On 2008-05-27, franz fripplfrappl wrote:

I have a small cabin 20x24. The floor joist system is comprised of
2x8x10 joists resting on outside wall and a center beam. The ends
of each joist are notched with the equivalent of a 2x4 tongue
resting on the walls and center beam.

Is this over a crawl space? The joists are notched on the bottom edge
and reduced in depth from 7.25" to 3.5"? That's an excessively large
notch and it represents a potential failure point. Is there any
splitting of the joists at the inside corner of the notches?

I would like to reduce/eliminate floor deflection sufficiently that I
will be able to install ceramic tiles with an appropriate backer board.

One simple option, depending on clearances, would be add two more
girders (support beams), to reduce the joist span in half. But this
would only be a good option if you could avoid further notching of the
joists.

Cheers, Wayne

Wayne Whitney wrote:
....
One simple option, depending on clearances, would be add two more
girders (support beams), to reduce the joist span in half. But this
would only be a good option if you could avoid further notching of the
joists.

Actually, that's a most excellent idea, Wayne...

And, if it is crawl space, could simply pier it in a few places (every
other or every third, say) and not need to worry about the height issue.
Would need an adequate base for each pier, however, of course...

--

On Tue, 27 May 2008 17:12:22 +0000, Wayne Whitney wrote:

On 2008-05-27, franz fripplfrappl wrote:

I have a small cabin 20x24. The floor joist system is comprised of
2x8x10 joists resting on outside wall and a center beam. The ends of
each joist are notched with the equivalent of a 2x4 tongue resting on
the walls and center beam.

Is this over a crawl space? The joists are notched on the bottom edge
and reduced in depth from 7.25" to 3.5"? That's an excessively large
notch and it represents a potential failure point. Is there any
splitting of the joists at the inside corner of the notches?

I would like to reduce/eliminate floor deflection sufficiently that I
will be able to install ceramic tiles with an appropriate backer board.

One simple option, depending on clearances, would be add two more
girders (support beams), to reduce the joist span in half. But this
would only be a good option if you could avoid further notching of the
joists.

Cheers, Wayne

There is a full basement in the building. In fact, a wood foundation
basement.

I have not noticed any checking of notched ends.

There is some blocking midway between existing joists.

Building was built about 25 yrs ago. Most likely by a reader of Mother
Earth News who smoked more than he read.



--

=================================================
Franz Fripplfrappl

On Tue, 27 May 2008 12:27:57 -0500, dpb wrote:

Wayne Whitney wrote:
...
One simple option, depending on clearances, would be add two more
girders (support beams), to reduce the joist span in half. But this
would only be a good option if you could avoid further notching of the
joists.

Actually, that's a most excellent idea, Wayne...

And, if it is crawl space, could simply pier it in a few places (every
other or every third, say) and not need to worry about the height issue.
Would need an adequate base for each pier, however, of course...

Shoring up the floor as described is OK but unfortunately I do not have
the space nor do I care to clutter the already small 20x24 basement with
extra support columns.





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=================================================
Franz Fripplfrappl

On 2008-05-27, franz fripplfrappl wrote:

I have a small cabin 20x24. The floor joist system is comprised of
2x8x10 joists resting on outside wall and a center beam. The ends of
each joist are notched with the equivalent of a 2x4 tongue resting on
the walls and center beam.

I would like to reduce/eliminate floor deflection sufficiently that I
will be able to install ceramic tiles with an appropriate backer board.

There is a full basement in the building. In fact, a wood foundation
basement.

I have not noticed any checking of notched ends.

As far as the notches go, if there is no splitting at the insidec
corner of the notches, then there is not currently an imminent
problem. But it is a poor condition you might wish to consider
addressing.

As for stiffening the floor system, simplest and easiest would be to
interleave 2x8x10s with existing ones, ending up with 2x8s at 12"
o.c. and halving your deflections.

Interleaving 2x6s wouldn't work very well--a 2x8 is 3 times stiffer in
bending than a 2x6 of the same grade and species. So assuming equal
deflections of the two members, the 2x8s will take up 3/4 of the total
load, and you'll only reduce the deflection by 25%.

Wit care, you could sister a 2x4 or 2x6 to the 2x8s. First, you
should put them at the top edge or bottom edge of the existing joists.
This will be stiffer than centering them. Given that the existing
joists are notched on the bottom edge, you should choose the top edge
for the sisters.

