Plasteringover the cracksin the UK’s social housing market

IntroductionQuick to install and cheap to buy, gypsum-plaster and plasterboard has become the go-to interior finishing of choice. However, this dominance has led to their perception as a one-size-fits-all solution. As such, they are often used ahead of more appropriate solutions despite their poor levels of breathability and a susceptibility to moisture ingress. This document will demystify some of the common misconceptions surrounding renovating plaster – a material once at the heart of the nation’s housebuilding process – and profile its benefits as a plastering solution for local authorities and housing associations responsible for maintaining significant quantities of ageing housing stock.

The social housing rental sector is one of the linchpins of the UK’s housing market, providing vital shelter to millions of residents across the nation.

Comprising of 3.9m properties across the UK, it currently represents 17% of all households nationwide (local authority: 7% and housing association: 10% ). Yet, with the UK’s population density rising, so too is the number of tenants currently living in social housing.

Worryingly, the construction of new publicly-funded social rental properties has rapidly declined since 2010. According to the National Housing Federation, 36,000 new social rental homes were started in 2010/11, however this number fell to 3,000 in 2011/12. In 2016/17, just 1,000 new homes for the social rental sector were started with government subsidies.

With just under three quarters of local authority housing stock, and nearly half of all housing association properties built between 1945-1980, a great strain is being placed on the sector’s ageing building fabric.

While steps are being taken to tackle these housing challenges, making a change to the specification and procurement processes of key building materials throughout social housing stock can significantly increase durability and reduce maintenance costs. Plaster is one such example, where a simple change to product specification could put an end to a long-lasting cycle of costly compensation and remediation.

Given the lack of a�ordable housing stock throughout the social rental sector, and in particular new-builds, families and young social housing tenants are having to live for extended periods of time – 11.3 years on average – in properties which were never built for the purpose nor occupancy level they are currently being used for.

Considering the age of much of the UK’s social housing stock, one of the biggest – and most well-documented – issues that can a�ect properties in this sphere is their susceptibility to damp, condensation and mould growth, with 6% of all local authority properties, and 4% of all housing association properties a�ected by the issue in 2016 alone.

Social housingstrains

Damp While damp can cause a number of aesthetic and structural issues for houses, it can also represent a risk to health, particularly for babies, children and the elderly, as well as those su�ering from respiratory conditions such as asthma. With over a quarter of social housing tenants over the age of 65, and over a third of properties in the sector home to children, damp represents a real health and safety red flag for local authorities and housing associations to be aware of.

Damp can appear in many forms, be it condensation, penetrating damp, or rising damp. Condensation is often visible on windows, and can be made worse by poor ventilation, heating or insulation. Penetrating damp stems from moisture coming through external walls or the roof, and can occur if there is a leak or plumbing issue. Rising damp is a particularly common problem for older properties, and occurs when moisture from beneath the building seeps into the brickwork and other building materials.

The presence of persistent damp could cause the property – or properties – in question to fail both the Decent Homes Standard, and the Housing Health and Safety Rating System (HHSRS). In such a situation, it would be the responsibility of the housing provider to not only cover the cost of the repair work, but also re-house the tenants in question for the duration of the remedial work.

With UK local authorities having paid out £35m on compensation and legal fees related to damp, leaks and damages from 2011-17 alone, it represents a significant drain on an already limited financial resource.

While factors such as insulation and glazing have been identified as contributing factors, one essential construction element which is regularly overlooked is plaster choice.

Plaster Pains

The majority of the UK’s post-war housing stock was constructed using traditional lime and cement-based plasters throughout these properties, largely to great e�ect.

One of the defining characteristics of a lime-based plaster is that, due the alkalinity and aseptic nature of the lime, it strictly inhibits mould growth – one of the most dangerous by-products of damp.

However, due to the rise in popularity of gypsum-based plaster – and its perception as a one-size-fits-all ‘wonder product’ – from the 1960s onwards, it soon overtook lime and cement-based products and became the plaster of choice. It has remained so to the present day, largely because one of the biggest di�erences between public and private sector housing, when it comes to construction and maintenance, is the specification process for building materials.

With housing association and local authority properties, building materials are by and large specified by the housing association or a procurement framework, rather than the contractor. Therefore, in the case of plaster, if any remedial work needs to be undertaken, the plasterer will often find that their materials have already been selected for them. In the vast majority of cases for the social housing sector, this will be a gypsum-based plaster.

However, one of the major product flaws of gypsum-based plaster is that it o�ers very poor levels of breathability, as it quickly absorbs and retains moisture from the surrounding atmosphere and substrate.

UK local authorities have paid out over £35m on compensation and legal fees related to damp, leaks and damages from 2011-17 alone

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Short of breath

It is this distinct lack of breathability which makes gypsum-based plaster highly susceptible to damp and black mould growth. Crucially, the problem is often exacerbated by local authorities or housing associations looking to make further cost savings, by attempting to cut energy wasted through heat loss.

For example, the increased use of double glazing and cavity wall insulation will improve the air tightness of a property. However, a by-product of this is a notable increase in condensation, which in turn creates further damp problems due to gypsum-based plaster’s tendency to absorb moisture. What’s more, the removal of air bricks has also hampered the breathability of older properties.

Treating damaged gypsum-based plaster is a lengthy and expensive process, with the plaster having to be removed, and the walls treated with a Damp Proof Course (DPC) before waiting for it to dry – which usually happens at a rate of 25mm a month – to receive a backing plaster. Crucially, if gypsum-based plaster remains on the local authority’s specification programme for remedial works, and is used again once the old plaster has been removed, then there is no guarantee that the problems will not return.

