Building Finishing FAQs

Please visit our contact us page where you can view an area map displaying contact details for our local Business Development Managers and Specification Managers.  Contact details for our Technical Team can also be found on this page should you have any technical queries.

For Applicators and Trade Professionals, Sika Parex render products are available to purchase through our nationwide distributor partners.

You can find details of a local stockist on our web page: Find a Sika Render Stockist.

Our Specification Managers will be happy to assist you with providing the most suitable specification for a Sika External Wall Insulation system.  Please visit our contact us page to send an enquiry.

Please visit the Downloads & Resources section on our website, or alternatively data sheets can be viewed on each individual product page.

Yes, our Mineral Render, External Wall Insulation (EWI) and Pointing Mortar training sessions are aimed at contractors, applicators and distributors who are looking to expand their knowledge or improve skills.  Further details can be found on our Sika Wishaw Training Centre web page.

Sika completed the acquisition of the French company Parex on May 23, 2019.  Sika and Parex are two strong companies that are highly complementary in product offering and channel penetration and this acquisition has expanded our product portfolio for the Building Finishing market.  Prior to this acquisition, Parex acquired established renders, insulated facades and aggregates company Enewall Ltd, based in Scotland.

Sika can provide colour samples for planning applications or for design consideration. These are generally available in a scraped finish. Other finishes can be provided to order. Colour samples are for guidance only and it is important that a test panel is produced on site for final approval.

If you have a specific colour you would like to match, contact Sika as we are able to offer special colours from a wider range.

Once a special colour sample has been approved there is a minimum order of one pallet of 48 x 25 kg bags.

Yes, always check all substrates for suction by splashing water onto the surface of the elevation going to be worked on. If the water drips down the wall, the substrate has little or no suction. If the water absorbs immediately into the substrate, then the substrate has high suction. When the above two scenarios are experienced, it is likely that the surface will need priming with Micro Gobetis 3000 or Fixopierre.  Please refer to our ‘Mineral Renders: Substrate preparation, water quantities and finishes’ technical information sheet  for guidance.

If the existing render substrate is well-bonded and there are no surface defects, delamination or cracks, then yes, new render can be applied over existing render.

No, as it will delay the curing time and compromise the chemical bond between the product and the substrate.  You may also see efflorescence staining on the blockwork.  If this is not removed completely from the substrate before the render is applied, the render will start to break down and delaminate.

Render should never be applied to a frozen substrate and the temperature should be 5° and rising before application should begin. Always protect newly applied render from freezing conditions. For more detailed information on cold weather applications, refer to the Technical Information sheet: Cold weather working - General guidance.

There are a number of reasons cracks appear in external render.  The most common are the substrate has cracks, bed joint reinforcement has not been applied at every two courses, above and below, or window or door openings or substrates and infill blocks are different strengths, which leads to differential movement.  Bed joint reinforcement is a requirement of NHBC, LABC, Premier etc.

This is caused by incorrect application of render, including: applying render to a wet wall; render is applied too thin; masonry joints are recessed or raked out; the mortar used to bond the masonry is of a weak consistency or the mortar joints haven’t had enough time to cure after construction of the masonry.

Yes, they can be repaired.  Please refer to our  ‘How to repair holes, Sika mineral render finishes’ technical information sheet for guidance.

Every building element moves and all movement joints in the substrate must be replicated in the render finish, or cracking will appear.  If it is a timber frame, then the movement joints in the timber frame (i.e. between panels) should also be considered in the render, even if they are not replicated in the outer blockwork.

Clear access for the application of the render must be given to avoid scaffold lines, including consideration to any internal handrails.  Scaffold lines are caused by different application techniques used, or in the case of rough cast, different spray angles.  Scaffold lines are a visual defect and not a technical defect. In most cases, this can be treated with an overcoat of Crylane, but not always.

Algae growth and stains are dependent on water, nutrients and in the case of algae, light.  This does not mean a façade is damaged, and most algae stains can easily be removed using biocides or steam cleaning.  However, if left too long, they can discolour the render. Sika Paraguard helps reduce this risk by providing a hygrophobic finish when applied as a final coat for a Sika render finish.

