Preloader start right after the page

I've got a problem with my website. I added a preloader which supposes to load before the page, but indeed it starts some millisecond after the whole page, so it gives a really unpleasant effect (the page is displayed for a millisecond and the preloader loses his main purpose).

So far my code is the following (it's a wordpress website): HTML

<body>
<header>Stuff in the header</header>
    <div class="loader-wrapper">
        <div class="loader"></div>
        <div class="loader-section section-left"></div>
        <div class="loader-section section-right"></div>
    </div>
</body>

JQUERY:

$(document).ready(function() {
    setTimeout(function(){
        $('body').addClass('loaded');
    }, 3000);
    var carousel = $("#carousel").flipster({
        style: 'carousel',
        spacing: -0.3,
        nav: false,
        buttons: true,
        scrollwheel: false,
    });
    $(".rotator").rotator();
});

UPDATED:

CSS:

.loader-wrapper, .rotator {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1000;
  }
  .loader {
    display: block;
    position: relative;
    left: 50%;
    top: 50%;
    width: 150px;
    height: 150px;
    margin: -75px 0 0 -75px;
    border-radius: 50%;
    border: 3px solid transparent;
    border-top-color: #8DC63F;
    -webkit-animation: spin 2s linear infinite; /* Chrome, Opera 15+, Safari 5+ */
    animation: spin 2s linear infinite; /* Chrome, Firefox 16+, IE 10+, Opera */
    z-index: 1001;
  }
  .loader:before {
    content: "";
    position: absolute;
    top: 5px;
    left: 5px;
    right: 5px;
    bottom: 5px;
    border-radius: 50%;
    border: 3px solid transparent;
    border-top-color: #8DC63F;
    -webkit-animation: spin 3s linear infinite; /* Chrome, Opera 15+, Safari 5+ */
    animation: spin 3s linear infinite; /* Chrome, Firefox 16+, IE 10+, Opera */
  }
  .loader:after {
    content: "";
    position: absolute;
    top: 15px;
    left: 15px;
    right: 15px;
    bottom: 15px;
    border-radius: 50%;
    border: 3px solid transparent;
    border-top-color: #8DC63F;
    -webkit-animation: spin 1.5s linear infinite; /* Chrome, Opera 15+, Safari 5+ */
    animation: spin 1.5s linear infinite; /* Chrome, Firefox 16+, IE 10+, Opera */
  }
  @-webkit-keyframes spin {
    0%   { 
      -webkit-transform: rotate(0deg);  /* Chrome, Opera 15+, Safari 3.1+ */
      -ms-transform: rotate(0deg);  /* IE 9 */
      transform: rotate(0deg);  /* Firefox 16+, IE 10+, Opera */
    }
    100% {
      -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
      -ms-transform: rotate(360deg);  /* IE 9 */
      transform: rotate(360deg);  /* Firefox 16+, IE 10+, Opera */
    }
  }
  @keyframes spin {
    0%   { 
      -webkit-transform: rotate(0deg);  /* Chrome, Opera 15+, Safari 3.1+ */
      -ms-transform: rotate(0deg);  /* IE 9 */
      transform: rotate(0deg);  /* Firefox 16+, IE 10+, Opera */
    }
    100% {
      -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
      -ms-transform: rotate(360deg);  /* IE 9 */
      transform: rotate(360deg);  /* Firefox 16+, IE 10+, Opera */
    }
  }
  .loader-wrapper .loader-section {
    position: fixed;
    top: 0;
    width: 51%;
    height: 100%;
    background: white;
    z-index: 1000;
    -webkit-transform: translateX(0);  /* Chrome, Opera 15+, Safari 3.1+ */
    -ms-transform: translateX(0);  /* IE 9 */
    transform: translateX(0);  /* Firefox 16+, IE 10+, Opera */
  }
  .loader-wrapper .loader-section.section-left {
    left: 0;
  }
  .loader-wrapper .loader-section.section-right {
    right: 0;
  }
  .loaded .loader-wrapper .loader-section.section-left {
    -webkit-transform: translateX(-100%);  /* Chrome, Opera 15+, Safari 3.1+ */
    -ms-transform: translateX(-100%);  /* IE 9 */
    transform: translateX(-100%);  /* Firefox 16+, IE 10+, Opera */
    -webkit-transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);  
    transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);
  }
  .loaded .loader-wrapper .loader-section.section-right {
    -webkit-transform: translateX(100%);  /* Chrome, Opera 15+, Safari 3.1+ */
    -ms-transform: translateX(100%);  /* IE 9 */
    transform: translateX(100%);  /* Firefox 16+, IE 10+, Opera */
    -webkit-transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);  
    transition: all 0.7s 0.3s cubic-bezier(0.645, 0.045, 0.355, 1.000);
  }
  .loaded .loader, .loaded .rotator {
    opacity: 0;
    -webkit-transition: all 0.3s ease-out;  
    transition: all 0.3s ease-out;
  }
  .loaded .loader-wrapper {
    visibility: hidden;
    -webkit-transform: translateY(-100%);  /* Chrome, Opera 15+, Safari 3.1+ */
    -ms-transform: translateY(-100%);  /* IE 9 */
    transform: translateY(-100%);  /* Firefox 16+, IE 10+, Opera */
    -webkit-transition: all 0.3s 1s ease-out;  
    transition: all 0.3s 1s ease-out;
  }
  .loaded .rotator {
    visibility: hidden;
    -webkit-transition: all 0.3s 0.3s ease-out;
    transition: all 0.3s 0.3s ease-out;
  }
  .no-js .loader-wrapper {
    display: none;
  }
  .no-js h1 {
    color: #222222;
  }

You can see this page in action at this address: http://larchedev.com/pip/

Any hint?

Solution

To make it work properly, you need to add styling as given below,

body {
    visibility: hidden;
}
.loader-wrapper {
    z-index: 99;
    display: block;
}

Then on window load,

$(window).load(function() {
    $('.loader-wrapper').hide();
    $('html, body').css('visibility', 'visible');
});