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Foundations

Today the foundations of a building are required to provide the basis for constructing a ground floor that is, or can be, both well insulated and free of thermal bridging.

The basic element for this is the means of connecting the floor and the rest of the superstructure with the ground.

In many cases the ground floor platform is built as an integral part of this, although it need not be.

Since the initial decision on how and what to build depends on site specific ground conditions, we offer a range of different intermixable foundation elements, all of which can be designed to fulfil our FocusonFabric, energy and CO2 saving concept.

 

Strip Foundations

Strip Foundations

Although the days of 'strip foundations' for everything are now long gone, this is especially true when developers have the opportunity to use (relatively) lightweight superstructures, like timber frame. In themselves these offer the opportunity to revisit the design and engineering of foundations, potentially resulting in a variety of time and cost savings.

However, strip foundations remain relevant because they are still a basic means of creating the substructure required for highly insulated over-site slabs, beam & block, and suspended timber ground floor structures.

This applies to all sizes and type of building, from small extensions, through domestic and low-rise residential development, to sizable multi storey, commercial and industrial buildings.

 

Piled Foundations

Piled Foundations

With a large body of technical knowledge behind them, the choice of piled foundations for any project is complex to say the least.

As well as sheet steel, tubular and concrete piles, timber is an often overlooked alternative, even though it has perhaps one of the longest histories in providing foundation support for everything from harbours and bridges to commercial, industrial and residential buildings.

In recent years short bored piling, requiring a concrete or similar ring beam on top to carry the building load, and mini piling has come to the for both for new buildings and retrofit underpinning requirements.

Helical or Screw Piling and Ground Anchors has a robust history having been developed and used for lighthouse foundations.

However, in all cases the question of insulation has to be addressed in the design and construction of the ground floor elements.

 

Augured Foundations & Walter Segal

These are a simple alternative to piled foundations.

A ground auger - usually about 600mm in diameter - is used to create a hole down to a solid ground base. This will itself probably be excavated and extracted by upto 300mm to ensure that this is the true solid base. Being particularly suitable for short, or shallow depths, and ideal for low rise structures, this is the system developed by Walter Segal in the early 1970's.

Noted for his seminal work as a Community Architect, Segal developed this as part of his simple system of construction based around timber frame.

Avoiding 'wet' trades, after the structural design has been engineered and point loads determined, holes are augured out as described above in positions to receive posts. The holes are then filled up to ground level with non-compressible material such as lean mix concrete or even crushed rock. These 'bases' are then capped off with pads of concrete or possibly a reinforced concrete paving slab to serve as a base for the above ground parts of the foundation. Structural posts are then set on top of these. Full details can be obtained from the Walter Segal Self Build Trust (WSSBT)

 

 

Simple Pad Foundations

Where ground conditions are solid and stable, it may be possible to simply remove top soil and construct a series of simple pads to carry a lightweight structure, such as a single storey timber frame building, above these.

Ground conditions
If it is intended that the building remain in place for a long time, or be permanent, then a base below the frost layer is advisable, as is avoidance of high water tables, etc.

But providing the pad base is sufficiently strong and able to spread the load over a firm ground base, then consideration for such an alternative could lead to considerable savings in time and cost.

Suspended & Other Floors
In this case the floor is most likely to be a suspended insulated timber ground floor, but consideration can be given to other forms.

Trees
There are other advantages of such a system, like the avoidance of tree roots and the ability to build quite substantial structures very close to trees.

 

Raft & Slab type foundations

Raft and Slab Foundations

Swedish Style Insulated foundations with built in under-floor heating option
Requiring minimal excavation (and resultant soil away) this highly insulated reinforced concrete raft is proofed against rising damp. With very low U-values in the order of 0,15, and the option of incorporating under floor heating as part of the construction, this unique foundation and ground floor slab provides a base for the timber frame superstructure

 

INSULSLAB foundations

Insulslab Foundations

These are based on a hybrid style steel fibre reinforced concrete (SFRC) raft set on expanded polystyrene blocks interlocked together to give detached house ground floor U-values down to 0.11 W/m2K. Compared with conventional beam & block or raft methods, tests have shown this to be over £1,000 per plot more cost effective for a typical 50m2 house footprint.

 

 

 

TECHNOPOR

Technopor Foundations

Using recycled, ground glass to provide a highly insulated base for the concrete slab / raft, developed and used extensively in Germany for Autobahn construction, this is a low cost, rapid alternative form of foundation

The glass foam granulate is equally suited to other forms of structure requiring highly load-transference such as multi-storey residential buildings, industrial construction, biogas plants, etc..

 

Suspended Floors

Timber Ground Floors
Suspended Timber FloorSuspended timber ground floors provide a good alternative to concrete slab and raft foundations and can be very economical

Although this used to be the usual way to build ground floors until the 1970's, they are still widely used in Scotland

Insulation is fixed either between joist or over floor deck in the conventional way and can deliver equal or better U-values than concrete or beam and block at much lower costs.

Care needs to be taken to provide good ventilation beneath the floor, but this may be well worth doing. While there are many other forms of insulation that can be used, SuperGlass provide some worthwhile notes on this.

 

 

Beam & Block Ground Floors
Beam and Block Ground FloorWhile this form of ground floor construction has become fairly common place across the UK, to meet the latest building regulations it must incorporate some form of insulation.

There are various ways of doing this, either under or over the beam and block construction, but Cellecta's patented system provides a quick and useful way to grasp the fundementals of this.

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