Evening,

I haven't been here for a while as I bought a house which
didn't need much work so apart from a big pergola and
some shelves I've done no DIY for two years. It's good
to see a few familiar faces...

Anyhew, my mind has turned to the notion of converting
our loft into two bedrooms and a WC. I'm still very much
at the feasibility study stage so far. I have an *excellent*
text by J Coutts on the subject which I would recommend
to anyone who wants to learn all about loft conversions -
it is on Amazon.

Most of the time, when a new floor is being constructed,
the format is two long metal beams (I-profile) with joists
between them. In most cases, the joists either sit in the
web (the sticky-in bit on the side of the I beam) or are
slung below the beams using joist hangers attached to
timber in the sides and on top of the beam.

What I want to know is, can you fix the end of a wooden
joist (say 75mm x 147mm) on *top* of one of these metal
beams? I have good reasons to want to do this, most of
which relate to the ideal position for the new staircase. If
it is possible, how does it work? Do you bolt packing
timber to the top of the metal beam and then fix the joist
to that?

A further query: if you can do the above, could you have
joists where one end is slung below one metal beam from
joist hangers and the other end is supported on top of a
(lower) metal beam?

Thanks in advance,
Al Reynolds

"Al Reynolds" wrote:

Anyhew, my mind has turned to the notion of converting
our loft into two bedrooms and a WC. I'm still very much
at the feasibility study stage so far. I have an *excellent*
text by J Coutts on the subject which I would recommend
to anyone who wants to learn all about loft conversions -
it is on Amazon.

Most of the time, when a new floor is being constructed,
the format is two long metal beams (I-profile) with joists
between them. In most cases, the joists either sit in the
web (the sticky-in bit on the side of the I beam) or are
slung below the beams using joist hangers attached to
timber in the sides and on top of the beam.

What I want to know is, can you fix the end of a wooden
joist (say 75mm x 147mm) on *top* of one of these metal
beams? I have good reasons to want to do this, most of
which relate to the ideal position for the new staircase. If
it is possible, how does it work? Do you bolt packing
timber to the top of the metal beam and then fix the joist
to that?

A further query: if you can do the above, could you have
joists where one end is slung below one metal beam from
joist hangers and the other end is supported on top of a
(lower) metal beam?


Surely this isn't within the scope of DIY.

You should consult a structural engineer, a loft conversion specialist
or, if all you want is some broad guidance as to what is and isn't
possible, your local building control officer.

Al Reynolds wrote:

What I want to know is, can you fix the end of a wooden
joist (say 75mm x 147mm) on *top* of one of these metal
beams? I have good reasons to want to do this, most of

Can't see why not. The harder bit might be "fixing" since you can't just
skew nail them to the beam. A row of noggins however should hold the
free ends sat on top of the beam in place.

which relate to the ideal position for the new staircase. If
it is possible, how does it work? Do you bolt packing
timber to the top of the metal beam and then fix the joist
to that?

I would just sit them on the top of the beam much as you would if it
were a wooden joist/wall plate.

A further query: if you can do the above, could you have
joists where one end is slung below one metal beam from
joist hangers and the other end is supported on top of a
(lower) metal beam?

Yup, no requirement to have the same support mechanism at both ends.

I had one case where I had one end supported on a mid span wall, and the
other end hung from hangers of a flitch that needed to be positioned
above some existing floor joists:

http://www.internode.co.uk/loft/floor.htm


--
Cheers,

John.

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

On 9 Jun, 21:17, "Al Reynolds" wrote:
Evening,

I haven't been here for a while as I bought a house which
didn't need much work so apart from a big pergola and
some shelves I've done no DIY for two years. *It's good
to see a few familiar faces...

Anyhew, my mind has turned to the notion of converting
our loft into two bedrooms and a WC. *I'm still very much
at the feasibility study stage so far. *I have an *excellent*
text by J Coutts on the subject which I would recommend
to anyone who wants to learn all about loft conversions -
it is on Amazon.

