How can I run a directive after the dom has finished rendering?

It depends on how your $('site-header') is constructed.

You can try to use $timeout with 0 delay. Something like:

return function(scope, element, attrs) {
    $timeout(function(){
        $('.main').height( $('.site-header').height() -  $('.site-footer').height() );
    });        
}

Explanations how it works: one, two.

Don't forget to inject $timeout in your directive:

.directive('sticky', function($timeout)

Here is how I do it:

app.directive('example', function() {

    return function(scope, element, attrs) {
        angular.element(document).ready(function() {
                //MANIPULATE THE DOM
        });
    };

});

Probably the author won't need my answer anymore. Still, for sake of completeness i feel other users might find it useful. The best and most simple solution is to use $(window).load() inside the body of the returned function. (alternatively you can use document.ready. It really depends if you need all the images or not).

Using $timeout in my humble opinion is a very weak option and may fail in some cases.

Here is the complete code i'd use:

.directive('directiveExample', function(){
   return {
       restrict: 'A',
       link: function($scope, $elem, attrs){

           $(window).load(function() {
               //...JS here...
           });
       }
   }
});

there is a ngcontentloaded event, I think you can use it

.directive('directiveExample', function(){
   return {
       restrict: 'A',
       link: function(scope, elem, attrs){

                $$window = $ $window


                init = function(){
                    contentHeight = elem.outerHeight()
                    //do the things
                }

                $$window.on('ngcontentloaded',init)

       }
   }
});

If you can't use $timeout due to external resources and cant use a directive due to a specific issue with timing, use broadcast.

Add $scope.$broadcast("variable_name_here"); after the desired external resource or long running controller/directive has completed.

Then add the below after your external resource has loaded.

$scope.$on("variable_name_here", function(){ 
   // DOM manipulation here
   jQuery('selector').height(); 
}

For example in the promise of a deferred HTTP request.

MyHttpService.then(function(data){
   $scope.MyHttpReturnedImage = data.image;
   $scope.$broadcast("imageLoaded");
});

$scope.$on("imageLoaded", function(){ 
   jQuery('img').height(80).width(80); 
}