Second, you would need to somewhat unload the existing joists before
attaching the sisters, using a temporary wall or jacks. Otherwise the
initial nail slip in the connection between the two members means that
you won't gain very much marginal stiffness in response to live load,
which is what you want to avoid tiles cracking. By unloading the
existing joists first, when you then reload the sisters with the dead
load, the initial nail slip should be taken up by the dead load, so
that for additional live load you will gain the full stiffness
possible.

Lastly, as another sometimes poster here (BobK) has convinced me, you
should use a construction adhesive between the new and old members,
and attach them together with many small nails. E.g. 0.131" x 3"
nails. This will allow the two members to work together as a
composite section more effectively.

Hope this helps.

Cheers, Wayne

On Tue, 27 May 2008 20:30:26 +0000, Wayne Whitney wrote:

On 2008-05-27, franz fripplfrappl wrote:

I have a small cabin 20x24. The floor joist system is comprised of
2x8x10 joists resting on outside wall and a center beam. The ends of
each joist are notched with the equivalent of a 2x4 tongue resting on
the walls and center beam.

I would like to reduce/eliminate floor deflection sufficiently that I
will be able to install ceramic tiles with an appropriate backer
board.

There is a full basement in the building. In fact, a wood foundation
basement.

I have not noticed any checking of notched ends.

As far as the notches go, if there is no splitting at the insidec corner
of the notches, then there is not currently an imminent problem. But it
is a poor condition you might wish to consider addressing.

As for stiffening the floor system, simplest and easiest would be to
interleave 2x8x10s with existing ones, ending up with 2x8s at 12" o.c.
and halving your deflections.

Interleaving 2x6s wouldn't work very well--a 2x8 is 3 times stiffer in
bending than a 2x6 of the same grade and species. So assuming equal
deflections of the two members, the 2x8s will take up 3/4 of the total
load, and you'll only reduce the deflection by 25%.

Wit care, you could sister a 2x4 or 2x6 to the 2x8s. First, you should
put them at the top edge or bottom edge of the existing joists. This
will be stiffer than centering them. Given that the existing joists are
notched on the bottom edge, you should choose the top edge for the
sisters.

Second, you would need to somewhat unload the existing joists before
attaching the sisters, using a temporary wall or jacks. Otherwise the
initial nail slip in the connection between the two members means that
you won't gain very much marginal stiffness in response to live load,
which is what you want to avoid tiles cracking. By unloading the
existing joists first, when you then reload the sisters with the dead
load, the initial nail slip should be taken up by the dead load, so that
for additional live load you will gain the full stiffness possible.

Lastly, as another sometimes poster here (BobK) has convinced me, you
should use a construction adhesive between the new and old members, and
attach them together with many small nails. E.g. 0.131" x 3" nails.
This will allow the two members to work together as a composite section
more effectively.

Hope this helps.

Cheers, Wayne

Thank you for the ideas.
By the time I finish this project, methinks it would have been better to
raze and rebuild. There's nothing as frustrating as trying to undo and
improve what someone else has done.



--

=================================================
Franz Fripplfrappl

"franz fripplfrappl" wrote in message

By the time I finish this project, methinks it would have been better to
raze and rebuild. There's nothing as frustrating as trying to undo and
improve what someone else has done.


I've been saying something like that quite often lately digging out my crawl
space and adding supports under the existing floor... It would have been so
easy to do this stuff during construction. Why didn't they leave room to
crawl in the crawl space? Arrrggg!!! (I wish I could magically lift up the
house for a couple of days...)

On Wed, 28 May 2008 04:31:38 -0700, Bill wrote:

"franz fripplfrappl" wrote in message

By the time I finish this project, methinks it would have been better
to raze and rebuild. There's nothing as frustrating as trying to undo
and improve what someone else has done.


I've been saying something like that quite often lately digging out my
crawl space and adding supports under the existing floor... It would
have been so easy to do this stuff during construction. Why didn't they
leave room to crawl in the crawl space? Arrrggg!!! (I wish I could
magically lift up the house for a couple of days...)


Alternative would be to pray for a tornado to move the
building to the next county. Start all over and build to correct all
that had been forgotten.



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=================================================
Franz Fripplfrappl