Posted: Thu Dec 05, 2002 10:14 pm
Once I have the base down and the edges are set, how much higher should the paviours be laid before a whacker plate is run over them.
If you read the page on Screeding you'll see that the amount of compaction is such a variable figure that's it's impossible for anyone to say that "the pavers need to be exactly so high above the finished paving level prior to compaction."
The reasons are...
<ul>
<li>the thickness of blocks varies between jobs
<li>the thickness of the bedding layer varies
<li>the 'compactibility' of the sand varies depending on type, source and moisture content.
<li>the degree of compaction is affected by the size/power of the vib plate
</ul>
The only accurate way to determine the degree of compaction is by trial and error. Some typical values are given on the Screeding page, but they may not work for you. However, they are a good place to start and, after 20-odd yrears of 'trial and error' we find that these figures are usually "there or thereabouts".
Do a test patch to see what works on your project.