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Unheated Frost Protected Shallow Foundations and Heated Frost Protected Footings Design and Installation - Legalett

Unheated Frost Protected Shallow Foundations, incorporating Frost Protected Footings Design and InstallationUnheated Frost Protected Shallow Foundations, or uFPSF’s, are a recognised alternative to more costly deeper conventional foundation designs used in colder regions subject to seasonal ground freezing and heave. Both of GEO-Slab's Unheated and Heated Frost protected slab on grade systems by Legalett provide complete protection from frost heave in supported slab designs. FPSF design allows footings to be placed above the freeze depth, by insulating the foundation and ground to prevent the earth freezing below the foundation causing heave and structural damage.

The earliest documented use of FPSF in the United States was by Frank Lloyd Wright in the 1930’s. Then in 1994, the US Department of Housing and Urban Development conducted several experimental projects, to verify the performance of existing European frost resistant design practices. As a result an FPSF Design Guide was developed, to serve as a basis for building code acceptance and standardization in the United States by the National American Home Builders Research Center.

In European Nordic countries well over a million FPSF’s have been constructed successfully over the last 45 years. In Scandinavia, for example, an Unheated Frost protected shallow foundation system is commonly used on both residential and commercial buildings, such as houses, townhouses, apartments, shopping malls, schools, low-rise office buildings, restaurants, gas stations, etc. whilst heated Frost Protected shallow systems like Legalett have been the preferred method for frost protection of foundations and slabs since the 1970’s.


Traditional FPSF’s are slow and complicated to design and build with their thickened edges and outstand details, and require careful attention to design details to ensure satisfactory freeze performance. Traditional FPSF’s generally require their extensive skirting because they are only designed as unheated floor slabs and these are more difficult to effectively protect.

GEO-Slab by Legalett has both unheated and heated products – with their air heated system being a unique approach of designing an FPSF by incorporating a forced air heating system as an integral part of the Frost protected structure. By combining a frost protected foundation and the heating system, GEO-Slab by Legalett shifts the bulk of the concrete away from the edge, and spreads it evenly through the insulated slab, maximizing the thermal mass of the slab for heating, and spreading out the load applied to the soil. This simplifies the installation of the GEO-Slab system, compared to other FPSF’s, in two ways - the GEO-Slab is the same thickness from one side of the building to the other, reducing installation time and cost by eliminating thickened edges and multiple concrete pours, and secondly, by reducing or eliminating the need for exterior frost skirting. The air heated system also eliminates the potential leakage and future maintenance of Hydronic sub floor heating at a fraction of the cost but with all the efficiency and comfort.

GEO-Slab by Legalett from Core Construction Products is simpler to install, quicker and hence cheaper and more energy efficient than traditional FPSF’s. GEO-SLAB IS THE FIRST AND ONLY COMMERCIAL FPSF.

Get things moving -find out how great, easy and cost effective it is to utilize unheated Frost Protected Shallow Foundations in your next project - Contact Core in under a minute here and Get an initial Free Consultation or Quote. 

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State of the Art Frost Line Behaviour Modeling

Legalett engineers use state of the art Finite Element Modeling for heat transfer to predict the frost line and use years of experience to design the perfect frost protected solution for your new green home construction.


  • Saves time, materials and money. No more limitation to building below the local frost depth to protect from frost heave.
  • Save on excavation, no more guessing about soil problems or hidden rocks, because GEO-Slab unheated and heated Frost Protected Shallow Foundations sit on grade.
  • No more crawl space issues.
  • All concrete pouring is completed at once with the Legalett structural insulated slab - Reducing construction time and costs. View a time lapse video of the GEO-Slab unheated frost protected shallow foundation system in action here  

The GEO-Slab frost protected structural foundation by Legalett is ideal for back walk-outs, poor soil conditions, lots with high water tables. NOTE: It is recommended that the top of the slab be a minimum of 20” above the ground water table.

From a slab on grade to fully buried structures and foundations - Core Construction Products West supplies GEO-Slab unheated and heated structural slabs from Legalett for both heated and non-heated buildings.


Get a free quotation for GEO-Slab Frost Protected Shallow Foundation System from Legalett quickly here Contact Core in under a minute here and Get an initial Free Consultation or Quote. 

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Frost Protected Shallow Foundation On Grade Below Grade Basement


The Advantages of Frost Protection using Air-Heated Floors from Core Construction Products 
  • Air is a safe and reliable heating medium 
  • Save on construction costs
  • Save on energy costs every year
  • Extend the building season in cold climates
  • Eliminate the risk of moisture damage and leaks from water filled heating pipes 
  • GEO-Slab by Legalett is the foundation for healthy, durable and cost effective Green Home Construction in Colorado and the Western US.

Unique Advantages of a Heated Slab System versus a Unheated Frost Protected on grade foundation and slab system

Warm air is recirculated through a closed loop piping system from a heater cast in the floor slab. The building envelope is completely insulated. GEO-Slab by Legalett uses expanded polystyrene as stay-in-place formwork and under-floor insulation in a single operation. The slab-on-grade GEO-Slab system costs less than conventional construction. The air you breathe is separate from the air used for heating so household odours are reduced and moisture, mould and mildew are eliminated whilst the patented heater box is insulated for quiet operation.

Very cost effective and reassuringly simple... The GEO-Slab system by Legalett is healthy, affordable and ecologically sustainable.

With GEO-Slab, the heat comes from the floor, eliminating drafts - feet are warm and any moisture is quickly and easily evaporated from the floors surface. Even the bath mat dries quickly after showering avoiding that musty smell we all know and hate in the shower room!

Legalett's GEO-Slab is a PATENTED and UNIQUE SYSTEM !

Hot water and electric floor heaters have been available and accepted in North America for many years. Legalett have improved on traditional home heating, for example in the hot water floor heater, water is heated by the building hot water system, be that solar, geothermal or heat pump or more traditional gas or oil and circulated to the GEO-Slab heater where the efficient exchanger system heats the circulated air system.  The alternative electric heater takes advantage of tiered electricity rates.  

The GEO-Slab system can:
  • be used for any building
  • be adapted to any energy source
  • regulate heat in different zones 
  • accommodate all floor coverings - ceramic, hardwood, carpet, linoleum
  • provide for barrier-free buildings (handicapped access)
  • be used below, on and above grade

Core Construction Products West helps provide the frost protected slab design and supplies all components, for simple and cost effective installation, following the building process from concept to move-in.

GEO-Slab's slab-on-grade foundations eliminate footings and frost walls for both substantial speed and cost savings.

When working in a cold climate as found in central and Northern America, or central Canada, use of GEO-Slab's construction heater extends the building season, cast in place with a removable cover for easy access. CCP West supplies GEO-Slab by Legalett air-heated floors for residential homes, retirement homes, schools & day-care facilities, churches, commercial & industrial buildings.

There is always a GEO-Slab frost protected shallow foundation design that works, whether unheated or heated!  - Contact Core in under a minute here and Get an initial Free Consultation or Quote. 

 Get my Free Quote or Consultation ► 

To watch a Heated Frost Protected Shallow Foundation construction pour in Canada, click here.

To find out more about Frost Protected slab on grade construction systems in Massachusetts or the Eastern US, click here

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