Exterior render with or without wall insulation

Exterior render is a plaster-based façade finish available in a range of colours, textures and grain sizes. It can give an existing exterior wall a clean and uniform new appearance.

Render can be installed without additional insulation or combined with external wall insulation. The correct build-up depends on the condition of the existing façade, the renovation goals and whether the thermal performance of the exterior wall also needs to be improved.

Before installation, the existing façade is inspected and prepared. The appropriate façade system is then built up before the final render finish is applied.

Not every façade renovation requires additional insulation. If the property is already sufficiently insulated or the main objective is to renew the exterior appearance, render can also be installed without additional external wall insulation.

The existing substrate is first checked for stability, cracks, loose material, moisture problems and other defects. Where necessary, the façade is prepared or repaired before the render system is installed.

Render without insulation can be suitable when you want to:

• modernise the appearance of the property;

• create one uniform finish across different façade surfaces;

• renovate a wall that is already sufficiently insulated;

• renew the exterior without adding a new insulation layer.

Suitability is always assessed based on the condition of the existing façade.

If you want to renew the façade while also improving the thermal performance of the exterior walls, render can be combined with external wall insulation.

EPS insulation boards are first installed against the outside of the existing wall. Reinforcement and base layers are then added before the final render finish is applied.

Insulating the wall externally allows the existing wall to become part of the insulated building envelope without reducing interior living space. Façade renovation and thermal improvement are therefore combined within one project.

The insulation thickness and full system build-up are determined according to the existing property, window and door junctions, sills, roof edges and the required insulation performance.

Exterior render can be installed without additional insulation or combined with external wall insulation. The most suitable solution depends on the current insulation of your property, the condition of the façade and what you want to achieve with the renovation.

Render without insulation

If your property is already sufficiently insulated and your main goal is to renew the appearance of the façade, render without a new insulation layer can be a suitable option. The existing façade is prepared before the new render finish is applied.

Render with insulation

If the exterior wall is poorly insulated or not insulated at all, render with external wall insulation can be more appropriate. The exterior wall is insulated from the outside before the render system is installed.

Both solutions renew the appearance of the property. The main difference is that an insulated render system also improves the thermal performance of the exterior wall.

During our assessment, we determine which build-up is technically most suitable for your property.

Exterior render is a versatile façade finish that can be installed without additional insulation or combined with external wall insulation.

Key benefits include:

• Renewed appearance: an outdated or uneven façade receives a clean and uniform finish.
• With or without insulation: render can be used purely as a façade finish or combined with external wall insulation.
• External wall insulation possible: the exterior wall can be insulated from the outside before the render is applied.
• No loss of interior space: the insulation is installed on the outside of the building.
• Many finishing options: different colours, grain sizes and textures are available.
• Suitable for renovation: render is particularly suitable for existing façades that need renewal.
• One complete system: with an insulated system, façade insulation and finishing are combined.

For rendered façades with external wall insulation, we use EPS insulation from Belgian manufacturer Hisfa nv, based in Hulshout. The boards are installed against the existing exterior wall and form the insulating base of the façade system.

The boards create a continuous insulation layer on the outside of the property. The façade system is then completed with the appropriate fixings, reinforcement layer, base coats and finally the selected render finish.

The required insulation thickness is determined based on factors including:

• the existing wall construction;
• any insulation already present;
• the required thermal performance;
• junctions around windows and doors;
• sills and roof edges;
• the technical possibilities of the property.

For render without insulation, no new EPS insulation boards are installed.

The visible render layer plays a major role in the final appearance of the property. Different colours, grain sizes and textures are available.

Whether the render is installed with or without external wall insulation, we determine which finish is technically suitable for the selected façade build-up.

When selecting the colour, we also take windows, doors, roofing, sills and other façade details into account to create a balanced overall appearance.

Not every existing exterior wall can be covered with render without preparation. We therefore inspect the condition and construction of the façade beforehand.

We assess factors including:

• stability of the substrate;
• cracks or damage;
• loose areas;
• moisture problems;
• flatness of the façade;
• existing finishes;
• junctions around windows, doors, sills and roof edges.

For render with external wall insulation, we also assess whether the façade is suitable for the installation of a new insulation layer.

Based on this inspection, we determine the appropriate preparation and façade build-up.

The installation process depends on the condition of the existing façade and the selected rendering system. For render without insulation, we inspect and prepare the existing substrate before applying a suitable exterior rendering system. When external wall insulation is included, EPS insulation boards are first installed against the exterior wall.

For external wall insulation, we use EPS insulation boards from Hisfa nv. The façade system is then built up with the appropriate fixings, reinforcement and base coats before the final render is applied. In both cases, particular attention is given to junctions around windows, doors, sills and roof edges.

An exterior rendered façade is exposed to rain, dust, algae and other environmental influences. Regular visual inspections and appropriate cleaning help preserve its appearance and condition.

The cleaning method must be compatible with the type of render and the condition of the finish. Excessive water pressure, aggressive cleaning products or unsuitable brushes can damage the surface.

If persistent dirt, algae or localised damage appears, it is advisable to have the façade assessed before selecting a suitable cleaning or repair method.

The price of exterior render depends on the property and the selected façade build-up.

The final cost is influenced by factors including:

• total façade area;
• condition of the existing exterior wall;
• preparation or repair work;
• accessibility of the façade;
• selected render finish;
• junctions around windows, doors and sills;
• and whether external wall insulation is included.

Render without insulation has a different build-up and cost from render with insulation. With external wall insulation, the insulation thickness, boards and technical junctions also influence the price.

We therefore inspect the façade and discuss the required solution before preparing a tailored quotation.

When exterior render is combined with new external wall insulation, renovation or energy-efficiency grants may be available depending on the region, property and current eligibility conditions.

These incentives generally relate to the energy improvement and insulation itself. Render without new external wall insulation therefore does not automatically qualify under the same conditions.

Eligibility rules can change. Check the current conditions on our grants page.

View completed rendered façade projects by Nu-Isoleren.

Answers about insulated render, Hisfa EPS boards, pricing, colours, maintenance, substrate preparation, installation and grants.