Expanding foam
Contents |
[edit] Introduction
Sealants are typically used to close openings between spaces that are too small for other materials such as concrete, timber or mortar to be used. They have a wide range of properties in terms of strength, flexibility, appearance permanence, solubility, corrosion resistance and so on.
Expanding foam filler is a common type of polyurethane filler. It can be sprayed into gaps such as those around windows and doors to stop draughts, fill gaps and dampen sound. It is designed to adhere to a variety of common building materials and can be water resistant.
[edit] Expanding foam characteristics
Foams can be divided into two different ways: type and purpose.
- Type of application: handheld dispenser or gun grade applicator.
- Purpose of application: Filling voids or securing materials through adhesion (these foams have a lower expansion rate).
Expanding foam filler is made up of materials that expand under different conditions, depending on its composition. One type of expanding polyurethane foam requires moisture in order to expand, which can make it sticky during the installation process. Another begins to expand when two different chemicals are mixed together. Dampening the surface that will be treated can help the foam set more quickly.
There are several differences between types of foam which should be clearly marked on the containers:
- Indoor or outdoor use.
- Sandable or paintable.
- Presence of HCFCs or CFCs (no longer permitted).
- Gun grade or handheld.
[edit] Possible dangers of expanding foam
It’s important to proceed with caution with the application process, since the chemicals can be toxic if they are not used properly. However, the substance should be safe once it has fully expanded and dried.
Basic foams can be flammable and may create toxic smoke if they are exposed to fire. There are some foams that can resist fire for a certain time when directly exposed to flames.
Cured foam should be protected from daylight or other light since this can degrade the effectiveness of the product over time. Dried foam can be painted, or otherwise covered, to protect it from light.
Expanding foam should be used relatively quickly once a can or gun is started, since the chemicals may not retain their effectiveness over time. It can also be difficult to remove or clean foam. There is a special type of chemical that can be used to clean wet foam, and in some instances, acetone can be used.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Design and construction industry podcasts
Professional development, practice, the pandemic, platforms and podcasts. Have we missed anything?
C20 Society; Buildings at Risk List 2025
10 more buildings published with updates on the past decade of buildings featured.
Boiler Upgrade Scheme and certifications consultation
Summary of government consultation, closing 11 June 2025.
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
From project managers to rising stars, sustainability pioneers and more.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.