Exterior cladding

What to consider

Sun and heat

Façades facing the sun get very hot, and dark stone absorbs more heat than light stone. Panels, anchors and the backing structure expand and contract daily. Joint widths and movement joints have to allow for this, and the engineer sets them.

Wind and sand

Wind load increases with building height and exposure, and it governs panel size, thickness and anchor spacing. Wind-blown sand also wears polished surfaces on exposed elevations over time.

Coastal humidity

Near the coast, humid, salty air attacks unsuitable metals. The grade of stainless steel or other metal for anchors and brackets is an engineering choice; corroding fixings can also stain the stone.

Anchorage

External panels are generally held with mechanical anchors (for example kerf, dowel or undercut anchors) into a backing wall or sub-frame. Adhesive or mortar alone is generally not relied upon for external panels at height. The anchor system’s supplier and the engineer define edge distances and stone thickness.

Water and joints

Joint sealants, drainage behind the panels and the way water runs off copings and sills all affect staining and long-term performance. Some sealants can stain absorbent stone at the edges, so compatibility should be checked.

Limitations and when to get technical advice

We do not supply fixing systems, calculations or façade drawings, and we cannot state that any material is suitable for a particular façade. Engineers usually need material properties such as flexural strength, density and water absorption, and sometimes anchor tests on the actual stone; we hold none of these, so testing of the specific lot may be required at the project’s cost and timing. Dark Emperador marble is not offered for exterior cladding here: marble is generally more affected by weathering and acids than granite, and polished marble outdoors tends to lose its polish. Our porcelain slabs come without manufacturer exterior data, so they are not proposed for façades. Black Marquina’s family is unconfirmed. Every cladding enquiry is treated as needing technical review.

Finish

Finishes are not recorded in our catalogue and are confirmed in your quotation. On exposed elevations a polished face will generally dull over the years from sun, sand and cleaning; honed or textured finishes change less visibly. A flamed finish removes some of the surface and can change the colour, which matters both for appearance and, because the effective thickness is reduced, for the engineer’s design. Agree the finish before the engineer finalises the thickness. See our finishes guide.

Thickness

We offer granite slabs in 20 mm and 30 mm. For exterior cladding, thickness is an engineering output, worked out from panel size, wind load, anchor type and the stone’s tested strength. Thicker stone is commonly specified for mechanically anchored external panels, but neither 20 mm nor 30 mm can be assumed adequate without that design. Please send the engineer’s specified thickness with your enquiry.

What to measure

Send the façade elevations and the panel schedule from your engineer or architect if you have them. Otherwise give the size of each elevation in metres, the intended panel size and the height of the highest panel above ground.

• Elevation width (m)
• Elevation height (m)
• Panel size from the façade drawing, width × height (m)
• Number of panels per size
• Height of the highest panel above ground (m)
• Corners, reveals, sills and copings: total length (m)

State the net cladding area in square metres (m²) per elevation, and attach the panel schedule if it exists. A façade usually has many panel sizes plus returns and copings, so the slab quantity depends on how the schedule cuts from the slabs available. We will confirm slab sizes so the cutting yield can be planned.

What we supply

We supply stone slabs. Façade design, structural calculation, anchor and sub-frame supply, panel cutting with anchor slots, installation, testing and authority approvals are all outside our supply. If cut panels are needed, ask in your request and we will confirm whether cutting can be arranged; anchor preparation is for the façade contractor.

Site conditions to tell us

• Building height, location and exposure (coastal, open desert, sheltered).
• Backing structure: concrete, blockwork or steel sub-frame.
• Access for installation: scaffold, mast climbers or gondola.
• Approvals needed from the consultant and authorities, and their timing.
• Covered, clean storage on site away from cement dust and traffic.
• Installation programme, so deliveries can be phased.

Natural variation

On a façade, shade differences between lots show up as visible patches across an elevation. Order and reserve the full quantity from one lot where possible, and agree how panels will be distributed if blending is needed. Even, uniform materials generally show lot changes less than strongly patterned ones. Ask how much of a lot is available before the design is fixed. See natural variation.

Technical documents

If your designer, consultant or client needs technical documents such as test reports, data sheets or certificates, list them in your request and we will tell you what can be provided for the materials you choose.

What affects the cost

• Stone thickness specified by the engineer.
• Panel schedule: number of sizes, returns, copings and cutting waste.
• Quantity reserved from a single lot.
• Finish, if a textured finish is specified.
• Material testing required for design or approval.
• Cutting and anchor slot preparation by the façade contractor.
• Phased deliveries and site access.

Delivery preparation

For façades, phased deliveries matched to the installation sequence reduce storage and handling damage. Store panels on timber, on edge, covered and away from cement and grout splashes, which can mark stone. Label cut panels to the schedule. Delivery terms are confirmed in your quotation; see delivery preparation and trade supply.

Samples and viewing

Ask whether a sample, a yard visit or a video viewing is possible. For cladding, also ask your engineer whether test specimens or a mock-up are required, since that may need larger pieces from the actual lot.

Care

Exterior stone mainly needs periodic washing to remove dust and sand, with clean water and a soft brush or a gentle low-pressure rinse. Avoid acid washes and high-pressure jets aimed at joints. Sealant joints and anchors should be inspected as part of the building’s façade maintenance plan, set by the façade contractor. See the granite care guide.

Alternatives

If natural stone panels prove impractical for the height, weight or approvals, engineered façade systems from specialist manufacturers are the usual alternative; we do not supply them. At ground level, a granite plinth or low wall with smaller pieces may be simpler than full-height cladding; see the landscape detailing page. Lighter-coloured stone generally gets less hot in the sun than dark stone. For interior walls, see the feature walls page.