# Rear vs Side Addition: Which Adds a Unit More Easily?

URL: https://multiplextorontobuilders.ca/guide/rear-vs-side-addition-multiplex/
Last-Modified: 2026-10-21
Tags: rear vs side addition multiplex, rear addition cost toronto, side addition new unit, addition for second unit

Decision Guide

# Rear Addition vs Side Addition: Which Adds a Unit More Easily?

Compare rear and side additions for creating or enlarging a unit: setback and lot coverage limits, cost bands, unit access and egress, and how likely each is to need a variance.

By 

The Multiplex Toronto Builders Crew

[/about/ →](/about/)

 · Updated October 21, 2026 · 5 min read

![Two-storey rear addition on a Toronto brick house with large casement windows](/images/featured/two-storey-rear-addition-on-a-toronto-brick-house-.webp)

## Two Ways to Grow a House

If your goal is to add a unit, or make an existing unit big enough to rent well, you can build out the back or out the side. Rear vs side addition for a multiplex is mostly a question of where your lot has room and what the setbacks allow. Rear additions usually win on cost and approvals. Side additions sometimes win on access and street presence.

![Side addition with a separate unit entrance along a side yard](/images/content/side-addition-with-a-separate-unit-entrance-along-.webp)

This guide compares the two. For the full service, see our 

multiplex additions

[/multiplex-additions/ →](/multiplex-additions/)

 page.

> **Most common answer**
> 
> On typical Toronto lots, a rear addition adds a unit more easily: more room, fewer setback conflicts and lower cost. Side additions shine on wide suburban lots and corner lots.

## Side-by-Side Comparison

| Factor | Rear addition | Side addition |
| --- | --- | --- |
| Typical cost (CAD) | $180K-$400K | $220K-$600K |
| Main limit | Rear-yard setback, soft landscaping, lot coverage | Side-yard setback, lot width |
| Variance likelihood | Lower on deep lots | Higher on narrow lots |
| Unit entrance | Side path or rear | Can face the street |
| Light | Rear and side windows | Front and side windows |
| Construction impact | Away from the street | Often affects driveway or side path |
| Structural tie-in | Rear wall of house | Side wall, often with roof work |

## Rear Additions

Most Toronto lots are deeper than they are wide, which gives rear additions room to grow. The limits are the rear-yard setback, the soft landscaping share of the rear yard and overall lot coverage. A two-storey rear addition often adds more floor area for the same footprint, which helps with landscaping rules. Rear additions can house a new unit with its own entrance from a side path, or enlarge the main unit while the basement becomes a separate rental.

## Side Additions

Side additions build into the side yard. On a 25-30 foot Toronto lot, there is usually little side yard to work with, so a variance is often needed. On wider suburban lots, common in North York, Scarborough, Brampton and Mississauga, side yards can be generous and a side addition may fit without one. Side additions can give a new unit its own street-facing front door, which tenants like. They usually cost more because of facade work, roof tie-in and relocating services that run along the side of the house.

## Unit Access and Egress

A new unit needs its own entrance and a safe exit path. With a rear addition, that usually means a side path to the back, which needs to meet width and lighting expectations. With a side addition, the entrance can be at the front or side. Either way, bedrooms need compliant egress windows and the new unit needs a fire separation from the rest of the house.

## Variances and Timing

A variance adds 4-6 months. If a side addition needs one and a rear addition does not, the rear addition can start much sooner. If both need one, compare the size of the variance: a small side-yard reduction is easier to approve than a large one.

## When to Consider Building Up Instead

If both rear and side are tight, a storey addition can add floor area without using more of the lot. It depends on your foundation, which needs an engineer’s assessment. Our guide on 

storey addition structural checks

[/guide/foundation-storey-addition-structural-checks/ →](/guide/foundation-storey-addition-structural-checks/)

 explains what that involves.

## Additions Outside Toronto

GTA cities set their own rules for additional units. In 

Brampton additions

[/service-areas/brampton/ →](/service-areas/brampton/)

, for example, the city’s additional residential unit by-law, entrance setbacks for side doors and ARU registration all shape the design. EHON does not apply there.

## A Quick Decision Guide

If you are trying to decide between a rear and side addition, these questions usually settle it.

1.  **How wide is your side yard?** If it is narrow, a side addition will likely need a variance. If it is generous, a side addition may fit.
2.  **How deep is your rear yard?** A deep rear yard can take a rear addition while keeping the required soft landscaping.
3.  **Where should the new unit’s entrance be?** A side addition can put a door near the street. A rear addition usually uses a side path.
4.  **What is along the side of the house?** Driveways, gas meters, hydro meters and water lines often run along a side wall, which adds cost to a side addition.
5.  **What is your budget?** Rear additions typically cost less: $180K-$400K versus $220K-$600K for side additions.
6.  **How much light do you need?** Rear additions face the backyard; side additions may face a neighbour’s wall at close range.

| Your situation | Likely better option |
| --- | --- |
| Narrow side yard, deep rear yard | Rear addition |
| Wide side yard, shallow rear yard | Side addition |
| Want a street-facing door | Side addition |
| Tight budget | Rear addition |
| Both tight | Consider a storey addition |

We test both against your survey and the zoning by-law in the feasibility report, so the recommendation is based on your actual lot rather than general rules.

## Getting a Price

The engineer’s assessment and a setback check come first. Then we design and fix the price. If you are weighing rear against side, we can 

price your addition

[/contact/ →](/contact/)

 both ways in a written feasibility report.

Quick Answers

## Frequently Asked Questions

### Which addition is cheaper?

Rear additions usually, at about $180K-$400K CAD compared with $220K-$600K for side additions.

### Do side additions need variances?

Often on narrow lots, because side yards are tight. On wider suburban lots, a side addition may fit within the setbacks.

### Can an addition become its own unit?

Yes, with a code-compliant fire separation from the rest of the house, its own entrance, kitchen, bathroom and egress.

Keep Reading

## Related Guides

Can Your Foundation Support a Storey Addition? Structural Checks First Explainer

[/guide/foundation-storey-addition-structural-checks/ →](/guide/foundation-storey-addition-structural-checks/)

Learn more about Multiplex Additions

Price bands, process, project photos and answers to the questions owners ask most.

See Multiplex Additions

[/multiplex-additions/ →](/multiplex-additions/)