From springy floors to creaky boards, timber floors can throw up a whole host of problems, both major and minor, during a renovation. Ian Rock investigates

One of the great joys of a renovation project is peeling back an old carpet to discover an original floor underneath that’s crying out to be restored. Even homes built as late as the 1960s and ’70s may harbour pleasant surprises such as pine floorboards with potential for stripping or, better still, hardwood parquet flooring gracing hallways and reception rooms. But old floors can, of course, also sometimes conceal less delightful surprises.

The Quick Read

  • Old homes may possess timber or solid (tiles laid on bare soil, or concrete) floors — usually a combination of both
  • A lack of ventilation beneath a timber suspended floor and/or damp can be major causes of problems
  • Excessively ‘springy’ floors (think ornaments vibrating with passing steps) could be a sign of a structurally unsound floor — investigate it early on in renovation work

Solid or Timber Floor?

In houses of all ages, the floors upstairs generally comprise some form of timber joist and board construction. From the 1970s, chipboard panels started to replace softwood boards, which in turn had superseded earlier hardwood. But when it comes to ground floors, these might traditionally have consisted of little more than a few flagstones or bricks placed directly over the soil.

The Victorian era saw the widespread introduction in mass housing with suspended timber floors, alongside rudimentary solid floors in hard-wearing areas such as kitchens and hallways. This winning combination persisted well into the 1930s, with solid concrete predominating throughout the second half of the 20th century, until the advent of the modern ‘beam and block’ suspended concrete floor in the late 1990s.

Of these floor types, the one which tends to give surveyors sleepless nights is the suspended timber variety — largely due to the potential risk of fungal decay and beetle infestation, which in extreme cases can lead to collapse. So it’s worth taking a moment to reflect on how these floors were built.

A typical example might comprise joists supported every 1.8m or so resting on timber wall plates over brick ‘sleeper’ walls or posts (known as piers). Joists might be sized about 200x50mm and capable of spanning around 3.6m without support. To reduce the risk of damp and timber decay, a good flow of air under the ground floor is important, so short brick sleeper walls were built in with a ‘honeycomb’ pattern; the gaps allow air to circulate. The air enters via small vents or airbricks sited in the lower walls.

Repairing Floorboards

One of the most common defects (and one of the most annoying) is the odd loose or creaky floorboard. Probably the worst offender is notoriously ‘squeaky’ modern chipboard, although this usually just needs screwing down to remedy the problem. However, before reaching enthusiastically for the toolkit, bear in mind that concealed pipes or cables may run beneath the surface; a metal and cable detector is a wise investment.

One of the most common causes of creaking is where floorboards have been cut and lifted up (usually to run central heating pipework within the floor), but have not been properly supported when repositioned. To secure the loose end of a floorboard, a new batten should be screwed alongside the old joist, extending it under the unsupported board which can then be firmly screwed down on top.

Boards also sometimes warp. The surface of twisted boards can be levelled by planing or by using a floor sander, once the original nails have been driven well below the surface. Do note that woodscrews are more effective than nails at pulling a board back against its joist.

Floorboards in most old houses will also likely show signs of past woodbeetle activity. Although normally superficial, in extreme cases wood-ridden boards can become soft and collapse underfoot, so the odd length may need replacing. Weakened or damaged boards can also be reinforced with a length of new board fixed underneath, spanning between the joists.

Excessively ‘Springy’ Floors

In most suspended timber floors a small amount of spring is normally apparent, particularly in upstairs rooms. However, excessive springiness – for example where nearby furniture and ornaments vibrate as you walk past – can be indicative of more serious underlying problems, and there can be many a cause too.

Some defects date back to the time of construction. In cheaper period houses or in poor-quality modern extensions the joists may be undersized or unbraced, where the original builders skimped on materials to save money. Similarly, the joists may be spaced too far apart, or the span might be a little too ambitious.

Most commonly, however, the cause is down to more recent botching — where joists have been weakened by deep notches cut in them to run pipes and cables. The basic rule for cutting is that notches should not exceed one-eighth of the depth of the timber and electric cables should be run in small holes drilled more or less centrally.

Other causes may be down to the removal of load-bearing walls underneath, leaving joists unsupported, or the timber may have been weakened by beetle boreholes or the rotting of joist ends.

