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Great expectations

What are designers’ and building users’ expectations of a floor? And what ways do heritage floors meet or sometimes fall short of modern requirements? Richard Aylen explains.

IN a previous CFJ, I discussed the fundamental reasons for preserving our built heritage. I talked about some of the typical floor structures that will be found, and how they should be assessed and adapted. I talked about how older floor types often function as a ‘system’, and the importance of understanding how and why they work, before making alterations or replacements. This time I want to continue by looking at designers’ and building users’ expectations of the floor and the ways in which heritage floors can meet, or sometimes fall short of modern requirements.

Thermal properties
In historical terms it’s only quite recently our Building Regulations Part L introduced the need for thermal insulation in floors. Therefore, many older floors will be uninsulated. Our expectations of comfort levels are quite different today compared with the past, so let’s first look at thermal properties of floors. Today we heat our homes to around 22degC, but in the ‘50s for example, the average indoor temperature was nearer 18degC.

For some community and mixed-use buildings the frequency of heating and the internal environment may vary widely depending on the type and amount of use the building will be put to. A change of use can have an effect both on the performance of an old floor or may influence which types of replacement floor can be used.

Uninsulated floors may make a space difficult to heat to a satisfactory level and the feeling of a colder floor under foot may be less acceptable than in years gone by. This is more likely to be a problem if a large proportion of the room’s perimeter is bounded by external walls, and especially so if the floor area is small.

Suspended timber floors can be insulated relatively easily by removing floorboards and fitting insulation and a vapour check. For solid, ground-bearing floors excavation is required to accommodate the insulation, concrete slab and floor finish and this is usually a more onerous and costly task than dealing with suspended timber floors.

Concerns about the effect of cement and concrete on global warming may also make this option less desirable. It may be possible to reuse the original floor finish if it’s an elemental or modular type such as tiles or timber, and it can be taken up with minimal damage.

Maintenance procedures will usually be determined by the floor type and what the client is using it for. Assessing an older floor properly will avoid damage to a treasured part of the building or may highlight the need for protection or replacement. As an example, if the building is used for medical purposes or food preparation, the floor may need to be disinfected and it may not be possible to maintain old timber, stone or grouted tiled floors in this way.

Where buildings are refurbished and remodelled new external doorways may be created and where fragile or valuable floor finishes will be trafficked from the outside the designer will need to include efficient entrance mat systems to keep dirt and grit off the floor.

Hazardous materials
Perhaps the most well-known floor finishes containing hazardous materials are vinyl floor tiles and their adhesive, which can contain asbestos. These products were sold in large quantities between the 1920s and ‘90s. Specialist removal and disposal, and subfloor decontamination is required if these are to be removed. However, if a new floor is to be installed over the tiles, they can be left in place provided they are protected, recorded, and managed correctly. If older suspended floors are opened up, it’s possible pipes within the void may be insulated with asbestos lagging. This must be treated with extreme care as it’s often friable and if disturbed, fibres can easily be released into the air.

Technical properties
Older floors used for commercial purposes will often need to fulfil certain technical criteria for them to be suitable for the new type of usage. For example, in ‘clean’ areas where a dust free anti-static finish may be needed for laboratories or environment-critical products, old stone, tiled or synthetic floors may not be suitable.

Slip resistance can be an issue in areas where spillage or contamination will occur. Timber floors can often be coated with a slip-resistant lacquer to make them suitable. A valuable old floor may also become stained or suffer chemical attack if the new use for the building isn’t compatible with the original finish.

One of the greatest challenges when converting older buildings for modern commercial use is accommodating new services, eg, for power, air handling, data and the like. Underfloor voids and raised access floor systems are routinely used in newbuild projects. In older buildings suspended timber floors may accommodate services with relative ease but solid floors can be more of a challenge.

If sufficient ceiling height is available a raised access floor may provide a solution as it may be possible to install this on top of the original floor finish.

Adapting buildings for sports, dance or similar activities will often require a sprung floor of some kind – something an older floor is unlikely to provide. Fortunately, many activity floor manufacturers have a range of systems that can be used in a non-destructive way on top of the original floor with minimal height increase. Examples include the Junckers Clip system which provides a solid hardwood, fully sprung floor only 32mm thick overall, or the UnoBat 45 system, a battened floor which is only 45mm thick.

When a change of use occurs the life span of the floor may be reduced if foot traffic levels should increase. This may mean preserving and overlaying the floor with a compatible new finish. Strength and load bearing capacity must also be considered, for example if an older building is converted to an arts centre, museum, or gallery the weight of exhibits may be more than the floor has been required to bear in the past.

Modern demands may not always be able to accommodate the somewhat uneven surface that older floors can provide.

