We have sash windows and got broken into last week due to poor security (just internal latches).
I want to install better locks on the windows to prevent the windows being opened past certain amount, but am having trouble finding a reference for how much of a gap is considered practically impossible to fit through.
Though I understand that people, even burglars, come in different sizes and shapes, is there an acknowledged security-industry standard distance to limit such a window-lock installation?
Best Answer
Most code states that all railing balusters must be spaced no more than 4" apart to prevent a child from inserting their head.
So, that is one measurement you could use...if you don't want anyone's head to get through: 4".
Of course, also make sure you can't get an arm through that could reach the window lock.
Edit by OP:
According to http://upload.wikimedia.org/wikipedia/commons/6/61/HeadAnthropometry.JPG Men's heads range from 5.1" to 6.5" at their widest point (and women's 5.2" to 6.1"; 1st to 99th percentile).
As such, choosing a maximum gap between 4" to 5" would prevent somebody ranging between a child and adult from entering through the space.