Similarly, if you cover lime mortared bricks with gypsum plaster or certain modern paints, (like weatherproof masonry paint which is non-breathable), you’re disrupting that same natural balance and again, trapping moisture. You’ll often see this where the face of brick has crumbled away (known as spalling). Remember I said some bricks are softer than others? If you replace lime mortar with a cement mortar, not only will you be trapping that moisture within the building itself (as it no longer has an escape route), but it will also cause those softer bricks to deteriorate. In theory, this may sound great, BUT when combined with period materials or within a period home, it simply doesn’t work and instead, traps moisture within the building. The materials they’re built with, like cement, prevent moisture from getting in or out and are NON-breathable. They’re built with much harder bricks, they’re designed to be waterproof, highly insulated and with zero draughts. Modern houses are built very differently from period buildings. The Problem with Modern Cement, Gypsum Plaster and Damp Proofing Paints on Period Buildings Which meant, these old buildings did not typically have damp problems.Īny moisture within the building had an escape route. Those draughty windows and warm coal fireplaces acted in favour of this natural drying cycle and because of these breathable materials, water was never trapped within the building. It would enter the lime mortar (or render) and then evaporate right back out. External moisture too, such as from rain would do the same. To put this into context for you, it would mean any internal moisture from drying clothes or cooking, for example, would penetrate the lime plaster and then simply evaporate back out. A natural equilibrium and the ability for buildings to “breathe”. Whether that’s in liquid form, or as gas, it meant there was a balance of intake and evaporation. What seems like poor choices in a world of modern technology, was probably once upon a time, clever design ideas.Īnd that breathable lime I was talking about? It allowed moisture IN and OUT of the building structure. They had chimneys to house coal fires to keep the house warm, cool cellars for storing food and even the single glazed draughty windows provided the ventilation a house needed. When victorian houses were built, they were designed for that era. All lime-based products! And what makes lime special? It’s porous, making it breathable. As was the plaster, any exterior renders and even the paint. In period buildings, traditionally when it was built, the mortar was made from lime. Yes, it’s all mortar and it all holds your house together, but the exact ingredients and ratios might be different. Some bricks are softer than others and likewise, some mortars are softer than others too. A bit like card, paper and kitchen roll, so to speak. You’ve seen cottages built in a collection of various sized local stones right? And you can tell the difference between period bricks and modern bricks? These materials are all slightly different. Not all buildings are built the same way. Period Houses are Made with Different Materials I’ve also linked some great sources at the end of this post where you can find more information about damp/breathability in old homes. I know this may all sound like a bit of a conspiracy theory against damp-proofing – but I’m going to share what I’ve learnt over the years and hopefully, it will at least make you think twice about certain techniques and to weigh up the different opinions before jumping down the “we need to damp-proof X-Y-Z” route. I spent hours reading information from experts and watching YouTube videos calling out damp-proofing techniques that just don’t work in period homes. However, there is A LOT of free advice on the internet (not all good advice, I might add!!) and lots of different platforms you can learn from.Ībout 7/8 years ago when we were in the process of selling our previous home, my eyes were opened around the questionable work within the damp-proofing industry. So I thought I would write a post and explain why.īefore I start though, I just wanted to say that I am certainly NO expert when it comes to buildings or building work in general. One question I’ve been asked a few times over the last few months is how we’ll be tanking/damp-proofing the basement. We’ve made great headway, but we still have plenty left to achieve before it’s anywhere near usable down there. Renovations in our old victorian basement cellar have begun, and although it’s very slow progress, this is a project I’m so excited to develop! So far, we’ve stripped back the walls, opened up the fireplace and we’ve even added in a window.
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