Urgent advice on a garage slab

This website and its content is copyright of U-Beaut Enterprises.
Any redistribution or reproduction of part or all of the contents in any form is prohibited other than the following:

♦ you may print or download to a local hard disk extracts for your personal and non-commercial use only
♦ you may copy the content to individual third parties for their personal use,  but only if you acknowledge
Woodwork Forums as the source of the material.