Most of the time, when a new floor is being constructed,
the format is two long metal beams (I-profile) with joists
between them. *In most cases, the joists either sit in the
web (the sticky-in bit on the side of the I beam) or are
slung below the beams using joist hangers attached to
timber in the sides and on top of the beam.

What I want to know is, can you fix the end of a wooden
joist (say 75mm x 147mm) on *top* of one of these metal
beams? *I have good reasons to want to do this, most of
which relate to the ideal position for the new staircase. *If
it is possible, how does it work? *Do you bolt packing
timber to the top of the metal beam and then fix the joist
to that?

A further query: if you can do the above, could you have
joists where one end is slung below one metal beam from
joist hangers and the other end is supported on top of a
(lower) metal beam?

Thanks in advance,
Al Reynolds

Dear Al
Yes is the answer. It is well within the scope of a DIY who is
competent. For the top of the beam you place a sole plate on the top
and bolt it onto the beam with, say, 12 mm (1/2") bolts at appropriate
centres - probably alternate flanges at about 600 to 800 mm making
each set 1200 to 1600 apart. Mark out where the joists are to go and
avoid those locations. Use a 2" square or round thick plate washer on
the timber and a normal nut and washer on the steel. Drill half way
across one side of the flange (ie 1/4 span of the whole steel). It is
also possible to use a Hilti gun and shot fire attachments but you
would have to hire that and they are a bit of a fierce tool!
Rather than tosh nail the joists to the plate I would use a Concept 2
screw driver but that is up to you. Unquestionably, you would need
noggings between the joists for lateral stability of that end. I would
also do this in mid span or alternatively use herring bone strutting.
At the other end do it just as you suggested
Chris George

"Bruce" wrote:
Surely this isn't within the scope of DIY.

You should consult a structural engineer, a loft conversion specialist
or, if all you want is some broad guidance as to what is and isn't
possible, your local building control officer.

Deciding what you want to have done and what is feasible is
certainly DIY - the structural engineer and the loft-conversion
specialists would be later ports of call, but there's no harm in
thinking about what's possible in advance. You don't need an
architect to decide what you want.

BCO would just tell me to ask a structural engineer. It's more
than his jobsworth to give me engineering advice.

Al Reynolds

"John Rumm" wrote:

Al Reynolds wrote:
What I want to know is, can you fix the end of a wooden
joist (say 75mm x 147mm) on *top* of one of these metal
beams? If it is possible, how does it work? Do you bolt
packing timber to the top of the metal beam and then fix the joist to
that?

Can't see why not. The harder bit might be "fixing" since you can't just
skew nail them to the beam. A row of noggins however should hold the free
ends sat on top of the beam in place.
I would just sit them on the top of the beam much as you would if it were
a wooden joist/wall plate.

That's good to hear. Are joists normally fixed down to the wall
plate?

No requirement to have the same support mechanism at both ends.

I had one case where I had one end supported on a mid span wall, and the
other end hung from hangers of a flitch that needed to be positioned above
some existing floor joists:

http://www.internode.co.uk/loft/floor.htm

Thanks that actually helps a lot to see the images. Are flitch beams
cheaper to fabricate/install than metal beams. I suppose one advantage
is that you can fabricate them on site?

Al Reynolds

wrote:
For the top of the beam you place a sole plate on the top
and bolt it onto the beam with, say, 12 mm (1/2") bolts at appropriate
centres - probably alternate flanges at about 600 to 800 mm making
each set 1200 to 1600 apart. Mark out where the joists are to go and
avoid those locations. Use a 2" square or round thick plate washer on
the timber and a normal nut and washer on the steel. Drill half way
across one side of the flange (ie 1/4 span of the whole steel).

All sounds eminently do-able...

It is also possible to use a Hilti gun and shot fire attachments but you
would have to hire that and they are a bit of a fierce tool!

That's sounds a bit dangerous! I always feel that I know where I
am with bolts.

Rather than tosh nail the joists to the plate I would use a Concept 2
screw driver but that is up to you. Unquestionably, you would need
noggings between the joists for lateral stability of that end. I would
also do this in mid span or alternatively use herring bone strutting.

