Window and Door Reveals

The surround of a door or a window, of which the bottom member forms the ledge on which you may choose to place an item such as an ornament, is technically referred to as the "reveal" or "liner". These words are used interchangeably.

The reveals can be made from a variety of materials, the type and colour is a matter of personal preference.

Reveals are usually structural members as they perform the function of securing the window or door to the structure of the building.

There are two common methods of fixing the reveals to the building structure, namely traditional nailing right through the reveal into the building structure, or the use of hidden installation brackets.

Traditional nailing leaves hammer and punch marks that can later be covered up by fillers, sanding and painting.

However, if you choose a natural timber show-wood finish, or a factory-finished material, then use of hidden installation brackets to preserve the unspoilt beauty of the material is worthy of consideration.

Please refer to the installation section of this website for details on installation brackets that are tested to comply with the relevant standards.

 

Timber Reveals for Aluminium Joinery

A basis for an Alternative Solution to NZBC B2 AS/1

 

Introduction

The New Zealand Building Code clause B2 requires a minimum 15 years durability performance of timber used for window reveals.

 

Window reveals are used internally and are protected from the weather. However, as there is the possibility of exposure to moisture, and a risk of attaining a moisture content conducive to decay, the New Zealand Building Code calls up the requirements of NZS3602:2003 to ensure a minimum 15 year durability.

 

Acceptable Solution

The New Zealand Building Code cites NZS 3602:2003 for the list of timbers, other than Pinus Radiata treated to H3*, which have durability suitable for use as window reveals.  This list is quite short and does not list the many suitable alternative timbers that can be used for reveals.

 

*Note: Only H3.1 (which does not contain copper in the preservative) is suitable for use in conjunction with any aluminium products.  H3.2 contains copper salts which corrode aluminium.

 

 

Alternative Solutions

The purpose of this document is to identify alternative timbers suitable for timber reveals and to provide the justification for their use based on widely accepted scientific timber durability ratings.

 

 

Artificial Durability

The timber reveals predominantly used in New Zealand for aluminium joinery are pre-primed finger jointed H3.1 LOSP treated Radiata.  This treatment ensures the minimum 15 year durability to meet the NZBC Clause B2 requirement as per NZS 3602:2003. This treatment is specifically designed for the timber species Pinus Radiata and its effectiveness is well documented.

 

All sapwood and many non-durable timbers may also be treated but there are some practical difficulties and limitations in undertaking this.  The uptake of the chemical treatment will vary from species to species, thus making it difficult for the treatment plant to guarantee the level to which it has been treated.

 

Natural Durability

There are many naturally durable timbers to choose from when selecting clear finished reveals.  Some of these, although durable, may not be suitable because of grade, size or length of feed stock.  We are no longer commercially milling some species, for example NZ natives such as Kauri, Rimu, Matai, Totara etc but, when properly selected, these timbers are durable and if available could be used as reveals.

 

Table 1 lists some indigenous and exotic timbers which have proven durability ratings that allow us to use them as an alternate solution to the timbers specified in NZS3602:2003

 

 

Table 1: Durability of Heartwood Timbers

 

Common Name

Durability     -             Class

Sustainability

Ref:

 

 

 

 

African Rosewood

MD                -                    3

 

c

Alaskan Yellow Cedar

D                    -                    2

 

c

American Black Walnut

VD                  -                   2

 

c

American Cherry

MD                -                 3-4

 

b

American White Oak

MD-D             -               2-3

Sustainably harvested

b

Balau

D-VD              -                1-2

 

c

Belian

VD                  -                   1

 

c

Calophyllum (Bitangor)

MD-D             -               2-3

 

c

Cedar Hardwood - Calantas

MD                -                    3

 

d

Cedar, Western Red

D                     -                   2

PEFC

a

European Oak

D                    -                    2

 

d

Hopea, heavy

D                    -                    2

 

c

Hopea, light

D                    -                    2

 

c

Iroko

D-VD              -                   1

FSC

c

Ironbark

VD                  -                   1

 

c

Jarrah

D                     -                   2

PEFC

b

Jatoba

MD                 -                   3

 

c

Karri

MD                 -                   3

 

c

Kwila - Merbau

MD-D             -               1-2

VLC

b

Lawson Cypress

MD                 -                   3

Plantation grown (NZ)

a

Macrocarpa

MD                 -                   3

Plantation grown (NZ)

a

Malas

MD                 -                   3

 

c

Malaysian Kauri

MD  - above ground -      3

 

b

Matai – NZ Heart

MD  - above ground -      3

 

b

Meranti

ND-MD           -               3-4

 

c

Nyatoh

ND-MD           -               3-4

 

c

Pacific Jarrah

VD                  -                   1

 

b

Pacific Matai

MD                 -                   3

 

b

Padauk

D                      -              1-2

 

c

Pilularis

D                     -                   2

Plantation grown (NZ)

c

Red Cedar (Sth American)

