My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



--
AnthonyL

On Friday, 12 February 2016 17:08:48 UTC, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



--
AnthonyL

Depending on the construction of the roof, you may be able to put some hangers in between the roof rafters/purlins and the "ceiling joists".
These could be wood or the metal strap you can buy at the builders merchants.
Latter is more convenient.

This sort of thing:-
http://www.screwfix.com/p/sabrefix-h...-10-pack/74769

Looks messier than extra joists but might not matter.

You can put in extra joists of same size between existing as alternative.
May not be practical if ceiling has already sagged, matter of degree.
Probably not practical to straighten the sag either.

On Friday, 12 February 2016 17:08:48 UTC, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



--
AnthonyL

Rule of thumb for joists in inhabited domestic room.
Joists @ 16" centres and 2" thick

Depth (in inches) needed is half of span in feet plus 2
So in your case half seven plus two = 6" (rounding up) or 5" rounding down.

So 5"x2" at sixteen inch centres. (As it's not an inhabited room.)

On 12/02/16 17:08, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



A diagram of how this opening works would be useful...

On Fri, 12 Feb 2016 18:46:38 +0000, Tim Watts
wrote:

On 12/02/16 17:08, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



A diagram of how this opening works would be useful...

A room, 2.1m wide to one side has been opened up into lounge on the
other side.

View fixed font


==================================== Side wall
| |
Kitchen |Room|Toilet Bedroom
______________|xxxx|_________________ Lounge, toilet and bedroom wall
|
Lounge | Bedroom
|
==================================== Side wall

xxxx = wall removed to open Room into Lounge and hence sag

Joists run Side wall to Side wall (~6.6m) using middle wall for
mid-way support.

One obvious solution is to use a support at xxxx from the living side
and make a feature eg archway of it. But what does it need to be?


--
AnthonyL

On 12/02/16 21:40, AnthonyL wrote:
On Fri, 12 Feb 2016 18:46:38 +0000, Tim Watts
wrote:

On 12/02/16 17:08, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



A diagram of how this opening works would be useful...

A room, 2.1m wide to one side has been opened up into lounge on the
other side.

View fixed font


==================================== Side wall
| |
Kitchen |Room|Toilet Bedroom
______________|xxxx|_________________ Lounge, toilet and bedroom wall
|
Lounge | Bedroom
|
==================================== Side wall

xxxx = wall removed to open Room into Lounge and hence sag

Joists run Side wall to Side wall (~6.6m) using middle wall for
mid-way support.

One obvious solution is to use a support at xxxx from the living side
and make a feature eg archway of it. But what does it need to be?



A simple solution is to strap a 6x2" or so beam where the wall xxxx was
and overlapping both sides.

1-2" angle iron screwed or bolted[1] between each joist and beam
intersection. Effectively you will hang the overspanned joists off this
and transfer load to the wall either side through the tops of the other
joists.

Bolt mid way between top and bottom or a number of small screws
It will give you a "hump" but it's simple - highly related to what I'll
be doing tomorrow...

On Fri, 12 Feb 2016 21:45:48 +0000, Tim Watts
wrote:

On 12/02/16 21:40, AnthonyL wrote:
On Fri, 12 Feb 2016 18:46:38 +0000, Tim Watts
wrote:

On 12/02/16 17:08, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



A diagram of how this opening works would be useful...

A room, 2.1m wide to one side has been opened up into lounge on the
other side.

View fixed font


==================================== Side wall
| |
Kitchen |Room|Toilet Bedroom
______________|xxxx|_________________ Lounge, toilet and bedroom wall
|
Lounge | Bedroom
|
==================================== Side wall

xxxx = wall removed to open Room into Lounge and hence sag

Joists run Side wall to Side wall (~6.6m) using middle wall for
mid-way support.

One obvious solution is to use a support at xxxx from the living side
and make a feature eg archway of it. But what does it need to be?



A simple solution is to strap a 6x2" or so beam where the wall xxxx was
and overlapping both sides.

1-2" angle iron screwed or bolted[1] between each joist and beam
intersection. Effectively you will hang the overspanned joists off this
and transfer load to the wall either side through the tops of the other
joists.

Bolt mid way between top and bottom or a number of small screws
It will give you a "hump" but it's simple - highly related to what I'll
be doing tomorrow...

But the attic is already boarded and if I take an underneath approach
I presume that everything can be pushed back up into place?

Does the boarding (t&g) add to strength of the joists or does the
additional weight counter this?