Unfortunately you cannot, due to strict specification requirements, including components, wind load calculations, fixing assessments etc.  External Wall Insulation Systems should be ordered direct from Sika after a specification has been issued and approved by the Sika Specification Team.

External Wall Insulation Systems protect the fabric of the building and reduce heating requirements. On heavy, dense, construction the building envelope may be used as a “storage heater”, ensuring a constant climate. External Wall Insulation helps to keep heat stored, making for a far more economical and ecological solution.

Heat loss through materials is known as ‘thermal transmittance’, which is measured in W/m2K. This is also known as the U-value. Typically a section 1m2 is tested which goes through the building. The amount of heat lost through that section is measured and a U-value given. The lower the U-Value, the better the material’s insulating properties.

You have a choice of either EPS or Mineral Fibre insulation boards, depending on the height and requirements of the project.  The boards are bonded to the external wall and can be additionally fixed with anchors, depending on the load-bearing capacity of the substrate, the wind suction load, and the insulation used.

Mineral Fibre insulation boards are vapour permeable, have excellent fire resistance (measured for reaction to fire) and are suitable for all buildings of all heights and boundary conditions when overall system achieves A2-s1, d0 to EN 13501-1.

EPS insulation boards are CFC/HCFC-free, lightweight and rigid and competitively priced.  Currently restricted for use below 11m and a fire strategy and firebreaks should also be considered for multi-storey blocks <11m.

Phenolic insulation boards are used for low rise External Wall Insulation Systems and have high thermal performance and impact and compressive strength.

Sika can offer advice on the insulation type at specification stage.

Thermal bridging is a phenomenon where heat can be lost through material ‘bridges’.  Where components with higher thermal conductivity penetrate or partially penetrate the insulating layer of the building, heat can be lost.  Examples of thermal bridging can be seen in concrete lintels or edge beams. Both can penetrate the inner leaf of a cavity wall, bypassing the insulation in the cavity.

Even mortar joints within a brickwork facade will create a thermal bridge, allowing greater heat losses.  Correct detailing at the design stage will remove the potential inefficiencies thermal bridges introduce. 

Sika can provide detailed drawings for insulating around openings, windows, doors etc.

Wind load is often the largest force applied to a façade and its values vary with the size, shape and location of the building.  Most rim zone forces are a negative suction load.  The number of fixings are directly related to the wind load calculations, the substrate pull-out capacity and the pull over performance of the insulation.  The render adhesion to the insulation is also evaluated.

The wind load on a building can be further divided into Normal Zones and Rim Zones.  A Normal Zone is typically within the middle of a facade where the wind load is at its lowest value.  A Rim Zone is where the load is at its highest and is typically at corners and edges of buildings.

Sika can assist with wind load calculations and the location of rim zones.

Façade insulation systems should be designed to ensure that the materials do not contribute to the fire and accelerate this spread of fire. There should also be no collapse of the system that would endanger the fire fighting forces or other members of the public.

The use of non-combustible Mineral Fibre insulation boards is the best option.  Additionally, firebreaks are used to prevent the rapid progress of fire spreading up the outside of a multi-storey building unchecked. They act as non-combustible, time delay buffers between areas where combustible materials or cavities may exist. Firebreaks should be installed at every floor level after the second storey and correspond with all vertical fire compartments. However, some Fire Officers may require breaks to be installed at every floor level.

The Building Regulations require the installation of cavity barriers at positions of compartment walls and floors. This stops the passage of fire via cavities created behind the insulation either by design or otherwise. This is also a requirement at window openings where cavities may allow fire up behind the back of the system.

When specifying EPS, full depth firebreaks are required to resist the progress of fire across the face of the building. This is an additional precautionary measure to further inhibit the spread of flame.

These should be of non-combustible material and designed and installed to meet the requirements of Part B of the Building Regulations and other industry guidance documents e.g. TGD19 and the Building Regulations (Scotland) and The Building Control Regulations Ireland. Mineral wool insulation is considered a continuous fire barrier.

