I'm fairly new to joinery on a builders scale, this is a
bit beyond putting shelves up! so please forgive what may
be an obvious question to some...

How to fix joists so they are stable in the middle of their
span without wanting to "wobble"? In other words should
they be fastened to the supporting beams underneath them
somehow or just left to "float" on them? More detail...

I'm replacing the attic floor that is 6 metres wide by 9
metres long. After removing the ancient floor (tons of clay
and shingles) I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls. On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing. The joists will
overlap by approx one metre in the middle of the 9 metre
span. The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends. Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level. Should
the joists actually be fastened down to the beams some how?
Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span? Any other suggestions?
--
David in Normandy.
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted.

In an earlier contribution to this discussion,
David in Normandy wrote:

I'm fairly new to joinery on a builders scale, this is a
bit beyond putting shelves up! so please forgive what may
be an obvious question to some...

How to fix joists so they are stable in the middle of their
span without wanting to "wobble"? In other words should
they be fastened to the supporting beams underneath them
somehow or just left to "float" on them? More detail...

I'm replacing the attic floor that is 6 metres wide by 9
metres long. After removing the ancient floor (tons of clay
and shingles) I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls. On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing. The joists will
overlap by approx one metre in the middle of the 9 metre
span. The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends. Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level. Should
the joists actually be fastened down to the beams some how?
Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span? Any other suggestions?

Use noggins - made from joist offcuts. Nail or screw the joists together
where they overlap, and skew nail them to the beams.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

www.tameside.gov.uk/tmbc8/note07.pdf

look at herring bone or solid strutting,we use solid strutting most of the
time,have seen flooring fail where plumbers ,have dislodged a herring bone
to put in the waterpipes

The message
from David in Normandy contains these words:

How to fix joists so they are stable in the middle of their
span without wanting to "wobble"? In other words should
they be fastened to the supporting beams underneath them
somehow or just left to "float" on them? More detail...

I'm replacing the attic floor that is 6 metres wide by 9
metres long. After removing the ancient floor (tons of clay
and shingles) I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls. On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing. The joists will
overlap by approx one metre in the middle of the 9 metre
span. The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends. Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level. Should
the joists actually be fastened down to the beams some how?
Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span? Any other suggestions?

When I replaced the hay loft in my 18' x 33' barn many years ago the
joists ran longways so I put in a couple of RSJs to replace the rotten
wood transverse beams which had been propped in the centre. IIRC the
joists are 7" by 3" with a fee span of about 12' either side of the
entrance. The joists overlap on the RSJs and I used off cuts at right
angles to keep the joists upright. Gravity holds the joists down. The
only doubt I had was that the RSJs were a bit flimsy but so far at least
they show no sign of buckling.

--
Roger Chapman

Roger Mills says...
Use noggins - made from joist offcuts. Nail or screw the joists together
where they overlap, and skew nail them to the beams.


Skew nailing, good idea, I hadn't thought of that. I'm so
used to putting nails / screws in at 90 degrees. Thank you.
--
David in Normandy.
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted.

ALex says...
www.tameside.gov.uk/tmbc8/note07.pdf

look at herring bone or solid strutting,we use solid strutting most of the
time,have seen flooring fail where plumbers ,have dislodged a herring bone
to put in the waterpipes



Solid strutting looks more rigid. That's a handy document
with the table of timber gauges and spacings. Thank you.
--
David in Normandy.
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted.

Hi David, there's quite a few points to raise, so one at a time...

I'm replacing the attic floor that is 6 metres wide by 9
metres long.
....
I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls.

OK. I'm assuming this is going to be a habitable space?

Floorboards on top of the joists and plasterboard below?

On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing.

Sounds about right. I would check the sizes/spans against the tables
in the (old version of) Part A structures of the Building Regs. I know
this is in France with different regs, but the approved documents
contain a lot of good sense.

The joists will
overlap by approx one metre in the middle of the 9 metre
span.

I'd be inclined to fix them together before placing them, so they're
dead straight (i.e. use a 3rd joist as a straight edge) by putting in
lots of screws (for example 6*80mm turbogold - buy a cordless impact
driver). Then place them, then pack underneath them as necessary.

I'd guess the oak beams are pretty uneven, and you have to pack the
joists both for beam contact and to bring the joists level with each
other? You might want to go round with a lighter (straight) timber to
figure out the high and low points both across and along the beams.

The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends.

Hopefully you've bought regularised joists (very straight, rounded
corners), with an appropriate strength grade (C16 or C24) - and
they've been preservative treated. Sounds like you won't have to cut
your joists at all, so treated end can go against the walls. In the UK
you would be required to fit plastic boots to the end if they're going
into masonry as additional rot protection - or use steel joist
hangers.

Maybe you have existing provision in the masonry for the joists? If
not, joist hangers will be easier.

Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level.

OK

Should the joists actually be fastened down to the beams some how?

Yes! Fix the packing under the joists to the beams, and/or fix the
joists (through the packing) into the beams. 2 screws at every
intersection, from either side, and skewed so they can't tear out
easily.

Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span?

Yes! 3 methods. Steel herringbones (cheap, very easy - recommended),
wooden herringbones (requires a bit more work/skill), solid noggins
(must fit tight, useful on odd joist spacings).

If joist twists even a little out of upright it looses a lot of it's
strength and rigidity.

For that sort of span, probably 3-5 rows of herringbones (these really
help stiffen the floor and kill resonances - as well as the essential
anti-racking. Use the steel ones, quick, easy - and you'll be glad you
put in lots of rows).

Floorboards should be nailed to the joists with nails 3x the thickness
of the boards. 2 nails at every intersection.

Remember wooden floors brace the masonry walls, as well as the walls
supporting floors. They need to be firmly fixed together for overall
structural stiffness.

Any other suggestions?

I'm a bit concerned that you're started on something of structural
importance without being aware of relevant building regulations or
common practice. A good place to learn more would be the standard city
and guilds books on carpentry and joinery - along with the building
regs (or appropriate French equivalents).

On 16 Mar, 09:27, David in Normandy wrote:
I'm fairly new to joinery on a builders scale, this is a
bit beyond putting shelves up! so please forgive what may
be an obvious question to some...

How to fix joists so they are stable in the middle of their
span without wanting to "wobble"? In other words should
they be fastened to the supporting beams underneath them
somehow or just left to "float" on them? More detail...

I'm replacing the attic floor that is 6 metres wide by 9
metres long. After removing the ancient floor (tons of clay
and shingles) I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls. On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing. The joists will
overlap by approx one metre in the middle of the 9 metre
span. The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends. Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level. Should
the joists actually be fastened down to the beams some how?
Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span? Any other suggestions?
--
David in Normandy. * *
*To e-mail you must include the password FROG on the
*subject line, or it will be automatically deleted.

Dave
I agree with Dom that you do not put the joist into the walls. Use
joist hangers and keep them clear. If you insist then Dom's plastic
boot (IE any thin poly membrane to isolate timber masonry contact is
essential.
You will need lots of packing and I would not worry too much about
levels - go with the flow of the timbers under!
Chris

says...
Hi David, there's quite a few points to raise, so one at a time...

I'm replacing the attic floor that is 6 metres wide by 9
metres long.
...
I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls.

OK. I'm assuming this is going to be a habitable space?

Floorboards on top of the joists and plasterboard below?

Yes. But putting down floorboards is likely to a year or
two down the line.


On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing.

Sounds about right. I would check the sizes/spans against the tables
in the (old version of) Part A structures of the Building Regs. I know
this is in France with different regs, but the approved documents
contain a lot of good sense.

I've checked against the table in the link posted by ALex
and the timber and spacings seem to be well within
tolerance.


The joists will
overlap by approx one metre in the middle of the 9 metre
span.

I'd be inclined to fix them together before placing them, so they're
dead straight (i.e. use a 3rd joist as a straight edge) by putting in
lots of screws (for example 6*80mm turbogold - buy a cordless impact
driver). Then place them, then pack underneath them as necessary.

Is a cordless (or mains powered) impact driver different to
a drill? Up to now I've been putting in screws for all DIY
with a standard Bosch mains drill, though it gets a bit
more difficult to hold when putting in large screws, it
tend to jump out of the screw slot without lots of force.



I'd guess the oak beams are pretty uneven, and you have to pack the
joists both for beam contact and to bring the joists level with each
other? You might want to go round with a lighter (straight) timber to
figure out the high and low points both across and along the beams.

I've used a laser level to find the highest point on the
highest beam and will use this as the "base" point and pack
all the joists to the same height as this. The beams are
very uneven, in places the packing will need to be up to
around three or more inches.


The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends.

Hopefully you've bought regularised joists (very straight, rounded
corners), with an appropriate strength grade (C16 or C24) - and
they've been preservative treated. Sounds like you won't have to cut
your joists at all, so treated end can go against the walls. In the UK
you would be required to fit plastic boots to the end if they're going
into masonry as additional rot protection - or use steel joist
hangers.

As far as I'm aware the joists are building regs compliant.
They are preservative treated already. The plastic boots
sound like a good idea, I'll look to see if they're
available in France. Joist hangers aren't really an option
because the walls are made of a mixture of rocks of
different shapes and sizes including very hard granite and
the mortar between them consists of a mixture of clay and
straw. Difficult to put any sort of plugs into the wall,
the clay is too soft and granite too hard. There are
existing holes in the wall so I intend to use those and use
cement mortar to fix the joists tightly into place.


