Posted: Fri Aug 23, 2002 6:16 pm
How do I lay individual slabs in gravel, incorporating a weed proof membrane as well? Do I need to put a sub base under them or do I lay each on a full mortar bed on top of the wpm?
Hi Michelle,
these are best laid on a full bed or mortar on top of the wpm.
Allow the mortar bed to be slightly larger than the size of the flag/slab - so, if you're laying 450x450mm flags, let the bed be at least 500x500. Use a 4:1 mortar (Class II ) and make it just damp enough to cling together. Level it out with a trowel, place the flag and tap it down to level so that it beds into the mortar completely. Without standing on the flag, test it for rocking with your hands and pack extra mortar into any low corners. If there is any movement of the flag on the mortar, it will only get worse with time.
Keep off the flags for at least a day while the mortar cures, and then they should be fine. :)