Lets start in the attic:
Truss trouble: Any tampering with an engineered roof truss compromises its strength and can create a dangerous condition. If you notice that truss elements have been cut by a previous homeowner to make more headroom, call in a structural engineer this is serious.
Wood Rafters: Probe rafters and bottom of roof deck with a screwdriver. Soft spots may indicate water damage or dry rot, especially if you see stains.Leaky roof: During a downpour, climb into the attic to look for leaking around chimneys, plumbing stacks, vents and skylights. Scan the underside of the sheathing for water stains.
Too much insulation: Battens that cover recessed lighting fixtures are a fire hazard, unless the fixture is "IC" rated. And blocking soffit vents can drive up energy and repair costs.
Clogged gutters: With gutters and downspouts in good shape, it's rare to get water backing into crawl spaces and basements.
Pushy plants: Branches can form a bridge to the attic for squirrels, rats and other critters. Overgrown shrubbery near the house encourages mildew to grow on siding.
Gaps around doors: Uneven spaces around doors and windows can indicate shifting of the foundation.
Cracked caulk: The sealant around doors and windows is vital in keeping water out. Replace as needed but don't be cheep you get what you pay for here.Peeling paint: Deteriorated paint not only looks bad, it also exposes wooden siding to weather damage.
Bad grades: Soil needs to slope away from the house at a grade of 3 inches for every 5 feet to avoid water infiltration. Extensions to downspouts to carry water 10 to 15 feet from the house is always best.
Living spacesShaky toilet: A toilet that wobbles can break the wax ring at its base, leading to major water damage. With every flush, water will escape and gradually rot the subfloor. One morning.
Overworked wiring: Normaly found in kitchen and bathrooms. Older homes are notoriously under equipped for the power demands of hair dryers, microwaves and large refrigerators. This leads to flickering lights, tripped circuits or even dangerous overheating. Non grounded three prong outlet swaps is another safety issue. At a minimum, a bathroom should have a dedicated 15-amp circuit and a properly wired GFCI outlet. A kitchen should be wired with a minimum of two 20-amp circuits and GFCI protected outlets at the sink area.
Moisture buildup: Mildew and peeling wallpaper indicate poor bathroom ventilation. Make sure the exhaust duct leads outside. Also, the CFM rating listed on the fan should at least equal the square footage of the bathroom. "The best bet is a fan with a 30- to 60-minute timer to draw moisture out when you leave.
Stuck doors and windows: Jamming can point to paint over issues, or whole-house shifting. I look for cracks above doors and windows, indicating the possibility of structural problems.
Water stains: Don't mask brown stains on ceilings or walls with primer until you find the cause. The likeliest source? A leaking pipe or shower pan. However, a persistent yellow-brown stain and off odor might mean that squirrels or rats are living in the attic above.
Faulty grout: Shower leaks can lead to rot in studs and wallboard. Run the butt of a metal flashlight across the bottom few tile courses and listens: "Click, click, click, thud. The deeper sound tells me a tile is loose or the backer is wet. he says.
Loose railings: "Give stairwell railings a good tug. You don't want your mom or a child grabbing it and it falls off the wall. Check the spacing of the ballasters, it should not exceed 4" if so call it out.
Crawl Spaces
Rotted wood: Probe joist ends and sill plates with a screwdriver or an ice pick. Soft spots may indicate wet or dry rot, especially if the floor above sags.
Holey joists: Poorly placed drill holes or notches for wire, pipe or duct can sap a floor joist's strength. What's safe varies by manufacturer, but here are some rules of thumb: No holes or notches in the top or bottom flanges of an I-joist. Even big holes could be OK in the center, but not the ends, of the framing. Drilled holes must be at least 2 inches from top or bottom and no greater than one-third the depth of an I-joist. Notches in a conventional lumber joist should not exceed one-sixth of its depth or penetrate the center third of the joist span.Termite tubes: Pencil-thick tubes snaking along joists may mean trouble. Break the tubes. If termites spill out or the tube is repaired in a few days, call an exterminator.
Heater noise: "If you hear your water heater gurgle, pop or snap, it's time to drain out sediment. Flushing 3 to 4 gallons prolongs the life of the heater.
Wire splices: Spliced wiring outside electric boxes is a sure sign that an unskilled electrician has been at work and a good reason to check out the rest of the home's wiring. "If I find sloppy work in such a visible place then what does that say about wiring hidden in the walls?"
Foundation cracks: Hairline cracks in a block or poured-concrete foundation are nothing to panic about. But watch for cracks that are both horizontal and vertical, or ones that are growing. Keep track of how wide they are; if they get bigger, call in a pro.