Trying to finish a basement, and where we intend to put a partition
wall with a door is right where a contractor left a 6" duct below the
floor joists. He did this to go under a piece of microlam that is
used of support in that part of the house.
I know better than to cut into the microlam, but can I purchase a some
ductwork that will flatten out in the area where it will pass under
the microlam and hug the ceiling ?
If I could recover 2" I could install a standard interior door without
6" duct is equivelant to 3 1/4" X 10" rectangle, so figure it will
hang down about 3 1/4". They sell 6" round to rect converter pieces at
Lowes or HD. You can get straight or a 90 deg converter if that helps
There may be such an animal, but I've never seen one. You might have
to cut the round 6" and move the elbows farther away from the beam,
then reinstall the elbows, and add the transition pieces with the
rectangular duct in between the elbows.
Prefab, probably not, at least at the box stores.
I see several choices depending on what your actual situation is wrt
The "best" would probably be to go back some distance on either side of
the glulam and insert a round to rectangular transition, go to a 45, add
sufficient length to reach the next 45 to horizontal transition, carry
it under the 'lam then reverse the sections on the other side. This
will give you the clearance at the low point with the side benefit of
minimizing and reducing existing pressure drop in the existing 4-90's at
the cost, of course, of making the transition on both sides longer.
Sorta' like (you'll need non-proportional font for this to have any
chance at all)...
O O O -> -- | | -- -> O O O
\\ |_| /
where the "O" is the round and the "-\\/" are the rectangular sections
and the arrows indicate the transitions. You could, of course, do the
first to elbows in round and transition going down but am assuming
you'll need that to be as tight as possible.
You may need the rectangular 45s made at a tin shop; the rounds should
be readily available or could use the adjustables if not.
A good tin shop is your friend...
You have enough problems now with the four 90s in close proximity.
dpb's suggestion of using 4 45s would help with the static pressure.
I'd do the 45s in round duct and use the transitions just on the flat
Of course other factors we can't see might prevent you from choosing
the extended, smoother transition solution.
That would leave him still at the same bottom height once he made the
return to horizontal is the problem. He needs to get to the lower
profile earlier. He could do it in the transition, but I figured might
as well just go ahead and make the transition, then the detour.
Reiterate what I said earlier and your agreement; this will be _less_
static pressure than previous using 4-90s. I don't see where OP gets
the "extra elbow" idea...
That's not necessarily so. He'll be working it backwards from the
rectangular duct which is placed up tight against the beam. The
bottom of the rectangular duct will be the same as the bottom of the
All of the height differential, connections and potential headroom
savings, will take place above that.
This I do not know. Maybe it's a time and materials job. ;)
Oval ducting is being used in new construction in our area and there
is some stock in local box stores like Menards IIRC. There were
adapters and transition pieces, some of which could work for you. They
are sized to go between partition studs.
An alternative would be asking a good sheet metal shop to price a duct
to duct adapter. The modest price may well be worth not having the
aggravation of cobbling together a run of oddball non stock fixtures.
Go to HD or Lowes and go to the sheet metal duct area, and put
together some pieces and see if it will work for you. Bring a ruler so
you know more or less where you would have to cut the existing 6"
When you look for the 90 deg part that has to around the beam, look
for a "short" 90 to give you max clearance. You might find it in the
section where they sell the range fans, dryer connections and
*You can get just about any duct configuration fabricated at a sheet metal
shop. Some A/C contractors have their own shops that fabricate or there are
independent companies around. Check your yellow pages. The cost may not be
too bad. You will need to at least provide them with measurements although
a rough diagram with measurements would be better. Maybe you need to
transition from round to rectangular.
You need to maintain the same number of square inches. If the
existing is 6" round, the square inch capacity is about 27 square
inches. Stop at any tin shop, explain your problem, ask them to
make a transition that will work.
If you are framing a wall directly under the glulam, add two lally
columns that are swallowed by the wall and go through the glulam.
Keep the whole world singing . . . .
RicodJour, The pic that you posted is almost exactly what I need. I
had imagined something like a transition offset to one side, but with
an elbow pointed upward. I will try to get a pic of the problem
The extra elbow(s) that I was talking about was the extra elbows
needed to run the duct back up in and through the floor joists. The
contactor after elbowing the duct under the microlam just suspended
the duct under the floor joists for the rest of the run. There is
room to run the duct through the joists and recover some ceiling space
in that area.
Uh, NO!. Leaving aside questions about possibly weakening the gluelam
out past the top pads on the lally columns, you are assuming the floor
under the base of the columns will handle the point loads. Sure, it will
PROBABLY work for a few years, at least until OP moves, but you can
never be sure. Any time you add a column to replace load-bearing
structure, proper procedure is to add a footer under it. At a minimum,
you need a plate to spread the load.
Or you could build the concrete footer/pad on top of the slab, but
that would be a less than optimal solution for most situations.
You're point though is taken. You can't rearrange a load path willy
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