Maybe you have existing provision in the masonry for the joists? If
not, joist hangers will be easier.

Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level.

OK

Should the joists actually be fastened down to the beams some how?

Yes! Fix the packing under the joists to the beams, and/or fix the
joists (through the packing) into the beams. 2 screws at every
intersection, from either side, and skewed so they can't tear out
easily.

OK.


Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span?

Yes! 3 methods. Steel herringbones (cheap, very easy - recommended),
wooden herringbones (requires a bit more work/skill), solid noggins
(must fit tight, useful on odd joist spacings).

Solid noggins sound easier to me.


If joist twists even a little out of upright it looses a lot of it's
strength and rigidity.

For that sort of span, probably 3-5 rows of herringbones (these really
help stiffen the floor and kill resonances - as well as the essential
anti-racking. Use the steel ones, quick, easy - and you'll be glad you
put in lots of rows).

Floorboards should be nailed to the joists with nails 3x the thickness
of the boards. 2 nails at every intersection.

Remember wooden floors brace the masonry walls, as well as the walls
supporting floors. They need to be firmly fixed together for overall
structural stiffness.

Any other suggestions?

I'm a bit concerned that you're started on something of structural
importance without being aware of relevant building regulations or
common practice. A good place to learn more would be the standard city
and guilds books on carpentry and joinery - along with the building
regs (or appropriate French equivalents).


I acknowledge I'm a beginner, but I'm trying to do a good
and structurally sound job and seeking advice with every
step. I have a reputation amongst family and friends in DIY
for very solid and over the top construction. If in doubt I
tend to over engineer, which is perhaps not the most
economical approach but certainly the safest and strongest.

Good idea about the C&G joinery books, I'll see if I can
find any to buy online. This sort of work is beyond the DIY
books I've got.

Thank you for your detailed reply.
--
David in Normandy.
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted.

"David in Normandy" wrote in message
...
Roger Mills says...
Use noggins - made from joist offcuts. Nail or screw the joists
together
where they overlap, and skew nail them to the beams.


Skew nailing, good idea, I hadn't thought of that. I'm so
used to putting nails / screws in at 90 degrees. Thank you.

I hate skew nailing, so I'd look at some "builders metalwork" solutions,
e.g. Toolstation's

http://www.toolstation.com/search.html?searchstr=47211

Use the proper nails, e.g.

http://www.toolstation.com/search.html?searchstr=10121

I mention Toolstation rather than Screwfix because the last lot of
framing anchors I bought from Screwfix were very flimsy affairs - much
lighter gauge than the ones they used to sell. No guarantee that
Toolstation haven't gone the same way.


--
Kevin Poole
**Use current month and year to reply (e.g. )***

I hate skew nailing, so I'd look at some "builders metalwork" solutions,
e.g. Toolstation's
....
I mention Toolstation rather than Screwfix because the last lot of
framing anchors I bought from Screwfix were very flimsy affairs - much
lighter gauge than the ones they used to sell. No guarantee that
Toolstation haven't gone the same way.

Agree about using builders metalwork, and agree that screwfix is
variable quality stuff. Catnic from a builders merchant is good.

However who bangs in nails with a hammer these days? Screws are so
cheap, and impact drivers are so good.

Is a cordless (or mains powered) impact driver different to
a drill?

See the diy faq. Cordless impact drivers are designed for *exactly*
what you're doing. They will be a revelation and mean you won't
hesitate to add extra fixings.

I've used a laser level to find the highest point on the
highest beam and will use this as the "base" point and pack
all the joists to the same height as this. The beams are
very uneven, in places the packing will need to be up to
around three or more inches.

Yup. Seen that sort of thing. You might find it easier to cut out some
"saddles" (i.e. jigsaw to cut out an appropriately weirdly shaped
piece of wood) and fix these in place. Then use flat shims to get the
support under the joists just right.

Joist hangers aren't really an option
because the walls are made of a mixture of rocks of
different shapes and sizes including very hard granite and
the mortar between them consists of a mixture of clay and
straw. Difficult to put any sort of plugs into the wall,
the clay is too soft and granite too hard. There are
existing holes in the wall so I intend to use those and use
cement mortar to fix the joists tightly into place.

Fair enough.

Solid noggins sound easier to me.

Traditionally, solid noggins were considered inferior to herringbones.
And they must fit tight. However with large screws pulling up an
irregularities, maybe it's neither here nor there.

I acknowledge I'm a beginner, but I'm trying to do a good
and structurally sound job...

Sorry if I sounded sharp previously. I'm sure you'll make every effort
to achieve maximum structural integrity.

These are good, especially vol 2.

http://www.amazon.co.uk/Carpentry-Jo...5676518&sr=1-1

http://www.amazon.co.uk/Carpentry-Jo...5676518&sr=1-1

says...
Is a cordless (or mains powered) impact driver different to
a drill?

