General, Wall Insulation & Rendering Frequency Asked Questions


Do you have approved installers in my area? 

Please complete the form on our contact page and we can put you in touch with our approved applicators for your area.  

External Wall Insulation

What is External Wall Insulation (EWI) / ETICS? 

External Wall Insulation (EWI) is the placement of insulating boards on the external surface of all the vertical walls of a building. This protects the building from fluctuating weather conditions, reduces heat losses from inside the building and will prevent external temperature changes from affecting the interior climate. EWI keeps homes warm in winter and cool in summer, ensuring a home with a pleasant atmosphere by eliminating sharp and high changes in indoor temperature. EWI will also reduce energy consumption terms of energy consumed for heating and cooling. 

Can I install External Wall Insulation (EWI) on a cavity filled property?

External Wall Insulation (EWI) is designed for a solid wall construction. You will need to seek further advice from a cavity extraction consultant for your specific needs.  

Why External Wall Insulation (EWI)?

Initially, the main reason for choosing an External Wall Insulation solution is that EWI will achieve higher thermally insulating results by protecting the walls from changes in outdoor temperature, taking advantage of the thermal capacity of the existing walls and more effectively avoiding thermal bridges. 

Therefore, with EWI, the maximum possible reduction in heating or air-conditioning costs can be achieved. Another reason for opting for EWI is to enhance renovations. If renovating the exterior of a building, opting for an EWI solution provides great flexibility for architectural and design choices. 

The disadvantage of indoor thermal insulation is the reduction of floor space in the house from the installation of the thermal insulation. In addition, the decommissioning of any objects found on the walls such as built in storage, wardrobes and radiators for example, and their subsequent reinstallation is time consuming and costly. 


Does External Wall Insulation (EWI) need planning permission?

There is no need for full planning permission to install EWI, unless you are living in a conservation area or a listed property. However, always check with local planning authority to be sure. 

What insulation boards are used for External Wall Insulation (EWI)?

The standard materials use as part of the Baumit EWI systems are Expanded Polystyrene (EPS), Mineralwool, phenolic insulation and wood fibre boards. 

View our systems here. 


What thicknesses of Insulation should I use?

The most common insulation thickness is 100mm, however a U Value check can indicate the appropriate thickness you will require. 

A full list of thickness can be found here: 

Baumit OpenTherm, EPS insulation boards

Baumit StarTherm, EPS insulation boards

Baumit Mineral Wool EWI Slab

Baumit StarTherm Nature, wood fibre board

What fixing do I need to use?

Depending on the substrate, we offer the following fixings: 

Baumit H3 Hammer Fixing, 75mm - Used on masonry 

STR U 2G, 115mm -  Plastic fixing used on masonry and concrete

STR H, 80mm - Metal fixing with screw thread used on timber


How long does the installation of an External Wall Insulation (EWI) system usually take?

Depending on the size of the project, usually a two-week period is enough to complete the project. 


What final finishes are available to complement the External Wall Insulation (EWI)?

Baumit has a variety of mineral and organic topcoat renders suitable for use will all our EWI systems, each available in a huge range of colours. 

Please refer to the Baumit Topcoats leaflet for our full range of renders.

How does External Wall Insulation (EWI) fit around existing pipes and services?

When installing EWI, all pipes should be extended and then returned into the existing outlets. 

Utility services should be treated according to the guidance of the utility provider.


Do you have a system for the plinth area?

As part of our External Wall Insulation system range we offer a specifically design Plinth System which uses a High Density insulation Board.

For further information you can visit our guide page here

Baumit Render

Can Baumit render be tinted to any colour? 

With over 888 colours in the Baumit Life range, we are confident we can find you the exact colour you are looking for. However, some of our renders are only available in certain colours. To find out which render you need, visit the Baumit Life website for our colour search tool. 

How do I clean render on the outside of my house? 

  1. Jet wash on a low fan setting (ensure mastic seals in place round all windows)

  2. Clean down the wall with soapy water

  3. Clean off with Baumit Fungo Fluid if algae or mould are present

  4. If the wall is coated in dirt you Baumit ReClean 


Are all Baumit render products sprayable?

Yes, all of the products in our render range can be spray applied. 

Can I add water to a topcoat to make it easier to apply? 

Yes, we would recommend no more than a cupful (5% of the product).


Does Baumit have a monocouche render?

No, we do not have a monochouce render in our product range. we have developed an alternative product, the Baumit UniRend System which has the appearance of monocouche but creates a breathable wall construction that is more flexible to avoid cracking.