What is a sliet?
Sliet (also sleet) is a Dutch, mainly historical term for a long, roughly debarked piece of timber: an unworked beam, a slab board or a thin trunk with its branches removed. There is no exact English equivalent. The closest terms are short timber pile, timber sleeper and, for the whole system, a timber grillage foundation.
Sliets in foundations
In the western Netherlands, walls and piers on soft clay and peat were founded on sliets from around 1300. They were usually short poles of about 2 m, driven close together. They did not reach the firm sand layer; instead they compacted the soft soil and carried load by skin friction. By the end of the 14th century they were driven between a grillage of timber beams running along the wall.
These foundations could shift easily, causing cracks in the masonry. Builders later found that a few long piles driven down to the sand carried at least as much as a whole cluster of sliets, and that method took over.
Loose loft floors
In Dutch farmhouses on the Veluwe, loose beams or poles laid across the timber frames formed the hayloft floor. These “balkslieten” could be moved around as needed.
Application
Many older buildings on soft ground, in the Netherlands and elsewhere, still stand on timber. If you own one:
- Groundwater level. Timber only survives as long as it stays fully below the water table. When the water drops, fungi get oxygen and pile rot begins.
- Warning signs. Sticking doors and windows, cracks in the facade or a building leaning or settling unevenly can point to a damaged timber foundation.
- Investigation. If in doubt, commission a foundation survey with a trial pit to see what timber is there and in what condition.
- Repair. Serious decay calls for foundation repair, usually with new piles. Do not dig alongside old foundations yourself; it can reduce their bearing capacity further.
Related terms
- Pile rot
- Foundation repair
- Foundation survey
- Groundwater level
- Pile foundation
- Round timber stake
- Hayloft
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