Question
What prepartion do I need to do & how do I do it: I have a brick paver patio & want to install some rock, (flat rock that I had left over from building a fireplace inside), & I am not sure how to do it. Can you give me some simple instructions or where to go on the internet for it. For instance DO I HAVE TO DO ANYTHING SPECIAL TO THE BRICK PAVERS BEFORE I START ON INSTALLING THE ROCK OVER IT? Any help would be great!
tks. so much,
Brenda

Answer
Hello,

I would suggest you consider installing a FIN drain under the rock but Im not sure if you would be able to obtain one and Im not sure if the FIN drain would hold up under the weight of the rocks. A FIN drain is a sheet of sandwiched geotextile with a hollow core for drainage. The top is permeable while the bottom is impermeable. Water seeps from above into the permeable top layer and then flows away on the impermeable bottom layer to an outlet. The design is similar to a baby diaper.

In addition to the FIN drain you might also want to consider drilling holes of 1/2 inch diameter through the bricks to aid drainage.

Sweep sand into the rock joints if the joints are narrow or use mortar if the joints turn out wider.

If you go with a mortared design you will not have to be concerned with drainage below through the bricks because that design will shed water off the top of the paving. I would not place very heavy rock on top of the brick but for rocks of up to medium weight things should be fine.

Installing the rocks over the pavers in the absence of a FIN drain would not be recommended because you will then not have good drainage.  Good drainage is very important for paving.   Without good drainage damage can occur from freezing and flooding.

Install the rocks over a sand base at least 4 inches thick.    Use concrete sand.  Do not use masonry sand as it is too fine and will not give good drainage,although it would be good swept into the joints between the rocks(if you intend to use swept joints)as it will repel water to some degree.    Use a gravel sub base,8 inches thick,if you have poor draining soil such as clay or silt.    Place filter fabric between the sand and gravel to prevent the sand from infiltrating into the gravel.   I do not know of any particular internet sites that would be of special help.   Just google the subject and see what comes up.   Good luck. Let me know if I can be of further help.

Mark Harshman
http://www.mahdrafting.com
Email: [email protected]

http://www.scribd.com/markscrib47