I think that´s the most important we should bear in mind in this works. Quality works wont give us problems at least for 20 years. A bad quality work will be in your life for the same 20 years. What do you prefer?
We can distinguish between quality in materials and quality labor.
To make sure you employ quality labor, try to have a look to another works they have built, or better, try to speak with their employers to have good references.
Let my advise you: When the same person works as a bricklayer, plumber, electrician, carpenter… Be sure no one can play all the games ( Peter Shilton was a fantastic goalkeeper, but never would make goals like Gary Lineker).
Quality material is related with a good labor too. You can´t demand a good collocation of a tile if it´s not really plan.
For quality in materials try to involve yourself in buying them. Don´t be guided only for price or aesthetic. Have a look to specifications: You´ll find the tolerances, joint distances, outdoor or indoor use, heat absorption for outside pool floors, kind of cement needed….
Materials have a two year guarantee, but you´ll need to prove you putted as specifications recommend.
Most materials needs CE mark : Windows, tiles, bricks, cement… And the list in construction increase monthly. Demand it if needed.
Nowadays due to “crisis” competition is fierce to obtain jobs. Some builders downs in quality to make better offers.
For example, when you buy tiles, they can be ceramic or porcelanic. The porcelanic are now fashionable (and expensive), but to stick them you need a special cement adhesive due its poor absortion capacity and it costs 10 € / 25 Kg sack. Meanwhile the conventional adhesive costs 3€/sack. Look at the specifications!Some buiders don´t buy the first one and save money but you will have problems probably past 4 or 5 years and you won´t know why ( Oh!Mistake , you will know because you read me...
Better! You won´t have problems because you read me before doing your house.
Another example: Narrow pipes are cheaper but if the diameter isn´t big enough you will have noise problems in you bath. It will be the same if stopcocks are bad.Each material will need a diameter, it´s not the same for copper, PVC,PPR,... Due it´s internal texture.
Remember: Always demand detailed estimates with material specifications to avoid problems.
P.D: Hamilton 1- Magic Alonso 1.