One method that can potentially solve your problem would be to slightly chage lines 21 and 42 in your code so that they look like this:

line 21:

.value(function(d) { return d.size + 20; });

line 42:

    : function(d) { return d.size + 20; };

(notice that all I did was add " + 20".

Here you have the modified jsfiddle: modified example.

Now, depending on your data you may want to do something else, maybe instead of 20 you can calculate lets say 1% of the sum of all values, but this is a basic idea that can be, I hope, your solid starting point.

Hope this helps.

And this is screenshot of modified treemap:

modified treemap

Related Query