One-part intumescent acrylic rubber.

  • A fire rating of up to 2 hours can be achieved
  • Class 2 surface spread of flame classification
  • Mean toxicity index 2.0
  • Good unprimed adhesion to most common construction substrates
  • Remains flexible
  • Easy to use, one-component sealant Resistant to ozone, ultra-violet radiation and temperature extremes

For internal perimeter pointing around door and window frames, where the integrity of fire walls need to be maintained, and in the small joints formed where fire rated partition sections meet.

Typical Properties

Specification writers: These values are not intended for use in preparing specifications. Please contact your local Dow Corning sales representative prior to writing specifications on this product.

abe Construction Chemicals - Dow Corning Firestop 400


DOW CORNING Firestop 400 Acrylic Sealant is a one-part, fire rated intumescent acrylic sealant designed for internal perimeter pointing of fire rated door and window frames, where the integrity of fire walls or partitions need to be maintained. It has good adhesion to a wide variety of substrates without the use of primer. It has intumescent qualities which enable the material to swell under heat conditions producing a fire and smoke resistant seal. DOW CORNING Firestop 400 Sealant does not emit halogenated byproducts under fire conditions.

Technical Specifications & Standards

DOW CORNING Firestop 400 Sealant has been tested to BS 476 Part 22/1987 in joint configurations, SGS (UK) Ltd. Test report No. J89325/1.

DOW CORNING Firestop 400 Sealant meets Class 2 of BS 476 Part 7/1987 for surface spread of flame, SGS (UK) Ltd. Test report No. J90327/2.

DOW CORNING Firestop 400 Sealant has a mean toxicity index of 2.0 when tested according to NES713, SGS (UK) Ltd. Test report No. J90726/2.

Fire Ratings

Fire test data is available showing that DOW CORNING Firestop 400 Sealant can achieve up to a 2 hour fire rating at specified joint configurations. The fire ratings achieved have been tested according to BS 476 Part 22/1987 and are specific to the conditions of testing. They do, however, provide a good indication of the expected performance of the sealant in fire situations. DOW CORNING Firestop 400 Sealant has been tested to BS 476 Part 7/1987 in accordance with the flame spread classification given in this standard. Results show the material has a Class 2 surface.

Users should satisfy themselves that DOW CORNING Firestop 400 Sealant is suitable for their specific application. Testing of a particular system may be required. To achieve a specific fire rating, all substrates being used in the system must have an equivalent fire rating.

Joint Design

abe Construction Chemicals - Dow Corning Firestop 400 Test Joint ConfigurationsLegend

  1. DOW CORNING Firestop 400 Sealant
  2. Backing material

When designing joints using Dow Corning Firestop 400 Sealant, the minimum width should be 6mm. Attainment of specific fire ratings is dependent on the joint configuration. Detailed information is given in Table 1.

Joint types that have been tested are shown in Figure 1. The type of joint selected will depend on fire requirements for the project and aesthetics of the building.

For additional information or assistance, please contact Dow Corning’s Technical Services Department.

Joint Preparation


Ensure that all surfaces are clean, dry, sound and free from frost. Clean all joints of loose dust, dirt, laitance, old sealants and other contaminants which could impair adhesion. Surfaces should be cleaned and degreased by wiping with a solvent, such as DOW CORNING® Silcon Cleaner or DOW CORNING ® R40 Reiniger, using a lint- and oilfree cloth.

Note: When using any cleaning solvent, always provide adequate ventilation. Avoid heat, sparks and open flames. Observe and follow all precautions listed on solvent container label or Product Safety Data Sheet.

It is recommended that DOW CORNING Firestop 400 Sealant is not applied to surfaces that are below 5°C (41°F) as it is impossible to guarantee a frost-free surface at these temperatures.


DOW CORNING Firestop 400 Sealant has excellent adhesion to most common construction substrates. If in doubt, or if unusual substrates are involved, please contact Dow Corning’s Technical Services Department.

Back-up materials

Closed-cell polyethylene foam backer rod or mineral wool should be used as specified in the fire test data. Masking Areas adjacent to the joints should be masked with tape to prevent contamination of the substrates and to ensure a neat sealant line. Masking tape should be removed immediately after tooling.


The joint should be tooled within 5 minutes of application to ensure good contact between the sealant and the substrate. Tooling of the sealant also gives a smooth, professional finish.


Uncured material can be removed by wiping with a dampened cloth. Cured material can be carefully removed by abrasion or other mechanical means.

Technical Services

Consult Dow Corning’s Technical Services departments for further advice on specific applications:

Dow Corning S.A.

Construction Technical Service

Parc Industriel

B-7180 Seneffe – Belgium

Tel : INT + 32 (0)64 88 80 00

Fax : INT + 32 (0)64 88 84 01


Dow Corning GmbH

Rheingaustraße 34, Postfach 130332

D-65091 Wiesbaden, Germany

Tel : INT + 49 (0)611 – 23 71

Fax : INT + 49 (0)611 – 237 610


Dow Corning Ltd.

Meriden Business Park

Copse Drive, Allesley, Coventry,

CV5 9RG – United Kingdom

Tel : INT + 44 (0)1676 52 80 00

Fax : INT + 44 (0)1676 52 81 00

Handling Precautions

Product safety Information required for Safe use is not included. Before handling, read Product and safety data Sheets and container Labels for safe use, Physical and health Hazard information. The Safety data sheet is Available from your local Dow corning sales Representative.

Usable Life & Storage

When stored between 5°C (41°F) and 23°C (73.4°F) in the original unopened containers, DOW CORNING Firestop 400 Sealant has a usable life of 12 months from the date of production.


United Kingdom:

DOW CORNING Firestop 400 Sealant is available in 380ml cartridge, (packed in boxes of 20) in white and grey.


DOW CORNING Firestop 400 Sealant is available in 310ml cartridge, (packed in boxes of 12) in white and grey.


DOW CORNING Firestop 400 Sealant is not recommended for external applications and has not been tested for use as a penetration seal. It should not be applied to building materials that bleed oils, plasticisers or solvents.

It is recommended to consult Dow Corning’s Technical Services Department for further advice in specific applications.

All acrylic based sealants are susceptible to a degree of shrinkage. This should be taken into account when applying the material.

This product is neither tested nor represented as suitable for medical or pharmaceutical uses.

Health & Environmental Information

To support customers in their product safety needs, Dow Corning has an extensive Product Stewardship organization and a team of Health, Environment and Regulatory Affairs specialists available in each area. For further information, please consult your local Dow Corning representative.

Warranty Information – Please read carefully

The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer’s tests to ensure that Dow Corning’s products are safe, effective, and fully satisfactory for the intended end use. Dow Corning’s sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment. Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted. Dow Corning specifically disclaims any other express or implied warranty of fitness for a particular purpose or merchantability. Unless Dow Corning provides you with a specific, duly signed endorsement of fitness for use, Dow Corning disclaims liability for any incidental or consequential damages. Suggestions of use shall not be taken as inducements to infringe any patent. 

Table 1: Fire Rating

abe Construction Chemicals - Dow Corning Firestop 400 Fire Rating

Table 2: Estimating Sealant Requirements

abe Construction Chemicals - Dow Corning Firestop 400 Estimating Sealant Requirements