House Additions: Build Up or Out?

Homeowners looking to add additional space to their house are always looking for information on the things they need to consider when deciding whether to build a second storey to their bungalow, or add an addition to the back of the house.  Following are some of the key items to consider when deciding whether to build up or out.

Lot Size

Lot size is often a determining factor whether to build up or to the back.  If you’re living on a small lot in an older part of Toronto, the decision is often obvious – the only possibility is to go up, by building a second storey, or sometimes even a third storey addition.  For homeowners on larger lots in Etobicoke, Mississauga, Richmond Hill, North York and Scarborough, there are often two possibilities – building up, or building to the back of the house.  Often times, the homeowner does not want to lose valuable backyard space to a house addition, so the decision is to build a second storey addition.  Other times, the desire to avoid stairs leads to a side or rear addition to a bungalow.

Cost & Budget

Second storey additions are typically are more costly project.  The cost of the addition portion of a second storey addition, or a rear addition may be similar.  But with a second storey addition, the main floor space is usually substantially renovated, with bedrooms being removed, and kitchen and living spaces expanded.  From our experience, a homeowner usually spend about 50% more on a second storey addition, with the additional monies being spent on main floor renovations.

Living Arrangements

A second storey addition requires the family to move out of the house while the addition and renovation work is being completed.  With a back addition, it is possible to remain in the house while the extention to the house is being built.

Existing House Structure

Second storey additions are a logical option for a bungalow.  If the existing house is a two storey, adding a third may be too difficult and costly.  In that case, a rear addition is the preferred option.

The existing house must be sufficiently strong to support a second storey addition.  If it’s not, then an addition to the back is a better option.  The best way to check this is to consult a structural engineer.

Zoning Regulations

With any house addition, zoning regulations are a key consideration.  Your municipal government will regulated the size and height of the home, as well as the distance it must be set back from the front, side and rear property lines.  If the property is near a ravine or ravine or watercourse, the property may also be under the jurisdiction of a conservation authority.  Properties to the west and north west of the city, such as in Caledon and Halton Hills, may also be under the jurisdiction of the Niagara Escarpment Commission.  A minor zoning variance can often be obtained if the addition does not comply zoning regulations.


Homeowners love their trees, and rarely want to cut them down to make space for a house addition.  Many municipalities also have strict regulations protecting trees.  Proximity to large trees may limit the ability to build an addition, especially if it involves foundation work that may impact on the tree’s root system.

Your Turn

Do you have questions or comments?  Send us an email and let us know.