--
AnthonyL

On 12/02/16 22:15, AnthonyL wrote:
On Fri, 12 Feb 2016 21:45:48 +0000, Tim Watts
wrote:

On 12/02/16 21:40, AnthonyL wrote:
On Fri, 12 Feb 2016 18:46:38 +0000, Tim Watts
wrote:

On 12/02/16 17:08, AnthonyL wrote:
My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike. 8" x 2" seems an awful lot.
Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.



A diagram of how this opening works would be useful...

A room, 2.1m wide to one side has been opened up into lounge on the
other side.

View fixed font


==================================== Side wall
| |
Kitchen |Room|Toilet Bedroom
______________|xxxx|_________________ Lounge, toilet and bedroom wall
|
Lounge | Bedroom
|
==================================== Side wall

xxxx = wall removed to open Room into Lounge and hence sag

Joists run Side wall to Side wall (~6.6m) using middle wall for
mid-way support.

One obvious solution is to use a support at xxxx from the living side
and make a feature eg archway of it. But what does it need to be?



A simple solution is to strap a 6x2" or so beam where the wall xxxx was
and overlapping both sides.

1-2" angle iron screwed or bolted[1] between each joist and beam
intersection. Effectively you will hang the overspanned joists off this
and transfer load to the wall either side through the tops of the other
joists.

Bolt mid way between top and bottom or a number of small screws
It will give you a "hump" but it's simple - highly related to what I'll
be doing tomorrow...

But the attic is already boarded and if I take an underneath approach
I presume that everything can be pushed back up into place?

I see,

My father did correct a sagging ceiling by jacking up a beam underneath
it - he used an array of large wood and wedges, but a couple of acros
would work more easily.

Expect some plaster repair work in the vicinity.

If you can support the beam underneath, the final solution will be good.


Does the boarding (t&g) add to strength of the joists or does the
additional weight counter this?


If it's well nailed or screwed, it will tend to spread the load and tie
the adjacent joists together.

On 12/02/2016 17:08, AnthonyL wrote:

My attic as been floorboarded but there is a sag where a room below
has been opened out leaving 2m unsupported.

The joists are 3" x 2". I've just been next door and he's replaced
these with 8" x 2" so obviously a lot less useable space and height.

Q1. What do I need under the 2m unsupported?

Under? Not sure I follow... A diagram would help.

Q2. I intend to use the attic for a bit of storage and maybe to put a
computer, desk and chair up there whilst doing projects such as
digitising slides and VHS and suchlike.

If you are planning to use it for extra working space, then you will
need to upgrade it to something a little closer to that expected of a
floor.

8" x 2" seems an awful lot.

The ideal way to do a floor in a loft is so that it is decoupled from
the existing ceiling. Typically you stick a 1" thick piece of timber on
the wall plate at the eves between the existing joists. Then you sit the
new joists on these, interspersed with the old ones. They will be taller
than the old ones, and hence the new floor will be well above the old
joists, and the bottoms of the new joists, well away from the old
ceiling below.

The last couple of photos here show what it looks like:

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

Can't I just double up with 3" x 2" or 4" x 2" even? Total span is
about 6.6m with supporting walls below at around half-way.

So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the supporting
wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more than
the building regs normally stipulate) you could drop down a bit - to say
150mm. Allowing for the spacer on the wall plate (and supporting centre
wall), that would give a new floor level about 4" higher than your
current one.


--
Cheers,

John.

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

John Rumm wrote:
So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the
supporting wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more
than the building regs normally stipulate) you could drop down a bit
- to say 150mm. Allowing for the spacer on the wall plate (and
supporting centre wall), that would give a new floor level about 4"
higher than your current one.

And this is when the big problem is encountered - trying to fit 150 or
170mm joists on a wallplate that won't allow that depth because of the slope
of the roof.
They may need to be cut down in height at the ends so as not to interfere
with the roof

On 12/02/16 20:01, Phil L wrote:
John Rumm wrote:
So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the
supporting wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more
than the building regs normally stipulate) you could drop down a bit
- to say 150mm. Allowing for the spacer on the wall plate (and
supporting centre wall), that would give a new floor level about 4"
higher than your current one.

And this is when the big problem is encountered - trying to fit 150 or
170mm joists on a wallplate that won't allow that depth because of the slope
of the roof.
They may need to be cut down in height at the ends so as not to interfere
with the roof



Normally just cut them at an angle to match the roof - which is how the
other joists will be cut.

