Smoke Detectors Radius Coverage and Clearance

It's all right here:NFPA Codes and Standards

In addition to the great NFPA link lyn provided, depending on your location there is a good possibility probability that the local AHJ (authority having jurisdiction) will have the final say with regards to detector/sprinkler requirements and placement.

You do not indicate your location but here in the USA there are localized, specific procedures that must be followed.

While the AHJ does follow NFPA, many jurisdictions have their own additional requirements that apply in conjunction with NFPA.

Your best bet would be to check with the AHJ to learn their requirements as a first step in this project.

You will most likely have to submit drawings and specifications to the AHJ for approval prior to construction so have a set of scaled, detailed floor plans drafted irregardless if this is a new build, remodel, or addition.

As far as specifics for the detectors and sprinkler heads, check with the various manufactures. Many will help with a preliminary design drawing (based on the initial drawing you provide them), will provide individual product cut sheets, and will furnish you with equipment cost estimates.

These drawings (marked up by fire detection and fire protection companies) and product cut sheets can then be submitted by you to the AHJ for approval. Most manufactures or their reps will provide this preliminary design service to you for little or no cost (on the assumption they will get the equipment sale).

Once the plans and specs are returned to you approved by the AHJ, remember to have them approved by the project A/E (architect/engineer) as well. This way everyone is on the same page and there should be no mis-communications thereby no problems when it comes to retention/final payout.

Good Luck.