I have come across several cases where the client ask for larger room sizes without realising what can be or should be the ideal room sizes
A Bed room with size,300 cm(10 feet) and 270 cm(9 feet) is more than sufficient to keep the largest normally used cot of size,180 cm(6 feet) x 155cm(5.5 feet).This room size will leave sufficient space on either side of the cot.There should not be any toilet door opening to this bed space as it will take passage space from this.So you have to have a space where toilet door can be opened.This space is normally indicated as dress space in plans even though the space may not be used for dressing.
If you want to keep a table on one side of cot,you will have to increase that side length by another 90 cm.So your bed space now goes up to 300cm x 360 cm.This size is normally considered as comfortable space for a bed room with dress and toilet nearby.Most of the apartments have bed room size as 300cm x 360cm..If you want to increase the bed space ,maximum you need to go in case of a villa can be 420cm x 390 cm(14 feet x 13 feet).Bed space above this is simply a wastage.
When you look at formal living room where you entertain your guests you have to see how many persons will visit you at a time.In a normal house not more than five people will not be using formal living room at a time.So there is no point in having very large living room.
Members of the family require a living space where they can sit and relax,watch TV,work on your lap top,listen to music away from place where guests sit and thus a space called as family living space is required.You can have Dining room on one side of this family living ,Pooja,access to stair also close to this space.There can be another family living space where you reach by climbing up stair in the case of two storey house.This space can also be combined with Home theatre even though some people prefer Home theatre space closed to avoid disturbance to other family members who does not want to watch TV or listen to music.Home theatre can ideally have a size of 450cm to 600 cm in length to 390 cm in width
When the room size or (loading span in structural engineering language) increases structural cost will increase due to more steel reinforcement required.So unless you really need it,do not increase size of rooms.Apart from structural cost,over all cost of house will also increase unnecessarily if you increase size of rooms without any reason or justification.
For keeping all necessary gadgets of Kitchen in workable distance is very important in Kitchen.If you have an unnecessarily large Kitchen,the person working in the kitchen will find it difficult as she will have to walk around kitchen a lot adding to her strain.I have observed that Kitchen with dimensions 270 cm x 240 cm(9 feet x 8 feet) is more than sufficient to keep all Kitchen facilities at a comfortable distance allowing lesser running around for the Kitchen user.You need to add to these dimensions only if you want to add an eating place inside Kitchen or an Island in the Kitchen just like in western houses.Check on possible dimensions required for adding a small dining space or island and then suitably increase dimensions of Kitchen in consultation with your Architect.
There has to be a utility space in the house where you can keep washing machine,ironing table,grinder etc.Keep it nearer to Kitchen and Family living space.Unless you live in Village areas,you do not require a firewood Kitchen or so called work area.
Guest bed room is rarely used these days as with increased availability of travel facilities and faster life nobody would prefer to stay overnight in the house of a relative.So go for guest bed only if you can afford it .
In the beginning of construction when you prepare plan of the house,you may feel like adding one more room though not essential and increasing sizes of rooms unnecessarily.But all cost indications given by your contractor and Architect can go wrong and construction cost can only go up in Kerala Conditions.So plan a house with dimensions of rooms just sufficient for your needs and definitely not bigger than required.Your Architect can guide you after understanding your needs in selecting ideal room sizes for your house.