Porotherm clay block walling system

Porotherm Accessories

Clay block tools and components specifically engineered to make laying as efficient as possible.

ZeroPlus Mortar

Specifically formulated for Porotherm

The ZeroPlus™ thin-joint mortar is specially formulated for the Porotherm construction system.

Unlike existing thin-joint and conventional mortars that are for use at 3°C and above, ZeroPlus mortar is designed to work at temperatures down to 0°C and above.

This helps reduce downtime and enables building programmes to extend through the winter months.


Mixing step by step guide

  • For a full bag mix, add approximately 3.1 litres of clean water to the bucket then add the powder.
  • Stir quickly and vigorously (using an agitator / paddle mixer) until a smooth, lump free consistency is produced.
  • Allow to stand for 10 to 15 minutes and then stir again.
  • Trasnfer the mixed mortar from the bucket into the special Porotherm mortar roller.
  • Apply mortar to a 5 to 6m length of horizontal joint using the mortar roller.
  • The speed of rolling and the angle of application must be adjusted to ensure that an even mortar layer is applied evenly from the roller, covering the entire surface area of the horizontal joint.

Do not mix with water that is partially frozen or is thawing. Mixing water should always be from a mains tap that has not been frozen.

In addition, early strength development will be reduced at low temperatures and therefore the blocks and mortar must be adequately protected at all times, with appropriate insulating covers prior to and after application, so that fresh masonry does not fall below 0°C. Mixing in an insulated bucket with an insulated lid is strongly recommended.


Processing time: Protected mortar; approximately 4 hours at 20°C, but will be extended at lower ambient temperatures and reduced at higher ambient temperatures.

Processing temperatureUse only when the air temperature is at least 0°C and rising. Please be aware that internal situations may be colder than external and any wind chill factor must be taken into consideration. Do not use when blocks or existing work are frozen.


This product contains cement and produces an alkaline reaction when it comes into contact with moisture/water. Therefore, ensure that skin and eyes are protected. If it should come into contact with the skin or eyes, rinse them thoroughly with water. Seek medical assistance immediately if it comes into contact with the eyes. Contains Chromium VI, however a reducing agent ensures that the Cr VI content of the mortar remains below 2ppm during the shelf life of the product. It may produce an allergic reaction. For full information please refer to the Material Safety Data Sheet.

ZeroPlus has been independently verified by Lucideon, an established UK testing and assurance company, for use at zero degrees.

Mortar Roller

Porotherm is a thin joint system that utilises a specially designed roller to apply the mortar, rather than a trowel used in more traditional construction methods. The roller plays a key part in allowing fast and easy application of the specially developed Porotherm ZeroPlus mortar onto the blocks, whilst achieving a strong and accurate bond with minimised waste to builders.

Wienerberger has launched a new and improved roller, which is much lighter than the previous model, that is easier to use as a result.  It also offers increased grip to builders due to a new rubber handle, which offers far greater comfort for the user, especially in cold weather. In addition, it is also extremely easy to clean.

This roller is available in the following sizes: 140mm, 190mm, 240mm and 365mm.

Wall Ties

The Porotherm system has its own specific type of wall ties which provide many benefits.

Due to the thin joints created with Porotherm, standard ties are not suitable. However, a range of purpose made, system-compliant stainless steel ties are widely available.

The range includes ties for internal wall junctions and internal/external cavity walls as well as party walls. The ties are manufactured from corrosion resistant stainless steel and are suitable for use in housing and commercial applications. These innovative range of wall ties for use with cellular clay blockwork allow for horizontal mortar bed joints of just 1mm.

Applying the Wall Ties 

Porotherm blocks use a two part wall tie. Placement of the flat strip part of the two part tie is very straight forward. Simply wipe the tie in the rolled out adhesive, turn it over and place back onto the block in the adhesive. The wire part of the tie can then be installed as the external façade is brought up.

Wienerberger Approved Parge

What is parge?

Wienerberger approved parge is a high performance modern parge coat that has been specially designed and tested for fast application onto Porotherm clay blocks. Engineered to increase air tightness and to optimise the sound and thermal performance of Porotherm clay block walls, prior to dry lining. Parge has been designed to be applied by brush or roller ensuring fast de-skilled application. An ultra-high polymer modified product, on application the cross linked polymers grab to the inside of the open joints then the X-pan technology takes effect, as the product starts to cure it expands, fully filling and sealing the joints.


The weather conditions for application and drying are critical. Do not apply if frost is forecast, in wet conditions when relative humidity (RH) is above 85%, in temperatures below 5ºC or above 30ºC, and for a min of 24hr after application. Do not apply to elevations in direct sunlight, or to substrates which are hot or below 5ºC. The render must be protected against any rain, direct sun or wind in the first 24 hours after application.


All surfaces must be sound, clean, dry and free of any material which may impair adhesion.


Wienerberger parge should be mixed with clean water at a rate of approximately 9-10 litres per 25kg bag, using a suitable drill with whisk attachment. Mix for 5 minutes, allow to stand for 5 minutes then remix. This process allows the chemical additives to dissolve and activate.

Note: Parge may stiffen on standing. Re-mix the product to regain a workable consistency but do not add any more water. Parge has an open time of 3 hours.


Product is to be applied to the internal, room facing block work (both block faces & joints).


Using a soft-headed broom, load the brush with the product then work the product into the joints, ensuring the product is filled into the joints. Once the joints are filled and loaded, stroke the material out in a horizontal manner to cover the face of the blocks, this will flatten the surface out, ensuring a level surface is achieved.


Approximately 20sqm per bag. Note: These estimates take no account of wastage.

Packaging and storage

Eco-parge is supplied 25kg paper sacks; palletised (40) bags and shrink wrapped.  When stored unopened in a dry place at temperatures above 5°C, shelf life is 12 months from date of manufacture.

Quality control

All products are factory blended, tested and packaged to quality control procedure in accordance with BS EN ISO 9001 series.


Wienerberger can supply a range of lintels to suit your building needs which include Porotherm clay composite lintels. Please see below for more information on steel lintels.

Steel Porotherm lintels are designed as a two part system. A box lintel is built into the Porotherm system as the internal skin is built up, then the external leaf clips into place as the face brickwork is brought up at a later stage. Lintels are bedded on traditional mortar, but your tray will be installed on ZeroPlus.

A good tip is to roll the block and not the DPM, and then turn the block and lay it on top of the DPM. Please note that if the construction is to include gas or radon membranes, these should always be laid within a bed of traditional mortar.  


Watch the Porotherm fixing video

Many 'off-the-shelf' fixings are suitable for use with Porotherm, covering the complete range of light to heavy requirements.

Tips and advice articles

Read more about Porotherm clay blocks and how to use them

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