Injection Drying

Adding flexibility to drying programmes

Following a flood or escape of water, traditional drying methods are not always the most appropriate techniques for drying the structure of a building.

Injection drying is an alternative option which complements the traditional systems that can be used to accelerate the drying process in many situations. This is achieved by introducing a flow of dry air directly into wet cavities behind walls, floors, ceilings or any other areas where moisture is trapped and inaccessible.

During Injection Drying, holes are drilled to enable pipes to target dry air into wet cavities, collecting moisture & venting it out of the construction, then dry air is forced down into the building construction via a hose system connected to pre drilled holes.

Injection drying

The advantage for property owners

Rainbow utilises turbine technology for their injection drying programme as it is specially designed to address trapped moisture within a construction. This advanced drying technique is unobtrusive and quiet. It avoids the need for costly strip out, removal and reinstatement of building materials such as concrete floors and walls.

By utilising injection drying techniques, major strip out, which can be devastating to property owners and tenants, not to mention very expensive, can often be avoided. The injection drying system can be installed quickly and allows people to continue to use the affected rooms without disruption. This drying regime also often avoids the need for alternative accommodation and costly removal and replacement for insurance companies.

Drying of trapped moisture

Many modern property techniques are complex in their construction. The need to insulate modern day building structures can produce conditions where surface drying techniques are unable to eradicate trapped moisture completely. 

In the event of a flood or escape of water, moisture can be forced into insulated areas and cavities of a building structure. In many cases there is no easy path for this moisture to return to the environment.

If left unaddressed the moisture could later migrate to other areas, causing further damage to previously restored or unaffected areas.

This process can sometimes take months before issues start to materialise and problems occur.

injection drying

A thermal imaging survey is often undertaken to concrete floors to ascertain the location of any underfloor pipes and assist in the marking out of points between pipes to allow the access holes to be drilled.

Providing a cost effective and highly efficient drying process

The injection drying system provides a drying solution that targets trapped moisture within building interfaces including floating floors. To gain access to these areas it is necessary to open paths to remove the trapped moisture. This process often involves drilling into the building construction to enable dry air to be forced through pipes to the affected area. The forced air then collects the  the construction leaving the affected area free of moisture and structurally sound.

It is essential that air movement is created throughout the affected area as with all drying techniques, the air is used to carry released moisture away from affected areas. This may require certain elements of the structure to be compromised in order to remove the moisture.

An initial site assessment and scope of works is needed to identify these requirements and in particular care should be taken to avoid damaging service installations, such as electrics and pipes hidden within the cavities.

Thermal imaging surveys can assist in locating these elements and care should also be taken not to damage the DPC of the structure. Once an injection drying system has been installed it is monitored using the vented air quality as a drying guide. As the dry air is forced through the construction, moisture is collected meaning the specific humidity of the vented air is increased.

The %RH of this vented air would also be high when measured. The graphs above are typical of the last days of the drying cycle of a floating floor.

The injection drying system is also very effective when addressing wooden floating floors, dot and dab walls, stud partitions and external wall cavities.

Typically one machine can address 35m2 of concrete floating floor, a typical construction in UK properties. The internal partitions are then created on top of this single slab, and as such a leak can easily migrate through the floor construction and affect other areas on the slab.


Injection drying provides a very robust and credible addition to the portfolio of drying regimes to the Damage Management industry. Its use in UK restoration projects has seen an increase over recent years due to its flexible nature, speed of drying and cost effective programme on many projects where the trapped moisture is inaccessible following water damage.

Contact your local Rainbow office for further information on injection drying

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