My home is a four piece modular colonial. The bottom two pieces have 2x6 ceiling joists. The top two pieces have open web floor trusses. There is about an inch-and-a-half gap betwen the 2x6 ceiling and the floor trusses above. That is, the floor trusses make NO contact with the 2x6 ceiling.

I discovered this setup when addressing a second floor water leak, which was a long-term problem repaired repeatedly. I felt it was time to investigate the possibility of mold growth due to the water leak. I opened the kitchen ceilng and found that it was 2x6 and faced with OSB on top. I opened the OSB and found that there was nothing resting on it.

The only contact points between the first and second floor are at the center of the house and at the edges. Sounds to me like an opportunity to raise my 7 1/2 foot ceilings. I would like to put in coffered or tray ceilings throughout the first floor, maintaining the original ceiling height at the edges of each room and raising the centers in a stepped fashion by three inches per step so that the center of each room is at a more normal 8 feet.

The question is "Should I?" I believe that the 2x6 ceiling serves only to hold the rim joists in place and keep the center beam from shifting side to side, but carry no weight but their own. I like the idea of the dead space between floors and intend to maintain it by not attaching the raised ceiling to the floor trusses, but to a structure that would be built between the trusses and would make no contact with them. This keeps sound transmission between the floors WAY down.

Are there issues I have not considered?

I have posed this question to the modular home manufacturer, but thought I would throw it out here as well while I wait for a response (been waiting two and a half days for a response already).

 

128 people looked at your post & no one answered. I believe that's because, an architect is needed to answer the question. No one wants to take the chance of saying YES & then something bad happens. What did the other forum say?

 

An online forum is not the ideal place to get an answer to a question like this, because too much depends on the exact nature of what you have now. If not an architect, I would, at a minimum, hire a structural engineer to assess your house and your plans, and give you a professional report.

 

Just my opinion but I would think the cost involved would not be justified by gaining less than two inches of height in the rooms.

 

I am an engineer, albeit not structural, and I say don't do it. There IS a reason why it was constructed the way it is and with only two inches to play with there is nothing to be gained. As Mitch points out it will be a fairly high cost (time and money) for almost no gain.

 

Hi kr, I have to welcome a fellow Mainer to the forum .

Although I do agree that some professional advice needs to be included in this process, I get most of mine right from my lumber supplier. He designs trusses and load carrying features and meets all local codes. And he does it for free.

The other part is I don't think he is talking about just 2", but fitting the new vaulted system up between the joists above, clever. He says: "and intend to maintain it by not attaching the raised ceiling to the floor trusses, but to a structure that would be built between the trusses" This could give him 1" clearance and 6.5" of added height. Add the drywall and you have an 8' ceiling.

There would still be problems to overcome as you discover what is up there, but I'm sure something, not all that complicated, can be done. But be sure local code officials approve and all is engineered properly.

Bud

 

Bud (thanks for the welcome) is apparently a more careful reader than the rest of you.

The referenced 1 1/2" gap is ABOVE the ceiling joists, above the OSB attached to their top and BELOW the floor trusses above, so that I have about 8 inches from the bottom surface of the ceiling sheetrock to the bottom surface of the floor trusses (1/2" sheetrock, 5 1/2" in 2x6's, 1/2" in OSB, 1 1/2" gap). I would be placing the 2x4's for the raised portion of the ceiling so that their bottoms were 1/2" below the bottom of the floor trusses, giving me a significant increase in ceiling height with minimal cost. I would be maintaining the original ceiling height at the edges of the rooms and adding 2x6's around the box I would be opening to resist lateral movement and to carry any weight distributed to them.

I have posed my question direct to the manufacturer (it was sent via email and forwarded to their engineering department on Monday of this week, I am still waiting for a response), not on an internet forum. This is just a place to cool my heels and maybe get a few words of wisdom while I wait.

I believe the engineering purpose of the 2x6 ceiling was two-fold:

1. To hold the structure in place during its 200 or so miles of transfit from factory to site.

2. One room includes a long span between support walls and a 2x6 beam (actually two stacked 2x6 beams) was needed to bridge that span and carry the house's weight.

I do not believe the 2x6's in that ceiling carry more than minimal distributed weight (no direct weight) and redistribution should be possible without sacrificing structural integrity.

 

Is the ceiling already eight feet?

 

Nope, I was reading carefully enough I did catch that he said 7 1/2' ceiling height

 

kr, are the 2x6 ceiling members redundant, meaning the floor joists above are holding the walls in place as well? It will be interesting to see what they say (if they reply).

Bud

 

Yes, the ceiling joists are redundant. This is a four piece modular. The ceiling of the first floor was in place for transit from factory to site, as was the floor system of the second floor.

The rim joists of the first floor are attached to the rim joists of the second floor via mechanical fasteners. It seems to me that the floor trusses should provide all of the lateral movement resistance that is required.

Current ceiling height is 7 1/2 feet. I want to raise it to 8 feet in a stepped fashion similar to that shown here: COFFERED CEILING DRYWALL... - SUSPENDED CEILING & DROP CEILING.

 

To clarify, the floor trusses of the second floor are attached to the upper central beam of the house and the upper rim joists at the outside of the house. The upper central beam rests on a lower central beam (where the four pieces join together). The second story floor trusses do not directly connect to the first story walls, but the rim joists for each story are attached to each other.

 

This was the response from the modular home manufacturer's engineering department:

"There is (sic) too many variables on this to give you a honest answer to this question without going to see this home personally. The best option would be for you to get a structural engineer to go take a look at the home.

Sorry about the delay in answering your questions, I was in training all last week and didn't have access to my emails."


Sounds like a cop out to me since they have full access to the blueprints. The only other variable is the foundation, for which they provided specifications, which a site inspection could not confirm since it is all covered and hidden (including the jack posts the site contractors installed, which are hidden within a 2x6 wall that we added when we finished the basement).

 

If they tell you it's ok, they become responsible, thus the same answer we often have to give, get an engineer to look at it. Since I don't even have the blueprints I'm in less of a position to advise than they are. It boils down to your call, but engineers are not that expensive, and a phone call even less. Stop over to EBS and see what they say. Tell them you are wondering if a truss member of some sort could be fit into position to make the modification all in one step. If they see a potential sale, maybe they will send someone out. Can't hurt and they are good folks over there.

Bud