That’s a massive extension. Lots of wasted space in dining yet you have study in walkway. If you want to keep study there either shift doorway to provide more protection to desk area or move desk to other side of hall. I have sketched an alternative given separate laundry and pantry which also could accommodate desk in one of those spaces as well as reducing length of extension by up to 750mm or thereabouts. Bed 4 also seems small and without a BIR. this could be addressed

And fireplace is shoved to corner. Why’

You also have a lot of triple sliding doors adding costs. Think about what is really needed for access versus ventilation and fly screens.

I can see the thought process for the study placement, I had the same plan with an old house. Are you at the max width for the extension? If possible making it a longer rectangle that includes the kitchen will be cheaper to build as it removes the unused space around the dining. Will you remove the door between the two bedrooms? It impacts on the functionality of both rooms. You could also consider having a European laundry in the study area and keep it separate from the pantry. Do you really need a butlers pantry?

Big reader like this

I don’t think the extension is too large. My dining is 5.4m x 3.5m and I use every bit for a large 10 seater dining suite and comfortable walking space around the area. The plans are showing the dining suite oriented the wrong way. A large dining table should be located at right angle to island bench..perfect. How many bedrooms do you need? Take out the door between bed 3 and 4 if not required. Or just put furniture in front of the connecting door..easy. Could bedroom 4 be used as the study. And when you show a study area, is this for true quiet study, or just a spot to put paperwork for house hold? If you need a true study area, then the hallway is not suitable. But to use as all wall storage/built in cupboards, is a good use of space. And depending how your household works, the “study” bench could just become a dropping area for junk. Not a good look for a entrance to your new extension. Are you happy to have your dirty socks and clothing in the same room as your food, in the combined laundry/pantry?

And as bigreader mentioned, maybe have a rectangle extension going length wise on land, not across the land. Can you post a site plan, so we know how the house sits on the block

Inspiration

And where is north compass point on your plans?

Hi thanks everyone for suggestion
I might reconsider moving laundry into Hallway and use existing plumbing on right side for a European style laundry. Initially I thought noise might be a factor as its close to sleeping zone so I decided to have it further back and combine with pantry.
The rear is facing south and as I am planning to do a rake or high ceiling with celestory window I was thinking having the dining and living horizontally orientated to the backyard and verandah instead of vertically. As it it was vertically like big reader suggested i will have verandah parallel to living space as well as driveway and carport and be looking at neighbours fence instead of backyard. It will also be westfacing in that instance so my celestory window will get full summer sun .
I quite like Kate's idea on splitting laundry and pantry apart and sacrifice some dining space . But also my intention was to have a 10 seater at some point and maximise living area.
Lots of ideas thanks.
Yes bedroom and 3 and 4 is slightly awkward will think about having a barn sliding door at some point but atm my main expense will be on the extension.
If I was to have European laundry in hallway is there any suggestion to reduce noise in hallway if appliances is running

2 layers of sound check plaster with small gap between them paying attention to no other gaps. Think about where close horse can go etc. but really are u running machine at night?

Thank you Linh Ha for the orientation of your block. With south at the rear, your current design is good. And the northern sun will get into the living area through the courtyard windows. You could keep the pantry and laundry as is, but have a dividing wall with a sliding door between the two areas.

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Your home will be a substantial size when completed. It deserves a laundry room, not a euro laundry.

what are the original walls, floor and roof built out of, is it a flat or sloping block, do you plan for the extension to be at the same floor height as the orignal house, how many steps are there from ground to original inside floors and please share a plan of the existing house showing current location of plumbing, a google earth view of the existing roof and a rough site plan showing the distance from the original house to the boundaries, size and location of carport, garage or other buildings and direction of north

some dimensions are hard to read so room sizes are based on estimates but i would never consider a boxed gutter and suggest that the easiest new roof option would be a simple low gable roof (as shown with dotted lines) to create a T shaped linked extension with skylight over north facing roof and bigger alfresco instead of a narrow verandah although a flat added verandah/pergola (with or without some transluscent roofing panels to avoid making inside rooms too dark) could be useful to provide covered access from carport through the entry court and rear alfresco entry....the old laundry has been converted into a shared bathroom with separate toilet/pwdr rooom and, after allowing for the extended central hallway, the original kitchen could be enclosed for a study area or walk in storage and maybe use a similar option for the old dining room or remove the dividing wall and make a more useful room size for the old bed 4 ...the new family and dining rooms are generous (central fireplace with offsett TV is better for viewing) but suggest that less sliding doors are more than enough and making the walkway between old dining room and extension narrower allows for a better size and shape for laundry (without external door) with more storage and counters for pantry and kitchen and the two smaller windows on the eastern side of the dining room retains more privacy from neighbours and space for a sideboard