Before I turn it on, I always look inside the glass front of a gas fireplace and the inside of your gas fireplace should never be wet!
Outside the house, a gas fireplace chimney flue should look something like this.
It would be metal, protrude from the siding, and not melt the siding around it.
It is connected directly to the fireplace flue.
Which is connected directly to the fireplace box!
It is a complete unit. Typically the framing around it is wood, so the unit has to be tight, situated properly and there should be no way for heat to escape.
Similarly there should be no way for water to get in.
Looking inside this fireplace unit, behind and above the ceramic logs, clearly there is rust, staining and even peeling paint.
This leaking has been happening for a while!
When I pointed it out, my clients had a problem with this.
Their previous house had a similar problem!
Water had gotten through or around the fireplace flue and box and into the wood-framed cavity itself.
Mold began to develop unseen inside that cavity, and then made its way into the walls beside the fireplace. They had a particular sensitivity, were not feeling well, and when it developed outside had to remediate the mold. It was not cheap.
And here in this house they are considering buying, they run into the same problem! A fireplace that is obviously leaking! This find was the one thing that would have rubbed them quite the wrong way!
I have to say, I seldom see such staining or rust inside a fireplace. In fact, I said to them, I could not remember the last time I had. But I always check.
My recommendation: never assume that things are performing as they are supposed to. It pays to check. Sometimes the seldom seen is! Sometimes the never-before seen is! It might just be the big elephant in the room.
Jay Markanich Real Estate Inspections, LLC 
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560
Good morning, Jay....with the cost of hiring a mason today, at least in New England, we rarely see anything other than a gas fireplace....I wonder how many home inspectors thoroughly inspect them....
You never know where there might be a potential hazard hiding....this is a place I am betting very few inspectors check !
Well that doesn't look so good! And, I'm sure you won't ever forget it.
Barbara - I look inside and turn them on. But if the pilot is not lit I do not light it.
S&D - you have to look! Even when you aren't used to seeing things. I check bedroom closet ceilings too, but have never found a hole. Stains yes, but never a hole.
Debbie - don't remember seeing it before, at least not like this. But it's hard to remember everything!
Morning Jay that does not look good at all. If the buyers had experience with it in the past I'll bet that is a deal breaker unless it's repaired.
SEE?? SEE??
No gas in my home.
I don't know how it came out James, but the buyers were upset. Experience is experience.
Lenn - so heat pumps freeze, wood fireplaces get chunky, gas fireplaces get wet, gas furnaces produce CO, and roofs leak into sun rooms (!) - and this is all just in my past few posts! We are all going to die.
Says he with a wink...
Can't say that I've ever seen water inside like that Jay, I could be a problem. No, it is a problem. Thanks for the explanation!
Sure Jay, but later is better than sooner. Defects in design and mechanical just makes home ownership more expensive for maintenance than needed.
I can't believe all of the "minor" stuff you find for your clients! Can't you just comment on the relevant or "major" things? Realtors must love you for being such a PITA :)
Jay, I have never run into this problem myself, but thanks for reminding us not to assume a gas fireplace is dry!
Thanks Jay!! I will make sure the inside of my fireplace isn't wet. Hmm, it is also a good time to make sure it is clean too. Another item to add to my to do list.
Cold metal, high humidity. low setting on the pilot light,, Is it possible to get condensation that may cause some rust stains and drip marks?
Jay is this usually a problem or is it due to a poor installation?
Yeah we see that a lot here. It is usually a condensation problem.
Jay: Good catch .. especially on this couple's behalf. I'm "pinning", tweeting, and sharing as many places as possible .. great info ...
Gene
Jay, when you first fire up a gas fireplace the glass fogs over---that is moisture from the combustion process. Anyway, that amount of moisture is common in a unit and can even drip down the glass depending on various factors. It can even cause some amount of rusting inside the unit over time. I guess what I am getting at is that "some" amount of moisture inside the unit is quite normal. Figuring out whether it is normal or leaking in from the outside might be difficult to determine.
