Preventing mold in a Los Angeles home

Prevention advice written for a general audience is mostly about humidity control, which matters a great deal in Houston and much less here. Los Angeles has a specific and fairly short list, and it is dominated by water arriving somewhere it was not meant to rather than by air being damp.

1. Make every fan actually go outside

The highest-yield thing on this list. Go into the attic with a light and follow the duct from each bathroom fan and the dryer. You are checking one thing: does it terminate through the roof or a gable wall, or does it end in the attic?

If it ends in the attic, every shower is putting steam onto cold sheathing, and that is the single most common cause of attic growth in this county. Re-routing a duct is a straightforward job for the right trade. While you are up there, check that insulation has not been pushed into the soffits, which blocks the airflow the assembly relies on to dry.

2. Put a vapor barrier over bare soil

If your house has a raised foundation, open the hatch and look at the ground. If it is bare earth, it is releasing moisture into the floor structure continuously, and it does not stop in summer. In the foothill communities subsurface flow keeps that ground damp through a completely dry season.

Sheet polyethylene over the soil is one of the cheapest corrections available on this housing stock and it changes the crawl space from a humidity source to a neutral space. While the hatch is open, count the foundation vents and check that planting or hardscape has not buried any.

3. Walk your irrigation while it is running

Not after. While it is running, in daylight, looking at the house rather than the plants. You are looking for heads throwing onto stucco, beds mounded above the slab edge or the foundation vents, and any zone that soaks the ground directly against the building.

Over a year, irrigation delivers far more water to one elevation of a house than rainfall does, and it does it in the same place every day during the months when nobody is thinking about water at all.

4. Send roof water away from the building

Los Angeles rain arrives in concentrated bursts, which means gutters either work on the day or they do not. Before the season, clear them, and then follow each downspout to see where it actually discharges. A downspout emptying two feet from the foundation is putting the whole roof’s catchment against the wall.

On hillside lots, check whether there is a drain at the top of the cut behind the house and whether it is still clear. On many lots of a certain vintage there was one, and on many of those it has been landscaped over since.

5. Check the condensate line before summer

Where the air handler sits in an attic or a closet, find the drain line and confirm it is clear and actually discharging outside. Look in the secondary pan for standing water or rust, and find out whether a float switch is fitted, because many systems have none and the first sign of a blockage is then the ceiling.

This is a ten minute check that prevents the most common August call there is.

6. Act inside the first two days after water

After a leak, a slab leak or a storm intrusion, the clock that matters is short. Growth can take hold within days on wet cellulose, so the fortnight spent seeing whether it dries out on its own is frequently the fortnight that converts a drying job into a remediation job.

Get air moving, lift what can be lifted, and get the structure measured rather than judged by touch. A wall that feels dry on the surface can be carrying water in the cavity for weeks. Drying to measured numbers is the difference, and it is also what makes an insurance conversation straightforward later.

What is not on this list

Whole-house dehumidifiers, ozone generators, antimicrobial paint and air purifiers all come up. Near the coast a dehumidifier genuinely helps where the source is ambient rather than a leak, and it is the one piece of equipment worth considering. The others treat air or surfaces while the water keeps arriving, which is the same mistake as cleaning a patch and leaving the fan ducted into the attic.

If you work through the six above and something still smells musty, that is useful information rather than a failure, and it is the point at which the free inspection earns its place. A good share of them end with no mold work at all.