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HELUZ winter mortars and masonry foam extend the building season

Nov 7, 2019

The air temperature during winter mortar processing and setting must not drop below -5 ° C

The first frosts are over this year, but the building season doesn’t have to end. It can be extended with HELUZ winter mortars designed for masonry blocks at temperatures between -5°C and +15°C. Likewise, HELUZ system masonry foam, is suitable for cold days, where moisture isn’t transferred from the binder to the bricks, as unlike traditional lime-cement mortars, water isn’t present in the binder.

Laying cement mortar bricks should be carried out at temperatures from + 5°C upwards and vice versa in frosts lower than -5°C it’s prohibited. But what can we do in the mild part of winter, when average temperatures between zero and + 5°C can be expected? HELUZ offers so-called winter mortars for masonry during winter (i.e. usually between November 1st, and March 31st) – they’re winter options for all HELUZ mortar mixtures, i.e. SBC thin-layer full-area mortars, SB thin-layer mortars, then also mortars for foundation, and TREND mortars, as well as the classic M5 masonry mortar. Bags with winter mortar are supplied in the same packaging as traditional mortars, except that they have a dot print printed on the side, in addition to the manufacture date, with the wording "winter to -5°C".

Another possibility is to use the HELUZ system walling foam in the winter to prevent moisture transfer from the binder to the bricks, as unlike conventional lime-cement foams, the foam doesn’t contain water. Masonry bricked with PUR foam achieves smaller masonry strengths, therefore it’s not possible to replace thin-layer mortars with foam without consulting the designer.

It’s possible to continue indoors in a closed building

“If it is only possible on construction sites, we recommend that you wait until the spring for masonry such external walls, exterior render or concreting the ceiling. It’s possible to work on constructions that are tempered,” recommends Ing. Zuzana Hejlová, the authorised HELUZ statistician. If the building is already "closed" in winter, it means that the walls are bricked up, the ceiling is finished and the building openings are covered, then the temperature inside the building doesn’t usually drop below +8 °C and therefore it’s possible to continue building work. Masonry work such as partition walls, interior plaster, etc., can be carried out” adds Ing. Zuzana Hejlová. 

The following principles must be observed for masonry in winter:

  • The material must be protected against adverse weather conditions. Unpacked brick pallets, individual chimney products and mortar bags must be stored dry at temperatures above -5°C, i.e. in covered warehouses. HELUZ masonry foam must be stored at least in a tempered building cell, as the temperature of the foam container itself must be above + 10°C (but also below +30°C).

  • When bricked, there must be no frost or snow on the bricks, nor must they be dusty or otherwise contaminated. All masonry materials must be dry and the bricks mustn’t be soaked during masonry (it’s recommended to soak the bricks from +10°).

  • The air temperature during mortar processing and setting must not fall below -5 °C. If winter mortars are processed at temperatures above 0 °C, it’s not necessary to pre-heat the mixing water, when bricking under freezing point (i.e. from 0°C to -5°C) it’s necessary to warm up the mixture water to 30°C. At the same time, winter mortar limitations are that they can be processed up to a temperature of +15 °C (it’s not possible to brick during the summer with so-called winter mortars).

  • Freshly bricked masonry must be protected from weathering (rain, snow, etc.) with a waterproof foil and the temperature must not drop below -5°C within 14 days after masonry. If polystyrene is stacked without joints under the protective foil around the entire wall in min. thickness 5 cm, the temperature can drop briefly to -10°C. This means that at temperatures below -5°C the masonry should no longer be lined with cement mortar and a more favourable forecast should be awaited.
  • A period of temperatures below +5°C isn’t included in the necessary technological break before static load of the masonry or before plastering (i.e. the technological break must be extended by this time).

  • If the building is already "closed" for winter, i.e. the external walls are bricked up, the ceiling is finished and the building openings are covered, then the temperature inside the building doesn’t usually fall below +8°C and building work inside the building can continue. The masonry works can be carried out, for example, masonry partition walls, interior plaster, etc.

  • Any underestimation of winter temperatures can lead to additional costs. When working in winter, work is slower, it’s also more difficult to maintain quality building work and it also affects the final amount of deformation of structures due to volume changes (such as shrinkage, expansion, creep). Especially for the magnitude of strain due to temperature changes, the initial temperature of the actual masonry or ceiling performance is decisive. The lower the application temperature, the greater the likelihood of cracks, either in the plaster or even in the structure itself.

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