What is efflorescence?

In chemistry, efflorescence (which means "to flower out" in French) is the loss of water (or a solvent) of crystallization from a hydrated or solvated salt to the atmosphere on exposure to air. Efflorescences can occur in natural and built environments. On porous construction materials it may present a cosmetic problem only (primary efflorescence), but can sometimes indicate serious structural weakness (secondary efflorescence).

Reference: Wikipedia

My paint cracks - what is wrong?

Cracking of paint can appear in several different ways. The most common occurs naturally as paint ages because the paint becomes too rigid to withstand the normal expansion and contraction of the surface. It also occurs when a top coat is applied to an undercoat that hasn't dried properly. Most paint cans list a recoat time that needs to be followed to avoid this problem. Alligatoring can also occur when more rigid paints, like alkyd or oil-based paints, are applied over more flexible paints, like water-based and latex.


What is lime?

Lime is a calcium-containing inorganic material in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. Historically used in buildings together with sand as mortar, renders, plasters etc.

Source: Wikipedia

What is cement?

Cement is a fine mineral powder manufactured with very precise processes. Mixed with water, this powder transforms into a paste that binds and hardens when submerged in water. Because the composition and fineness of the powder may vary, cement has different properties depending upon its makeup. Cement is the main component of concrete. It's an economical, high-quality construction material used in construction projects worldwide. Cement is made by grinding together a mixture of limestone and clay, which is then heated at a temperature of 1,450°C. What results is a granular substance called "clinker," a combination of calcium, silicate, alumina and iron oxide. 

What is a pozzolan?

A pozzolan is a siliceous or siliceous and aluminous material which, in itself, possesses little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties.[1] The broad definition of a pozzolan imparts no bearing on the origin of the material, only on its capability of reacting with calcium hydroxide and water. A quantification of this capability is comprised in the term pozzolanic activity.[2] Pozzolana are similar materials but only of volcanic origin

What is trass?

Trass is the local name of a volcanic tuff occurring in the Eifel, where it is worked for hydraulic mortar. It is a grey or cream-coloured fragmental rock, largely composed of pumiceous dust, and may be regarded as a trachytic tuff. It much resembles the Italian pozzolana and is applied to like purposes. Mixed with lime and sand, or with Portland cement, it is extensively employed for hydraulic work, especially in the Netherlands; while the compact varieties have been used as a building material and as a fire-stone in ovens. Trass was formerly worked extensively in the Brohl valley and is now obtained from the valley of the Nette, near Andernach.

What are the benefits of water glass / silicate?

Potassium silicates form an insoluble bond to the Ca compounds in the substrate. The reaction product can be as deep as 6 mm. This chemical bond gives a strong surface, while still damp diffusion open which allows breathing. Often used as binder in paints and as sealant for porous renders and other mineralised surfaces. Also used for consolidation of porous natural stone.

Why should I use a premix for my restoration project?

Premix products are produced with a thorough quality control. In big batches this ensures a stable quality in compositions and properties as declared in standards and control documents. This control makes it easy to trace production and recipes in all projects. 

What kind of masonry blocks are traditionally used?

Traditional masonry blocks are bricks in different dimensions and colours. The colour is a result of the clay composition and burning process. Other building blocks are natural stone (boulder, local shaped stone, transported or imported). Normally used stones are limestone, sandstone and soapstone due to easy fitting of the stone. Granite is often used for foundations. Other building blocks are unburnt clay, early concrete blocks, aerated calcium silicate blocks and light-weight aggregate blocks (e.g. Leca®). Also found is slag (residue) from local industry.

What is a mineral-based mortar?

A mineral-based mortar is composed of sand, lime and/or cement. It can also have additions of glimmer and pigments. Different composition and sand distribution gives different properties and uses.


What is damp proofing?

Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Damp problems are one of the most frequent problems encountered in homes.

What is cement-free water proofing?

Cement-free water proofing is damp proofing with the use of materials based on lime and/or other materials that can comply with a substrate that contains lime as a binder.

Why should I use lime-based products?

Lime is one of the oldest materials used for gluing blocks together to build a construction. Lime was used as a binder up until the start of the 20th century when cement overtook it as the leading material. Lime should be used in constructions where lime has been used originally to ensure corresponding flexural and compressional strength. But lime-based products can also be used in new builds. It has exceptional indoor qualities and yields damp diffusion open materials. Also see expertise. 

