Piling foundations support many historic structures such as
canneries,
wharves, and shore buildings. The old
pilings present challenging problems during restoration as they age and are destroyed by
organisms
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and f ...
and decay. Replacing the foundation entirely is possible but expensive. Regularly inspecting and maintaining timber piles may extend the life of the
foundation.
Historic use and treatment in water
Timber pile construction in the
aquatic and
marine environment
Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmen ...
has a long history in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...
dating as far back as the
bronze and
stone age in
Switzerland.
Swiss lake dwellers
During severe droughts in
Switzerland in the mid-nineteenth century, lake areas that had been previously
inundated with water, were exposed to reveal ancient
archaeological
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landscape ...
remains of various types of timber piling support assemblies that served has foundations for both individual houses and community buildings. The design of these timber assemblies varied by the time of occupation, whether during the bronze or stone age, and also by geological conditions where the timbers rested.
The communities were called the Swiss Lake Dwellers and were located in various fresh water lakes around
Zürich
, neighboring_municipalities = Adliswil, Dübendorf, Fällanden, Kilchberg, Maur, Oberengstringen, Opfikon, Regensdorf, Rümlang, Schlieren, Stallikon, Uitikon, Urdorf, Wallisellen, Zollikon
, twintowns = Kunming, San Francisco
Zürich () i ...
and other areas in Switzerland. During the archaeological excavations, many of the piles dissolved after being in contact with air.
Early building piling foundations in Venice, Italy
In
Venice
Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto region. It is built on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The isla ...
, some of the early piling foundations were built on timber piles. The early Venetian constructors used building techniques that included using impermeable stone supported by wooden rafts and timber piles.
The timber piles did not rot because they were set into the mud at the bottom of the
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons' ...
which prevented oxygen and harmful microbes from reaching them.
Historic treatment and preservation in marine waters
Treatment methods used prior to 18th century
Over 2,000 years ago, wood builders were aware of
marine borers and decay and protected wood using crude extracts and various chemicals.
Further study on how to address marine borer activity and decay accelerated in the 18th century.
Treatment methods revived in 18th & 19th centuries
In the 18th and 19th centuries the study of
wood preservation
Wood easily degrades without sufficient preservation. Apart from structural wood preservation measures, there are a number of different chemical preservatives and processes (also known as "timber treatment", "lumber treatment" or "pressure treat ...
was revived due to the deterioration of the timber pile dikes that protected Holland as well as the high level of decay and marine borer activity in English Navy ships.
The early dikes in
Holland
Holland is a geographical regionG. Geerts & H. Heestermans, 1981, ''Groot Woordenboek der Nederlandse Taal. Deel I'', Van Dale Lexicografie, Utrecht, p 1105 and former province on the western coast of the Netherlands. From the 10th to the 16th c ...
were supported by timber piles.
Creosote
Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics.
Some creosote types were ...
derived from coal processing, was discovered in the mid-18th century to prevent timber pile decay.
The development of
Creosote
Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics.
Some creosote types were ...
pressure treatment by
John Bethel
John Charles Bethel (born January 15, 1957) is a Canadian former professional ice hockey left winger. He played in the National Hockey League (NHL) for the original Winnipeg Jets.
Bethel was born in Montreal, Quebec. He played three seasons at ...
was also an important advancement in timber piling construction.
Historic buildings supported by timber piles may either be either treated with creosote or
chromated copper arsenate.
Types of wood used
In the United States,
Douglas-Fir
The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three ...
timber piles are used most often in the
Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
while Southern Pine are used most commonly on the East Coast. Douglas-Fir is used most commonly used on the west coast due to its high strength, renewability and low cost.
Piling deterioration problems
Marine borers
There are three groups of marine borers in West Coast waters including
gribbles,
shipworms
The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, including ...
, and
pholads, and each differs in the type of damage it causes.
Gribbles
A Gribble (Limnoria) is a destructive
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...
that burrows into the wood surfaces.
Unlike other marine borers, gribbles travel easily from timber to timber using the wood for food and shelter.
Gribbles burrow to a shallow depth but can still reduce pile diameter by one inch per year; a gribble infested pile typically has an hour-glass shape at the tide line.
Shipworms
Shipworms
The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, including ...
(Teredolite) are wood-boring bivalves that burrow deeply into submerged wood. Although piles attacked by shipworms may appear sound on the surface, they may be completely riddled with a maze of tunnels.
Shipworms can spread to new wood only when they are in the free-swimming larval stage.
Once they attack and bore into the wood, they become imprisoned within it.
Ancient mariners, realizing that shipworms were imprisoned in the wood of their ships, would sail far up river and remain in fresh water for a number of months to kill the shipworms.
Experienced divers look for siphons that project from the wood or use sonic devices to estimate the extent of internal damage.
Shipworm and gribble attacks can also be detected
by immersing untreated wood panels and destructively sampling them at monthly intervals.
Pholads
Pholads, rock-burrowing
clams, burrow into and damage untreated wood in warmer waters near
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only ...
and
Mexico
Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...
and along
Oregon
Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...
beaches boring only into the surface of the wood.
Ensuring that the shell of the wood is undamaged will keep this Pholad borer at bay.
Insects
Wood above the waterline may be attacked by a number of
insects
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...
, including
termites
Termites are small insects that live in colonies and have distinct castes (eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the epifamily Termitoidae, within the order Blatt ...
,
carpenter ants, and
beetles
Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, Elytron, elytra, distinguishing them from most other insects. The Coleoptera, wit ...
.
One beetle, the
wharf borer
The wharf borer, ''Nacerdes melanura'', belongs to the insect order Coleoptera, the beetles. They belong to the family Oedemeridae, which are commonly known as false blister beetles. Wharf borers are present in all the states of the USA except ...
(''Nacedes melanura''), can attack untreated or damaged treated hardwoods and conifers with high moisture contents by tunneling extensively and leaving behind dark brown fecal matter that further degrades the wood.
Wood decay
Wood decay describes wood in all stages of fungal attack, from the initial invasion of
hyphae
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one or ...
into the
cell walls
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
to the complete destruction of the wood.
Wood-inhabiting fungi are most common on timber piles above the water surface since the lack of oxygen below water inhibits fungal growth.
Methods of detecting decay
Incipient decay may develop in untreated pile tops within 1 year and reach the visible, advanced stage, termed rot, within 2 to 4 years and can extend 4 feet or more from the internally rotting areas of a Douglas-fir pile.
A triangular blade scraper, a sharp shovel, or a dull probe are useful when inspecting piles for surface deterioration or marine borer attack because they allow the inspector to estimate the depth of deterioration.
Because untreated wood can often be exposed while these tools are being used, a preservative solution or paste should be applied to exposed areas.
Cracks
Cracks that have developed after the wood has been treated are highly susceptible to borers, insects and decay in the right conditions. Cracks need to be evaluated during an initial pile inspection to ascertain depth, location and treatment condition.
Decay treatment options
Liquid preservatives
Apply a liquid preservative to cutoff tops of piles and timbers by flooding them
with hot creosote (150 to 200 °F),
pentachlorophenol in
diesel oil, or
copper naphthenate
Copper naphthenate is the copper salt of naphthenic acid. Naphthenic acid is a term commonly used in the petroleum industry to collectively refer to all of the carboxylic acids naturally occurring in crude oil. Naphthenic acids