I'm in the real estate development building game and well positioned to help.
The thing that I don't like about architects is that for a start, they charge you money to make a small house feel big, which begs the question "why not avoid paying an architect and plow the savings into making the house big in the first place?" (which is what I did).
The other thing that I don't like about architects is that they're often out of touch with how much it costs to build what they're designing. One of my competitors paid an architect $200k to design a structure that mixed rendered corefilled concrete blocks with corrugated sheet metal with aluminium waferboard to produce a "modern" look. Unfortunately, mixing materials pumps your build price up by as much as 30%, and with the cost of managing all of those building techniques/trades, he could have simply covered the entire building with a polished granite facade (which is far and away a superior product and would have oozed style)
In the past, architects were necessary because good house designs were hard to find, and plans drawn by hand. Today, you can find endless house designs online, and have them drafted for you very cheaply.
I would advise you to talk to a builder about the costs and benefits of various building styles/layouts at the design stage, because they understand the mechanics and logistics of the build. For example I designed my building to suit standard lengths of blocks, tiles, plywood, and reinforcing steel. That way, I minimize waste, eliminate the labour and cost of cutting material to throw away that I could otherwise incorperate into a larger building, and speed up the build. Why buy big pieces of material only to pay a worker to cut them down to size and build a smaller place, when you can design to put in whole lengths with no waste and no labour to cut, thereby building a bigger structure?
The other thing that I would advise is to allow retrofitting as much as possible. For example, I prefer the inclusion of suspended ceilings, conduits, and service alcoves/ducts, so that if something changes in the build along the way or you decide to add something later, you can simply run the new wires/pipes/whatever within the ceiling cavity or in those service areas. Putting in conduits/extra wiring before you close your wall/ceiling with plasterboard (or whatever) is cheap. Adding the same stuff later is expensive because of demolition, rebuilding etc. Another example is that fixing a leaky pipe in a ceiling cavity is much cheaper than fixing the same pipe embedded in a concrete slab.
Another thing to consider is how contractors and builders work - often, builders will see design flaws at the design stage and say nothing about them. Then, when you've signed a contract, will mention the error and charge you an excessive variation fee to "fix" the problem. Therefore, make sure that your plans are as well thought out and detailed as possible from the outset. It is quite common in my neck of the woods for building costs to rise 20% above contract price because of this issue.
Then there's the issue of finishings. Do not settle for a building contract that says "standard plumbing/electrical fittings to be installed" or anything that resembles that kind of language, because in the building world, "standard" means "cheapest". When you find yourself in that scenario, you either end up with sub standard fittings or have to overpay to put something decent in.
Try to pay attention to the positioning of power outlets, cabling/antenna outlets, telephony, light switches etc, because contractors tend to put them wherever they feel like. A good way to go about it is to decide on these details when you have your final design locked in. Then, sketch in a few different arrangements for furniture/beds/lamps/phones and make sure that the location of your outlets/sockets/switches suits these possible arrangements, and is specified in the contract. Nothing sucks worse than having an exquisitely designed house that looks great when empty, and then having cables/cords running all over the floor when you put in furniture and actually live in it. In that way I agree with one of the previous posters - put in lots of extra cabling before you close the walls and it's cheap to do so.
Lastly (I could go on all day) consider sourcing materials yourself, particularly higher ticket finishing items such as granite bench tops, high end porcelain tiles, tap fittings (well. not so much but still, big savings to be made) - to give an example, my local price for man made caesar stone benchtops is $700/m. To import the same thing directly from china or indonesia, the landed shipped price is $30/m. It doesn't sound like a big deal, but these little savings build up significantly over the life of the build. Just make sure you watch the lead times for acquiring those materials so that theyre available for use when needed. Of course don't leave all your materials on site either, because they may be stolen.
Building a house is a bit like getting ready for a fight, with that old muay thai adage - "train easy, fight hard. train hard, fight easy". Good preparation is key, and avoids lots of heart ache/cost blow outs
btw are you planning to coordinate the contractors yourself, or to engage the services of a builder?
edit: forgot to talk about common features
Walk in wardrobes are some of the most overrated things on the planet. Women love them, but make sure that if you absolutely have to put on in, that you put a door on it. Ive seen houses where walk in robes are part of the hallway into the bed room without a door - which means that you see a giant messy wardrobe and sniff sweaty shoes every time you walk in and out of your bed room.
Ensuites - putting these in doesnt cost much if done at the design stage. Traditionally, only the master bedroom has an ensuite. Personally though, what with children living at home longer plus the growing trend of cohabitation, houses with ensuites to multiple bedrooms are becoming very desirable. If you put them back to back between adjacent bedrooms so as to piggy back supplying services/removing sewerage, you can add ensuites very cost effectively.
Spa baths - even if you dont want one and just want a bathtub, it's usually a good idea to make sure that there is an electrical circuit for a spa bath motor in case you change your mind later. Lots of people dont like baths at all, but women with children tend to really like them, which helps with house values should you want to sell.
Oh and id insist on tiles in wet areas to be floor to ceiling. Its really annoying when builders try to save money by only tiling up 6 feet off the floor - you then have to constantly repaint, you end up with mold problems etc - not fun.
um, Ill shut up now. I get excited about designing dwellings - it's good fun
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