MD                 -                   3

 

c

Redwood

MD                 -                   3

 

a

Rimu, NZ heart

MD                 -                   3

 

b

Rosewood - PNG

D-VD              -                1-2

Community Based Logging

c

Saligna – Sydney Blue Gum

MD-D             -               2-3

Plantation grown (NZ)

c

Sapele Mahogany

MD                 -                   3

FSC

c

Southland Red Beech

D                      -                  2

 

c

Southland Silver Beech

MD                -                 3-4

FSC

c

Spotted Gum

MD-D             -               2-3

 

c

Sucupira

VD                   -                  1

 

c

Surian (Island Cedar)

MD-D             -               2-3

 

c

Tallowwood

VD                   -                  1

 

c

Tasmanian Blackwood

MD                 -                   3

 

c

Tasmanian Oak

ND-MD           -               3-4

PEFC

b

Tatajuba

D                     -               1-2

 

c

Taun

MD                 -                   3

 

c

Teak

D                      -                  2

 

b

Totara, NZ heart

VD                   -                  1

 

c

Vitex

D                      -                  2

 

c

Wenge

D                     -                   2

 

c

Yaka

D                     -                   3


b

 

Keys to Table 1:

Durability & Class - Column 2:

                                                   

Durability:                                                                            Class:      

VD = Very Durable                                                               Class 1 = > 25 years in ground

D = Durable                                                                           Class 2 = 15-25 years in ground

MD = Moderately Durable                                                 Class 3 = 10-15 years in ground.

ND = Non Durable                                                                Class 3 = 5-10 years in ground.

(In New Zealand and Australia the MD and ND ratings are combined as class 3).

All sapwood is perishable and is rated Class 4 = up to 5 years in ground.

All references are from Ensis Report by Dr Mick Hedley and AS 5604, amongst other sources, and refer to Australia and New Zealand Durability classes.

 

References: Column 4

a     In NZ Standards NZS3602:2003

b     Dave Page and Mick Hedley – Ensis Wood Processing 2004 report for WANZ

c     Dave Page and Mick Hedley – Ensis Wood Processing 2005 report for NZ Timber Importers

 

Sustainability: Column 3

FSC = Forest Stewardship Council

PEFC = Programme for the Endorsement of Forest Certification

Plantation Grown = Planted for the purpose of milling

Sustainably Harvested = Small wood lots grown for milling when trees are mature

VLC = Verified Legal Compliance

 

More About Timber Certification Schemes:

 

FSC     Forest Stewardship Council

This is probably the most well-known Certification Scheme. The FSC is a very large international organisation established to promote responsible management of the world's forests. They have a high level of environmental, legal and traceability requirements and certificate holders are subject to annual audits. 

They have strict Chain-of-Custody requirements, so that only someone who has an FSC Chain-of-Custody certificate and has bought timber from an FSC Certified supplier/forest may sell that timber as FSC Certified to be  used in situations like Greenstar buildings which require FSC timber for certain criteria points. For more info: visit their website at www.fsc.org/

 

PEFC     Programme for the Endorsement of Forest Certification

The Programme for the Endorsement of Forest Certification is an international non-profit, non-governmental organization dedicated to promoting Sustainable Forest Management (SFM) through independent third-party certification.  PEFC works throughout the entire forest supply chain to promote good practice in the forest and to ensure that timber and non-timber forest products are produced with respect for the highest ecological, social and ethical standards. Thanks to its eco-label, customers and consumers are able to identify products from sustainably managed forests.

For more info: visit their website at http://www.pefc.org/

 

AFS    Australian Forestry Standard

Australian Forestry Standard Limited is a not-for-profit Australian company who developed, own and manage the Australian Forest Certification Scheme.  This scheme essentially has two parts:

1) The Australian Forestry Standard (AS4708): A standard by which forestry organisations should abide by in order to sell timber they have harvested as AFS Certified.

