Moisture in a farm building: where does the water under the roof come from?

The roof covering, flashings and connections require inspection. At the same time, the internal conditions must be assessed. Not all ventilation openings should be sealed in the belief that every air path is a leak. The steel structure and the building envelope need protection from water, but the building must also allow moisture generated during use to escape.

A machine returning from the field may have wet wheels, body and implements. Once the gates are closed, the water gradually evaporates. If the steel hall does not have adequate air exchange, humidity rises. This also applies to melting snow. Limiting the problem begins with organising parking and maintaining order, not solely with the choice of roof.

When planning the building, indicate whether it is to serve only for storage or also for washing and servicing equipment. Each of these functions places different requirements. Heating a wet room without proper moisture removal is not a complete solution. In a steel hall, temperature, ventilation and the way the floor is used must be coordinated.

Grain, potatoes and vegetables should not be treated as one group for storage purposes. They differ in their requirements for temperature, humidity and air exchange. A steel hall provides space and protection from the weather. The storage technology must be matched to the specific crop and the time it remains in the building.

Ventilating the space under the roof does not replace aerating the grain heap. Installing sandwich panels does not dry the material brought in from the field. Monitoring of conditions and appropriate handling of the crop are needed. Steel structures should account for the equipment and installations associated with this function. Their suspension must not be haphazard.

A sandwich panel restricts the flow of heat through the building envelope. With the right choice, the risk of very cold surfaces on the interior side can be reduced. However, connections and penetration points also matter. A steel hall with well-insulated walls can still have local problems where the plinth or door frame is poorly executed.

In uninsulated buildings, a fleece that retains condensation under the sheet metal is sometimes used. Its capacity is limited and it needs conditions in which to dry out. It is neither an insulation layer nor a substitute for ventilation. It therefore cannot be promised that the fleece alone will keep a steel hall dry regardless of the amount of water brought in and the way it is used.

The method of air exchange follows from the function and geometry of the building. The supply and exhaust locations matter, as does the influence of wind and temperature. A natural solution may suit one application and be insufficient for another. In a steel hall, ventilation should not be selected on the basis of footprint area alone.

Make sure that racks, stored crops and machinery do not block the designed flow paths. A change of layout can weaken a previously correct arrangement. If ducts and fans are installed, their fixing points must be agreed with the steel structure design. Penetrations through the building envelope also require sealed details.

A regular record of temperature and humidity helps to identify the relationship between farm operations and conditions in the building. Checking the roof, gutters and the condition of coatings is also useful. Damp areas should be assessed before damage develops. It is not worth limiting yourself to drying a visible stain if its cause remains unknown.

For a new steel hall, establish the expected sources of moisture during design. For an existing building, start with a diagnosis before ordering additional insulation. The steel structure and building envelope may require repair or upgrading, but the decision should match the identified problem. An effective plan combines the building, ventilation and storage method.

During inspection, pay attention to areas concealed by equipment. Behind tightly placed items, conditions may differ from those in the centre of the building. Maintaining access to the walls makes it easier to spot condensation, soiling and the first changes to the coating. It also makes it easier to find their actual cause.