Foundations

The following articles describe material and technological processes of historical foundations, sorted by historical period.

Foundations of Roman buildings

The first foundation structures appear in Romanesque buildings. Foundations have been made only from quarry stone, or stone masonry with clay binder. At ground level was the base firmly cemented with lime mortar. The base was often covered with slate slabs, forming an insulating layer and basis for above-ground walls.

Wooden buildings were mostly founded on low wooden racks, short wooden stilts on shallow foundations of stone and gravel-sand layers.

Fig.: Foundations of quarrystone.

Foundations of Gothic buildings

Deeper foundations from quarry stone reinforced by pillars from the large stone blocks were used. The strip foundation had untreated rock face and was made from stone, or there was simply stone and mortar thrown into prepared foundation excavation. Furthermore the foundation on wooden grid situated on wooden piles or masonry foundations (wells and foundation strips) were used. A layer of clay was used as water-isolation.

Sometimes foundations were formed by sleeper walls on which arched barrel strips were deposited.

On poor load-bearing soils were foundations based on oak or alder piles hammered in thickly side by side with spaces filled with stones. Alternatively, the pilots carried out a wooden grillage for the walls foundations. Piles had to be carried out so that they are consistently below the ground water.

Foundations of Renaissance buildings

Mostly stone foundation strips on lime mortar were used. At great depths of footing bottom brick pillars with arched strips were used that carried the load-bearing walls. On poor load-bearing soils pile-driving (pilot length = wall height, diameter piles = 1 / 12 the length of piles) was used.

Foundations of the 19th century

Brick foundation strips of quarrystone , brickwork or both mixed were used. More recently concrete blocks with stones were used. In the mid-20th century empirical methods have been gradually replaced by designing the foundations by permissible stresses method applied to foundation soil.

Compression of less bearing soils

Wooden piles hammered in thickly side by side (diameter 150-200 mm, length 1.5 to 2.5 meters) below the level of groundwater. Alternatively, instead of wooden piles, sharp stones interlaced by gravel (total height min 1m) were used.

Fig.: Compression by short densely hammered in piles.

Graded foundations extension

Made of stone, brick or mixed masonry, concrete later. The ratio of grade is 1:2.

Fig.: Graded foundations extension.

Extension of the foundations by compacted gravel-sand mound

Sharp sand used, deposited in layers (layer 150 to 300 mm, total height 1-2 m). Shed during the process, rolled or compacted (bearing resistance of 0.2 to 0.3 MPa). Impossible to be used in places with flowing ground water. In the case of stable groundwater level  sheet pile walls were made on the sides of a sand mound (min. 300 mm below the groundwater level).

Fig.: Extension of the foundations by compacted gravel-sand mound.

Mound of stone

In the case of ground water near the footing bottom stone mound with spaces filled with sand was used.

Subconcrete

A layer of concrete (strip foundation) with a thickness of 0.5-1m.

Foundation piers

Used in locations with sufficient load-bearing foundation soil in considerable depth (more than 6m).

Horizontal wooden grid

Grids were made by planks and from beams. Planks grids were used mainly in setting up on the sands and made of 2 layers of planks (70 to 100 mm thick), in 2 directions and in crossing joined with wooden nails. Beams grids were made double-layer, from pine beams (width 200-250mm, height 240 to 300 mm) with distance between beams from 0.6 to 0.8 m, the spaces between beams were filled with quarry stone, or concrete. On top of foundations was a wooden floor (50 to 120 mm thick).

Horizontal concrete grid

Usually concrete around steel girders.

Foundation of the pile grid

On the piles (span of piles from 0.8 to 1.2 m, pile gridiron min. 0.5 m below underground water level) a grid of longitudinal and transverse sleepers or a concrete slab (thickness 0.5 m) were deposit, the spacing between the beams was filled with quarry stone, or concrete. On top of foundations was a wooden floor.