Laying Paving To A Pattern – Using Black And White Materials

There are occasions that a Landscaper will come across a new problem – or a situation that one has not encountered as yet. (That is the nature of being a landscape contractor – every scheme can throw up new and interesting difficulties. Rise to the challenge! ) Garden designers may also find the following technique of interest when drawing up specification details.

Such an occasion was a contract to construct a highly complex section of paving, designed  as a carpet, complete with an intricate repeat pattern, resembling a large domestic rug. Indeed, the design called for an ‘indoor living room’ to be built outdoors.

Complete with two stainless steel ‘armchairs’ comprising steel structures, hollowed as cages or baskets, infilled with buxus sempervirens to represent easy chairs and a circular table made out of polished slate, with a copper floral arrangement fountain set thereon, the plan was to build a garden that appeared as an extension to the main house – not a garden, but another ‘room’ when viewed from indoors.

The garden was situated in Chelsea, with very limited access, through the house and down a winding metal staircase. The plot was approximately 3m x 5m, affording absolutely no room to work and store even the smallest amount of material.

The materials to be used for the project were small water worn slips of black slate, each the size of a 50p coin, and white marble pebbles, smooth and approximately round or oval in shape, all to be laid closely fitted. ‘neighbour against neighbour’. The plan specification called for black cement colourant for the slate and white cement for the pebbles, i.e. each material to be pointed in the appropriate mortar colour.

A narrow channel to be left around the whole carpet to provide something resembling a drainage solution, the first problem was to secure the edges of the micro materials.
There was no written or drawn specification – it was up to the contractor to sort it out!
The following description and specification is that I chose to use – others may have different solutions!

The edge of the work was secured by using two black roofing slates on edge, overlapped by 50%, and mortared into position – bearing in mind that there was little room for mortar due to the drainage requirements. These slates were not pointed, simply left as a clean, thin, black edge. (I often use this slate on edge technique to edge brick paths and patios where movement or ‘migration’ may be an issue. Set the slates 25mm lower than the brickwork, and visually lose any impression of an edge detail)

The main area (60%) of the carpet was in white pebbles, gently sloping towards the base of the table/fountain (the fountain workings are worthy of a long screed in their own right!), with a formal pattern of straight lines, laid as double tracks, with a Paisley style whorl pattern repeated in between the double tracks.

The laying was carried out in the traditional method of setting out the main details to levels and falls, with the outer slates and inner double tracks providing the points to which all other works were obliged to follow.

The Paisley details were made from 25mm plywood, carefully sawn to pattern. These ‘blanks’ were set into place as work progressed, until all of the white pebbles were fixed into position and fully pointed with white mortar. Any other technique would have resulted in a nightmare, trying to keep the two mortar colours from contaminating the other!
After a few days – until the white pebbles were firmly secured by the mortar – the plywood blanks were removed and the resultant ‘holes’ left clean and clear for the black slate slips.
To avoid any colour contamination, cling film was placed into each hole, with plenty of overlap to keep the white work clean. The black slips and black mortar were laid in the normal way – using the cling film to keep black and white separate.

Again, after a few days (this method does depend on the weather/temperature, so double check before proceeding), the cling film was removed by tearing. The ‘slip plane’ between the two materials is so thin it does not compromise the strength of the finished project.

Unfortunately, due to client confidentiality, I am unable to show any photographs or name the (very well known) garden designer. I hope the description will provide sufficient detail to help with any scheme involving two different colour mortars where cross contamination may be problematic.