For a crawl space
- Area and shape
- More floor means more liner, and more piers and corners mean more cutting and sealing.
- Headroom
- A space a person can kneel in is quicker to work in than one that must be crossed lying flat.
- What has to come out
- Old plastic, wet insulation, debris and stored belongings all add labor and disposal.
- Water
- A damp-only space needs no drainage. One that takes in water needs a trench, a basin, a pump and somewhere to send the discharge.
- Wood repair
- Replacing or reinforcing joists and beams is priced by how much is damaged, and that is often not known until the insulation is down.
- Liner and insulation grade
- Thicker, reinforced liners and foam board on the walls cost more than thin sheeting and nothing else.
- Electrical
- A dehumidifier or pump needs an outlet. If there is none under the house, an electrician and a permit are part of the job.
For a basement
- Length of drain
- Interior systems are priced by how many feet of wall get a drain.
- What is in the way
- Finished walls, a bathroom, a furnace or stairs along the route all slow the work.
- Depth, for exterior work
- The deeper the footing, the more soil moves, and the more protection the trench needs.
- Access for machines
- Where an excavator can reach, digging is quick. Where it cannot, the work is done by hand.
- Pump setup
- One pump, or a main pump with a battery backup and an alarm.
Comparing two proposals fairly
Line them up item by item. If one includes a dehumidifier, wall insulation and wood repair and the other is a liner alone, they are prices for different jobs. Ask each company to itemize, and ask the one that left something out why it thinks the house does not need it. Sometimes that company is right.
Ask what happens if hidden damage turns up once work begins: how you will be told, and how the extra will be priced. And ask whether there is a fee for the inspection visit before you book it.
Cheaper first steps
Cleaning gutters, extending downspouts and correcting the slope of the soil cost little next to any system, and they sometimes solve the problem outright. A company that mentions them first is giving you useful information. The yard drainage page lists them.