2) The Chain of Custody Standard (AS4707): A standard for timber traders to abide by in order to sell timber as AFS Certified.  It details requirements to ensure that product is not mixed with non-certified timber, administrative procedures and how to ensure that all timber is traceable. The Australian Forestry Standard is recognised and approved by PEFC.

For more info; visit their website at http://www.forestrystandard.org.au

 

CSA    Canadian Standards Association

The Canadian Standards Association has created CAN/CSA-Z809, a set of standards governing timber forest and chain of custody.  Similar to Australian Forestry Standards, the CSA has one standard on Forestry Management, and one on Chain of Custody.

The Canadian Standards Association's Forestry Standard is recognised and approved by PEFC.

For more info: visit their website at http://www.csa-international.org/product_areas/forest_products_marking/

 

Eco Timber

This is a lesser known scheme, currently operating in the Solomon Islands.  Its requirements are similar to, but not as strict as, FSC with the intention to slowly become closer and closer to FSC.  It has been done like this to allow villages who previously had no certification to slowly progress to FSC over a period of many years.  Some of the main benefits for this scheme are that more profit is returned to the local community and a lot less damage is done to forests.

Greenpeace endorse this scheme and for more info visit their website at http://www.greenpeace.org/new-zealand/campaigns/ancient-forests/protecting-paradise-forests/eco-forestry

 

VLC     Verification of Legal Compliance

Verification of Legal Compliance ensures that the administrative requirements of permitting, planning, taxes or fees, and harvesting, as well as a broad range of applicable and relevant laws and regulations related to forestry, have been met.  Legality verification services are available to forest management enterprises as well as to companies producing, manufacturing, trading, and selling wood products and to companies wishing to verify the sources of products they purchase. For more info: visit their website at http://www.rainforest-alliance.org/

 

 

TIMBER DURABILITY

Ref: http://archive-nz.com/page/822179/2012-12-03/http://www.timspec.co.nz/Learning-Centre/Durability-Explained-45170.htm

 

What is Durability?

Durability, or more specifically the measure of a timber species’ durability, is an estimation on how long that timber will perform under different external conditions, either with no ground contact (above ground) or the tougher requirement of “partially buried” or “in contact with the ground”.  Generally, timbers are grouped into one of four groups; Perishable/Non-durable, Moderately Durable, Durable and Very Durable.

 

Perishable/Non-durable timbers are only suited to internal usage, where they will always be fully protected from the weather.

Moderately Durable timbers are only somewhat durable, and should be avoided for use externally.

Durable and Very Durable timbers are well suited for external use, but still have a limited in-ground lifespan.

 

The sapwood of virtually all timber species is not durable. For this reason durability specifies the durability of the heartwood.  The only exception to this is Maple, which does not have a definable heartwood, but as this is a non-durable timber anyway it is never an issue.  Also of note, is if a timber is fully protected at all times, (usually this can only be guaranteed by using it internally) then there is no reason why it would rot at all, as it is the exposure to moisture that causes timber to rot.  Decay can form because of insect damage too, which can be harder to control.

 

Determination of a Timber's Durability

Generally speaking, most timber durability’s are learnt by placing 50x50mm heartwood stakes outside, either in the ground or above the ground. These are then checked periodically until it has been deemed that there is sufficient rot formed or insect damage to declare it decayed.

 

Life Expectancy of Timber Durability Classes

Due to the variable nature of trees and the variation in timber that can occur within the same tree, these life expectancies should be taken as a guide only.  The location of use should also be considered, e.g. durable timbers may last for a lot longer than 15 years in the hot dry Australian Outback, but would rot and decay very quickly in the cool damp Fiordland.

 

 

Durability Class

Fully Protected

from the weather

Above Ground

but exposed to

the weather

In-ground contact

and exposed to

the weather

Class 1: Very Durable

50+

40+

25+

Class 2: Durable

50+

15 to 40

15 to 25

Class 3: Moderately Durable

50+       

7 to 15

5 to 15

Class 4: Perishable/Non-durable

50+

0 to 7

0 to 5

 

Click here to go to list of Timber Reveals Suppliers

Click here to go to the report on timber durability