Yes the noggins at the end where the joists rest on the beam would
seem pretty much essential in this application.

Thanks for all the help people,
Al

Al Reynolds wrote:

"John Rumm" wrote:
Al Reynolds wrote:
What I want to know is, can you fix the end of a wooden
joist (say 75mm x 147mm) on *top* of one of these metal
beams? If it is possible, how does it work? Do you bolt
packing timber to the top of the metal beam and then fix the joist to
that?
Can't see why not. The harder bit might be "fixing" since you can't just
skew nail them to the beam. A row of noggins however should hold the free
ends sat on top of the beam in place.
I would just sit them on the top of the beam much as you would if it were
a wooden joist/wall plate.

That's good to hear. Are joists normally fixed down to the wall
plate?

Quite often they are just skew / tosh nailed to stop the end being
kicked about - there is no real structural need for it.

No requirement to have the same support mechanism at both ends.

I had one case where I had one end supported on a mid span wall, and the
other end hung from hangers of a flitch that needed to be positioned above
some existing floor joists:

http://www.internode.co.uk/loft/floor.htm

Thanks that actually helps a lot to see the images. Are flitch beams
cheaper to fabricate/install than metal beams. I suppose one advantage
is that you can fabricate them on site?

They may or may not be cheaper depending on what you are comparing with.
Larger ones are easier to handle on site, and you easily fix joist
hangers to them.

--
Cheers,

John.

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

Al Reynolds wrote:
"Bruce" wrote:
Surely this isn't within the scope of DIY.

You should consult a structural engineer, a loft conversion specialist
or, if all you want is some broad guidance as to what is and isn't
possible, your local building control officer.

Deciding what you want to have done and what is feasible is
certainly DIY - the structural engineer and the loft-conversion
specialists would be later ports of call, but there's no harm in
thinking about what's possible in advance. You don't need an
architect to decide what you want.

The structural stuff is also DIYable with a bit of research.

BCO would just tell me to ask a structural engineer. It's more
than his jobsworth to give me engineering advice.

Ours was quite happy to suggest solutions as well to be fair. One
example: The architect had originally drawn our plans with a flitch beam
over the bay window at the front of the house - each end resting on the
front wall - this was because the strength of the lintel over the bay
was unknown, and it seemed safer to use a beam here as a stringer to
pick up the ends of the floor joists that would have otherwise been
sitting on the lintel. However in reality there was no way of actually
positioning it where he had drawn it, since you would have to cut
through the existing loft floor joists, and that would leave the bonnet
roof over they bay unsupported since it was held by the joists in
cantilever. The BCO suggested putting the beam above the existing joists
and using long hangers to suspend the joists below its level. This also
necessitated attaching one of the other flitch beams to to its end -
which represented a significant change in the load at the end of the
beam. I modelled the change in the demo version of Superbeam, told the
BCO it was still in spec, and he was happy to proceed on that basis.



--
Cheers,

John.

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

Another thing occured to me ... in the Building Regs approved
document A, page 23, it says:

Loading on walls

2C23 Maximum span of floors: The maximum span for any
floor supported by a wall is 6m.

My house is 8.5m gable-to-gable by 5.5m eaves-to-eaves.

The current roof timbers therefore run at right-angles to the 8.5m
length. To get new wooden joists to run in the same direction as
the current timbers (headroom is at a premium) I would need two
steel beams running along the long length of the house between
the gables so that I could suspend the joists between them.

Could anyone familiar with the regs tell me if the "span" of the
floor would be 8.5m because that's how far apart the gables are?
This would appear to make hanging the floor off the end-gables
a no-go if that is the case.

I know this is going to be a lot of steel, but if I put in two steel
beams parallel to and close to each gable (and possibly more in
the middle), supported by the side walls, then used these to
support two further beams running along the length of the property,
would that mean the floor span is now only 5.5m?

