David Gunton's Hardwood Floors, hardwood flooring, parquet, marquetry and boards, especially wideboards, in oak, ash, maple, beech, walnut, cherry, and many other woods.
David Gunton's Hardwood Floors.
Grange Lane, Winsford,
Cheshire, CW7 2PS
Tel: +44 (0)1606 861 442
Fax: +44 (0)1606 861 445
wideboards@gmail.com


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Fixing Methods

By David Gunton.


Awarded 1999

The Worshipful Company of Carpenters Special Award in Recognition of Outstanding Achievement in the Restoration, Re-Creation, New Design and Quality of Craftsmanship at Windsor Castle.

Introduction to fixings.

This section deals with the hard mechanical fixings of parquets, marquetries and boards. There are also numerous other fixing methods involving adhesives, clips and 'snap-click' moulded tongues and grooves which will be dealt with in another article. Mechanical fixings may be utilised in conjunction with other fixing methods. The following are merely explanations of the application of each type. Techniques for the perfect application of each fixing are not explained lest you fall asleep before finishing the article.

Pinned Parquet and Marquetry.

The pins in parquets and marquetry are placed during fitting to hold the parquet battens firmly in place until the adhesive cures. Once the adhesive has cured, the pins serve no useful purpose. Therefore, if it possible to lay the parquet without using pins, they should not be employed.

There are circumstances where the floor layer will wish to pin because he is obliged to kneel on new laid parquet which might otherwise slip in the yet to set adhesive. Panel pins were commonly used and the writer does not look back longingly to the many days spent on his knees and elbows, placing, punching and filling thousands upon thousands of pins in many floors.

Today, air fired pins have replaced hand placed pins. Some air fired pins are very fine, headless and are automatically punched 2 or 3mm below the surface.

Punching down of pins.

The sanding process of old parquets and marquetries sometimes exposes some, most, or all of the pins that were used when the parquet was fitted. The sanded pinheads show shiny and visible or the filler that covered them is loosened and comes away during vacuuming. Many customers choose to have the heads punched home and the holes refilled. This is a long-winded and tedious process carried out by hand.

The pins are punched with a fine-headed socket punch. This has a head only very slightly larger than the shaft of the pin. The punch head has a shallow socket depression that helps to accurately locate the exposed shaft and prevent slippage of the punch. The larger the punch used, the greater and more visible the resulting hole.

The sanding process sometimes exposes the pinheads. If not punched and filled, they remain visible as a tiny polished steel head - frequently 6 or more to each batten. Visually, they do not offend in old parquets, being part of the aged character. Nonetheless, many customers prefer them punched and filled. However, this activity should only be carried out providing it does no harm to the floor, and great harm can be done to very old parquets by punching pins.

Most parquet is fixed with steel pins. Steel pins corrode. They corrode in most timbers because it is their natural behaviour to react with even the tiny amounts of water and oxygen they may be exposed to over the decades of changes in moisture content of the timber. In oak - the most common parquet timber - steel corrodes in reaction with chemicals in the oak. Corrosion causes several effects. There is expansion of the diameter of the pin. The corrosion binds the pins very firmly in the oak from the expansion and from the 'gluing' effect of the rust. Punching down corroded pins, so that they disappear and can be filled, can do more damage than good. Oftentimes, the parquet splits around the nail. Until around 1950, parquets were fitted with brittle adhesives made from animal bones. Sometimes the shock of the hammer blows causes shearing of the glue line. The batten then lies fixed to the sub-floor only by its pins - and sometimes not even by them if the parquet is worn or sanded thin and the pins have been punched through the remaining thickness of the batten. Over time the loose battens will curl, split under foot traffic and generally wear badly. Therefore, leave well alone if this type of damage is likely to occur.

Nailing.

Parquet and marquetry should never be nailed, but nailing of board floors is historically correct, even of some hardwood floorings, particularly of wide boards. However, though softwood boards of 125mm width and greater have commonly been face fixed with nails, it is my opinion that hardwood floorings do not look attractive when fixed with nails through the face if the board width is less than 150mm. Boards narrower than this should be secret nailed through the tongue. If a face fixing is necessary due to unusual atmospheric conditions or poor sub-floor, then drilling, countersinking, screwing and plugging should be employed.