I had to do that when sliding in a new 8x2".

On 12/02/2016 20:01, Phil L wrote:
John Rumm wrote:
So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the
supporting wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more
than the building regs normally stipulate) you could drop down a bit
- to say 150mm. Allowing for the spacer on the wall plate (and
supporting centre wall), that would give a new floor level about 4"
higher than your current one.

And this is when the big problem is encountered - trying to fit 150 or
170mm joists on a wallplate that won't allow that depth because of the slope
of the roof.
They may need to be cut down in height at the ends so as not to interfere
with the roof

Indeed - the top will probably need cutting to match the rafter angle at
the ends.


--
Cheers,

John.

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

On Sat, 13 Feb 2016 11:04:29 +0000, John Rumm
wrote:

On 12/02/2016 20:01, Phil L wrote:
John Rumm wrote:
So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the
supporting wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more
than the building regs normally stipulate) you could drop down a bit
- to say 150mm. Allowing for the spacer on the wall plate (and
supporting centre wall), that would give a new floor level about 4"
higher than your current one.

And this is when the big problem is encountered - trying to fit 150 or
170mm joists on a wallplate that won't allow that depth because of the slope
of the roof.
They may need to be cut down in height at the ends so as not to interfere
with the roof

Indeed - the top will probably need cutting to match the rafter angle at
the ends.



OP here; couple of thoughts:

1)Couldn't I bolt some 4x2 onto the 3x2 - I've then got extra
thickness and not much loss of height

or

2) Couldn't I bolt some 1/4" plate either side of the 3x2? Or is that
just too messy?

--
AnthonyL

On 13/02/16 14:50, AnthonyL wrote:
On Sat, 13 Feb 2016 11:04:29 +0000, John Rumm
wrote:

On 12/02/2016 20:01, Phil L wrote:
John Rumm wrote:
So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the
supporting wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more
than the building regs normally stipulate) you could drop down a bit
- to say 150mm. Allowing for the spacer on the wall plate (and
supporting centre wall), that would give a new floor level about 4"
higher than your current one.

And this is when the big problem is encountered - trying to fit 150 or
170mm joists on a wallplate that won't allow that depth because of the slope
of the roof.
They may need to be cut down in height at the ends so as not to interfere
with the roof

Indeed - the top will probably need cutting to match the rafter angle at
the ends.



OP here; couple of thoughts:

1)Couldn't I bolt some 4x2 onto the 3x2 - I've then got extra
thickness and not much loss of height


It needs to be fully bonded, glued and screws every foot or so,
otherwise if the beams can slide, they are not much better than one of
the beams by itself.


2) Couldn't I bolt some 1/4" plate either side of the 3x2? Or is that
just too messy?


If you follow the plate with an inch of good solid wood, you now have a
flitch beam

Downside is 3x2 is not much to be drilling holes every foot or two.

On 13/02/2016 14:50, AnthonyL wrote:
On Sat, 13 Feb 2016 11:04:29 +0000, John Rumm
wrote:

On 12/02/2016 20:01, Phil L wrote:
John Rumm wrote:
So your effective span can be taken as 3.3 m or so (you would probably
use two joists at that length - that meet side by side on the
supporting wall)

For a 3.3m span using C16 grade timber, you would need 50x170mm cross
section timbers to meet modern building regs. However if you are not
worried about the floor feeling a bit bouncy (and since its decoupled
from the ceiling, you need not worry about it deflecting a bit more
than the building regs normally stipulate) you could drop down a bit
- to say 150mm. Allowing for the spacer on the wall plate (and
supporting centre wall), that would give a new floor level about 4"
higher than your current one.

And this is when the big problem is encountered - trying to fit 150 or
170mm joists on a wallplate that won't allow that depth because of the slope
of the roof.
They may need to be cut down in height at the ends so as not to interfere
with the roof

Indeed - the top will probably need cutting to match the rafter angle at
the ends.



OP here; couple of thoughts:

1)Couldn't I bolt some 4x2 onto the 3x2 - I've then got extra
thickness and not much loss of height

You could but you have to find a way of making them behave as a single
beam. Also any deflection will also show on the ceilings below.

You could try gluing and screwing, or using ply gussets on wither side.
TBH, new joints in the gaps are so much less hassle.

2) Couldn't I bolt some 1/4" plate either side of the 3x2? Or is that
just too messy?

Again more work for not much gain.


--
Cheers,

John.

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