Codes & Standards for Masonry Heater Construction

This is a pre-draft in process but I am publishing it so that it is available for immediate reference and to begin the forum topic!

Introduction

This article provides a summary of references addressing/perscribing requirements/methods masonry heater construction. It is a direct result of our hands-on experience in the field.

There are two important documents presiding over the construction of masonry heaters in North America. These are the International Residential Code[1] and the ASTM E1602 Standard Guide for Construction of Solid-Fuel Burning Masonry Heaters[2].

US Masonry Heater Building Codes

“International” Residential Code (IRC)

Masonry Heater construction is addressed in section R1002 of Chapter 10 of the IRC, entitled “Chimneys and Fireplaces”.

R1002.2 Installation. Masonry heaters shall be installed in accordance with this section and comply with one of the following:

1. Masonry heaters shall comply with the requirements of ASTM E 1602; or

2. Masonry heaters shall be listed and labeled in accordance with UL1482 and installed in accordance with the manufacturer’s installation instructions.
Chapter 10 of the IRC

What this means basically is that manufactured masonry heaters should have a UL listing while custom masonry heaters should follow the guidelines set forth in the ASTM E1602 standard. This pass-through reference means that the majority of the code referring to custom masonry heaters is in the ASTM standard, which is a less readily available document.

ASTM E1602 Standard for Solid Fuel Masonry Heaters

The ASTM E1602 Standard for Solid Fuel Burning Masonry Heaters is the defining document of best and safe masonry heater construction practices.

EPA & Emissions Regulation

Masonry haters do not currently require EPA certification. This determination was made because of their recognized inherent clean-burning nature and also to give time for the industry to futher develop testing standards. It is difficult to compare masonry heater emissions directly to wood stoves with a g/hr rate because the heat generated by a masonry heater in a couple of hours is stored and continues to radiate into the next day.

Building Code in Canada

In new construction, the masonry heater is ideally drawn into the architectural plans. The ideal level of detail begins with placement of the masonry heater in the floor plan with consideration for adequate clearance to combustibles. The foundation of the masonry heater should be addressed in the overall foundation plan. For homes with joist-supported floors, the floor framing plan should show clearly the boxed out opening for the masonry heater. Note that there is a 2″ clearance perscribed for structural members which carries over from fireplace code and therefore the rough opening in the joists should be 4+” larger in both plan dimensions than the footprint of the masonry heater. It is also important that the chimney for the masonry heater be clearly located in the roof framing drawing.

It is ideal to also have an interior elevation drawing of the masonry heater and/or a section at the masonry heater including its chimney and nearby rooflines. This drawing gives a sense of the masonry heater in the space, shows that the heater meets adequate clearances above the heater and also is an important tool for chimney estimating, planning, and purchasing.

@PabloK, it is an honor to have your presence in the forums! For those that don’t know of @PabloK 's work, he is very active in both heater construction and education in Argentina. I came to know of his work through his Instagram account:

Thank you for listing these relevant ASTM standards. The ASTM E1602 Standard Guide for Construction of Solid Fuel Burning Masonry Heaters has been the most relevant and the one I am most familiar with since it is specifically referenced in the building code. As a professional heater builder, it has been worthwhile to have a copy and be able to reference it when any questions came up with local building officials. I would like to write a follow-up article summarizing its most important specifications.

I had no idea about the “ASTM E2778 Standard Specification for Custom Tiled/Mortared Masonry Heaters (Stoves)”. My guess is that it was put together by a contingent of heater builders that were part of AMHOP, a now apparently defunct association of heater builders that had split off of the Masonry Heater Association (MHA). Does anyone on this list have any familiarity with the contents of this standard? Is it worth purchasing?

@mheat (Norbert Senf), is an authority on the final two you cited which have more to do with efficiency testing:

I should say also that I published the article that started the thread rather hastily in order to start this thread and that I look forward to improving it. Discussion here will certainly lead to its improvement.