A not-quite loft conversion
 

All,

I've decided that getting my plans past the BCO would be easy compare to
getting them approved by the missus, but I still have a big loft space that
is being wasted, and I do need the storage.

So, the new plan is to fit proper load bearing floor into the loft (2"x10"
for the 16' span, raise them an extra 1" off the wallplate to stop them
interfering with the plasterboard ceiling below when they deflect). I plan
to leave access via the loft hatch exactly as before, so that is not extra
"livingspace", just a loft with a decent load bearing floor. At a later
date, I'll come back and put the staircase in, insulate the roof, fire
alarms, electrics, plumbing etc and make it a proper conversion.

Can anyone see any snags with this? Obviously I want to do the load bearing
floor such that when I do the loft conversion for real, it is suitable, so
any suggestions appreciated.

Cheers

Chris

Chris Styles wrote:
All,

I've decided that getting my plans past the BCO would be easy compare to
getting them approved by the missus, but I still have a big loft space that
is being wasted, and I do need the storage.

So, the new plan is to fit proper load bearing floor into the loft (2"x10"
for the 16' span, raise them an extra 1" off the wallplate to stop them
interfering with the plasterboard ceiling below when they deflect). I plan
to leave access via the loft hatch exactly as before, so that is not extra
"livingspace", just a loft with a decent load bearing floor. At a later
date, I'll come back and put the staircase in, insulate the roof, fire
alarms, electrics, plumbing etc and make it a proper conversion.

Can anyone see any snags with this? Obviously I want to do the load bearing
floor such that when I do the loft conversion for real, it is suitable, so
any suggestions appreciated.

Cheers

Chris

A 250mm deep joist 25mm up off the wallplate is [potentially] going to
need a significant chamfer at the ends to stop them protruding throught
the roof. The BCO may well not approve this unless the joist is
strengthend at the bearing or calculated to prove it is OK.

Any purlins to be removed?

dg

Chris Styles wrote:

Can anyone see any snags with this? Obviously I want to do the load bearing
floor such that when I do the loft conversion for real, it is suitable, so
any suggestions appreciated.

Sounds reasonable enough... you may have to do something slightly "non
final" at the loft hatch otherwise you may find yourself with a joist
flying right over the opening making access difficult.

Depending on your loft hatch you may well find getting long beams into
the loft space impossible without making some form of access hole
through the side of the roof. Having at a minimum some scaffolding tower
in front of this would be a good idea. Next time I do one I would also
put a jib on the top of the scaffold and add an electric winch!

Think about where you may need dwarf walls, or other supporting
structures since you will need to size the joists to carry these point
loads as well and not just the uniform distributed floor loads.

See if there is anything else on my floor construction page that helps:

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 |
\================================================= ================/

dg wrote:

A 250mm deep joist 25mm up off the wallplate is [potentially] going to
need a significant chamfer at the ends to stop them protruding throught
the roof. The BCO may well not approve this unless the joist is
strengthend at the bearing or calculated to prove it is OK.

I had 200mm deep joists, and as you suggest needed to chamfer them at
the front of the house where the original pitched roof was to remain.
The BCO seemed ok with that though.

One downside of chamfering though is if you want to add a full depth
dormer later - you will no longer have an easy way to fix the rear wall
of it to the ends of the floor joists without having to fix little
extensions onto each of the joists


--
Cheers,

John.

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

"John Rumm" wrote in message
...
Chris Styles wrote:

Can anyone see any snags with this? Obviously I want to do the load
bearing floor such that when I do the loft conversion for real, it is
suitable, so any suggestions appreciated.

Sounds reasonable enough... you may have to do something slightly "non
final" at the loft hatch otherwise you may find yourself with a joist
flying right over the opening making access difficult.

Depending on your loft hatch you may well find getting long beams into the
loft space impossible without making some form of access hole through the
side of the roof. Having at a minimum some scaffolding tower in front of
this would be a good idea. Next time I do one I would also put a jib on
the top of the scaffold and add an electric winch!

Think about where you may need dwarf walls, or other supporting structures
since you will need to size the joists to carry these point loads as well
and not just the uniform distributed floor loads.

See if there is anything else on my floor construction page that helps:

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

Thanks John.

I had a good look at your site before (after my last loft-conversion
posting), and it is an inspiration and damn scary all at the same time :-)

Cheers,
Chris

"dg" wrote in message
oups.com...

Chris Styles wrote:
All,

I've decided that getting my plans past the BCO would be easy compare to
getting them approved by the missus, but I still have a big loft space
that
is being wasted, and I do need the storage.

So, the new plan is to fit proper load bearing floor into the loft
(2"x10"
for the 16' span, raise them an extra 1" off the wallplate to stop them
interfering with the plasterboard ceiling below when they deflect). I
plan
to leave access via the loft hatch exactly as before, so that is not
extra
"livingspace", just a loft with a decent load bearing floor. At a later
date, I'll come back and put the staircase in, insulate the roof, fire
alarms, electrics, plumbing etc and make it a proper conversion.

Can anyone see any snags with this? Obviously I want to do the load
bearing
floor such that when I do the loft conversion for real, it is suitable,
so
any suggestions appreciated.

Cheers

Chris

A 250mm deep joist 25mm up off the wallplate is [potentially] going to
need a significant chamfer at the ends to stop them protruding throught
the roof. The BCO may well not approve this unless the joist is
strengthend at the bearing or calculated to prove it is OK.

How would I go about strengthening them? Do you mean like bolting an extra
bit of 250mm joint (say) 1m long with the same profile, so that it is
thicker for a little bit leading up to the chamfer

Any purlins to be removed?

Nope, the house is 3 years old, and the roof comprises of the finest 2"x3"
trusses you can buy (for ~£10 each)

The main reason I dont want to board the loft as I did at my last house is
that the trusses have a 16' span, about 10' at the apex, but the only
internal tie goes from the apex to the mid point of the joist. The trusses
at the last house had a larger span, but had internal ties in a "W"
formation, so it look quite substantial.

I'm going to have to get a structural engineer in to work out how to remove
these when I come to do a conversion. I had wondered if I'd be able to put a
16' steel parallel to the joists, put a vertical steel off of that at the
mid point, then run a third steel from the gable to the top of the vertical
steel, running along under the apex to take the weight. Given the the only
tie inside the joist is a direct vrtical to the midpoint of the bottom of
the truss, it would seem that it is only a vertical load that needs to be
taken.

Maybe I should take a picture, so you can all see what I mean (and then all
breathe in sharply through your teeth... "Oooohhh, tricky...." :-)

Cheers

Chris