The Self Build Self Help Site Floor design

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Floor Tiles

The design and build of the house base, up to finished floor level, requires planning at the outset. The architects plans may be specific in every aspect, but may also leave the opportunity for options during the build.

The options for preparing the base to DPC are:

Although you may have a preference for either of these, the nature of the soil, the bearing capacity and the slope may determine whether a suspended floor is required - your architect should have inspected the site and will determine the best construction. The notes below outline the differences.

The construction types in these pages are suitable for a number of finished floor surfaces, the most usual being carpets, laminate, solid timber flooring, engineered wood flooring (here a real wood top layer is laminated onto
a plywood under layer), ceramic/stone tiled floors, vinyl tiles.

And bear in mind the option of underfloor heating - water and electricity based systems. Electric underfloor heating - find detailed information on floor central heating at hot-floors.com, a leading UK supplier of underfloor heating.

Ground bearing floor

This consists of solid fill to support a concrete slab. If there is sufficient depth then ask your architect if a large gauge sub-base could be used. This is the cheapest backfill but is very difficult to handle, get level and compact so, if you do use it, you will need to finish off with smaller gauge sub-base such as scalpings. Even if the delivery lorry can unload into the build you will need a digger, telescopic handler or JCB type machine to get the sub-base into place.

If the depth of infill will exceed 600mm then there is a greater likelihood that the sub-base will compact over time and the concrete slab must be re-inforced (or a suspended floor used). This is usually done by getting a re-inforced concrete mix from the readymix company - where synthetic fibres are added to the mix (rather than re-inforcing the concrete the hard way, with steel mesh (ferro-concrete).

The SAP requirement for insulation will most probably require insulation at the slab level. This insulation can be put all under the slab or, as we prefer, split equally above and below the slab. Which of these options used will affect the SAP calculation putting some above the slab increases the insulation effectiveness and may reduce the total amount of slab insulation required this may, for example, replace a cavity type insulation with expanded polystyrene a cheaper type of insulation.

The slab is usually poured concrete to a depth of 100mm, and 150mm for garage floors.


Click on diagrams for a larger view

Diagram where insulation  confined to below the slab

insulation confined to below the slab

Diagram where insulation  above and below the slab

insulation above and below the slab

The architect's foundation plans will show which internal walls, being 'load bearing, will need foundations. Some internal walls can be built off the slab.