Question & Answers

The use of lime mortar is becoming increasingly common as an ecological alternative to cement based mortars. Designers are rediscovering the benefits of its use, not just for the repairs of historic structures, but also for new-build construction. There is an increasing amount of published information to assist the designer and Limetec also offer support through the design process to ensure correct specification and application of product. However, there are often certain questions raised regarding the use of lime mortar. To dispel any myths, typical questions and answers are detailed below;

Q1: Does it takes longer to lay bricks when using lime mortar?

A1: There is very little difference in the build rate when using lime mortar. The process is slightly different, but daily lift heights of 1.5m are achievable. The main issue that dictates speed is the quality required on the finished work. High quality projects rarely lay more than 300 to 500 bricks per man per day.

Q2: Is the mixing procedure more complex?

A2: The mixing time is increased to allow for full integration of the lime and water, but by following the guidelines from Limetec, the overall process time will be satisfactory.

Q3: Generally lime mortar is slow to set, does it lead to slow build rate?

A3: See question 1, the reality is that whilst lime mortar develops its strength more slowly, this is an actual benefit which allows the mortar to breath and be flexible, and does not reduce the build rate under normal working conditions.

Q4:  Is lime mortar is more susceptible to frost?

A4: In its hardened state, lime mortar is actually more resistant to frost damage due to its flexible nature. However, in its fresh state, protection must be given as is also the case with cement based mortars. (Refer to Limetec Winter Conditions guidelines)

Q5: Is it true you cannot use lime mortar in winter conditions?

A5: Guidelines for using lime mortar are not below 5C on a falling scale and 3C on a rising scale. Basically the same guidelines for cement based mortars. (refer to Limetec Winter Guidelines) It is possible to continue brickwork providing adequate protection is given.

Q6: Can cement be added to the lime mortar mix to speed up the setting?

A6: Under no circumstances should cement be added to a lime mortar mix as this will undermine any benefits used in the design / specification process.

Q7: Lime mortar is generally more expensive than cement based mortar?

A7: Yes, it is more expensive due to production cost of lime vs cement, basically down to volume of production. As more lime is produced, cost will reduce. However, as mortar takes up approximately 10% of brickwork, the cost difference is insignificant considering the benefits gained from using lime mortar.