How Cement Destroys Old Buildings
Okay, that’s maybe a bit of click bait, but the title still stands true, cement can destroy older building materials.
I am going to talk mostly about stone built properties but the same principle stands for older brick and timber framed buildings.
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You may live in an area where stone built properties are scarce however, if you live, or have ever visited Yorkshire, you will have likely travelled through villages or towns full of stone built properties. We spend a lot of our time surveying older stone properties and advising clients on the most appropriate repairs and the most suitable preventative measures to undo the poor maintenance techniques of home owners that have gone before them.
It’s time people understood correct maintenance of these buildings to prevent unnecessary future repair costs.
The basic premise of these buildings is that the external walls were incredibly thick and designed in such a way that water ingress was to be expected. You read that right, they were designed to allow water to enter them.
But… water was only designed to enter roughly the outer third of the wall and natural evaporation would help to balance the moisture and prevent it reaching the inside face.
The Mortar used was made from lime. Lime is a softer building material and is designed to assist with evaporation from the external wall due to its breathability.
The evaporation taking place through the mortar joints helps to preserve the masonry.
Cement - The Reliance on Modern Materials
Working with Lime is difficult, expensive, and time consuming for modern contractors and in an industry that is currently booming, speed of installation equals more profit.
Cement is simple to work with, quick to install and readily available. All of which improve those all important profit margins.
Now, cement is great and has its purpose but it must be used on properties where low porous masonry is used. More modern properties use this type of masonry, and they’re designed in such a way that moisture is not absorbed like it is with older, porous stone properties. Therefore, cement is suitable because it has a similar porosity to the masonry that has been used.
These properties of cement are what damage older masonry that has a higher porosity. Essentially, the installation of cement does two things (1) it reduces the surface area of the external walls where moisture can evaporate (2) it forces moisture to evaporate from the stone face, rather than the mortar joint.
(1) The reduced surface area of the external wall restricts the evaporation area and can ultimately lead to damp inside a property (another blog, for another time)
(2) Mortar joints are sacrificial. They’re designed to need re-pointing throughout the building lifespan and because of this design, moisture evaporates predominantly from the mortar joints. Once cement is used, it completely changes this process so that moisture evaporates from the stone face and in turn, the stone starts to become the sacrificial part.
Additionally, we often inspect historic and traditional properties that are full or part timber framed. Over time, when repairs are carried out, cement rendered panels have been used in place of the original materials. This cement render causes moisture to become trapped and over time begins to cause decay to the timber frame.
As these properties contain load bearing timber, If left untreated, this can lead to significant structural issues.
The following image is taken from an inspection carried out by a nationwide leading historic building consultancy, Heritage House, a company that we occasionally work with, whose work we have incredible respect for.
You can see the well established decay on the timber frame caused by moisture becoming trapped by the inappropriate use of cement. This damage to the timber is irreversible and if load bearing capacity is weakened, the timber may need to be replaced, at the very least, expensive repairs will be required however, this gets even more complicated because where buildings are historically listed, complete replacement of timber is the bottom of the priority list.
You’ve all seen the Only Fools and Horses sketch with Triggers broom and it’s 17 new heads and 14 new handles. It’s obviously not the same broom that he originally had.
Now, we know that’s just a comedy sketch, but the principal holds true when dealing with historically listed buildings. The more we replace/repair, the more of the history becomes lost.
If there’s one thing you take from this blog, let it be this. Cement on an older building, will eventually turn your house into triggers broom!
If you want to get in touch about how we can help you maintain your older house, or for a survey on a property you’re purchasing, our contact details are below.
☎️ 0113 887 1941