Hello all
I've just moved into a bungalow which I'm considering putting a loft
room into.I've been trawling through all the loft room posts on this
site and various other sites so I thought I'd throw it open to advice.
The building is a 1972 detached, pitched roof with gables with the roof
apex gable to gable as opposed to back to front.Concrete roof tiles
held up by 10 roof trusses,constructed from 35mm x 150mm timber.The gap
to be spanned is 18ft 6" wide and the joists run front to back and are
approx 30 ft long.(no internal supporting walls)
I plan on putting a floor in that is independent of the present one and
supporting the roof (possibly) with purlins of some form,wether it be
timber,steel or a composite of both.
The problem part is the headroom,at present there is 2m to the bottom
of the rafters which are 150mm,thus I should be able to fit the
required insulation and get a 50mm ventilation gap,so hopefully the
only extra space taken up at the top will be that which the plaster
board occupies.
What I am interested to know is,as I haven't got access to software to
calculate necessary sizes,is it possible to span an 18 1/2 foot gap
with timber ? - if so what would the dimensions need to be,I'd prefer
to work in timber or possibly construct a flitch beam
I only intend on putting one room up there with a dormer at the back
and a velux at the front.The stairs will access directly under the
apex,flush with the wall so will have 2m head room,if the present floor
height remained unchanged.

Is there a minimum requirement for headroom within the room,it wouldn't
be a problem for me as I'm 5'8",but obviously the world is generally
full of taller people than me.

Also - do the fire regs regarding escape route from bottom of stairs to
nearest door to outside apply to bungalows too,ie that any door opening
onto said route is solid.

Thanks

On 29 Dec 2006 12:53:37 -0800 Dob wrote :
What I am interested to know is,as I haven't got access to software to
calculate necessary sizes,is it possible to span an 18 1/2 foot gap
with timber ? - if so what would the dimensions need to be,I'd prefer
to work in timber or possibly construct a flitch beam

Not easily, particularly since headroom is a factor. You would need to
take the advice of a structural engineer.

I only intend on putting one room up there with a dormer at the back
and a velux at the front.The stairs will access directly under the
apex,flush with the wall so will have 2m head room,if the present
floor height remained unchanged.

Is there a minimum requirement for headroom within the room,it
wouldn't be a problem for me as I'm 5'8",but obviously the world is
generally full of taller people than me.

The only headroom rules relate to staircases and landings, but
substandard headroom is likely to be a major turn-off for most potential
buyers. I suspect that any design is likely to involve a floor level
that is higher than the top of the existing joists.

Is the property detached? If so, I'd be inclined to think about a total
roof reconstruction to make proper rooms possible.

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

Tony Bryer wrote:

On 29 Dec 2006 12:53:37 -0800 Dob wrote :
What I am interested to know is,as I haven't got access to software to
calculate necessary sizes,is it possible to span an 18 1/2 foot gap
with timber ? - if so what would the dimensions need to be,I'd prefer
to work in timber or possibly construct a flitch beam

Not easily, particularly since headroom is a factor. You would need to
take the advice of a structural engineer.

I only intend on putting one room up there with a dormer at the back
and a velux at the front.The stairs will access directly under the
apex,flush with the wall so will have 2m head room,if the present
floor height remained unchanged.

Is there a minimum requirement for headroom within the room,it
wouldn't be a problem for me as I'm 5'8",but obviously the world is
generally full of taller people than me.

The only headroom rules relate to staircases and landings, but
substandard headroom is likely to be a major turn-off for most potential
buyers. I suspect that any design is likely to involve a floor level
that is higher than the top of the existing joists.

Is the property detached? If so, I'd be inclined to think about a total
roof reconstruction to make proper rooms possible.

