Miriam Gurgel said the second-storey addition to her neighbour's home has cut out the northern sun, creating a shadow in the afternoon that casts across most of her home's back yard.
The extension also has two large windows that now look straight into her bedroom, and Mrs Gugel said the "physiological damage" it was doing to her family has them considering their future in the home.
She said after speaking to City of Rockingham planning officers, she learned the property extension was approved because it met the City's criteria. But no one from the City came to visit her property to see what impact the extension could have on it.
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READ NOWDespite being "really pissed off" with the situation, Mrs Gurgel doesn't blame the owner of the neighbouring property and said the responsibility was the City's.
"They obviously thought it was OK because the City said it was OK," she said.
"They didn't do it on purpose, they just did what they wanted and it was up to the City to take care of it, it was their responsibility. They shouldn't have approved it.
"It has been damaging to our family and we are over it; the psychological damage is greater than any damage the building has done."
As a published author in Brazil on architecture and design, and a former UWA lecturer on the subject, Mrs Gurgel said she was well versed in building codes and was confident the extension should never have been approved.
According to the Residential Design Codes of Western Australia with regards to visual privacy, there are a number of basic measures that should be taken to prevent extensions overlooking neighbouring properties.
Mrs Gurgel said none of these measures had been included.
The City of Rockingham did not respond before deadline to Courier inquiries.