I'll never itemize or sign a contract with a penalty clause. Check local and state laws regarding how large of down payments are allowed.

I would like the contract to be fair to both parties. I would agree that itemizing material and labor is not something I need to know, so it will probably be omitted. It seems to becoming more common in contracts, though

How would you handle schedule delays ? What do you think of the other contract terms?

Start and completion dates - most will not agree to that. You would need a commercial contractor.

For a relatively small job like that, the contractor/company/subs/reputation and previous customer satisfaction are the biggest factors. Company/individual customer satisfaction has a huge impact.

For a simple porch, basic building materials are lumber, footing/pier materials, roofing materials, flooring materials and trim materials. Extras like lighting/guttering or special installations materials are also included. Manufacturer access? No idea why that is needed. Builder access has to be what is needed for construction.

Cost itemization would be an upcharge, it takes a lot of time to do that, and there has to be a percentage for over cost items and labor. Example, you selected a certain product which was installed as speced by the manufacturer. That product failed to provide the service as intended by the maker. The installer now has to remove that material and reinstall new materials. That cost should not be required to be eaten by the installer. You should pay that cost and recouped by you from the manufacturer. That also negatively impacts the finish date. Also, the daily price of building materials often can change daily. An estimate(which is all any competent builder will provide) is simply a best guess.

Start/finish times/dates are also an estimate. There are hundreds of reasons a set time cannot be met. What does a contractor do, for instance, if they schedule the job and the customer is in a car wreck/hospital for a week? Does the customer pay for the weeks lost labor?

Down payments often are figured by a contractor to minimize loss. Again, if the customer is incapacitated/etc., the contractor has purchased materials and may be out that money. Since I was a one man business, I had the customer buy materials so I was not subject to a loss if problems arose. My payment came in the form of labor and incidentals. I also encouraged the customer to inspect daily to be assured of proper installation methods(Which I would gladly explain and give internet research info to back my info).

Permitting cost money, both in the permit fees and time to obtain them. Often work does not need a permit, depending on local regulations. I once remodeled a guest bath(flooring/vanity replacement/painting/trimming/window replacement) with no permits. And spoke with the local building inspector almost daily(he was inspecting a job next door) who was aware of what I was doing and agreed I was legal. The key? One job at a time. No permit needed to rep-lace the window. None to paint. None to replace the vanity or install flooring as individual jobs. Put any two together, permits were needed.

The requirements for licensing/insurance/permitting are location requirements. Example, in my location, licensing requirements were different for every little township(over 30 in the KC Metro, for instance). No way could I afford the license fees for all those. I had insurance(Half a million dollars, since I was a small business). I knew building codes for most of the areas and could legally operate without a license.

No way would I guarantee materials for more than a manufacturer would. My part had an implied warranty. If there was a problem in the first two years, I would inspect and discuss the problem. If it was my fault, I fixed it at no cost to the customer. In 8 or so years, I had one instance where there was a question. I fixed the problem even though it was not an installation issue(the wood failed and I felt I should have seen the problem at installation---ergo, could have been my error).

The rest is pretty standard. I guess. Why do I guess? I never, in 8 years signed a contract for a job. I got all my work by referral and word of mouth or new customers watching me work on a job. My references were available and happy to talk to folks. My guarantee was satisfaction---attained by daily customer inspections or trust.

Time for completion is completely company size/experience driven. What a six man crew can do in one day might take an individual a week. Extreme example of this is building a Habitat for Humanity home. I helped build over 50 of those on Saturdays. Took 6 to 8 months. The record for building(starting with a completed slab) is just over 3 hours and 26 minutes.

Contractor laws vary from state to state. You will be best served by consulting a local attorney with construction contract expertise.

Best wishes for a successful project.