In the aftermath of flooding resulting from a hurricane or extreme weather event, repair work will typically include full or partial removal of saturated and/or damaged interior finishes, insulation, exterior sheathing and building paper/membranes in the affected walls and floor assemblies while often leaving the exterior brick veneer in place.
The removals also typically damage through-wall flashings and may expose structural issues and other previously hidden problems such as blocked weep holes in masonry veneers.
Spray foam insulation has great potential as a repair/retrofit tool but its use in the retrofit scenarios described above have to be carefully considered and implemented. Reinstatement of a properly functioning wall assembly can be complicated. Due to the extensive removals, it will usually be necessary to:
- Clean and allow all existing materials to fully dry
- Reinstate a cavity/drainage layer behind the exterior masonry
- Tie cavity drainage schemes into existing flashings and repair them as necessary at the base for the walls where existing materials have not been removed
- Tie the cavity drainage scheme above the repaired area into the scheme being used in the areas being repaired
- Repair any structural or weep hole drainage defects,
- Replace insulation and services before applying interior finishes.
Drainage mats and membranes may form a key feature of the retrofit. However, existing features such as brick ties and lintels may complicate the installation of these materials and make it difficult to obtain proper layering at joints.
It has been suggested by some within the building industry that using spray foam may avoid the need for some of the features identified above. However, the fact that spray foam can adhere to adjacent materials and can repel moisture does not mean it can form a perfect barrier, let alone fulfil all of the performance features of all the materials that were originally installed.
Icynene recommends that spray foam should only be used in situations where a properly functioning cavity drainage scheme is part of the wall system. If this is not done, there is a risk that water will penetrate to the inner wall as a result of inadequate control of drainage above the retrofit, and it could remain in the wall as a result of inadequate drainage at the base of the retrofit. This could very quickly lead to serious moisture and durability problems. By only spraying foam insulation directly onto masonry veneer walls the development of a proper cavity drainage scheme is not assured.
For these reasons, Icynene recommends that flood retrofits be done under the direction of a competent Building Envelope Specialist/Architect. We believe that in the vast majority of retrofits, spray foam will be a key, cost effective tool for repairing heavily-damaged buildings. Using spray foam in conjunction with sound Building Science principles is key to avoiding problems, minimizing risk for our customers and protecting our reputation.
If you have questions or ideas about how a particular issue should or could be addressed, Icynene’s Building Science and Engineering team can be reached for best practices input and assistance.