Build 165 — April/May 2018 — 31

Steps 1–2 – Roof/wall junction construction sequence.Figure 2

wall framing (insulation omitted for clarity)

upper wall underlay lapped over upturned roof underlay

Step 2 – self-adhesive flexible flashing membrane fitted around junction and folded across the roof underlay turn-down

lower wall underlay

Step 1b – roof underlay turned down over lower wall underlay

wall framing (insulation omitted for clarity)

purlin

roofing

Step 1a – roof underlay turned up under upper wall underlay

Roof-to-wall junction detailThe BRANZ helpline has been asked recently about how best to detail the tricky junction between the top edge of a monopitch roof and an adjacent wall above. Here is one suggestion.

DESIGNRIGHT

BY ALIDE ELKINK, FREELANCE TECHNICAL WRITER, WELLINGTON

DESIGN DETAIL FOR JUNCTION BETWEEN A MONOPITCH ROOF AND AN ADJACENT WALL ABOVE

WE CONTINUE the Build series on roof-to-wall

junction details not included in Acceptable

Solution E2/AS1 to the New Zealand Building

Code clause E2 External moisture.

This detail occurs at the junction between

the top edge of a monopitch roof and an

adjacent wall above (see Figure 1).

Steps for installationFigures 2–5 illustrate the steps of the construc-

tion sequence for the detail with a sheet cladding

material over a drained and vented cavity.

Step 1: Install roof and wall underlay over

framing. Turn the roof underlay up under adjacent

wall underlay (1a) and overlap the lower wall

underlay (1b).

Step 2: Fit a self-adhesive, flexible flashing

membrane over the junction. Cut and fold a section of

the membrane across the roof underlay turn-down.

Step 3: Install apron flashing over the roofing

with upstand over upper wall underlay. Apron

flashing to have at least the minimum upstand

height and roof cover required by E2/AS1.

Step 4: Lap an additional layer of wall

underlay or fix self-adhesive, flexible flashing

tape over the apron flashing upstand.

Step 5: Install cavity battens to lower wall.

Step 6: Install internal corner wall flashing

over cavity battens on the lower wall. The corner

flashing must end behind the barge flashing.

Step 7: Install lower wall cladding over cavity

battens and then install fascia board.

Junction detail location.Figure 1

2-storey

fall single storey

junction at top edge of monopitch roof and adjacent wall above

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32 — April/May 2018 — Build 165

Steps 3–4 – Roof/wall junction construction sequence.Figure 3

Steps 5–11 – Roof/wall junction construction sequence.Figure 4

Step 8 – install fabricated corner flashing over apron flashing and fascia

Step 3 – apron flashing over roofing

Step 3 – apron flashing turned up wall Step 4 – lap an additional layer of wall underlay or flexible flashing tape over apron flashing upstand

Step 5 – cavity batten trimmed at closer height to allow wall underlay lap

Step 6 – install internal corner wall flashing over cavity battens

Note: All flashing dimensions (turn-ups and laps) to meet requirements of Acceptable Solution E2/AS1.

Step 10 – install cavity closer

upper wall underlay

Step 9 – install barge flashing over roofing and fold down over fascia board

fascia board

Step 7 – install lower wall cladding over cavity and then install fascia board

Step 11 – install cavity battens to upper wall

150 mm

150 mm

75 mm

75 mm

75 mm

fabricated corner flashing fitted over apron flashing before barge flashing installed

Build 165 — April/May 2018 — 33

Step 8: Install fabricated corner flashing over

apron flashing and fascia.

Step 9: Install the barge flashing over the

roofing and fascia board.

Step 10: Install cavity closer above apron

flashing maintaining the minimum gap required

by E2/AS1 (generally 35 mm).

Step 11: Install cavity battens to upper wall.

Step 12: Install cladding over the cavity

battens cutting the cladding to fit around the

apron flashing as required.

Some specifics from E2/AS1Specific requirements in Acceptable Solution

E2/AS1 include that there must be:

● a 75 mm minimum wall cladding cover over

the upstand

● a gap between the wall cladding and the

roofing as given in E2/AS1 Table 7

● roof flashing cover over the roofing as per

E2/AS1 Table 7, depending on wind zone and

roof pitch. Step 12 – Roof/wall junction construction sequence.Figure 5

wall cladding

Step 12 – wall cladding cut around apron flashing as required

seal flashing to fascia and cladding

8 — June/July 2018 — Build 166

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BNTR00333 BRANZ FP 210x275 Solutions Studio.indd 1 4/13/18 5:01 PM

Letters

Don’t forget the stop-endDEAR BUILD,

I am writing to point out a technical defect in the article Roof-to-wall junction detail (Build 165, pages 31–33). As drawn, the details do not close off the cavity to water entry blown by wind up the slope of the roof on the apron flashing.

The fabricated corner flashing needs a stop-end, with the stop-end 35 mm minimum high up to the bottom of the cladding, then cut back to also close off the cavity up to the top of the flashings. The cladding cavity closer would then butt into the stop-end, or the stop-end could be 50 mm high and the cavity closer could pass over the top of it. The cladding

beyond the roof would then be sealed to the stop-end and the corner flashing at the vertical joint between the two.

The junctions are very complicated, and it is important to get them right! LEIGH MARSHALL : AUCKLAND

BRANZ comment Thank you for your feedback. Adding a stop-end as you suggest is a good idea to add another layer of protection.

It is important that adding a stop-end does not introduce additional weak points, such as needing to notch in a cladding or other mate-rial to accommodate it. Our revised fabricated saddle flashing incorporates a simple stop-end to stop water passing over the top of the detail while not impacting on the cladding above.

150 mm

75 mm

75 mm

150 mm

75 mm

50 mm20 mm

WRITE TO US: Build welcomes letters

but reserves the right to select which

to publish and to edit letters to fit

the space available. Send your letters

to the Build Editor, Freepost BRANZ,

Private Bag 50 908, Porirua City or

email Annemarie.Crampton@branz.co.nz.