They're subcontractors. These for-hire crews are often the muscle behind building projects and their very presence can be an eye-opener for homeowners who thought the general contractor would do all the work. This is particularly unnerving when contractors make cameo appearances at your project as they juggle any number of projects simultaneously.

It's all the more reason to make sure "subs" are on the discussion agenda as you take bids and talk with prospective contractors.

Usually, subcontractors are specialists. That's good, because few contractors are truly jacks-of-all-trades. Specialists are valued during crunch time when intricate tile cutting and stonework, woodwork or finishing details are worth every penny.

Still, there are pesky financial and performance issues with subcontractors that homeowners should be aware of.

If your agreement with the contractor stipulates payment at certain portions of the job, you'll need assurances that subcontractors will be paid on time and in full. If the contractor skips payments or "shorts" amounts due to the "subs," these freelance workers are within their rights to file liens against you until they receive payment. Liens can have all sorts of negative implications for your project. In new construction, liens can hold up title to the property.

Your financial agreement should stipulate that the contractor is responsible for material costs so subcontractors don't rack up high margins that, in turn, are ratcheted up again by the contractor. And do subcontractors have the necessary licenses and insurance that your locality demands?

In question for many projects is the general contractor's ability to communicate your wishes and rules to subcontractors. The trickle-down effect is problematic for homeowners. If the contractor doesn't convey discussions on quality and scope of work or brand of materials, the subcontractor may assume — wrongly in many cases — they have carte blanche to proceed in any fashion they wish.

Make sure you and your contractor are crystal-clear about who is allowed on the job site and who has responsibility for riding herd on subcontractors.

Indeed, nothing is more frustrating than workers who go AWOL in mid-project. It's tough on homeowners who feel they're the ones who have to pick up the phone to find the missing subcontractor and cajole them back to the job. That should be the contractor's job.

How the contractor works with subcontractors can be a performance incentive in a construction contract, particularly when it comes to staying on schedule.

The background and referral checks you performed on bidders may not extend to subcontractors. Ask your contractor to provide you with evidence of a subcontractor's good performance on financial and work quality issues. You may want to involve some key subcontractor candidates in your initial interviews so that all sides know what is expected and when.