Ultimately, this is where local authorities and housing associations have both the opportunity and capacity to make a change; not just to their specification, but to the whole-life costs of their properties, and the living conditions of their tenants. Persisting with the use of gypsum-based plaster in ageing housing stock will do little to reduce the prevalence of damp, and will only serve to add further cost – be it maintenance or compensation – into a section of the UK housing market which is already under immense strain.

The alternative is for local authorities to switch their plaster specification for older properties back to a lime-based product, such as a lightweight renovating plaster.

Over a quarter of social housing tenants are over the age of 65

65+

Another supposed issue was drying time. On the contrary, a lime-based renovating plaster actually dries faster than gypsum-based plaster, and can be fully dry in just 24 hours. As such,

redecoration can commence the following day in most scenarios. What’s more, when it comes to repairing moisture-related damage, gypsum-based plaster cannot be used until the wall is fully

dry - a process which can take weeks. Even then, the risk of salts passing through newly applied gypsum can create e�orescence, and if the problem returns then the gypsum-based plaster will

simply break down.

Renovating plaster, on the other hand, can be directly applied to damp walls treated with a DPC, so there is no need to wait for the walls to be fully dry, and they can be ready for paint in a

matter of days. Salt inhibitors will also prevent discolouration further down the line. In real terms, this translates to lower levels of inoccupancy due to maintenance work.

As already touched upon, lime-based renovating plasters have fallen out of favour among housing association and local authority procurement frameworks.

Aside from the quick installation times and perceived cost-savings of gypsum-based plaster over renovating plaster, a number of misconceptions surrounding the latter have contributed to its decline. However, delving deeper into the facts around renovating plaster – coupled with understanding product developments linked to modern variants – can allay some of these misconceptions.

Short of breath

First and foremost, there was a perception that it needed specialist skills to install, over and above the level of even experienced plasterers. However, when it comes to renovating plasters, they can be applied in the same way as gypsum-based plasters, directly onto most sound mineral substrates.

While the skill of mixing and applying renovating plaster may have fallen o� the agenda of plastering colleges some years ago, it has slowly started to make an appearance in recent years. Ensuring young tradesmen are exposed to it at the start of their career can only benefit the wider industry as a whole. For experienced plasterers, a number of training courses and CPDs, including those from Tarmac’s Limelite team, are readily available to bridge the knowledge gap.

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Inadequate insulation was another criticism often levelled at renovating plasters. Again, this simply is not the case as renovating plaster can deliver a thermal conductivity value on average three times lower than gypsum-based plasters. This increased thermal e�ciency is due to the use of expanded Perlite, which improves the insulation properties of the wall – making it warmer to the touch – as well as reducing the density.

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One of the defining characteristics of a lime-based

plaster is that, due the alkalinity and aseptic nature of the lime, it

strictly inhibits mould growth – one of the most dangerous

by-products of damp.

A final point worth clarifying is around cracking and shrinkage. While this may have been an issue with past product compositions for renovating plasters, modern variants tend to include

synthetic fibres which can increase the cohesive characteristics – making the surface more resistant to wear and tear over the years - and prevent cracks from forming.

In short, lime-based renovating plasters represent a highly breathable plaster solution which delivers balanced moisture movement through the construction fabric. In turn, this breathability allows the substrate to dry naturally and prevents damp and mould growth.

While the balanced movement of moisture through the substrate will play a huge role in preventing damp from occurring, it is again worth noting that the aseptic qualities of a lime-based product will further curb the spread of mould and bacteria. Given the negative health impact mould can have, the value of this further barrier to its growth should not be underestimated.

Conclusions

Ultimately, given that most local authorities and housing associations are in charge of their own specification processes and procurement frameworks, making the change to a lime-based renovating plaster could make a sizeable impact on the amount of money spent on remedial damp problems, in particular those stemming from the use of gypsum-based plaster in older housing stock.

While maintenance budgets are often tight, the whole-life cost benefits of using a lightweight lime-based renovating plaster balance out its slightly higher up-front cost. Damp, and its associated complications, is not a new issue for the social housing sector. Yet its persistence is a real worry which, given the average age of the UK’s social housing stock, is likely to continue to remain a significant problem for local authorities and housing associations. The poor moisture handling ability of gypsum-based plaster is a key trigger for damp, and the only way to truly tackle the issue is to reconsider its use during the specification process.

Not only is making the switch to renovating plaster an accessible way for councils to save money in the long-term, it can also promote a safer and more comfortable living environment for tenants.

For stakeholders in the social housing market keen to make a change to their specification, it is strongly advised to approach suppliers who understand the challenges associated with this sector of the housing market and have an open and honest conversation about the most appropriate solution for their housing stock. Doing so will not only benefit the properties in question, but all the tenants who live there too.

Tarmac’s lime-based Limelite RenovatingPlaster has been developed for use in renovation projects, providing a modern, sympathetic solution to traditional plastering requirements.

The breathable nature of Limelite Renovating Plaster allows controlled moisture passage through walls, meaning it is ideal to use on traditional substrates, single skin properties and in areas that have previously su�ered from damp or flooding.

This breathability enables substrate to dry naturally, meaning Limelite Renovating plaster can provide a fast and e�ective long-term solution for damp remediation repairs in both domestic and commercial properties.

Limelite Renovating Plaster also incorporates polypropylene fibres to control shrinkage, reduce cracking and crazing, and improve the flexural strength of the finish.

The Limelite Renovating System, comprising of Limelite Renovating Plaster and Limelite High Impact Finishing Plaster, holds BBA approval as a complete breathable plaster system.

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Telephone: +(0) 3444 630 046

Email: limelite@tarmacbp.co.uk

Address: Limelite - Tarmac Building Products LtdInterchange 10Railway DriveWolverhamptonWest MidlandsWV1 1LH