to a culture of distrust between clients and contractors, as homeowners feel blindsided by escalating expenses that were not initially disclosed. According to industry data, the average renovation project in Toronto goes 33 percent over the original bid!
At Greening Homes, we do things differently. Transparency is at the heart of our process. We ensure that projects are properly costed out at the start to minimize surprises. We also update clients weekly.

A builder may tell you that their general contract (GC) fee is 10 or even 5 percent, but be careful. Our industry is notoriously opaque and most contractors make greater margins in other ways, including selling marked-up materials, or with side deal arrangements with their trades. In comparison, Greening Homes’ GC fee is 20 percent, and we make sure clients know exactly what they’re paying for. If we get a 40 percent discount on materials from a supplier, we pass that savings directly to our clients, adding our 20 percent fee on top of the discounted price—not the inflated one, as most builders do. That 10 to 5 percent fee is actually well more than double when you factor everything in.
Choosing the right builder is about more than just cost. Renovations are long, complex projects, and unexpected challenges will arise. You need a builder you trust—someone who is upfront about costs, communicates openly and collaborates with you to navigate these hurdles. The relationship you have with your builder is as important – perhaps even more so – than the numbers on the page.
Don’t learn the hard way
I’ve had homeowners come back to me after hiring a contractor who offered the lowest bid, regretful because their project went way over budget or was plagued with problems. They realized too late that the cheapest bid isn’t always the best choice.
Avoid these pitfalls by planning thoroughly, asking the right questions, and working with a builder who values transparency and trust. The road to the home of your dreams should not be paved with bad intentions.
By Chris Phillips, Founder and President of Greening Homes Ltd.
Photos by Yvonne Bambrick.