How to install sandwich panels over an existing masonry wall

Establish the extent of masonry repairs and address the causes of leaks or rising damp before cladding begins. Covering a wet wall can slow drying and make further deterioration difficult to spot. Structural defects also need to be assessed while the wall is accessible.

The subframe provides an even bearing surface for the panels and transfers their weight and the wind loads to the supporting structure. Choose anchors for the actual substrate, whether solid brick, hollow masonry, concrete or another material. Determine anchor type and spacing for those particular conditions.

The design should specify the subframe members, their connections, the anchors and the panel fasteners. It must account for the offset from the wall and the forces that arise from it. A long screw driven through old render provides no evidence of adequate bearing or a durable connection.

Assess the existing masonry and the new panels as one wall assembly. Check temperatures through the layers, water vapour and the potential for drying. If the design includes a cavity, define its purpose. Ventilation depends on the planned air inlets, outlets and closures.

The extra layers also affect how the complete wall performs in a fire. Check whether the assessment for the panel covers its use over masonry. Include junctions at floor levels and at the roof when assessing the new façade as part of the building.

A thicker façade changes reveal depths, sill projections and access to doors. Check that windows and doors will open fully and that flashings discharge water clear of the new wall face. Detail the plinth to protect the lower panel edges and keep this dirt-prone area accessible for inspection.

Locate pipes, vents and cables before the panels go into production. Detail each penetration to suit its function. Attach fixtures to masonry or structural members designed for their loads. A thin panel facing alone provides insufficient support for arbitrary brackets.

After repairing the substrate, install the anchors and subframe. Check the frame alignment and corrosion protection, then prepare the specified sealing tapes, bearings and starter details. Inspect and accept the subframe before the panels conceal it.

During installation, check that the correct face points outwards, the joints close properly and the fasteners apply the specified pressure. Protect the coatings and remove metal swarf as work proceeds. Resolve deviations in the subframe before fitting flashings. Photographs of the exposed anchors and connections will help at handover and during later repairs.

Allow for masonry preparation, the subframe and anchors, panels, flashings, access equipment and labour. For a 100 m² wall, an illustrative budget might allow €3,703 for panels, €1,967 for the subframe and anchors, and €2,199 for the remaining work. The total is about €7,869 excluding VAT. These rounded amounts illustrate how to build up an estimate.

The actual budget depends on the condition of the wall, its height and the number of openings. Compare quotes covering the same work. Include masonry and sill repairs wherever they are needed, and allow for investigation of areas whose condition will only become clear when opened up.

At handover, inspect flashings, seals, drainage paths and the junctions with existing building elements. After the first spell of heavy rain, examine the interior and the foot of the façade. If you find damp, trace its source before applying additional sealant.

Keep the subframe drawings and anchor specifications. They show future installers where a replacement panel can be supported and how loads pass through the assembly. Retain access to any areas of the original masonry that need continued observation.