Low-maintenance eco materials
For a building material to be truly green, it needs to offer more than simply being lowcarbon to produce. Nigel Griffiths looks at why longevity is a big part of the equation
To be truly sustainable, you need to consider the life-cycle impacts and costs of building products, says Nigel Griffiths
When you’re evaluating and deciding between different construction products, the whole life cycle (including manufacture, maintenance and disposal) should be a critical piece of the sustainability puzzle. So, if eco credentials are a top priority for your project, then the solutions you specify need to be durable and relatively low-maintenance if they’re to make a real contribution to achieving your goals.
The word ‘relatively’ is important, as we of course accept that some materials need periodic maintenance or even replacement. For example, painted timber window frames will need refinishing every few years in order to keep the timber protected, dry and free from rot – but they’re still a great option in terms of life-cycle sustainability.
One thing to bear in mind is that, when a material is described as ‘low maintenance’, it often turns out this means ‘impossible to maintain at all’. If you can’t repair an item, then it has to be replaced at some point – so the cost and environmental impact of doing this must be taken into account, and it may be much higher than you originally envisaged. PVCU windows are a good example: most builders don’t have the necessary tools or skills to repair PVCU, so when one component in a window breaks, it’s common to have to replace the entire frame and casement.
Here’s a quick guide to some of the materials that, used well, make an attractive choice for whole-life sustainability.
Masonry & render
I’m starting with this because it probably has the greatest impact of all our building materials. Across much of the UK, we still construct most of our new properties from leaves of masonry, and in general it needs barely any maintenance.
Today’s bricks are fired hard, and the cement mortar that binds them together is much harder than the lime-based versions that were used up until the end of the First World War. As a result, modern masonry is effectively waterproof (at least for above-ground purposes).
Lime mortar, by contrast, wears back over time due to the freeze/thaw cycle. It’s used alongside softer, more porous bricks, so water enters these units and finds the easiest path back out: the joints. In winter, when freezing occurs, the lime mortar wears back imperceptibly. So every 100 years or so, a lime-constructed building may need some modest repointing on exposed elevations.
As most people now know, it’s essential to repoint a lime-mortared traditional building with – you guessed it – a suitable lime mortar. Switching to cement products will block that passage of moisture, leading to decay in the adjacent brickwork. Inevitably, the new mortar falls out and in some cases the wall is ruined. The point here is that it’s crucial to identify the best material for the work at hand. As long as you do that, you should enjoy a low-maintenance result that will last for decades. If you’re keen to learn more about energy efficient masonry construction, see page 73.
Just like its mortar counterpart, cement render is a hard material. This means it’s prone to cracking, especially if it’s applied over a building that’s likely to move – such as a heritage property or a modern eco home (whether its constructed with timber frame, hemcrete or straw bale).
When cracks occur in cement render, they serve to attract moisture (by capillary action). This becomes trapped behind an impervious layer, leading to damp and associated damage to human health and the structural fabric. This is why lime render, which has the capacity to flex with the building, is preferred on both traditional and eco projects.
Try to use cement-based products in this kind of context, and they simply won’t last as long – which will become an expensive maintenance issue. In fact, it’s very common to see large sections of cement render missing where it has parted company from a different kind of substrate.
Some of the newer renders developed for modern construction have the colour mixed in, so damage doesn’t show up as easily and the repair is a single step process.
Timber
This is probably the next big-ticket item in most self build or renovation projects. Structural timber is normally located within the dry shell of a building, so shouldn’t need any maintenance at all over the property’s lifespan.
Keeping it dry is the essential part: treating timber won’t prevent rot if there’s a fault and it comes into prolonged contact with moisture in a poorly ventilated space. It may rot less quickly, but it will still fail. It’s not rocket science to get this right – we build timber homes all the time, after all, and they can last for decades or even centuries.
Wood is also regularly used to clad buildings – that is, to form a rain screen that prevents moisture penetrating into the structural fabric. Many types of timber can do this job with no treatment (boosting their eco credentials). Cedar, oak, sweet chestnut and many others are sufficiently rich in natural oils and, although they will silver quickly, they will not rot unless moisture becomes trapped. There are plenty of properties around with hardwood cladding which has lasted over 100 years but, even where it fails, the replacement of a rainscreen is not the worst job in the world, as long as the underlying structure is sound.
