What is Substructure?

Substructure is a term used to describe anything from the top of the ground floor slab level down.

Most of the elements which make up what is referred to as Substructure take the weight of the building sitting on it and transfer it into the ground below. They include:

Insulation - can be installed above or below the structural slab. Used to reduce heat loss into ground below a building.

Most buildings are heated spaces, if they are not separated from the colder ground below it could lead to issues such as condensation.

Build up for a 'floating floor' arrangement with insulation above structural slab

Structural Slab - Typically made from reinforced concrete. This is the horizontal base a building sits on. It transfers the loading from the building into the foundations below.

If there is a basement this would be the Basement slab, otherwise it would be the Ground Floor slab.

Reinforced concrete slab being poured

Damp Proof Membrane (DPM) - a membrane material used to prevent dampness from occurring through water rising up.

Typically made of plastic material such as polyethylene and rolled out in sheets underneath the structural slab.

DPM laid out underneath where slab will be cast

Basement - a below ground space which could be partially or entirely below ground. Typically constructed with reinforced concrete walls and floors.

There are many other considerations for basement construction which will be covered by a seperate post.

A reinforced concrete basement

Foundations - the lowermost part of a structure that distributes the weight and transfers it to the ground underneath.

Typically involve casting concrete into the ground. There are many types of foundations including: strip foundations, piled foundations and raft slabs. We will explore these in our Types of Substructure post to follow.

Ground Heave Protection - a compressible material laid underneath the ground floor slab and sometimes around the perimeter of the foundations.

This is required on sites where the ground has the potential to heave. Grounds like clay swell when they are wet, this could push up into the structure and cause damage. The compressible material absorbs this ground expansion and stops it making contact with the structure.

Specially designed polystyrene sheets used for ground heave protection

Blinding - A thin layer of low-strength concrete applied over the ground before construction starts. It protects the surface, acts as a barrier against moisture, and provides a clean, level base for the subsequent construction works.

Hardcore - a solid, coarse layer of material. Made up of crusted stones, broken concrete or rubble and used as a base to provide stability. Blinding is placed on top of hardcore in more instances.

Hardcore

Definitions

Reinforced concrete - concrete with embedded steel inside to increase strength and durability

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Posts to Follow

We plan to go into more details on Substructure and add sections on:

• Design

• Types of Substructure

• Logistics

• Temporary Works

• Build Sequence

• Health, Safety & Environment

• Quality

• Programme

• Commercial

Please let us know if you found this post useful using the chat function. We'd love to hear from you - is there anything in particular you'd like for us to focus on next?