New Zealand Concrete Masonry Association

GUIDE TO WETCAST

BUILDING A BASE

The first step is a correctly prepared sub-base, this should be formed exactly the same way as paving. The only exception is if the area is to have vehicular traffic, if this the case, a bed of concrete 100mm thick is required. It is necessary to ensure good drainage, failure to do so may result in efflorescence problems and discolouration of the Flagstones.

MIXING MORTAR

Mix wet mortar onto a flat board to avoid contaminating the area and to assist mixing. We recommend 5 parts brick sand to 1 part cement. If adjacent to the house, prepare your patio at least 15cm below the damp proof course and make aure it slopes gently away to allow rain water to run onto the garden, in most case a slope of 25mm:1000mm is adequate. Lay a patio a few millimetres below the level of any lawns to make grass cutting easier.

PLACING MORTAR

Fist sized dabs of mortar are usually more than sufficient for securing the Flagstones, but if you want to add heavy garden furniture, then we suggest the use of a full bed of mortar, of 20mm-30mm in depth. Care should be taken to ensure that cement is kept off the surface of the paving as it can cause staining.

LAYING

If possible, lay paving along an already established edge or use a string line, in order to make sure that all the others remain straight. Once in place, gently bed in and check that the surface is level. Depending on the type of Flagstone being laid, spacers can be used in order to allow a jointing gap.

FINISHING

It is best to lay full Flagstones first and then cut any odd shapes and sizes that you may need. For the best results we recommend hiring a masonry saw. Prior to cutting, mark accurately using the end of a bolster chisel or a pencil as indicated. Careful planning will help minimise cutting. When all cutting is done, you can fill the gaps between the Flagstones. This mix should be forced into the joints with a bricklayers pointing trowel and struck up to form a uniform surface to the pointing. Excess pointing mortar should be swept off the Flagstones once dry.

The area being grouted can be much improved by adding coloured oxide to compliment or contrast the overall appearance. The Flagstone may also be pointed with a stablised Gap Fill Sand.