What is the difference between a mortar and a render?

Both mortars and renders are mixes of aggregates and different binders. When composing the mortar, the type and amounts of each component as well as the size and distribution of the aggregate are designed for a specific use. Generally speaking, a render is a mortar applied on a vertical surface. It has often higher workability than masonry mortar.

What is the difference between a plaster and a render?

Generally speaking, a render is a mortar used outside on a façade. A plaster is a mortar used inside on walls. Traditionally, many of the indoor products were based on gypsum (e.g. plaster of Paris), hence the name plaster.


How can I insulate my cold masonry building?

There are different ways of insulating your old building. Make sure that you comply with the national/regional regulations. Be also beware that outside insulation will change the easthetic appearance of the building. Indoor insulation is possible- but then be aware of changes in dewpoint in the wall. This can induce frostdamages on the outside. Be also aware of cold bridges in areas not insulated. There are a continuos development in insulating systems. Please contact your local Weber orgaisation to be fully updated on solutions and regulations.

Can I paint with acrylic paint on a limebased substrate?

No, you cannot paint with organic paint on a limebased substrate. Lime needs small amounts of damp and CO2 to maintain its properties. A dampdiffusion paint-system is necessary to obtain this and most organic paints do not compy with this. Some organic paints also need a hydrophob surface to get a good enough adheson. This hydrophobation will inhibit the necessary dampdiffusion openess. Organic paints will alo often trap moisture  and increase the risk of damages on the render. Organic paints will often crack and peel on these substrates.

How do I apply a lime render?

Lime renders are applied as normal renders. Follow information in product datasheets and traditional procedures. Reduce strength and particle size outwards to deal with capillarity and reduce tensions. Use mortars of the same quality as the original.

How do I fix a damaged run moulding?

Usually, damaged material is removed carefully. Using a prepared mould, new mouldings are built in thin layers - usually 10 mm per layer - forming the shape carefully. Reduce strength and particle size outwards to deal with capillarity and reduce tensions. Use mortars of the same quality as the original. If bricks are used as the core, these should be replaced if damaged.

How do I remove old paint?

You can remove old paint with the use of chemical treatment (products chosen depending on type of paint), sandblasting, limestone blasting or by grinding the surface. Be aware that many old organic paints can contain hazardous chemicals.

How can I mix my own lime mortar?

You can mix your own lime mortar with the use of hydrated lime as dry powder or as wet slaked lime. Use an aggregate with a particle size distribution adapted to your use. Follow product datasheets when mixing for mixing times (approx. 20 minutes), water demand and sand amount. Premixed lime mortars are quality assured and with few deviations in properties.

What kind of test methods could be used to identify a mortar?

The best way to identify a mortar specimen (binders and composition) is a mix of chemical and petrographic analysis. Be aware that specimens of a high age can have alteration products giving somewhat different binders and compositions than the original. The aggregates can easily be identified as the lime dissolves in acid. Petrographic analysis identifies the type of aggregates and the composition of the binders as per today. 

Can I work with limebased materials in cold weather?

The carbonation process stops at temperatures below 5 degrees Celsius. This carbonation process will not restart when temperatures increase if free water in the mortar freezes. The mortar/lime will be sandy. The carbonation process is long (approx. 1 mm per week from the outside surface), and the carbonation process of a normal thick render can be up to 2-4 months. The carbonation process is slower at lower temperatures and extremely high or low humidity.


What does preservation involve?

Preservation involves keeping an object from destruction and seeing to it that the object is not irredeemably altered or changed. The word preservation is most commonly used in relation to architecture and built environments

What does renovation involve?

Renovation simply means to make an object look like new. The object to be renovated is just a base or starting point for the client/designer’s imagination. The object, materials and method of construction, historical importance, or place in time are not critical. The object itself does not place restrictions on the work to be done.

What does conservation involve?

In conservation, the absolute maximum amount of the original material, in as unaltered a condition as possible, is preserved. Any repairs or additions must not remove, alter or permanently bond/cross-link to any original material. All repairs or additions must be reversible and removable without affecting the condition of the original material now, and in the future.

I have a protected facade- what do I do?

Get in touch with your local authorities or organisations to get help. Owning a protected building can give you rights to tax relief and financial help, but also rigid conservation rules. Your local Weber organisation can help with finding the right authorities to contact.