We understand the importance of clear, accurate information when specifying timber joinery. Here you’ll find answers to the most frequently asked questions from architects, designers, and other industry professionals working with JMF systems.
Below if a brief explainer video that covers what JMF does and who we are.
JMF is always happy to assist with any consent issues you may be having. While most projects breeze through with no issues, there are always some BCOs who will ask for further information. Please contact us with the details of the project including the joinery schedule and the council’s questions and we can assist from there.
JMF have worked with technical experts from BRANZ to identify the maximum dimensions of all frames while remaining compliant. We recommend checking all frames prior to specification using the JMF Engineering Calculator.
You can also find more information on dimensions by heading to Resources > Compliance Resources.
Please contact us if you need help accessing or using the calculator or the resources pages.
We bring the sill tray out to just behind the drip edge of the sill and fit a proprietary mould that is sealed to the building / under side of the sill tray, we do this as you can never be sure exactly what point the sill is going to strike on the weather board.
When JMF tested the installation of its suite, we used a sill tray for cavity and non-cavity installations. This was considered best practice for timber joinery at the time and easily passed the testing we completed. We will be doing further testing in the next few years, so we are very open to ideas and suggestions on how other industry experts would handle these details.
JMF did not test with a jamb batten inside the trimmed opening. We typically have a lot more cover over the weather board with facings that eliminated the need for the jamb batten. This has been accepted practice and never raised concerns with compliance.
Yes, we would deem this to be an acceptable alternative although council may still ask for proof at the time of consent application, which would need to be provided through a verification method. JMF has not tested this system however you could prove historically that this works.
Yes, JMF has tested the installation of timber joinery into several cladding systems, there are drawings and details available online.
Whilst timber joinery is outside the scope of E2/AS1, our tested system meets the requirements under E2/VM1 as we have tested both our installation details and completed testing to NZS 4211.
Yes, timber’s superior thermal performance means our products comply with the new code in all climate zones. Double glazing will always be required to meet the new R-values and in some situations, thicker frames or higher performing glass will also be required. We recommend talking with your joiner to discuss the R-values that are achievable with timber.
JMF has a calculation tool available to all manufacturers of JMF joinery to calculate specific R-values of our joinery.
We recommend reaching out to your nominated joiner directly as there are many factors that influence the R-value such as glass selection. However if you are not at that stage yet and needing R-values for consent stage, head to our calculations page and submit a request through there.
When using H1/AS1 Table E.1.1.1 to determine the R-value of generic vertical windows and doors for housing, an opaque panel within a glazed door needs to be treated separately. See comment 3 in H1/AS1 E.1.1.2. When calculating the door R-value using the method described in H1/VM1 Appendix E, the entire door can be treated in its entirety.
Only the H1/AS1 Schedule method restricts the skylight area, and specifies minimum skylight R-values. This skylight area restriction is unchanged from the previous Fourth Edition H1/AS1, but the minimum R-value has increased. When using the H1/AS1 Calculation method or the H1/VM1 Modelling method there are no skylight area limits and no minimum skylight R-values. Irrespective of the chosen compliance method, the method for determining what R-value a particular skylight achieves has changed and now requires the inclination angle of a skylight to be considered as this significantly affects thermal performance. To meet the new, increased R-values, some suppliers may use triple-glazing in their skylight products, however, this is not prescribed.
In short, when replacing joinery you do not need to increase the performance of the joinery but you cannot decrease it. This means you cannot decrease the thermal performance of the building by replacing with lower performing joinery.
The 40% glazing area limit of the H1/AS1 Calculation method relates to the total wall area of the building, not to particular elevations. See H1/AS1 2.1.3.2 and relevant definitions in Appendix B.
JMF does not have this in our current suite, but it is certainly something to consider for the future. We will be doing further testing and additions to the suite in the coming years and we are open to suggestions and input so we can ensure we are testing products that meet the demand of customers.
This is something we will consider for future testing. Because timber joinery does not have a channel that it slides in like aluminium does, it is a much more complicated detail to achieve. We will certainly consider and take this on board when we begin planning for our next round of testing.
Yes! We are continually looking to improve and further develop the suite. We are looking forward to a new round of testing when the next updates to NZS 4211 come into play.
We will be collaborating with our joiners and specifiers during this process.
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