Choosing the Right Materials for a Period House Renovation

When it comes to undertaking a period renovation and bringing an older home into the 21st century, you will most likely be aiming to improve thermal performance and the home’s overall efficiency while keeping its attractive and characterful features intact.

A big part of this is respecting the charm of the original property by ensuring your material choices sit seamlessly in the building fabric and do not disturb the initial foundations or structure.

Traditionally constructed houses were often created from soft, permeable and flexible materials – typically earth, lime or clay mortars and plasters binding soft bricks, stone or timber. So, when renovating a period home, you should try to replace like-for-like. However, this isn’t always possible or practical.

Here, I’m going to explore which materials could work well for your renovation – from insulation and render, through to windows and rainwater goods.

Upgrading the Building Fabric in a Period Renovation

>Walls in older homes are designed to breathe – they draw moisture in and then allow it to evaporate in a balanced cycle. So, specifying permeable materials is crucial to maintaining this ecosystem.

“It’s often better to use natural insulation up against the wall and cover this with a steel mesh,” says Matt Aitkenhead, managing director at Stonewood Builders. “This enhances thermal performance and keeps the wonky character of the wall.”

Materials like sheep’s wool, woodfibre, hemp, cellulose and cork are hygroscopic – meaning they absorb moisture from the air in the home. So, these materials attract any water that is lingering in the atmosphere to keep your home healthy while maintaining their good insulation levels.

Natural spray insulations, like Corksol’s Spraycork, can be applied directly to external or internal walls with minimal wall build up – and it’s through-coloured so acts as the final finish on the outside.

“The application method means you lower the chances of thermal bridging, too, as you can spray the insulation right up to window reveals,” says Joff Ward, MD at Corksol.

Corksol’s spray insulation provides a breathable thermal and acoustic barrier

Using natural, breathable materials helps maintain a healthy living environment, as you’re preventing condensation and damp from building up.

You could use modern, rigid insulation boards, but you must leave an air gap of around 5mm so that the original wall can still breathe and perform as it was meant to. Place the boards too close and they’ll absorb moisture from the wall and trap it, which can cause damp and mould.

This route will typically be cheaper but it will leave you with an inauthentic but easy-to decorate smooth surface. Just bear in mind this will mean losing some of the character of your period property.

Up in the attic, insulation boards can work, so long as you ensure there’s a breathable membrane between them and the roof. “If you insulate too tightly and don’t allow for ventilation, you can end up with condensation building up behind the boards, rotting the rafters,” says Matt.

In serious cases, this can result in structural failures. Natural options like Thermafleece sheep’s wool can help mitigate this risk.

Natural insulations, like Thermafleece, are ideal for upgrading a period property as they wick away the moisture and keep a healthy environment indoors

Warm floors are key to feeling comfortable in your home, which is why we love underfloor heating so much. But floors in heritage homes tend to be inherently cold and draughty. Luckily, suspended floors can be insulated fairly easily – just drape a breathable membrane between the timber joists and fill the spaces with natural cellulose.

Solid floors are a bit trickier. “Avoid the urge to use a cementitious screed as this will push moisture to the walls and lead to rising damp,” says Matt. “Instead, foam glass aggregate with a lime-based mortar is a breathable method that allows moisture to escape. Plus, you can still embed UFH into it for a cosy ambient temperature.”

This is more time-consuming to dry out, and expensive to lay, but will help you avoid structural issues by allowing the house to breathe as it was designed to.

Deciding on a heating system for your self build or renovation? Choosing Between Radiators and Underfloor Heating

Foamed glass aggregate has been compacted here to form an insulated, breathable sub-floor

Read More: Home Insulation: Best Ways to Reduce Heat Loss & Stay Warm

Using Mortar, Render & Plaster in a Period Renovation

If you need to repoint or re-render any damaged walls, try to match the materials already there as closely as possible.

A lime mortar mix is much more suitable than cement. “If you use harder, modern materials, moisture will seep into your original bricks or stones, with nowhere to go,” says Matt. “This can result in cracks as the materials expand – the water needs to go somewhere.”

Lime putty products are among the best options here, and can be bought mixed and ready for use. Hot-mixed mortar needs to be blended on site (which does need a little consideration from a health and safety perspective) but it’s easy to work with and performs really well.

“If you’ve got a particularly attractive exterior, like original stonework, you might not want to alter the appearance too much,” says Joff. “However, if you’re planning on using external wall insulation anyway, something like Spraycork is through-coloured, so can double up as the render finish.” It also offers the textured wall effect that’s a staple of many period homes, so you keep that character.

More Inspiration: Follow this Real Life Period Renovation

Architectural Bronze Casements supplied stunning heritage look windows to this thatched property

Natural plasters like lime and clay-based ones are your best bet to maintain the balance of moisture as this allows the walls to breathe. “Consider using lime-based paints, too – though this will need more coats and time than modern emulsions,” says Matt.

Conversely, modern vapour-closed plasters and paints will seal moisture in the wall and can result in damp issues and bubbles forming. Limewash paints can be a cost-effective way to get the mottled look, and modern versions come in a variety of colours.

Specifying the Windows for a Period Renovation

Where possible, it’s better to repair surviving original windows, rather than ripping them out and starting fresh.
The wooden frames used for properties built prior to the 20th century are usually high quality and very durable but have been neglected over time – a competent joiner should be able to tell you if they’re salvageable.

Metal units are notorious for thermal bridging, and in some cases you won’t be able to replace single glazed windows for double glazed – such as in a listed building – but secondary glazing can normally be installed inside to keep the warmth in.

If you’ve got poorly performing plastic units, then replacing these with modern timber, metal or PVCu ones that have been designed for heritage homes is a good option.

“Our timber alternatives look like flush wooden frames, keeping the property’s charm intact, but with barely any maintenance and exceptional thermal and acoustic properties,” says Jo Trotman at The Residence Collection.

The Rooflight Company’s Amy Cole adds that “the aesthetics of original Victorian cast iron skylights can be achieved without sacrificing on energy efficiency.” Their Conservation Rooflight has been designed specifically with heritage homes in mind.

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