You can also refer to the guidance given in BR135 “Fire performance of external thermal insulation for walls of multi-storey buildings”.

A drained Mineral Fibre system must have fire barriers specified to meet the requirements for fire control on a building. A fire barrier strategy is detailed in the Building regulations as follows:

(1) In England, Ireland and Wales continuous horizontal fire barriers are normally required after the 2nd storey/beginning of 3rd storey, and every storey thereafter. In Scotland they are required at every storey.

(2) Vertical fire barriers may be required to provide fire compartmentation between adjoining rooms. The requirement and location of these fire barriers should meet Fire Officer/Building Control Specifications.

(3) Cavity fire barriers are needed to close the cavity at all openings such as windows and doors. This is a requirement for mechanically fixed systems, where a cavity is present.

Specification of fire barriers is entirely at the discretion of the designer and the designer must satisfy themselves that relevant requirements regarding passage of fire are fulfilled.

The Building Regulations 2010, Approved Document B was updated in 2018 when the government banned the use of combustible materials for external walls of residential buildings over 18m tall.  The regulations were then updated in 2022 to cover residential buildings between 11m and 18m in height. 

Updated provisions in Section 12 for residential buildings (purpose groups 1 and 2) with a storey 11m or more in height.  Any building that is used for overnight stays (residential buildings) will ban the use of combustible material above >11m in England, Ireland, Scotland and Wales.  The new rules will only apply to future new-build projects, not existing properties or schemes that are already underway.  Some combustible materials on buildings between 11m and 18m can be used, but only as part of a system that has passed a large-scale test.

The most common facade material for External Wall Insulation Systems is a seamless, rendered finish.  These can be thin coat synthetic, acrylic or silicone enhanced, high performance renders.  Wet and dry dash aggregate finishes are also a popular choice for social housing or new build developments.  Sika has a range of mineral renders in a one coat or top coat finish and these can be applied to many different substrates including vertical masonry and concrete walls.  Visit our product pages for more information.

Most recognised system designers will carry some form of third-party accreditation. This shows that the systems assessed are fit for purpose and how they relate to the industry benchmarks set by the governing standards bodies.  The Sika Parextherm External Wall Insulation has an ETA certification and Sikatherm External Wall Insulation has a KIWA certification.

There are two types of guarantees that are typically given for an External Wall Insulation System installation.  This is the standard 10 year materials warranty and also the extended 25 year guarantee. The 10 year guarantee provides peace of mind for the materials used within the installed External Wall Insulation System, and is provided by Sika, the system designer, to the client.

The 25 year guarantee is typically for funded works and this includes an insurance backed guarantee provided by the External Wall Insulation System installer to the client. When this is in place, Sika will typically also provide a 25 year materials guarantee.

Yes, to help you with project designs, we can supply bagged samples or pointed sample panels to allow sign off from your client.

Sika's specification team are happy to support you with this.

To ensure adequate bonding of the new mortar to the masonry, it is important that the old mortar is removed to a minimum depth of twice the joint width, and that any residual dust is removed from the joint.

If the masonry is porous, joints should be wetted down priorto repointing to prevent excessive suction.

Yes, Sika Parex® Historic Mortar can be injected into joints as narrow as 5mm and depending on the joint width, will penetrate to a depth in excess of 100mm, allowing for the deepest of joints.

The rate at which mortar dries can be affected by the porosity of the brick/stone being pointed and associated substrate.  Suction rate can be determined by applying water either by brush or spray to the brick/stone surface and observing the rate at which the water is absorbed.

Excessive suction can be controlled by spraying the area to be pointed pre and post pointing.  Failure to control excessive suction may lead to the formation of cracks and fissures forming once the mortar has cured.  The pointing of brick slips with very little suction, or alternatively high suction, will greatly affect the point at which the mortar may be tooled off and this factor needs to be considered from an operational perspective. This effect is even more marked at low temperatures or unusually high temperatures.  It is essential to protect the pointed façade, whilst curing, during freezing or wet weather.