Frost wall or frost protected wall construction is to prevent soil beneath the building from freezing for protection of foundations in freezing temperature climates. Types of frost walls, their requirements and uses are discussed.
Frosting is a serious issue for the building structures during the colder climates. These undesirable effects are more pronounced and observed on the building foundation.
Any damage to the building foundation will affect the whole stability of the structure. In regions where the frosting is a persistent issue, the most common remedy is to construct deep foundation that will be lying over a footing level much below the frost line.
Hence the construction of buildings and structural elements in extreme climates is a very challenging procedure. The temperature characteristics of the building materials used for the construction is a sole factor that influence the construction.
The concrete placing and mixing in colder climate results in the contraction of the mix. These contractions of concrete will result in internal stresses.
If these issues of contraction and the internal stresses are not taken into consideration seriously there will be extreme issues of internal strain. The internal strain accumulation is a great danger for the structural integrity and the serviceability of the structure.
Need for Frost Protected Wall
Frost protected wall is constructed with an intention to prevent the soil around the building from freezing under high freezing temperatures. A form of heat conversion is used to transfer from the building to the soil beneath so that the soil does not freeze.
Fig.1: Construction of Frost Wall Foundation in Freezing Temperature
As we know from the basics of soil mechanics, the soil matrix consists of voids that is filled with water and air. In dry soil, these soil voids will be filled with air. In the case of saturated soils, the voids will be filled with water that will get converted into ice under freezing temperature. The volume of water in a void will increase when the water is converted into ice.
The soils underneath the foundation is mostly filled with water. If the construction is on a colder region, these waters will get converted into ice. Any fall in temperature will melt the ice into water. Hence a procedure of freezing and thawing is experienced. This will result in an upward showing of the structure due to expansion and contraction.
Fig.2: Penetration of water in the interior of building as the walls get wet
This frost heaving phenomenon will increase with the conversion of water in soil into ice. These frozen ices in the soil is called an ice lens. These ice lens will push the nearby soil mixture extensively. Any structure that is lying over such expanded soil will shove the structure in the upward direction.
Hence the only way to prevent such issues is to bring a means that will stop the freezing of the soil. The frost wall is such a unique technique implemented widely for this purpose.
What is Frost Wall?
The frost wall can be defined as an insulated wall that are constructed around the periphery of the foundation. These are constructed deep and beneath the frost line. As the frost wall are placed beneath the soil, the foundation won’t be subjected to upward pressure from the frost heave process.
The term frost wall is also used to mention walls that are constructed above the ground in the interior of the building structure. This will hence act as an insulation to maintain warmth for the building interior. These frost walls also collect heat from the structure and prevent the soil surrounding the building from freezing and related issues.
Types of Frost Wall
Based on the requirements of the load, temperature and the building features there are different types of frost wall that can be constructed. One such classification is:
- Load Bearing Frost Walls
- Non-Load Bearing Frost Walls
Load Bearing Frost Wall
This construction of frost wall will place the responsibility of foundation over the frost wall. The frost wall will itself act as a foundation wall by constructing it beneath deep the soil.
This will be clearly constructed beneath the frost line of the area. These type of frost walls are constructed in extreme weather conditions (freezing temperatures).
Non–Load Bearing Frost Walls
As the name implies, these frost walls are constructed just as an insulating wall. This is constructed in homes that are not insulated. These insulated non-load bearing walls will be constructed inside the building.
Non – load bearing frost walls helps in preventing the escape of heat through the foundation. The interior frost wall constructed must not be in contact with the exterior wall. Special care should be taken while constructing the same.
A gap is maintained between both the walls. It is also recommended to have a barrier to prevent moisture else the moisture will get converted into ice within the wall structure.
Requirements for Frost Wall Construction
The construction of the frost wall provides better performance if all the structural elements that accompany this construction too are of required properties.
Some of the basic features related to its requirements are mentioned below:
- The basement wall constructed beneath the wall must be patched to prevent any open gaps. Mostly these basement walls are constructed with the help of cinder blocks. The gaps can be filled with the help of brick fillers.
- If the basement walls are constructed with concrete, it is necessary to clear any cracks present in it with the help of a paint sealer. Special paints are available in the market that will help in preventing the penetration of moisture into the basement.
- All structural elements must be built with a primary intention to prevent moisture penetration.
Application of Frost Wall
Below mentioned are the working and the construction of the frost wall for the preventing the shallow foundation from freezing and for non-heated buildings.
Frost Wall for protection of Shallow Foundation
The frost wall constructed with an intention to protect the shallow foundation is non-bearing frost walls. This type is used where the frost wall construction as a deep foundation is not at all feasible for the area or it does not bring any sort of economy.
The frost wall here is constructed by leaving a specified gap as per the constructor recommendation with the foundation. This is arranged such a way that the soil does not lose the heat from it.
These types of frost wall construction are constructed surrounding the foundation so that the heat radiated from the building is warmed up efficiently.
Fig.3. Insulation horizontally throughout the foundation
A rigid foam of insulation is constructed on the exterior of the foundation vertically and on the basement of the foundation horizontally. The construction of these insulation makes the heat formed within the interior of the building to move down the soil and prevent them from freezing.
Fig.4.Horizontal and Vertical Insulation for the frost walls
Frost Wall for Non-Heated Buildings
The frost wall explained in above case provides warmth for the building only if the building constructed is a heated building. This type of frost wall won’t work for an unheated building type.
An alternative for such issue is to design a horizontal layer placed under the foundation of the entire building. This horizontal layer has to extend throughout the building area outward also. There is no form of vertical insulation provided.
The insulation provided are laid over the layer of gravel. Hence, the warmth will be entrapped within the soil and prevent the soil from freezing.