Springy upper floors in older houses could also be due to old structural movement where walls have bowed out and parted company with the joist ends. With ground floors, the joists rely more on sleeper walls or brick piers supporting wall plates underneath, and these may have settled or are insufficient in number for the span.

So what can be done to remedy this issue?

Where floors suffer from being overly springy and weak, they can normally be stiffened by wedging blocks of wood known as ‘noggins’ inserted between the joists. Fitted at right angles these should brace the joists either side to stop them moving sideways and ‘flexing’ (typically there are two lines of noggins about 1.5m apart crossing a room, or at least one at mid span). Where notches have been cut for pipes, joists can be stiffened by attaching straps or metal plates alongside.

In severe cases it may be necessary to strengthen the floor by installing additional joists bolted alongside the existing ones. If the joists are too few, then one can be added in-between each existing pair. For added strength these could be wider than the originals (or deeper, if you don’t mind replacing the ceiling). Or you could perhaps install a substantial supporting beam – or a boxed-in steel – at mid span under the ceiling below.

If the cause is due to supporting walls having been taken out, urgent structural repairs are likely to be needed and a structural engineer consulted. Defective or missing sleeper walls or brick piers under ground floors will need to be rebuilt or strengthened.

Where main walls have bowed out, steel ‘shoe’ joist extenders can re-establish the connection between the joists and the wall. Alternatively, joists can be tied back in and strengthened by inserting steel ‘helical bars’ through the wall from outside and bedded in resin.

Rotten or Infested Floor Timbers

Soft, spongy floorboards underfoot in one or more areas and damp smells are typical symptoms, and common weak points include the sides of chimney breasts or by the main entrance doors where damp has been allowed to penetrate over time.

But the most common cause of decay or woodbeetle in timber ground floors is due to dampness aggravated by a lack of subfloor ventilation. In Victorian houses the joists were traditionally built into pockets in the main walls; so if walls are persistently damp the joists can eventually start to rot. This is particularly the case in locations very exposed to wind and rain (or leaks), where pointing is badly eroded, or where inappropriate modern cement mortar has trapped damp in old solid walls. Even where the joist and wall plates don’t touch external walls, debris may have fallen down and bridged the gap.

Suspended timber floors to kitchens and bathrooms can be particularly at risk from hidden plumbing leaks and condensation behind fitted units, too. Other sources of damp include defective water supply pipes run in from the street under the house.

There may be an insufficient number of airbricks for air to flow freely under ground floors, or the airbricks may have been sealed or rendered over in a misguided attempt to prevent draughts. A lack of ventilation can permit a build-up of dampness, eventually leading to fungal decay and woodbeetle attack. Where the house has an extension or conservatory with a modern concrete floor, there should be ventilation ducts extending through the new floor to the new outside wall.

To remedy the problem, begin by lifting boarding over joist ends or spongy areas, checking their condition and resolving the cause of any damp. Rotten wood should be cut out and remaining timbers treated. Once dried out, new treated timbers can be fitted. Joist ends in walls should be protected with a DPC (damp-proof course) or new joists hung from steel hangers.

Clear any blocked airbricks, replace damaged vents, or fit additional terracotta or plastic airbricks. Where an extension has blocked off old airbricks, it may be possible to improve airflow by fitting ‘periscope’ vents channelled to the exterior.

Sloping Floors

In older buildings it’s not uncommon, with time, for floors to slope in tune with settlement of the main walls, and this is not usually a concern. Sometimes large gaps are also evident to skirting boards, or there’s a pronounced unevenness or a hump in the floor.

Internal walls that support floor joists often had little in the way of foundations and may have settled more than the main walls, or joists may have warped under the weight of heavy furniture over many years. Where a floor surface has a distinct hump or ridge, it may be due to the joists having settled either side of a supporting beam underneath (e.g. a new steel).

If the settlement is old, no attention may be necessary. Otherwise, repairs are the same as those for springy floors, with noggin bracing struts fitted between the joists and with the screwing down of any loose boards. Humps in the floor are not normally a serious problem either, but can be improved by lifting the boards and packing the joists to make them level.

Image: iStock

Ian RockAbout the Author

Chartered surveyor Ian Rock is director of the survey price comparison website and author of the Haynes Period Property Manual.

Image: John Lawrence

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