Heritage Portland Stone Bricks
This section covers the use of Heritage Portland Stone bricks on typical building projects but does not give specific design advice and expert advice should be sought where required.
Heritage Portland Stone includes all the distinct geological characteristics of our Portland Whitbed seam which ties in with historical use on Portland Stone buildings, including St Paul’s Cathedral.
The Natural Stone Masonry in modern Scottish Construction, gives some useful background information on differing types of walling and construction methods and typical design details and sketches. It is important to read this document together with any new guidance in the relevant British Standards, but typically the Heritage Portland Stone Bricks can simply replace clay bricks in most applications.
We offer a full range of brick specials along with standard bricks. Bespoke Portland Stone features such as stone quoins, window surrounds, string and coping courses are available to order.
Designed like a typical cavity wall construction but with a stone brick rather than clay brick as the outer facing. Appropriate insulation, cavity ventilation, water management, movement joints and fixings will need to be incorporated into the design.
Movement Joints
Steve Webb has completed some calculations which show that due to the higher compressive strength of natural stone there is the possibility of fewer movement joints.
Movement joints are located at the corners of the buildings and intermediate locations where necessary. The rules of thumb for movement joint spacing is as follows;
| Stone | Clay | |
| Vertical | 20m (8m from corners) | 12-15m (8m from corners) |
| Horizontal | Up to 5-6 Storeys* | Lesser of 4 storeys or 12m |
*This needs consideration and is dependent on design and detailing
All calculation should be carried out by a qualified engineer on a project by project basis
The stones are normally directly attached using appropriate fixings to the loadbearing structure or may form part of the loadbearing structure. The wall should be constructed to ensure no staining can migrate from the structure into the stonework. Care needs to be taken relating to control of moisture so we would recommend looking at tradition designs where the surface water is diverted from the façade with regular projections. The incorporation of a suitable DPC should be carefully considered but waterproofing the face or the rear of the wall to stop moisture penetrating is normally not advised.
The joint sizes will depend on the design, but it is assumed that the typical brick joint of 10mm will be used in most applications. Bedding mortar can be 1:1:6 or 1:2:8, White Cement, Hydrated Lime, and Washed Sand. Avoid sand containing clays or other contaminates that could leach into the stone bricks. The mortar should not be stronger than the stone itself and the hydrated lime should not be replaced with a proprietary plasticiser as chemicals within these products may react or discolour the stone. Lime mortars may be appropriate in some applications but may need a longer curing period.
Heritage Portland Stone Bricks can be used beneath the Damp Proof Course (DPC) layer, but there are several key considerations to keep in mind. The primary concern is that, due to their porous nature, these bricks can draw water from the ground, potentially causing staining. While this staining affects only the aesthetics of the stone and not its strength or performance, it is important to manage this aspect carefully. Effective water management is crucial to help prevent staining. Ensuring proper drainage and minimizing water exposure to the bricks can significantly reduce the likelihood of staining.
All Albion Stone’s production is certificated to the ISO 9001 kitemark, meaning the quality system is independently audited by BSI representatives. For detailed Technical Data, please see technical data sheet. The CE Certificates and Declaration of Performances are available when the bricks are delivered.
The compressive strength of our Heritage Portland Stone typically falls within the range of 40 to 60 MPa, positioning it at the upper end of masonry bricks and approaching the level required for engineering bricks class B. Notably, it boasts frost resistance, as evidenced by BS EN 12371 standards, showing only a 15% strength loss after frost cycles between 14 to 168. Additionally, it is classified as A1 for fire resistance, offering a high level of safety and durability.
The Heritage Portland Bricks are manufactured to the same size as standardised metric size brick 215mm x 102mm x 65mm high and to the tolerances set out in BSEN 771-6 for the D2 category where the height, length and width are +/- 2mm.
Shear bond strength test is project specific as it depends on the brick, mortar and site workmanship. We therefore quote the generic figure of 0.15N/mm2 from the BS EN 771 which is the same figure that has been quoted on our walling stones for the last 30 years. Should you wish to conduct a project-specific shear bond strength test, Albion Stone is pleased to provide bricks for this purpose.
The pallets contain 300 stone bricks which, assuming stretcher bond and 10mm joints, provides a coverage of approximately 5m2. Pallets are wrapped in recyclable plastic and weigh approximately one tonne. The plastic is primarily for protection during transport and is not suitable for long-term site storage. We suggest you avoid prolonged external storage.
Heritage Portland Stone typically weighs 2.2 tonne per cubic meter, giving each Portland Stone Heritage Brick a typical weight of 3.15kg, so a little heavier than a typical clay brick.
The stone will not require cleaning to safeguard its durability; cleaning is purely a cosmetic requirement.
The effects of algae growth and bird fouling can be limited with a regular cleaning regime using a little water with a soft bristled brush. For the removal of this, and more ingrained contamination call the Lithofin Technical Line for specific guidance.
Cleaning and surface repair of a larger façade should be carried out in accordance with BS 8221‑1 and BS 8221‑2 and the Stone Federation guide to Best Practice on the Cleaning of Internal and External Masonry Surfaces guidance by suitably qualified operatives on a cycle depending on the building design, the local climate and orientation of the facades, and the levels of atmospheric deposits deemed acceptable by the client.
Albion Stone, a fourth generation family business pride ourselves on having a helpful and skilled workforce as well as modern and traditional manufacturing process to enable us to produce the highest quality Portland Stone with minimal environmental impact.
