You are only allowed to deduct maintenance costs if they are directly related to the part of the house that is used as workspace at home.
According to the Canada Revenue Agency (CRA),
"To calculate the percentage of work-space-in-the-home expenses you can deduct, use a reasonable basis, such as the area of the work space divided by the total finished area (including hallways, bathrooms and kitchens).
For maintenance costs, it may not be appropriate to use a percentage of these costs. For example, if the expenses you paid (such as cleaning materials or paint) were to maintain a part of the house that was not used as a workspace, then you cannot deduct any part of them. Alternatively, if the expenses you paid were to maintain the work space only, then you may be able to deduct all or most of them.
If your office space is in a rented house or apartment where you live, deduct the percentage of the rent as well as any maintenance costs you paid that relate to the work space."
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