Building and Construction - Flooring Attic

Author

Flooring Attic

Tom Ghormley

2006-04-21, 4:21 pm

I have a Victorian house with a huge attic I want to floor. The ceiling
joists are true 2X4 set on 16" centers. The fellow who is helping me do this
said he would put 3/4" tongue & groove plywood on the 2X4s and call it done.
I've never attempted anything like this before and worry that we will need
to sister in some more wood i.e. 2X6 or 2X8. I also am not sure about the
3/4" plywood.
Can anyone give me a source for the info I need to be sure?
Answers to tom1024@mac.com will be appreciated. Thanks.

RicodJour

2006-04-21, 4:21 pm

Tom Ghormley wrote:
> I have a Victorian house with a huge attic I want to floor. The ceiling
> joists are true 2X4 set on 16" centers. The fellow who is helping me do this
> said he would put 3/4" tongue & groove plywood on the 2X4s and call it done.
> I've never attempted anything like this before and worry that we will need
> to sister in some more wood i.e. 2X6 or 2X8. I also am not sure about the
> 3/4" plywood.
> Can anyone give me a source for the info I need to be sure?
> Answers to tom1024@mac.com will be appreciated. Thanks.

I'll go to the effort of answering your question, and let others
benefit from the open forum, if you'll come back and read the answer.
Fair enough?

What you're proposing is very common and presents some very real
problems. 2x4s are not allowed as floor joists. Period. Putting that
heavy duty plywood floor is just inviting the floor to get heavily
loaded and/or occupied. Plywood on weak joists builds a weak floor.
Heavier plywood on weak joists might produce a _weaker_ floor.

You definitely need to beef up those joists. What size members need to
be sistered on is dependent on how you will be using the room, the
anticipated loads and the location of the bearing walls below. Since
it is entirely possible that you will be adding a substantial load, you
may have to rework some of the structural supports all the way down the
line to the footings under columns in the basement.

In other words, no one who has not seen the house can give you anything
except a totally wild-assed guess. You need to have a pro look at the
situation and design you a solution. It's money well spent.

R

Bob Morrison

2006-04-21, 5:21 pm

In a previous post Tom Ghormley wrote...
> I have a Victorian house with a huge attic I want to floor. The ceiling
> joists are true 2X4 set on 16" centers. The fellow who is helping me do this
> said he would put 3/4" tongue & groove plywood on the 2X4s and call it done.
> I've never attempted anything like this before and worry that we will need
> to sister in some more wood i.e. 2X6 or 2X8. I also am not sure about the
> 3/4" plywood.
> Can anyone give me a source for the info I need to be sure?
> Answers to tom1024@mac.com will be appreciated. Thanks.
>

Tom:

I hope you will follow Rico's excellent advice -- quoted below:

"You definitely need to beef up those joists. What size members need to
be sistered on is dependent on how you will be using the room, the
anticipated loads and the location of the bearing walls below. Since
it is entirely possible that you will be adding a substantial load, you
may have to rework some of the structural supports all the way down the
line to the footings under columns in the basement."

"In other words, no one who has not seen the house can give you anything
except a totally wild-assed guess. You need to have a pro look at the
situation and design you a solution. It's money well spent."

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Nehmo Sergheyev

2006-04-22, 4:21 pm

Lots of people discover their attic and exclaim, "Wow, look at all that
space!", and they envision ways they could use it. But unless designed
for it from the beginning, it's very expensive to turn that space into
living space or even storage space.

Is there insulation up there? If not, add that. That can be your
project.

--
(||) Nehmo (||)

Grumman-581

2006-04-22, 5:21 pm

"Nehmo Sergheyev" <nehmo54@hotmail.com> wrote in message
news:1145733078.409204.170060@t31g2000cwb.googlegroups.com...
> Lots of people discover their attic and exclaim, "Wow, look at all that
> space!", and they envision ways they could use it. But unless designed
> for it from the beginning, it's very expensive to turn that space into
> living space or even storage space.

Yep, too many builders figure that no one will ever see the attic, so they
just throw things together up there... Wires and flexible ductwork going all
over everywhere... Add to that the difficulty in bringing full sheets of
plywood and sheetrock into the attic and it just gets to be a pain in the
butt to even covert it to a minimally acceptable storage area... My previous
house had a lot of attention to detail in the construction... The attic was
large enough that you could walk around most of it and the first crosspiece
was well above your head... All the ductwork was the commercial type
sheetmetal type... A good portion of it was floored, especially around the
water heaters and the two geothermal heat pumps... Sufficient lighting for
being able to examine things without having to necessarily bring a
flashlight... All the wires were nice and neat on raceways around the
perimeter of the attic... Just goes to show you that you can get quality
construction sometimes...

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