A1 and A2 rated building board guidance & DensDeck clarification
Bauder are seeing more and more instances where specifiers and insurers are requiring the use of building boards with A1 or A2 reaction to fire classifications in roofing applications particularly for upstands
Why are we sending this update?
We are increasingly finding situations on site where a building board is being used for upstands or decks without 3rd party approval for the product being suitable for use in flat roof situations. There are many types of A1/A2 rated boards with widely variable properties. The correct naming and checking of what is actually being proposed is essential to ensure that products are specified correctly.
Why are we sending this update?
Specifiers are looking for Bauder to take responsibility over product selection. it is important to highlight that the manufacturer of boards is to confirm its suitability in a flat roof situation Bauder will not take responsibility over specification or guarantee of roofboards in any scenario
the authorising party assumes design liability for the construction. there is a duty of care on the part of the designer to ensure that all components are fit for purpose compatible with other components and approved for use by all manufactures and suppliers who would issue a warranty for the flat roofing system and/or its components which otherwise may become invalid
Which is the most suitable board type to use?
Cement-Bonded Particle Board appears to be the most suitable for flat roofs. We have attached a document to this update, which was put together in a cross-industry approach by SPRA/LRWA/NFRC and should be used to give guidance as to which boards are suitable and which ones are not:
The below table is taken from the document: GUIDANCE FOR THE USE OF BUILDING BOARDS WITH A1 OR A2 REACTION TO FIRE CLASSIFICATIONS IN FLAT ROOFING
Insurers
NHBC, Premier & LABC Warranty insurers all ban the use of Magnesium Oxide boards; regardless of whether they are Sulphate or Chloride based boards.
Why are MgO board banned by these companies?
The insurers ban MgO boards due to the potential corrosive effect on the fasteners. MgO boards release moisture and chloride ions which can corrode metal fixings. They have experienced issues across Europe where this has occurred. This ban relates to MgO boards used in both the field area and upstands. To be clear, gypsum is not a type of MgO.
What issues can occur using the wrong type of product?
The below issues are a few we have come across to date, but its not exhaustive:
- Mechanically fixing insulation—gettng a good fixing can be a problem.
- Fixing the top leading edge of the capping sheet—again, gettng a good fixing can be an issue.
- Fixings corroding due to the wrong type of fixings being used.
- Boards left exposed and absorbing moisture which can lead to de-bonding of the membrane.
- Boards not suitable unless fully supported.
Is Bauder DensDeck Prime 5.4mm a product which can be used for upstands or the deck?
Simple answer is no.
Bauder DensDeck Prime is a 6.4mm thick gypsum based non-combustible protection layer with a fibreglass mat face. The product is intended for commercial roofing applications to reduce the impact of roottop fires and improves compressive performance of the roof system, especially when trafficked. Bauder DensDeck Prime can be utilised as a ‘cover board’ between the waterproofing and insulation layers.
Where DensDeck prime 6.4mm must not be used:
- On to structural deck as a roof board
- Over a metal deck to support the waterproofing
- As an upstand board or to cover the parapet to support the waterproofing
- An official FM Insured project following FM rules - assembly build-up - this should be products that are part of a system build-up - insulation to be FA fp or BauderROCK.
What systems has DensDeck Prime been tested with?
- Reinforced bitumen membrane system.
- Bauder Thermofol (adhered and mechanically fixed).
Where can DensDeck Prime 6.4mm be used?
- As a cover board, on top of insulation & beneath the waterproofing system in a warm roof scenario
- As a coverboard, on top of PIR insulation between insulation and waterproofing as an alternative to FM approved insulation instead of FA fp where the insurer will accept it.
- As a coverboard, on top of PIR insulation between insulation and waterproofing as an alternative to non-combustible
- insulation instead of BauderROCK/BauderGLAS where the insurer will accept it.
- On top of BauderROCK insulation between insulation and waterproofing as an alternative to non-combustible insulation instead of BauderGLAS where the insurer will accept it.
- As a recovery board (fully supported) over existing systems - mechanically fixed. Contact fixing supplier for fixing type and pattern.
- Bauder DensDeck Prime can be installed in both mechanically fixed and bonded methods (subject to project specific wind load calculation).
What A1/A2 fire rated products does Bauder recommend for upstands and decks?
Bauder does not endorse any particular products. It is for the manufacturer of the boards to confirm its suitability in a flat roof situation. We have carried out peel tests with Cement Bonded Particle Boards and the results have been very positive.
The link shown will take you to a supplier of this type of board for them to guide you in the right direction: www.euroform.co.uk/versapanel/
If you have any questions, please do not hesitate to contact us.
Richard Clennell
RBM & Insulation Product Manager
07824 539684