Hiding in Plain ‘Site’

Mortar made from a sand and cement blend has long been one of the staple products across the UK’s housebuilding sector. However, just because it is tried, tested and familiar, doesn’t necessarily mean it is always the best product in the long run. In fact, making small changes to mortar specification, can lead to significant cost savings for housebuilders, simply through using an often-overlooked material – cement lime mortar.

Here Iain Betts, an expert in mortar from Tarmac’s Building Products team, outlines the benefits of using a cement lime mortar that housebuilders may not be aware of.

Housebuilders are under greater pressure than ever before to deliver high volumes of affordable housing, with the government estimating that more than 200,000 new homes a year will need to be built to meet the demand. However, with the construction industry plagued by a number of issues, ranging from skills shortages to rising construction costs, how can housebuilders make the cost-savings needed to deliver ‘affordability’ without compromising on quality?

Mortar is often viewed as a commodity product that is interchangeable with minimal effects to the appearance and function of masonry. However, making small changes to such a high-volume material can transform a housebuilding project, with larger sites being able to magnify both the cost savings and performance benefits on offer.

Sand and cement mortar is generally perceived as a modern alternative to cement lime mortar, and is often specified due to its availability and ability to quickly set with a strong hold. However, it isn’t always the optimum choice, and can lack the flexibility and breathability required for long-lasting performance. For those housebuilders looking to make a real difference to their bottom line, moving away from the automatic specification of sand and cement mortar could provide the answer.

For starters, cement lime mortar offers an increased yield of typically 12-15 per cent over traditional sand and cement mortars, immediately resulting in significant cost savings for housebuilders. A greater surface area can be covered as the lime provides the optimum void fill of the sand present in the mix, and with a better bond created between bricks and blocks, there is greater durability for longer-lasting buildings.

The lime present in the mix also improves water retention and cement hydration, to deliver more precise contact between the brickwork and mortar. Similarly, it offers more effective resistance to rain penetration, wind and the subsequent effects of wetting/drying and freezing/thawing. This is thanks to the better bedding of bricks and blocks, correct filling of prep-end joints and maximum void fill which makes the bond created incredibly strong. Furthermore, its inherent crack control and self-repair properties mean it requires far less maintenance than sand and cement mortars. The breathability of a cement lime mortar also makes it less likely to trap moisture which can lead to a wealth of issues in the long-term including damp and the deterioration of masonry.

Using a cement lime mortar can also promote a higher quality finish than sand and cement variants, resulting in lower post-construction maintenance and repair work. This can also help ensure NHBC guarantees are not called into question.

For contractors, cement lime mortar is easy to use, aiming to minimise waste and provide ultimate strength to reduce both material and labour costs. In addition, the mortar retains its consistency to remain workable, completely filling vertical and horizontal joints in brickwork and masonry.

Finally, from an aesthetic perspective, there’s no doubting that a cement lime mortar can have a huge impact on the exterior of a property, ensuring it looks its best at all times. Some building components contain soluble salts that can reach the external surface, but lime-based mortars reduce the likelihood of this unsightly efflorescence as there is less water in the structure compared to a sand and cement mortar.

Moreover, mortars containing lime are more flexible, making them able to absorb the movement of buildings both during and post-construction as well as delivering autogenous healing. In general, lime-based mortar doesn’t tend to crack; yet if it does occur, it is more likely to be micro-cracking than the major cracking associated with more brittle sand and cement mortars.

In any building project, consistency is also key and opting for a factory-mixed cement lime mortar such as Tarmac’s Truspread, can guarantee quality and consistency irrespective of the delivery method, throughout every stage of the build. Tarmac’s Truspread is available in multiple delivery methods including Ready to Use, DSM and bagged.

Final Thoughts

Mortar is an essential element of any housebuilding project, no matter the size or scale. However, just because a housebuilder has always used one variant, does not mean it may be the most effective. Given the pressing demand for affordable homes across the country, housebuilders are having to look more closely at their margins to ensure they really can deliver ‘affordability’. Making a change to the specification of high-volume items, such as mortar, in favour of products which can deliver a greater yield or faster application times, is a sure-fire way for housebuilders to cut cost out of the construction process without compromising on quality. Change can sometimes be a difficult thing to action in the construction industry, but given the overwhelming demand for affordable homes, there really is no time like the present.