Strengthen Your Foundation

Basement Additions

Protect your basement from moisture and water damage with reliable systems designed to keep your space dry year round.

What is a Basement Addition?

A basement addition expands your home’s footprint below grade, often combined with underpinning or an above-grade addition to create significant new living space. It involves excavation, foundation work, and structural integration to safely extend the basement beneath new or existing areas of the home.

It’s an ideal solution when you want to maximize square footage on your existing lot without sacrificing yard space or relocating.

Why Build a Basement Addition?

Maximize space on your existing lot

A below-grade addition expands your usable square footage without giving up backyard space, making it ideal for tight urban and downtown properties.

Expand without leaving your home

Adding space to your current property gets you the room you need while staying in the neighbourhood you love, avoiding the cost and stress of moving.

Create flexible, multi-purpose space

New lower-level square footage can become anything from a family suite to a home theatre, gym, or rental unit, designed around your goals.

Add significant long-term value

Well-planned additions expand both the function and the market value of your home, delivering a strong return on your investment.

Our Process

A Precise, Engineered Approach

Consultation & Feasibility

We assess your lot, existing structure, and goals to confirm what’s possible below grade. This on-site evaluation lets us recommend the right approach and provide a realistic scope, timeline, and estimate before committing to a plan.

Design & Engineering

Our team prepares the architectural design and structural engineering needed to safely extend your basement. We coordinate the drawings and calculations that the build and the permit process will rely on.

Permits & Approvals

We manage the building permits, engineering approvals, and municipal inspections your addition requires. Handling this upfront keeps the project compliant and on schedule from the start.

Excavation & Structural Work

Using engineered sequencing, we excavate and build the new foundation, integrating it with your existing structure. Your home stays fully supported throughout as the new space takes shape.

Waterproofing & Finishing Prep

We waterproof the new foundation, complete drainage, and prepare the space for finishing. The addition is left structurally complete and ready for the next phase of your project.

Recent Projects

Basement Additions Toronto Projects

Before & After See the Transformation

Our Work →

Broadview North

Upper Beaches

East York

The best service I ever got. The owner of the company came in person before and after the job was done. Great customer service. The job was done fast and the best quality. Very impressive. I would recommend anyone who needs job done fast and headache free. As a side note the payment process was all automated. That part was also fast. Unbelievable. I will definitely contact for my next project. Thank you!

Nadia Shykula

/ Google Reviews

Our older, lower (6′), mostly finished basement needed to be expanded to allow for an elderly family member to join our household. Rock Bottom came recommended by a friend of a friend and did not disappoint. The price was competitive (but not cheap) for gutting the basement, taking our floor down to get us a finished height of 8′ with new drains, sump pump, backwater valve and hot water heating pipes with manifold. The team was always punctual (6 days a week), always cheerful, and highly effective. From start to finish their work took 5 weeks (the estimate was 4-6). Our GC noted how rare that is with underpinning work, and a builder friend noted the quality of the floor’s finished surface. Additionally, our semi-detached neighbour’s basement is almost finished (the team is still punctual, cheerful and effective).

Matthew Cole

/ Google Reviews

Rock Bottom renewed my faith in contractors. They were unbelievable responsive, available to answer all of my questions at every step. The crew was early every day and put in long hours to get the job as quickly as possible. There were a couple of surprises discovered when they dug down and none of it impacted the price I paid. The crew was friendly, happy, and incredibly hard-working. I cannot recommend Rock Bottom highly enough. I’d hire them again in a heartbeat. I’m thrilled with my new basement!

Charlie G

/ Google Reviews

Excellent service and workmanship. Personnel was very knowledgeable and accommodating with schedule updates. Project was on time and on budget which is all you can ask for

Paul

/ Google Reviews

So happy we chose rock bottom for our underpinning project. The team was amazing and did an incredible job. Throughout the project they were in constant communication with us and when they were finished, left the site in perfect condition.

Joshua S.

/ Google Reviews

Ready to Transform Your Basement?

Roncesvalles