Settlement of the subfloor, movement of timber framed buildings, sagging or rotting joists or old repairs not being carried out properly can all result in an undulating floor, or one that’s not level.
Levelling and repair may be needed for functional or safety reasons. But that isn’t always the case. I was involved with a project in Georgian townhouse where the joist had sagged over the centuries but the client was happy with a characterful uneven floor, so the solid hardwood floorboards were screw fixed through the tongues to provide a new squeak-free floor finish.

The division of older buildings into apartments will often mean the floors on upper storeys will need to be upgraded to reduce sound transmission between properties. The Building Regulations Approved Document E takes a slightly more flexible approach for adaptations of existing buildings compared with newbuilds. If an existing building has never been used as a dwelling before it’s likely that some form of acoustic insulation will be needed.

Taking up the original floor finish to fit insulation or high-density infill materials can present challenges because any additional layers on top of the floor can restrict ceiling height and cause dramatic level changes at thresholds. Options may include overlay floor systems using acoustic underlays, often containing a mixture of high and low density materials such as foam and dense rubber sheets. If there are no further options to modify the floor it’s sometimes possible to fit an acoustic ceiling to the accommodation below.

One of the fundamental questions relating to heritage floors when new users move in is: ‘will it look right?’ Talented designers have a way of combining old and new interior styles in innovative ways and the floor, being one of the largest exposed surfaces, can be used as a feature around which other design ideas are created.

Some floors, such as hardwood are designed to be refurbished and this can present the opportunity to change the colour of the surface by using coloured oils or primers without affecting the integrity of the floor material.

A solid hardwood floor is often a favourable option for conservation officers in heritage buildings because timber floors have been a prominent feature of our built environment for so many years.

Stripping up any redundant floor will usually have an impact on global warming. This occurs on several levels, including the energy and plant used for removal and replacement. The new finish will consume raw materials, highlighting the importance of using sustainable materials with low embodied carbon. The effect on global warming could partially be offset if the old floor finish can be recycled, or better still, repurposed for use in another location.

When it comes to disposal of the old floor, some products can be recycled or reused, but other types, such as synthetic finishes will normally go to landfill or incineration. It’s interesting to consider many traditional floor finishes such as wood, stone, tiles, and the like are far easier to repurpose or recycle as they’re made from non-hazardous materials with a basic composition.

The current popularity and relatively high prices paid for reclaimed building materials indicates that designers relish the opportunity to use these materials. One suspects they’re unlikely to feel the same about old floors containing plastics, resins and more complex manmade materials.

Within the construction industry attitudes towards sustainability are increasingly influenced by current policies such as the RIBA 2030 Climate Challenge – a set of targets adopted by UK architects aimed at reducing global warming.

There’s also a growing number of construction industry initiatives through larger main contractors and other interest groups to promote a circular economy, reduce carbon emissions and waste. In this context removal of the old floor and disposing of it would seem to be a last resort.

Historical value – what will the conservation officer allow?
The conservation officer may insist the floor has to remain fully intact or allow some limited repair or refurbishment. Depending on the historical value of the floor it may sometimes be taken up and re-laid if work to the base is required.

Where a floor is to remain the conservator’s aim is often to repair and preserve rather than full restoration. Restoration often implies the floor will be brought as close as possible to ‘as new’ condition, or at least a degree of improvement beyond what is actually defective.

This can therefore include replacing elements that may not actually have failed… this can even mean not bringing an old building up to full thermal insulation standards if it would mean removing or altering original floor structures. Conflicts may arise between the building owner’s needs and the wishes of the conservation officer.

When failed parts of the building need to be replaced conservators sometimes prefer modern interventions to be visible to achieve a level of ‘honesty’ and to reflect the fact the repairs are part of the building’s history. This isn’t a new concept and is often visible in the ways buildings have been extended or repaired in the past; the style of each alteration reflecting the era in which it was made.

Aesthetically it may be more acceptable to have visually contrasting finishes rather than trying, and possibly failing, to achieve an exact match. With stone and wood floor finishes, especially for prestige buildings, an almost perfect match can be achieved if the same species of wood and surface finish is used, and for stone repairs it’s sometimes possible to obtain new stone from the same quarry that was used by the original builders centuries ago.

In my previous column we looked at how some older floor structures were designed and the ways they can be adapted for modern use or protected from damage. This time around I’ve looked more deeply into how the client or building users’ needs can be met. Even though a floor can be repaired and made good it doesn’t necessarily mean it’ll be fully suitable for its new purpose.

What I hope I’ve shown is when dealing with floors in heritage buildings, it’s crucial not only to fully understand the design and condition of the floor, but to understand the clients’ needs and the impact of the way it’ll be used and maintained.
Richard Aylen is technical manager, Junckers

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