We renovated an older house two years ago... as in, pretty much gutted the place.
One thing that drove me mad was getting
Offerte (estimates/bids) for the various projects. Look for firms advertising '
Gratis Offerte', and make sure it really is gratis even if you decide to go with another firm, as some firms charge for their time to put an estimate together. Two firms actually refused to give me an
Offerte if I had another firm also bidding on the project - apparently calculating an estimate is too much time to invest if one is not guarenteed to get the work.
Before you begin, do make sure that you understand what does or does not need a
Baubewilligung (building permit).
So - some folks I recommend:
Fredi Stocker, C&S Renovation, Bachaustr. 27 8806 Bach, 055 442 4218, Handy 079 691 4631 - Painting, plaster work, exterior stucco/plasterwork, tiling, and generally figuring stuff out. A great guy.
Calendo AG, Sihlstr. 38, 8001 Zürich, 01 212 6969 - Electrician - My house, which was a byzantine mess, is now wired up to code.... these folks are quite good.
Eric Huser AG, Neutalstr. 10, 8852 Altendorf, 055 451 18 90 - Plumbing and heating. Good with finding solutions to old house problems.
Glasmanufaktur Buttikon AG, 8863 Buttikon 055 363 31 11 - Glass Manufacturer - used him to create two unusual glass walls in place of shower stalls - good at finding solutions to odd spaces.
Walter Rusch, Ofenbau, Oberdorfstr 35, 8852 Altendorf 055 442 66 38 - Fireplace, Cheminée, Kachelofen builders. Rebuilt my defective fireplace, and didn't even bat an eye when I decided - after installation - that the whole thing needed to be moved 30cm

. Very helpful folks.
Schnyder AG, Industriestr 2, 8808 Pfäffikon, 055 416 16 20 - Roofing. I didn't expect to have to repair the roof, but so it is with a renovation project... not nearly as expensive as I had feared, job well done.
Erich Stocker, general contractor, S&S AG, Scherrstr 3, 8033 Zürich, 01 368 88 00... This is a qualified recommendation. Herr Stocker did a wonderful job of pulling our renovation together and making sure it got done within budget and on time (which, I now know, is something of a minor miracle in Switzerland.) I truly liked working with him and would use him again...BUT... he works for an architectural firm, Schellenberg and Schoz... and we were quite dissatisfied with the architect. So, if you have a job where you don't need an architect's involvement, just a general contractor, I would heartly recommend Mr Stocker. I would not use this firm for any architectural services however.
Troesch Sanitas for plumbing fixings - good prices, wide selection, etc.
http://www2.sanitastroesch.ch/d/index.php
Unfortunately, none of these folks speak much English. While my German is passable, I unfortunately didn't speak much construction-ese, in any language, when I began this project

. Funny how you never learn truly useful words in language class.
Also:
Max Sennhauser, Maur, 01, 980 14 78 or office in Tschiertschen, 081 356 10 29 - architect and builder. We first considered a house in KT ZH which would have been pretty much a tear-down and used this firm to do an inspection. He was very thorough, giving us a detailed report on all aspects of the house and an estimate of the costs of renovation. He certainly seemed to know what he was doing, and had very good ideas. Ultimately we did not buy that house, and opted for KT SZ instead. Herr Sennhauser didn't work then in SZ - Had he been available we would have used him on the house we finally bought. He's certainly worth talking to.
Not strictly renovation, but someone you should know about
:
Marcus Inauen AG, Talstr 17, 9113 Degersheim, 071 371 13 59 or Alpenstr 5, 8640 Rapperswil, 055 210 08 77 - Furniture maker. Herr Inauen is a true master craftsman - he designed and built my library bookcases, several tables, chairs, dressers, cabinets, desks, etc. for us. His work is simply stunning - he uses walnut, cherry, beech, oak, almost any wood you would want. He can make just about anything, and will discuss different styles with you. (I've had him make pieces to complement my Arts and Crafts/Stickley/Macintosh things.) He has a small showroom in Rapperswil, but he'll also be happy to show you around his workshop in Dagersheim SG if you need more ideas as to what he can do. And surprisingly, his prices are very good considering that you have a top quality, custom piece - several of his pieces were less expensive than similar mass produced stuff from places like Mobitare, etc.
Firms I would never use again:

Sabez Kitchen, Volketswil - terrible job, all around. I'll probably re-do the entire kitchen in a few years.

Bau-Beratung-Management AG, 8820 Wädenswil. These were the folks our bank provided to do the house inspection prior to the sale.
Good luck with your project....
edited, 'cause I thought twice about posting negative comments. PM me if you want details.