We just moved into a newly built house about 3 months ago. This house is built by demolishing very old house. We have Methane like smell in whole house for last 3 months and getting worse now. It smells worse in evenings and when rains outside. My builder is telling me that this is from soil outside and he didn't run any tests to confirm it. Please advice how we can find the source of this smell and what are fixes?
Thanks.

I would suggest contacting the plumber that did the plumbing on the house if you can't locate the origin of the smell. Check all fixtures for p-traps, and make sure there is water in all traps, including washer drain, floor drains, water softener standpipes, etc. The installing plumber should be able to track this down. If the home is less than one year old, this should all be covered under new house warranty through either the general contractor or plumbing company. I assume the plumbing was done by a licensed plumber and was inspected per code, correct?

Hi Pau, go with MGD's advice. FYI methane is colorless and odorless gas.
Good luck

Ha, I was going to mention the odorlessness (not a real word) of methane, but just assumed they were getting a sewer smell.

[QUOTE=;] Dad as a retired coal miner I tend to take the word methane a little to serious. Happy holidays

Hey, I don't blame you a bit. I think many people take it too lightly when associated with sewers. I think many lives are saved due to the smell associated with sewer tipping them off to a potential problem. You didn't have that "luxury" in the mines. I personally know of people that have died in sewer manholes because they didn't wear the correct breathing equiptment. Im with you parttime. Methane is nothing to be taken lightly. And a Merry Christmas and happy New Year to you and yours.

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My builder is telling me that this is from soil outside and he didn't run any tests to confirm it

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Your builder's blowing smoke up your skirt. Sewer gas contains methane and sewer gas raises with hot air and descends with cold air. Winter air, rain and evening temperatures would cause the odor to get worse.
My bet's on a open vent in the attic. There are tests for leaky and open vents. A smoke or peppermint test where they fill your vents and then check for leaks.
I would have this checked ASAP. Sewer gas is harmful to your families health and the methane content's explosive.