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


Yes the property is detached.
What I was considering was putting two beams across the narrowest span
and running joists alongside the current ones.The size of the main
supporting beams doesn't matter too much as they can be at the side of
the room to be constructed and be the base of the dwarf wall rising to
the rafters,so if I could use joist hangers on the main supporting
beams that have the cup that holds the joist lower than top of the main
beam I may be able to get enough headroom? if that makes sense

DOB wrote:

The problem part is the headroom,at present there is 2m to the bottom
of the rafters which are 150mm,thus I should be able to fit the
required insulation and get a 50mm ventilation gap,so hopefully the
only extra space taken up at the top will be that which the plaster
board occupies.

You may want some insulation under the rafter to combat the thermal
bridging effect of the timber...

What I am interested to know is,as I haven't got access to software to
calculate necessary sizes,is it possible to span an 18 1/2 foot gap
with timber ? - if so what would the dimensions need to be,I'd prefer
to work in timber or possibly construct a flitch beam

Gut feel says fairly substantial at that span (i.e. 250mm) (I would go
do the sums, but I just killed the computer with the software on it!) -
you can download the demo version of Superbeam from Tony's site:
www.sda.co.uk

You have the added complication that you may need the new floor to carry
some roof load via your purlins (or more likely a dwarf wall).

I only intend on putting one room up there with a dormer at the back
and a velux at the front.The stairs will access directly under the
apex,flush with the wall so will have 2m head room,if the present floor
height remained unchanged.

Seems unlikely, unless you go for a steel floor - even then I would
anticipate some gain in floor height.

Is there a minimum requirement for headroom within the room,it wouldn't
be a problem for me as I'm 5'8",but obviously the world is generally
full of taller people than me.

Only over the stairs. However I would have though anything less than
about 6'6" would make for a very "close" feeling room even if you could
stand up in it.

Also - do the fire regs regarding escape route from bottom of stairs to
nearest door to outside apply to bungalows too,ie that any door opening
onto said route is solid.

Don't think so.


--
Cheers,

John.

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

John Rumm wrote:

DOB wrote:

The problem part is the headroom,at present there is 2m to the bottom
of the rafters which are 150mm,thus I should be able to fit the
required insulation and get a 50mm ventilation gap,so hopefully the
only extra space taken up at the top will be that which the plaster
board occupies.

You may want some insulation under the rafter to combat the thermal
bridging effect of the timber...

What I am interested to know is,as I haven't got access to software to
calculate necessary sizes,is it possible to span an 18 1/2 foot gap
with timber ? - if so what would the dimensions need to be,I'd prefer
to work in timber or possibly construct a flitch beam

Gut feel says fairly substantial at that span (i.e. 250mm) (I would go
do the sums, but I just killed the computer with the software on it!) -
you can download the demo version of Superbeam from Tony's site:
www.sda.co.uk

You have the added complication that you may need the new floor to carry
some roof load via your purlins (or more likely a dwarf wall).

I only intend on putting one room up there with a dormer at the back
and a velux at the front.The stairs will access directly under the
apex,flush with the wall so will have 2m head room,if the present floor
height remained unchanged.

Seems unlikely, unless you go for a steel floor - even then I would
anticipate some gain in floor height.

Is there a minimum requirement for headroom within the room,it wouldn't
be a problem for me as I'm 5'8",but obviously the world is generally
full of taller people than me.

Only over the stairs. However I would have though anything less than
about 6'6" would make for a very "close" feeling room even if you could
stand up in it.

Also - do the fire regs regarding escape route from bottom of stairs to
nearest door to outside apply to bungalows too,ie that any door opening
onto said route is solid.

Don't think so.


--
Cheers,

John.

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


Thanks for quick response

Regarding thermal bridging - what depth of insulation is advisable
under/over the rafters?

DOB wrote:

Regarding thermal bridging - what depth of insulation is advisable
under/over the rafters?

The usual recommendation is for 50 between and 35 under - but that
assumes 100mm rafters. In your case I would expect you would get away
with 20 or 25 below and say 70-80mm between.

--
Cheers,

John.

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