Gravel Protection Grid

Many terrace surfaces don't offer a flat and even surface but consist of a number of square or rectangle tiles which are only loosely connected through gravel. Problems arise when you try to clean such a terrace with a pressure washer - the pressure washer will clean the surface of the tiles just fine, but will also blow out the gravel between the tiles, creating a huge mess and possibly even damaging any insulation material (styrofoam) that may be underneath.

The purpose of the Gravel Protection Grid is to protect the gravel between your terrace tiles throughout the cleaning process.

Prior Art
This page went online on May 29, 2009.

According to an email from a Kaercher representative (Kaercher being the world's largest manufacturer of pressure washers) of October 6, 2008, the damage that pressure washing can do to the above mentioned type of construction is a known issue, and a solution wasn't available at the time.

There are no known patents that solve this issue.

Further Development
There are no known new developments since this page originally went online on May 29, 2009.

Problem Analysis
The hard water jet aimed at removing small particles of dirt and algae from a surface will indiscriminately blow away larger objects such as gravel that aren't firmly attached. Due to the nature of water, trying to aim the water jet more precisely will do little to reduce the problem as the water jet will be deflected by the tiles and still blow out a considerable amount of gravel once it is aimed closer towards the tile edges.

Approaches to avoid the gravel being washed out by the water jet:
 * Cover the gravel so it doesn't get hit by the water jet
 * Fasten the gravel so it getting hit by the water jet doesn't have any consequences

Further Requirements
Solution should by operable by the same person who also applies the pressure washer. Pricing needs to be reasonably lower than the pressure washer itself.

Solution
In the proposed solution, a Gravel Protection Grid keeps the water jet from making contact with the gravel. The bars of the grid are rounded so it can adapt to various gap sizes. Additionally, the middle junction is slidable so it can be used in areas where immovable objects or walls wouldn't allow positioning of the full grid. To make sure the Gravel Protection Grid itself isn't dislocated by the water jet, it should be be fastened by extra weight (the recommended method is to stand on it).

The bars of the current prototype were borrowed from IKEA's "Grundtal" towel rack. The full material cost including screws and bolts is less than 15 Euros.