Ōamaru Stone is a natural material, not a manufactured article and its performance as a building material has been proven over the past 100 years.
When the stone is removed from the quarry, it has a large moisture content, and when the milling of the stone is complete it will stay damp and soft for some considerable time.
When milling of the stone has been completed it is placed on timber pallets up to 1.60 tonne in weight. These pallets have the top covered when they leave the quarry but are not usually wrapped, to allow air movement around the stone and to allow the dispersion and evaporation of water.
If the stone has been shrink wrapped for transportation purposes, the wrapping should be removed immediately once the stone is placed on site. It is important to remember that as the stone dries it becomes harder and stone shall not be laid until 3-4 weeks after milling. If stones are not sufficiently hard enough they are more easily damaged.
On site pallets should be stacked clear of mud and have any shrink wrap removed. This will allow for side ventilation to continue the drying process. The top covering of the pallets can remain in place to stop weather penetration.
On all foundations, whether they be concrete or filled concrete block, three coats of D.P.C. such as Mulseal, shall be applied to the top to form a damp proof cover prior to the laying of the first course of stone. This is essential to prevent any dampness rising into the stone.
There may be a slight variation in the heights of the stone after milling, and the layer should have random checks on sizes prior to setting out story rods. Maximum bed depth shall be 6-8mm.