Red Mantle Lightweight Chimneys

Philosophy-Methodology-Build process

Introduction

1. Red Mantle lightweight chimneys are a factory pre-fabricated unit that is presented to the building

[usually by crane]. The chimney ‘shroud’ is designed and manufactured with fibreglass using well known and proven modern composite construction methods.

2. Two types of build: (1) 100% fibreglass structure with a moulded brick patina on the surface.

(2) 100% fibreglass structure clad with 15mm thick brick veneers. 3. The chimney shroud is lowered over and attached to an engineered support truss/frame that is

connected to the building and flashed to code and weathertight.

4. The Red Mantle system is Patented. [No.598820]

Quakesafe Philosophy

1. Red Mantle designer Nick Williams developed the current technology to assist homeowners in replacing their old URM chimneys with a safe and lightweight alternative after the 2011 Canterbury

earthquakes. 2. We help preserve the beauty of NZ heritage and architecture through innovation, technology, and

design.

3. Building solutions that meet the rigors of modern building codes require innovation through craft - a passing of the mantle and a new way of doing things.

4. For instance, we have created a new craft using fibreglass, moulding and advanced film industry

techniques to re-create stunning, safe, and secure chimneys for homes and buildings affected by recent earthquakes.

5. We are accepted as an excellent solution for heritage and insurance chimney replacements

Engineering

1. Chimney support truss/frame and all connections to the building are fully engineered to NZ code requirements, and consider wind and earthquake loadings.

2. Producer statements (PS1, PS3, PS4) and memorandum of design (MOD) are supplied along with

sketches for the build and connection. 3. Construction monitoring (CM4) oversight will be undertaken.

Brick veneer preparation and bonding

1. Brick veneers for cladding are usually selected from the best of original heritage brick stock supplied from the original building [for heritage authenticity].

2. New brick stock may be used if suitable visually. 3. All brick stock is diamond machined to minimum 15mm and treated for bonding in the Red Mantle

factory environment.

Truss/frame build and install

1. Truss/frame builds are constructed in either timber or steel.

2. The timber/ply clad or steel [engineered truss/frame] is manufactured either in the Red Mantle factory or onsite. This is then installed and connected to the building as per the engineering specification and NZS3604.

3. Truss/frame is then flashed to the roof penetration using code compliant E2/AS1 methods and wrapped with building wrap...at this point it is essentially weathertight [except for the top opening which will be covered prior to the replica chimney shroud being installed.]

Internal Truss / Frame View Truss / Frame Pre-Wrap Chimney / Shroud Install

Chimney Shroud construction

1. The Red Mantle chimney shroud is a one-piece structural fibreglass construction that is lifted over and down onto the timber support truss/frame.

2. The chimney shroud is cut to suit the pitch and contour of the roof that will receive it to ensure a good

fit and authentic visuals. 3. The fibreglass chimney shroud is structurally stiff and is a one piece monocoque build. 4. The chimney shroud is water-proof, rot-proof, and rust-proof, stiff and lightweight.

5. Further weather tightness and protection of the fibreglass chimney/shroud/truss assembly is achieved by cladding the monocoque fibreglass box with real brick veneers (mostly cut at 15mm). These are bonded down to the surface with high tech flexible epoxy adhesives from Nuplex or Sika.

6. The surface of the composite chimney/shroud structure is 100% abraded with 36 grit grinding discs to ensure a clean and dry surface for maximum adhesion of the brick veneer to the box (testing has shown failure of this bond joint is not achieved prior to brick disintegration).

7. Bonding and placement of the brick veneers to the fibreglass structural box is completed manually and all brick veneers are 100% covered with adhesive [backside] prior to placement to ensure maximum bond strength and adhesion.

8. Brick veneers are machined to minimum 15mm, dried and treated prior to bonding. [Factory]

Installation

1. The finished composite box structure (chimney shroud) is then lowered on top of the already built and flashed timber or steel frame until it rests on the internal support brackets (located inside the

chimney shroud). 2. Further attachment of the shroud to the frame is made with tech screws which are applied fitted with

neo water tight washers. [See pic… BRANZ deck detail as an acceptable solution to stop ingress of

water]. These are also an acceptable solution for roof cladding fixture.

3. The tech screw and neoprene washers are then further covered with a flexible mortar. This is mainly

for authentic visual requirements, but it does add yet another layer of weather tightness/rain shield to the tech screws themselves.

Flashing/E2 requirements

Below is a review of the Red Mantle build methodology using the philosophy for managing water known as the 4 Ds – deflection, drainage, drying and durability.

Truss/frame

1. Red Mantle methodology uses the truss/frame support as an engineered connection to the building. The truss/frame is flashed to code (E2) and made weathertight. It is engineered for strong and safe connection to the building and is code durable (15+ years)

2. Construction in timber: Composed of LVL H1.2 90x45 framing clad with H3.2 F8 grade structural Ecoply. The ply forms a primary line of defence and is secured to the timber framework with stainless steel nails or screws.

3. Construction in steel: Truss/frame will be hot dip galvanised or painted to AS/NZS 2312. If ply clad, ply will usually be H3.2 F8 grade structural Ecoply 9mm.

4. As a secondary line of defence the truss/frame is flashed to the roof penetration using known E2

code compliant methods of flashing in a material of choice. i.e. lead, copper, Wakaflex, Butynol, Coloursteel. (see below from E2/AS1). The ply truss/frame is then further wrapped with a non-absorbent underlay/wrap which is sufficiently overlapped and edge taped/sealed with Marshall

flashing tape (BRANZ appraised 846).

5. The truss/frame itself is able to deflect water and drain if wet. The flashings at the base (around the roof penetration) are E2 compliant and will deflect and drain as required. The truss/frame/wrap is able to dry and the construction is code durable (15+ years) and fully engineered.

Chimney Shroud

1. The base construction method and materials used (fibreglass) on the chimney shroud are well known and tested (like a boat hull or yacht mast) and are water-proof, rot-proof, and rust-proof. This type of construction will not flex at the corners.

2. The addition of the chimney shroud over the truss/frame adds further to the deflection of water and protection of the truss/frame below.

3. The chimney shroud brick veneer surface sits 55mm off the truss/frame and shelters/deflects water

from the under lying E2 flashings on the truss/frame to roof. 4. The cavity formed between the inside of the chimney shroud and the truss/frame consists of a 10mm

gap for ventilation and drying (if required).

5. The chimney shroud also has an in-built 20mm cavity which is part of the chimney shroud internal construction (see below pic). This has a smooth non-absorbent surface and will dry quickly if wetted.

6. As noted above the fixings with 14g tech screws are sealed with complaint solution neoprene

washers which are further covered with flexible mortar. 7. Further lines of defence are provided with deflection and durability of the composite chimney shroud

by cladding with brick veneer. The brick veneer is suitably durable.

8. The chimney shroud is made weathertight at the top opening by construction of a fitted lid. This has a tight fit and laps over 75mm whilst carrying the top most course of brick veneers. It is tech screwed to the chimney shroud and can be removed for future maintenance of flues.

9. The chimney lid often will require a pot on top to run flues. The pot/up-stand is made from stainless steel, is part of the lid construction and is 100% water-tight. The pot top opening is flashed using traditional flue flashing cones (refer pics below).

Chimney Shroud Interior Chimney Shroud Exterior Without Lid

Lid + S/S Lined Pot Chimney Shroud Lid + Pot+ Flues

Racecourse Hills Homestead, Darfield, Canterbury

St Andrews College

Te Koraha House

30 Fendalton Road