Implications of 900mm eaves

We have a large north-east facing (about 35 degrees east of north) street frontage and are custom designing a home in the Hills District - Two storey home and about six rectangular windows each on the ground floor and the first floor facing the street.

Likely we will go with a custom builder - I am trying to understand the implications of choosing 900mm eaves instead of 600mm or something smaller. Intent is for the eaves to provide summer shading from mid-November to mid-March. We would like to maintain a roof pitch of atleast 22 to 25 degrees (lots of solar PV and solar hot water).

Has anyone recently done this with a builder in the Sydney area? What are the cost implications? Can we get a higher roof pitch and the 900mm eaves (future expansion area in the attic)?

(Our designer is suggesting we keep to 600mm eaves)

I am sure it can be done but it could be expensive. Your trusses would be entirely different to cantilever 900 rather than 600 and even more so, if you have a higher roof pitch.

At the end of the day, just about anything can be done if you are prepared to pay for it.

Adrian, That's was what I thought - Thing I am trying to work out is if the costs for 900mm eaves are likely to be "dramatically" higher than those for 600mm eaves. Any thoughts on what sort of cost increase I might be looking at?

Any advice from anyone else who has considered this cost or has gone through with it?

My present build (with a tin roof) has 900 eaves (pitched off the internal load bearing wall) and an internal clear span of 12 metres) which gives an effective overhang of about 760mm from the external wall. There was no significant extra cost for the trusses for the 900mm overhang other than I require a structural fascia.

My previous build had 1200mm overhang and a tiled roof. This required serious rafters i.e. 300mm deep rafters.

The other thing you need to consider is that going for a wider roof overhang plus a higher pitched roof would result in lower eaves.
What is your stud height for each level - 2440 mm ?

Stewie

Ground floor to ceiling is 2700mm. Thinking behind the pitched roof at a min 25 degree pitch was (a) we can create a bit of attic space down the track (b) we can stick solar pv

Bit that's confusing me is why does the wider overhang have to mean lower eaves? Can you not have wider overhang (eg 900mm eaves) AND higher pitch (say 25 degrees)? Feel like I am missing something in my understanding.

I'll do you a couple of quick drawings to illustrate my point a bit later.

Stewie

You need to make an assessment based on the summer and winter sun. See below.

http://blog.2030palette.org/swatch-prof ... r-shading/

Actually, a lower pitch would give you higher eaves...

JD here are a couple of drawings from my archives and altered to suit your circumstances.
The detail is a standard brick veneer house with a floor to ceiling ht of 2700mm, a roof pitch of 25º and the usual way a trussed roof is fixed to the timber frame.
The first here shows a 450mm eaves overhang leaving a floor to eaves ht of 2350mm

The second shows exactly the same but with a 900mm eaves O/H leaving a floor to eaves ht this time of 2145mm


The third is a non-standard way of doing the trusses where the bottom chord of the truss goes all the way to the fascia. Doable but not how they are usually done and I'd bet a fair bit more expensive due to the fact that the bottom chord would be taking most of the roof load plus it would have to be beefed up considerably. You would also end up with a higher ridge ht compared to either of the other two examples.



Stewie

Stewie, that makes sense now! Thank you so much for yout effort. I think the designer was trying to suggest option 3. Now I understand the rationale for difference in cost. Your explanation is exactly what I needed.

As long as you are aware of how the roof pitch to eaves overhang works and the implications, you can make adjustments to suit as per 1960'sMHomes suggestions too.
Have you had a look at the solar orientation thread on these forums? Lots of info there too. I think I've posted up a couple of drawings similar to 1960'sMHomes above in that thread as well.
viewtopic.php?f=31&t=55057
and passive solar buiulding in Sydney
viewtopic.php?f=35&t=71561

Stewie

Thanks for the advice, everyone. We have gone with 900mm eaves and 25 degree roof pitch. Builders feedback that there will be a marginal increase in cost (low $$$$).