Moisture is not the only issue, though, as the sun can cause problems on southerly elevations. We have wider extremes of climate in the UK than you might think, and long periods of excessive heat can cause cupping or splitting of exterior cladding, depending on the design and method of fixing. UV rays can also break down any finishes applied. For this reason, painted timber cladding is a maintenance headache – so I’d recommend avoiding this if you can, even with modern paint technologies.
Some people worry about insects and timber, but this shouldn’t be a major problem. I’ve actually had issues with wasps when using unprotected softwood cladding – the creatures seem to enjoy using the silvered outer layer for building their nests. The resulting effect is a little unsightly (and bizarrely audible in nesting season) but it will take decades for this to lead to a need for any actual upkeep.
Internally, timber is superbly low-maintenance, especially if left unpainted. Hardwood flooring lasts indefinitely, which can’t be said of carpets. Even stains, scratches and dents can normally be easily repaired with a little sanding.
Roofing materials
The first principle of building is a dry hat and a good set of boots (ie to get the roof and foundations right). It follows that you want the materials that form the covering to be as long lasting as possible. For pitched roofs, natural slate or high quality clay tiles can easily last two centuries or more – but some modern equivalents are much less durable.
Except for repairing localised damage, you can’t really maintain a roof covering. So you just need to select the most durable products available to suit your design needs. This is especially important for flat roofs, which have a much shorter life and can often require attention within a generation. There is some evidence that metals can last longer than bituminous materials, depending on the thickness, reinforcement and protection, so always do the maths and don’t skimp on quality here.
Rainwater goods
Access prices (ie hiring scaffold) have risen sharply in recent years, as we’re all becoming more risk averse. The cost of getting up to guttering – especially on buildings beyond two storeys – can be many times the price of the materials needed for repair or replacement. With this in mind, it pays to select the best products you can.
Plastic is cheap, but it decays with UV light and becomes brittle. As a former builder, having put ladders up against many gutters, it’s clear that plastic has limited inherent strength and even less as it gets older. So I’d suggest you consider metal rainwater goods.
Copper and cast iron are expensive, but look fantastic. Galvanised steel can be a good middle ground: it’s more expensive than plastic, yet it doesn’t flinch when a ladder is leaned against it and is not affected by UV light. And when you take into account the cost of access, it’s likely that galvanized steel will deliver a saving in the medium term – as well as potentially reduce environmental impact. For more on specifying rainwater goods, see page 117.
Glazing
How many of us have had to replace a double glazed unit where the seals have broken down and moisture has condensed between the window panes? Whether glazing replacement can even be considered a maintenance activity is dubious, but given the cost and impact of this material, it’s really not something we should have to do.
It’s not that double glazing is inherently bad, just that poor quality windows are effectively unmaintainable. The same is true of the complex extras you can now specify, such as coatings, inert gases and integral blinds. These technologies can bring plenty of benefits, but most of them are impossible to repair if they fail. So look for products that are well-made and have good, long-term warranties attached – and make sure they’re installed correctly.
Paint & finishes
Repainting is probably the most common job people get involved with on a DIY basis. As a rule of thumb, high sheen (gloss) options are more durable than matt. In addition, oil-based finishes tend to last longer than water-based versions, but it pays to do your research carefully.
Early eco-friendly, low-voc paints lacked the durability of mainstream products – but technology has moved on considerably and they’ve caught up. Exterior finishes are also far better than they used to be, and microporous paints and flexible coatings can both add to durability.
It seems logical that the most long-lasting paint will be the easiest to maintain, but it’s worth thinking about whether a coating is needed at all. One area that gets a thrashing is skirting boards – especially if someone in the household tends to be a bit too enthusiastic with the vacuum cleaner. Hardwood skirtings don’t show these marks and an occasional (10-yearly) application of oil or wax is quite sufficient to maintain their lustre.
The low-down
Decision-making in this area is highly nuanced. You are comparing prices now with potential costs further down the line, factoring in maintenance cycles, and trying to work out the relative environmental impact of material production, along with that of labour and access.
What is certainly clear is that quality pays. So, buy the best you can afford, and your repair and upkeep bills will be lower in the fullness of time. Wherever possible, choose materials that simply need no maintenance at all over a very long lifespan, and you should be able to enjoy your (new) home safe in the knowledge that you won’t need to get the ladders, paintbrushes or chisels out any time soon.