What does a house weigh? Some mental heavy lifting

Q: How much does the average house weigh?

A: First, we need to define "average," then we need to define "house." But, in general, the average house today is about twice as big as the average house 50 years or more ago. But an older house (depending on exact age) will have solid lumber wall sheathing and floorboards instead of plywood, will have heavy lath and plaster walls instead of drywall and likely will have more masonry work.

So when we say "house," does that include the extremely heavy concrete foundation, concrete garage or basement floor? With all those variables, how could we possibly figure out how much a house weighs? There are three methods:

• Totaling the weight of the individual components.

• Pulling out a scale and actually weighing the finished product. (That would be one awfully big scale, but house movers tell me that most houses weigh in at between 80,000 and 160,000 pounds. Of course, this is sans foundation and concrete floor slabs, and house movers typically are dealing with older, smaller structures that have been stripped of many components (but not always).

• Rules of thumb around the construction industry are 200 pounds per square foot for a single-level home, 275 for two levels and 350 for three levels. This figure is predicated on no heavy features such as tile roofing or extensive masonry work, but includes foundation.

To check it out, I built a hypothetical 1,600-foot, single-level home in my head and on paper, based on known delivered weights of given materials. It totaled 345,000 pounds (including 160,000 for the foundation and 30,000 in the garage floor), compared to the rule-of-thumb house weighing in at 320,000. Pretty close! Of course, what good is a house without a deck? In my hypothetical house, I added a deck, a gazebo and a hot tub, which pretty much explains the difference. Adding in the weight of a foundation, slabs, appliances and fixtures to the house-mover's figures, we cross-check pretty well.

Refiguring for the "average" 2,200-square-foot, two-level newer home, rule of thumb comes it at 605,000, which I suspect is on the high side. Why do I think that's high? Because the foundation hasn't increased dramatically in size over my hypothetical single-level house. But then again, I don't have a scale that big, so what do I know?

Q: We have a basement that has walls separating the living space from the crawl space under other portions of the house. The crawl-space side of the wall is open studs with insulation, no sheathing. Should there be something else to cover the insulation, or is that construction adequate?

A: Exposed insulation is fine in an unfinished space. No worries. If you think about the floor insulation you may or may not have in the crawl space, it is as exposed as the insulation in your attic.

Q: My dryer vent is very near my outdoor heat-pump compressor. A lot of lint gets stuck in the grille. Is there a way I can prevent this?

A: Don't heat when you do laundry? Seriously, if there is a way to re-route the vent pipe, that is your best option. You also could install a box with a cleanable screen in the dryer vent pipe, which would catch 99 percent of the lint that goes through there. Lacking that, tie a length of panty hose onto the end of the vent outside. This should catch the lint and allow the steam to escape. But be sure to clean or replace it every load, since it will start to back up the vent.

Q: The fire sprinkler went off in the unit directly above ours. The back half of the condo was soaked, and we moved out. The insurance companies are inspecting and discussing. A former neighbor said there was a law pertaining to the replacement of furnaces and water heaters having water encase them. The furnace/gas hot-water-heater closet was one area under the deluge. I am concerned about mold. Where can I go, what should I have inspected and by whom?

A: I am not aware of any public law requiring the replacement of wet mechanical equipment. You or the neighbor may be confusing a rule or bylaw some condominium associations impose on residents requiring replacement of water heaters after a given time period to prevent leakage and flooding by old equipment. Furthermore, this is not to be confused with the mandatory hot- tub bylaw my hypothetical neighborhood has imposed.

If you are concerned about the mechanical equipment, and rightly so, have a heating/mechanical contractor inspect and service both for safety, duct-system mold and rust. Replacement may be necessary, but not always. Duct cleaning and sanitizing are a very good idea in this case.

As far as mold in the floors, walls, ceilings, etc., hopefully the insurance companies and water-damage restoration professionals have done an adequate job. In the vast majority of cases, if cleaned up, dried out quickly and treated, mold will not form. In order to give yourself further assurances, hire a mold/indoor air-quality specialist or industrial hygienist.

Darrell Hay is a local home inspector and manages several rental properties. He answers reader questions — call 206-464-8514 to record your question, or e-mail dhay@seattletimes.com. Sorry, no personal replies. More columns at www.seattletimes.com/columnists.