Best Windows For Basement Second Suites

When folks ask me what things to look for in order to find a property that will function well as a legal second suite, the top issues are:

  • Zoning compliance
  • Parking arrangements
  • Ceiling height of the basement
  • Separate entrances

And right up there would be basement windows (or lack thereof) – since basements comprise the vast majority of second suites.

Often, my clients are concerned about windows in the basement because they are necessary for egress (a fancy code terminology for escape).

Try to open the window first

Try to open the window first

Yes that’s important - but there are other aspects to consider.

In this article, we’ll get into these things, as well as how to identify a basement that has an ideal window setup for turning into a second suite. We’ll also discuss the best strategies for adding new windows, or enlarging existing ones.

We’ll also briefly cover some implications to consider when adding or enlarging windows. The objective here is to give you some ideas on how to maximize the function of windows for their intended purpose in basement suites, while reducing the costs associated with the work.

Let’s get started!

Why Are Windows In Basements Necessary?

1.       Egress  - So we mentioned this earlier. Most codes require at least one egress window in basement second suites (true here in Ontario).

This is in case of a fire and the occupant is unable to access to main door to get out of the unit. There needs to be an accessible window large enough for someone to crawl through onto safety.

Casement type windows are great for egress 

Casement type windows are great for egress 

2.       Natural Lighting - Contrary to popular belief, windows for egress is not the most difficult to achieve. Rather, getting windows large enough to meet the natural lighting requirements for the space is typically the challenge – especially when you have larger spaces.

The idea is that we want to create a comfortable space, and not a dungeon. So there are provisions for that which require minimum sizes for windows.

This is typically calculated based on allocating a percentage of floor space for that area that has to be glazing – and different spaces have different percentages.

A sample of one of our recent permit drawings where we had to indicate how the window was to meet the minimum 2.5% floor space requirement in the bedrooms

A sample of one of our recent permit drawings where we had to indicate how the window was to meet the minimum 2.5% floor space requirement in the bedrooms

3.       Natural Ventilation

Ventilation requirements are also a consideration, although if you have adequate windows for egress and lighting, the requirements for natural ventilation are typically met.

In many instances, you may be able to substitute natural ventilation with mechanical ventilation if it’s too difficult to achieve the former.

Which Windows Are Best?

So if you’re out shopping for a home with the intent of snatching up a nice high and dry basement for a sweet condo-like legal apartment, what kinds of windows do you want to look out for?

1.       Higher window above grade – This is great because a) it typically means you have a higher basement, and b) if you have to increase the height of the window, it’s easier to do – without necessarily bringing it down below grade.

Higher windows above grade gives you greater flexibility

Higher windows above grade gives you greater flexibility

2.       Wider windows – On the flip side of the same coin, wider windows also means that increasing the height will typically not involve any structural changes

3.       As many as possible – No brainer. The more windows the better.

4.       Adjacent corner windows – Windows that are adjacent in the corners are ideal for large common spaces, such as living and dining rooms.

How To Maximize The Use Of Your Windows

Whenever we design a legal suite, there’s a number of factors at play, and it gets complicated. Often it becomes a trade off based on cost and ideal layout. We have to consider many things, such as unit size, room size, as well as “no fun stuff” like plumbing, electrical and mechanical systems.

But we usually figure things out, and focusing on room layout based on the window locations is often one of the best strategies. So how do we go about it? Here are some strategies.

1.       Don’t place windows in rooms where they are not required - Many codes don’t require windows in spaces like kitchens, bathrooms, laundry areas, or mechanical rooms. Why waste these perfectly good windows when you can use them in the required places such as bedrooms and living rooms?

2.       Save the big ones for the living room - Often the codes will ask for a greater window area in the living and dining rooms. So save those big ones or the adjacent corner ones for these spaces.

3.       Maybe you can “borrow” some natural lighting – Occasionally there’s no way around it. There happens to be a window in a space that doesn’t require it. Some municipalities may allow you to use the lighting from that space for another space where it is required, as long as it’s in the direct line of sight of the window.

4.       Redefine the space – Not enough natural lighting by a few square inches? Maybe shrinking that bedroom or increasing the closet space may do the trick.

Once you’ve done so many, you start getting quite creative.

In most cases, you’ll have to add at least one window or enlarge an existing one to meet the requirements. Very rarely have we been able to get away with existing windows as-is.

So here are some important considerations when you are doing some work to add more.

Implications of Enlarged or New Window

1.       Structural – This is huge. Whenever you’re opening up a piece of the foundation wall for a window, this is structural work, and you must ensure that there is proper support for the opening in the form of a lintel (sometimes referred to as a header).

Depending on the weight of the structure above, this will need to be sized accordingly with the appropriate materials. For example, a wood framed wall with siding may simply be supported with lumber, whereas a solid masonry wall will typically require a steel beam. In some cases, too many or too large of an opening can compromise the lateral support structure of the floor system with the foundation – therefore careful design is paramount.

Support above an enlarged or newly opened window is very important

Support above an enlarged or newly opened window is very important

2.       Frost Depth – Lowering windows too much can affect the depth that frost can reach. This can cause damage to the foundation wall or footing.

3.       Window Wells – Whenever you go below the grade, you’ll need to put in a well. This is expensive because it means digging all the way to the footing and connecting a drain. In many cases, it may be cheaper to put in a new window opening.

Whenever window wells are built - they need to be properly drained into the weeping tile - don't forget to check for gas lines before digging!

Whenever window wells are built - they need to be properly drained into the weeping tile - don't forget to check for gas lines before digging!

4.       Clear Opening – If the opening is for egress, it has to meet certain criteria and it has to be a CLEAR opening, meaning no obstructions. You can’t include the frame or any other hardware that may be blocking the opening. Know what’s required in your area and in your circumstances.

5.       Proximity to Property Lines – This often gets ignored, but there are code rules around how close a window can be to the property line. This is mostly for fire safety reasons. This is why new window openings work best either in the front wall or rear wall, where you don’t have neighbouring property lines close to you.

There you have it! You probably never thought you’d read this much about basement windows did you? But it’s incredibly important for converting single family homes to 2 legal units.

In case you don't have your spider suit handy, tempered glass is better for safety if you have to break the glass.

In case you don't have your spider suit handy, tempered glass is better for safety if you have to break the glass.

This is just brief overview of the topic of basement windows - be sure to work with knowledgeable designers, architects and contractors when doing this type of work.