Ascii-art (Times New Roman for correct scaling):
-----------------------------------------------------------
| I I I
I |
| I HHHHHHHHH I HHHHHHHH I HHHHHH I |
| I I I
I |
| I I I
I |
| I I I
I |
| I I I
I |
| I HHHHHHHHH I HHHHHHHH I HHHHHH I |
| I I I
I |
-----------------------------------------------------------
I = eaves-to-eaves beams H = beams in gable-to-gable direction

To be honest, by the time I'd done all that, I'd probably be
better off just going through the hassle of lowering the ceilings
or raising the roof!

Al

wrote:

It is
also possible to use a Hilti gun and shot fire attachments but you
would have to hire that and they are a bit of a fierce tool!


When I think of the careful, thorough and detailed training that my
company gave operatives, supervisors and managers alike in the use of
Hilti guns, I shudder at the thought of Joe Public being able to hire
and use one with absolutely no safety training.

In message , Al Reynolds
writes
Evening,

Most of the time, when a new floor is being constructed,
the format is two long metal beams (I-profile) with joists
between them. In most cases, the joists either sit in the
web (the sticky-in bit on the side of the I beam) or are
slung below the beams using joist hangers attached to
timber in the sides and on top of the beam.

Hi Al,

I don't know if it helps but for our loft conversion, the new floor
joists sit in between the existing joists directly onto the existing
wall plate. No steel required whatsoever. I appreciate from your later
posts this may not be do-able, but something for you to think about.

It was a royal PIA to get them all in in this manner, but worth it. We
have saved valuable headroom and a shi*load of money on steel.

Whilst there is no steel in the floor, the engineer decided the existing
purlins should be replaced with steel. The new steel purlins have a
timber plate bolted to the top (this means there is somewhere to fix
dwarf walls with normal hammer and nail rather than messing about with a
Hilti).

The various flanges, bolt holes etc were all part of the steel
spec/drawings sent to the fabricator and they arrived on site as such.
There was no working the steel so to speak, myself.

Hth
Someone

On Jun 10, 11:20 pm, Bruce wrote:
wrote:

It is
also possible to use a Hilti gun and shot fire attachments but you
would have to hire that and they are a bit of a fierce tool!

When I think of the careful, thorough and detailed training that my
company gave operatives, supervisors and managers alike in the use of
Hilti guns, I shudder at the thought of Joe Public being able to hire
and use one with absolutely no safety training.

Google "Austrian roofer" for plenty of incentive to be careful

On Tue, 10 Jun 2008 21:48:12 +0100 Al Reynolds wrote :
My house is 8.5m gable-to-gable by 5.5m eaves-to-eaves.

The current roof timbers therefore run at right-angles to the 8.5m
length. To get new wooden joists to run in the same direction as
the current timbers (headroom is at a premium) I would need two
steel beams running along the long length of the house between
the gables so that I could suspend the joists between them.

Could anyone familiar with the regs tell me if the "span" of the
floor would be 8.5m because that's how far apart the gables are?
This would appear to make hanging the floor off the end-gables
a no-go if that is the case.

The span of the beam is measured between centres of bearings, so if
there is 8.5m between the faces of the walls and you have 100mm
bearings, the span will be 8.6m. Spanning beams across this distance
generally doesn't make sense.

Without knowing the details, it might be possible to put a front/rear
span breaker beam at first floor ceiling level, tucked into a corner
where a partition meets the ceiling: when boxed in it would be
relatively inconspicuous.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

Martin Bonner wrote:

On Jun 10, 11:20 pm, Bruce wrote:
wrote:

It is
also possible to use a Hilti gun and shot fire attachments but you
would have to hire that and they are a bit of a fierce tool!

When I think of the careful, thorough and detailed training that my
company gave operatives, supervisors and managers alike in the use of
Hilti guns, I shudder at the thought of Joe Public being able to hire
and use one with absolutely no safety training.

Google "Austrian roofer" for plenty of incentive to be careful


Here's one from today's London Evening Standard:

http://tinyurl.com/5sz3r3