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Old 05-02-2008, 02:11 PM   #1
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dans basement office


I'm looking at finishing off my basement to use as an office and have several questions. Due to limited finances I'll probably end up doing most of the work myself.

House is about 20 years old and is in north metro atlanta. 2 basement walls are a concrete foundation and are concrete all the way up. A 3rd wall is running down a slope and starts with concrete all the way up and then finishes with concrete only half way up and wood construction the rest of the way up.

The last wall is an interior (of sorts) wall to the garage.

I'm thinking of finishing off 1/2 and putting in a dividing wall. The half I'm looking at finishing would *not* include the 1/2 foundation wall.

I've been in the house for 4 1/2 years and have never seen any evidence of water. After a big rain though you can feel that the air is more humid.

My questions are

1) In various places I see the advice "check with your local building codes". How/where do I go about doing this? One code item in question is ceiling height. I have exactly 8 feet from the concrete floor to the bottom of the floor joists so obviously my finished floor to ceiling height will be somewhat less. In fact I'll have to make it probably a foot less in a few isolated area to deal with some sewer drains and hvac ducts.

2) I've seen varying advice on proper wall insulation and construction. Are there any problems with using construction adhesive to put up 1/2" foam and then put up a standard 2x4 stud wall using a pressure treated base plate? I'd then put fiberglass insulation between the studs after wiring.

3) There are some doorways right now where the structural part of the frame are made with kiln dried 2x4's. The bottom edge touches the concrete floor. Is this a problem? I thought you needed pressure treated for all wood contacting the concrete floor?

4) Assuming my construction details in #2 are correct, whats the right thing to do right at the top of the walls? The concrete foundation wall stops a little below the bottom of the floor joists. There is a piece of wood lying on top of the foundation wall and the floor joists then rest on that. Do I just stop the foam at the top of the foundation wall and then stuff in fiberglass? Or should that area stay hollow?

5) I was thinking of using ceiling tiles to make it possible to access things like phone lines down the road in case I needed to. That way I wouldn't have to tear out drywall. Then again, maybe with some planning I can avoid that need. Any thoughts on a drywall ceiling vs a suspended ceiling? Actually the ceiling may have to wait because I'm on a bit of a hard schedule here and I may need to occupy some of this space as an office before it is fully completed.

The timing of this couldn't be worse since I still have probably a month to go on a major bathroom remodel upstairs, but such is life.

Thanks in advance


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Old 05-02-2008, 04:10 PM   #2
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dans basement office

That's a lot of questions!

1) The city you live in should have its own building inspection office. Call City Hall and ask to speak with a buiding inspector or the building official. They should be willing to answer your questions.
The IRC code requires a 7' ceiling height in habitable spaces such as your basement. You can usually frame around beams and ducts to within 6'6" of the floor. Exceptions on this are often made depending on circumstances, and are at the inspector's discretion. Ask!!!

2) If you ask me, the 1/2" foam is a waste of time. I certainly wouldn't glue it in. Foam board will also make installation of the code-required firestopping incredibly difficult. A vapor barrier and some faced faced fiberglass batts will do just fine.

3) The code prohibits non-treated wood from being in contact with concrete. It is a bad practice. Whether or not it will actually be a problem just depends on the house.

4) This is one of the places that firestopping is required. Ask your inspector ahead of time. 3/4" plywood or 2x dimension lumber can be used to fireblock the vertical wall space from the horizontal floor joists (and furdowns and soffits). Around here we also allow tightly packed unfaced fiberglass to be packed into the void to limit vertical to horizontal travel of smoke, air, and fire.

5) I'd vote for drywall. I don't think a grid ceiling in a residence will ever add much (if any) value. Plus, the grid ceiling will really sacrifice headroom.
Ever consider painting the floor joists, pipes, and ducts a dark color like black or dark green like they do in bars and restaurants???

As for the humidity, if you were to serve the basement with some HVAC outlets as well as some return-air vents, you might have less trouble with humidity. A dehumidifier would help as well.

Also, are you going to wall off your furnace and water heater into a smaller space? If so, combustion air very well may be an issue. If you are, give me the btu/h input rating of the furnace that is on the sticker inside the service door on the furnace (75,000 btu/h's or more usually), as well as the size of you water heater. I'll also need the rough dimensions of the room they're in. It is normally easy to fix, but can pose a carbon monoxide hazard if they're in too small of a space. If the furnace has PVC vents, this is a non-issue. If it has a metal vent, it will need your attention. The solution normally involves just adding a couple combustion air vents in the mechanical room wall so it shares air with other basement living spaces. I can assist you with that if need-be.

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Old 05-05-2008, 11:14 AM   #3
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dans basement office

f#2, I wonder how the original builder got away with it. Then again I've seen a few other things that didn't look like good choices.

#5, I like the paint suggestion. If I paint first I can spray it and not worry so much about a mess. I'm assuming I'd need to make sure any wiring is protected by conduit or armored cable since the ceiling wouldn't be there to cover/protect it?

The furnace and hot water heater would be in a smaller space although for now, that "smaller" space would be something like 200 square feet instead of 350 or so like it is now. In other words, I'm looking at probably just doing half of the basement. From memory it is a 50,000 btu unit in the basement (I have another identical furnace in the attic for the 2nd floor plus a really cold winter night is 20 degrees here). I'll have to check on the water heater size. Furnace is an 80% AFE unit so we're in the metal vent range, not pvc.

If I were to build a closet around those two and finish the whole basement, how much room would I need to allow around them? The furnace and hot water heater are right next to each other.

Is the IRC something that is readable by mere mortals or is it painful to get any details out of it?

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Old 05-05-2008, 12:01 PM   #4
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dans basement office

Painting Romex wire is no big deal. It is PVC, so it will take paint. Just don't paint inside any of the electric boxes and you'll be fine.

You need 50 cubic feet of space for every 1000 btu/h's of your gas appliances. 200 square feet with 8' ceiling is 1600 cubic feet. Divided by 50 cubic feet that is 32, so that room can support 32,000 btu/h worth of equipment for combustion air. That isn't enough. Fact is, 350sf isn't enough either, because with the furnace and the water heater (assuming 40 gal) you're running about 90,000 btu/h...That would take 4500 cubic feet of space (approx 560 square feet).

Combustion air can be taken from other sources such as ventilated attics or outdoors. Too bad the inspector didn't catch this. It is pretty common, and there are millions of homes with the same issue, but there is always a chance of a problem.

So you understand, here's the hazard. If enough fresh air isn't provided for the units to burn in the combustion process, more carbon monoxide is produced as a product of the combustion.

To allow the full space of the finished and unfinished portions of the basement to provide combustion air (not enough but better than just 200sf), the code requires two holes through the wall. One withing 12" of the floor, one within 12" of the ceiling. I'd go with big return-air wall grills that cover two stud spaces. They're probably 34 x 10??? No ducting required, just holes to allow airflow.

I'd also install a carbon monoxide detector near the furnace and water heater. That would be a good measure of safety given what you have to work with.

As far as working space requirements, typically 30" is required in front of the furnace, but it is often manufacturer-specific. Serviceability is the issue.

The IRC is fairly readable. It isn't a how-to guide by any means. Finding what you're looking for can be a challenge for someone who doesn't know where to look. There are "commentary" guides for the IRC that are essentially code books with plain english explanations that sometimes help. They're very expensive but most of the big bookstores carry them. Send me a message if you need anything and I'll see what I can do.
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