I'd just call it a weatherboard house . I suspect the windows are later replacements -- originally it would have most likely had standard wooden windows IMO .

Any addition on the rear that is too modern will look strange IMO , unless you do the front the same , which means getting rid of at least most of the weatherboards , and the windows , and then a more modern balustrade , then the roofing -- getting pretty close to a knock down rebuild , especially if you do a sympathetic style and that may need new trusses etc .

I'd certainly investigate sticking with mainly weatherboard and similar tiles , with polished wooden floors , and window frames that are similar to the existing ones .

Weatherboard would be one of the tougher styles to make modern - it is what it is , just make it a bigger and slightly tidier version of what it is IMO .

I was thinking it was 50 60s post war

I’d call this a post war bungalow and I disagree with @potty999, the windows do look original. It’s almost like they were wanting to do an Art Deco type steel window but couldn’t afford it or maybe source it. Strip it back and there of echos of a future Mid Century feel of the late 50’s and 60’s. That is where I’d start in terms of feel. As for an addition, don’t try to make it the same, go for contrast.

I would agree with pottsy. Keep the outside the same as the original house but you can go more modern on the inside. Perhaps you could vault the ceilings in a new living area and add large doors instead of windows to the rear

you should start designing from inside out with a new floor plan and that will help suggest how to attach the extension but matching the angle of the roof and using plain external wall cladding should make it easier to blend new with old...share the old floor plan for some suggestions

1950s maybe 60s weatherboard. B ut I agree with Pottsy, the windows look later. Proportion with the segments & thin edges look 70? (but I'm no expert).  Anyway.. anough time has past to call it all 'mid century'. 

Google Modern Mid Century. Big in the US according to the TV garb I watch. Nice airy extention with similar flooring will be a great enhancement for you to enjoy.

The 1950s weatherboard is evident in the corner window on the right hand section. The windows pictured are 80s faux colonial, I suspect that they were replaced in the 1960s section when the bullnose was added. The bullnose and the windows were common in the 80s. It’s a hybrid. If you go to “Homes to Love Australia” either on Insta or Pintrest you’ll see quite a few Australian extensions. You have a choice of a clearly modern extension or a proportional extension. Architects def favour a clearly modern addition that shows distinct delineation between old and new. I think those look a bit like mullet houses but they seem to win the awards. A proportional extension would echo roof heights and materials, ceiling heights, windows and cladding. You need to decide which you prefer before speaking to an architect. FWIW I wouldn’t make an architect my first point of call if you’re just starting out on planning.

The corner window is a classic of the 50 60s post War Houses built with brick and weatherboard Check out the current series of The Block., Charming Street in MEB

Thank you all very much for your help and advice. I think the key question for us to resolve is whether or not we knock down and rebuild, or whether it’s worth us retaining some of the original house that you can see.

We ultimately want to end up with a ‘modern farmhouse’ style, but functionality-wise do need to make some additions to the current footprint and do some limited internal rearranging (although wouldn’t need to do much to the front of the house internally). We can see some actions we can take to give us easy wins in bringing the existing house in line with this vision, but equally it might not be worth the trouble.

I’m terms of the ultimate vision, we can list off the features we want, and we can share plenty of Pinterest references in terms of the style we want to achieve, but that is the extent of our knowledge here.

I think, as Paul Di Stefano Design helpfully stepped out, we need to get some preliminary advice from a design professional to help form our thinking before more advanced steps in drawings/documenting everything etc.

Has anyone seen some good threads on Houzz that I could read as some education before taking this prelim step?

I gather you don't want to double its size , and remove too many internal walls ? My gut feeling then would be that , unless you have totally fallen out of love with the house , to do say up to $100-120,000 of alterations and additions , make it a bit bigger and flowing a bit better . Depending on where you are , knock down rebuild will be at least 3 times that , and you may be overcapitalising for the area ?

One other thought , just to confuse things , is rather than knock down , you said it was moved there from an orchard from what I can gather ( or was the orchard removed from around it , and other houses built there ? ) , so maybe you can get $20k or whatever for it , and the new buyer moves it , presumably to some cheap land somewhere ? Generally if you have expensive land , you do an expensive build , but a cheaper rural town may be what this is destined for ?

Not on Houzz. But have a look at Undercover architect. Also Three Birds Renovations is aimed at the home owner and focus on the style you’re after. BuildHer Collective have some good online resources. If you’re just going to refresh a couple of rooms in the existing house have a look at Katrina Chambers - not flashy but a good place for a beginner to start to get in the mind set. Great people here will help you with floor plans improvements. Then you could talk to the design professionals that offer their advice here on Houzz.