I have never seen this. It's a good catch by you. I'm sure the buyers are so happy they hired the right home inspector.
Geez, I was beginning to panic until I read the comment #20 from Charles. Ours does have a bit of moisture when we first turn it on - but, apparently that's normal. I will be sure to look for this problem in homes I sell Jay. Thanks for the heads up. D
I have seen both interior condensation and leaking from the cap. Hope they were able to get it fixed asap.
Thanks for the tip. This is something I never considered. Personally I have a wood burning fireplace, but for my buyers I will make sure the inspector looks for this possible issue.
HI Jay,
There is moisture and then there is too much moisture, when it causes rust and peeling, its most likely the later, thanks again for the great tips.
Have a Great Week and a Pfanntastic 2014
Jay,
Great info!!! Thanks for sharing it with us. I'll definitely be on the lookout for this type of problem.
I think so too Tom. Don't remember seeing it myself.
I know Lenn. I was a tweaking you.
Certainly the biggest cherry picker out there Joshua, and he pretends it is a problem. Today I had an attic with about a TON of vermiculite insulation! Minor stuff...
Not good to hear Brian! It is uncommon for me.
Get in there Rosie! Start cleaning! Photos please...
There is always some condensation Dwight, but in my experience it goes away quickly.
Don't know Mike. I really can't remember the last time seeing this, so I referred it's further inspection to a specialist.
Juan - you are not far from me! It seems rare to me. Condensation, in my experience, burns off quickly.
Gene - they have good protection here too. My report and photos were complete.
Charlie - I see the brief cloudiness but it goes away in seconds. But I have never seen condensation drip down the glass! Whatever it is here, given the rust it has been happening for a while!
Thanks Tammie. They were most upset.
Debb - Charlie's comment is very odd by my experience. I know there is some condensation, but I have never seen that much.
I have not heard since Scott. Would love to hear the resolution, and diagnosis.
Athina - every kind of fireplace has its own issues. We have to be vigilant.
Peter - agreed. I don't know how much is too much though!
Glad to contribute to your info base Trisha!
Put hole through a wall and never check it....you will eventually have a leak.
Could be Than. But from my experience leaking like this is unusual.
Jay, thanks for posting this: I never heard of a gas fireplace leaking water! Now I know they can leak and will be on the look out.
Well hopefully someone will fix it before it becomes a fire hazard? And before mold starts in the walls inside the chase. I think all chimneys whether they burn wood, coal, or gas need to be maintained, inspected, cleaned as needed, and monitored for signs of water leaks. Good thing you noticed this.
Me neither Pamela. But it is what it is, and interestingly not this buyer's first dance.
Jeff - they were most concerned about the mold potential. As to how to fix it I don't know! They will figure it out though.
Jay,
As usual, I love reading home inspector posts! I would never have even thought to check for moisture in a gas fireplace. Thanks for the enlightenment.
I would never have thought to check that but will in the future. I would check the outside thing though as we've dealt with a couple of old historic homes that needed repairs on those due to leaks. Thanks for the great tips!
I see the word mold and can practically start coughing.
Until now I didn't either W&J! I always check the inside though!
Kaye - it would be interesting to see gas fireplaces in historic homes. I love to inspect them, but typically the old masonry fireplaces are still there.
Cheryl - yummie! And when you taste it does it taste like chicken?
Could be a leak, but like others have said, not uncommon to see rust inside these fireplaces. Does however bear further investigation.
It did Jim. And they did. I got a call just last night from my clients there who got a report stating mold UNDER the fireplace box, on the sub floor. So they backed out. They set up another inspection last night.
It was a lot of moisture over time, and the fireplace guy said probably more than just condensation. But nobody can say for sure obviously.
Hi Jay. Thanks for spreading the word. I now know what to look for.
I'm glad you learned something Linda!