Until someone invents a round head nail with an attractive head, modern nails continue to look ugly. I have seen a number of narrow strip floors fixed through the face with shiny round lost head nails. These are an abomination! Worse, the fixers do not even take the trouble to neatly line the nails through across the boards, so the nail heads appear to stagger drunkenly and irreverently across the floor. (This was - and maybe still is -a very common method of fixing in Australia. I will be interested to hear from Australian flooring contractors as to why this is so. What's going on over there, cobbers?) Round flat head nails do not even bear discussion. Use of these to face fix hardwood flooring is a travesty.

However, there has long been a tradition of fixing wide boards through the face with mild steel cut brads which copied the style and shape of earlier blacksmith made nails. Blacksmith made nails can still be bought at vast expense. For more modest prices, those bought today from builders' merchants are stamped out of mild steel sheet, but they perform well enough.

As a result of this long tradition, we have become culturally accustomed to regard as attractive, or at least, aesthetically acceptable and 'authentic', the sight of the rigidly oblong heads of mild steel cut brads showing their presence in the face of wide board floors. In the Georgian and Victorian period, in quality floors, these were punched below the surface, the resulting hole being filled with glaziers' putty or coloured carnauba wax.

Until the 1950's hardwood joists and dense virgin grown softwood was used for joists. The timber immovably grips mild steel cut brads when driven into hardwood joists. In oak joists, iron nails corrode and become glued by the iron oxide to the timber. Traditional cut brad nails driven into dense softwood will also hold well, particularly if they become slightly corroded.

Since the 1920's many softwood board floors, and now chipboard sheet floorings, have been fixed with smooth, slender shanked, round lost head nails into softwood joists. These nails do not hold well. Even cut brads do not hold well, particularly because they have an elongated wedge shape. They create a wedge shaped socket in the wood. The softwood is plantation grown, lacks density and does not grip the nails firmly forever. Once the nail becomes loosened it never recovers its grip on the socket. Boards fixed with nails above softwood joists eventually work loose and begin to creak. Hammering the nails in further will sometimes improve things for a short time, but eventually the creak will return. Boards fixed with screws or screw nails, or serrated shank nails do not work loose and the boards are much less likely to creak in the short or long term. However, the heads of these screws and nails are not suitable for exposure on the face of hardwood floors.

Screwing.

For every successful installation of wide boards inadequately fixed, there are many that have failed to remain stable and flat. The reason these exceptional floors have remained flat and gap free is because the timber was fitted at exactly the right moisture content into a very stable environment. When I began creating hardwood floors in the late 1960's it was recommended that all hardwood boards above 100mm wide should be face fixed. This rule has been broken more in the breach than the observance since. I have heard tell of boards up to 300mm wide that are fixed only by secret nailing through the tongue. I have seen boards of tangentially sawn American white oak at 250mm wide that have been secret nailed and have remained flat and true. However, these successes are the exceptions, not the rule. For every successful installation of wide boards inadequately fixed, there are many that have failed to remain stable and flat.

The best, most attractive and most secure - and most costly - method of fixing wide boards is by drilling into the face, countersinking the hole not more than half the thickness of the board, screwing through the board to the joist, batten or plug in the screed, and then fitting a plug into the hole above the screw. This is vulgarly known as 'screwing and plugging'. The screws should be set at about 30mm from each edge and at around 400mm centres down the length of the boards. These figures are guidelines and should be adjusted to suit the timber, joist spacing, loadings and aesthetics.

Some architects insist that stainless steel or brass screws be used to fix oak boards and traditionally manufactured oak parquet panels. This is intended to avoid the problem of corrosion between oak and mild steel which weakens the screw and causes blackening of the oak around the fixing. There are some problems associated with stainless steel and brass screws. Both are weaker and the heads are easily damaged. Overtightening to pull boards down can cause the heads to shear off. If convenient, thicker than usual screws should be employed to improve their strength. However, mild steel screws and nails have given good service over many centuries and there are some advantages to the corrosion such as its capacity to glue to the timber. Some people like the age conveyed by the 'blueing' of iron oxide.

Plugging.

Plugs are usually made on site by the craftsman of the same timber and are fitted with the grain in line with the board. Careful selection of the plugs can result in most blending into the background. Alternatively, the plugs may be made a feature of the floor by setting them cross grained, cutting them as end grained, or using a different coloured timber or even an entirely different material such as coloured plastic.

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