See the diy faq. Cordless impact drivers are designed for *exactly*
what you're doing. They will be a revelation and mean you won't
hesitate to add extra fixings.

I've used a laser level to find the highest point on the
highest beam and will use this as the "base" point and pack
all the joists to the same height as this. The beams are
very uneven, in places the packing will need to be up to
around three or more inches.

Yup. Seen that sort of thing. You might find it easier to cut out some
"saddles" (i.e. jigsaw to cut out an appropriately weirdly shaped
piece of wood) and fix these in place. Then use flat shims to get the
support under the joists just right.

Joist hangers aren't really an option
because the walls are made of a mixture of rocks of
different shapes and sizes including very hard granite and
the mortar between them consists of a mixture of clay and
straw. Difficult to put any sort of plugs into the wall,
the clay is too soft and granite too hard. There are
existing holes in the wall so I intend to use those and use
cement mortar to fix the joists tightly into place.

Fair enough.

Solid noggins sound easier to me.

Traditionally, solid noggins were considered inferior to herringbones.
And they must fit tight. However with large screws pulling up an
irregularities, maybe it's neither here nor there.

I acknowledge I'm a beginner, but I'm trying to do a good
and structurally sound job...

Sorry if I sounded sharp previously. I'm sure you'll make every effort
to achieve maximum structural integrity.

These are good, especially vol 2.

http://www.amazon.co.uk/Carpentry-Jo...5676518&sr=1-1

http://www.amazon.co.uk/Carpentry-Jo...5676518&sr=1-1



Thanks for the links. Time to buy a book!

There is a link from one of the books you mention to this
one which people have rated 5 stars - what do you think?

http://www.amazon.co.uk/Manual-First-Second-Fixing-
Carpentry/dp/0750681152/ref=pd_sbs_b?ie=UTF8&qid=1205676518
&sr=1-1

--
David in Normandy.
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted.

David in Normandy wrote:
Roger Mills says...
Use noggins - made from joist offcuts. Nail or screw the joists together
where they overlap, and skew nail them to the beams.


Skew nailing, good idea, I hadn't thought of that. I'm so
used to putting nails / screws in at 90 degrees. Thank you.

The other option to noggings is to use herringbone straps - either
smaller wood offcuts (say 2x1") or the shop bought metal straps. The
metal straps are easy to fix since they just nail on.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

David in Normandy wrote:

Is a cordless (or mains powered) impact driver different to
a drill? Up to now I've been putting in screws for all DIY
with a standard Bosch mains drill, though it gets a bit
more difficult to hold when putting in large screws, it
tend to jump out of the screw slot without lots of force.

An impact drive solves this problem:

http://wiki.diyfaq.org.uk/index.php?title=Impact_driver

the mortar between them consists of a mixture of clay and
straw. Difficult to put any sort of plugs into the wall,
the clay is too soft and granite too hard. There are
existing holes in the wall so I intend to use those and use
cement mortar to fix the joists tightly into place.

If you make a very dry pack mortar mix (just damp sand and cement is
usually enough) and ram it well in, then you should get little if any
shrinkage in the mortar.


Yes! 3 methods. Steel herringbones (cheap, very easy - recommended),
wooden herringbones (requires a bit more work/skill), solid noggins
(must fit tight, useful on odd joist spacings).

Solid noggins sound easier to me.

Note that rather than skew nailing them, you can just stagger them a few
inches such that you nail through the joist side into the end grain of
the nogging.




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

There is a link from one of the books you mention to this
one which people have rated 5 stars - what do you think?

That does look good, thanks. We look forward to you posting a review!

David in Normandy wrote:
I'm fairly new to joinery on a builders scale, this is a
bit beyond putting shelves up! so please forgive what may
be an obvious question to some...

How to fix joists so they are stable in the middle of their
span without wanting to "wobble"? In other words should
they be fastened to the supporting beams underneath them
somehow or just left to "float" on them? More detail...

I'm replacing the attic floor that is 6 metres wide by 9
metres long. After removing the ancient floor (tons of clay
and shingles) I'm just left with four massive oak beams
(literally tree trunks) spanning the 6 metre width. These
beams are built directly into the stone walls. On the
advice from a joiner friend I've bought 30 joists (5 metres
x 50mm x 150mm) to lay at 40cm spacing. The joists will
overlap by approx one metre in the middle of the 9 metre
span. The far ends of the joined joists will be cemented
directly into the supporting stone/clay walls, so this
should hold them upright at the ends. Between the walls the
joists just rest on the four big beams, with a little
packing here and there under them to get them level. Should
the joists actually be fastened down to the beams some how?
Perhaps some noggins nailed between the joists would keep
them "upright" and wobble free in the middle of the 9 metre
span? Any other suggestions?

Google 'herringbone bracing' 'coach bolts' and the like.