Installation of Ōamaru Stone veneers
Specifications for handling and laying other than set out below shall comply with relevant building bylaws.
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 quarried the limestone has a natural moisture content. As the large quarry blocks sit in stacks, the stone dries and hardens.
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. 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.
Weep holes & ventilation
- After the foundation has received the damp proof coating and all lines set out and prepared, spread mortar as for normal brick or block work.
- Lay first course to line, do not wet the blocks, perpendicular joints are to be no greater than 5mm. When all first course is laid in the area where working, vee joints shall be filled prior to laying the next course of stone. To fill these vee joints take mortar and by adding water, thin this mix to a grout. Pour this grout into the vee joint with the use of a dipper, topping up till completely filled prior to bedding the next course.
- In laying the next course, only spread sufficient mortar bed for one stone at a time. Before placing this mortar bed, the stone shall be wet by pouring water from a dipper.
- As each course is laid repeat the system to fill all vee joints.
- Bedding mortar shall not be used for pointing. All joints shall be raked to a depth of approx 8mm to allow for pointing.
- Prior to pointing, it is possible to take a tool such as a rasp and straighten all horizontal and perpendicular joints. This gives nice clean edges to the stone and removes any minor chipping.
- Once these joints and lines are straight, pointing may continue.
- At no time shall the veneer bed width be less than 90mm.
- Seal all stone work after laying and pointing has been completed and after stone has dried to an even colouring. This is done with a waterproofing silicone such as Aquellux.
- Any fungus or mould apparent before this application can be removed by wire brush and if necessary, sprayed with a moss or mould killer.