Hi - I'm after some structural joist cutting type advice and figured
this would probably be a good starting point! :-)

First of all, I'm very confused by the structure of our 1900's
terraced flat so I've taken some pictures to accompany this post which
I hope will help!

Basically, I want to fit some (rather substantial) loft ladders
however I'm a bit stuck when it comes to locations for them and am
left with little alternative but to run them perpendicular to the
joists. The opening required for the ladders is 120 x 70cm (47 1/4" x
27 1/2") and the ceiling joists are 12" apart (12" gap that is). The
joists are 2 1/2" x 2 1/4" by the way.

Unfortunately this means cutting 3 joists in order to fit them in!
(see http://www.pciq.co.uk/pics/newopening.jpg - new hole marked in
red). Now that wouldn't bother me too much if it wasn't for two
things:-

1. Our ceiling joists appear to be held up by 1x1" bits of wood
nailed to 1x4" bits of wood which are somehow attached to the walls
(see http://www.pciq.co.uk/pics/joistends.jpg - I'm sure I'm missing
something here but see for yourself!)

2. There would appear to be a large king post (11' high) supported by
two 2x7" joists held together in the middle somehow which look like
they're resting on our ceiling joists (see
http://www.pciq.co.uk/pics/kingpost.jpg)

There are NO load bearing walls in our flat (other than the outside
walls of course) so can anyone explain the structure of our house?

Anyway, my plan was to basically cut the three joists to create the
opening and install some new 2 1/2" x 4" joists to support the cut
joists - these would be morticed and screwed together for extra
strength. This is much easier explained if you look at this:-

http://www.pciq.co.uk/pics/plan.gif

Yellow = new opening
Black = ceiling joists
Blue = new 2 1/2 x 4" joists
Brown = 2x7" joists (spanning 30')
Red = King post (11' high)

So basically, the profile of the new joists (shown in blue) would be
like this: http://www.pciq.co.uk/pics/profile.gif

My only concern here is that the entire weight of the ceiling, the
loft ladder (and people on the loft ladder), the contents of the loft
and potentially the king post would be supported by the bits marked
'A' on plan.gif. Should I extend the 'Blue' supports out further (to
the next set of joists either way) to spread the load? My only
concern is that it would potentially weaken even more joists by
morticing into them.

Should I be concerned? Should I employ the services of a structural
engineer? Should I sell my loft ladders?

As a side note to all this, does anyone know why we appear to have
ready made joist holes in our walls above the ceiling joists? (see
http://www.pciq.co.uk/pics/joistholes.jpg and
http://www.pciq.co.uk/pics/joisthole.jpg)

Thanks for taking the time to read this epic - I look forward to ANY
responses!!

Cheers,

Andy

My only concern here is that the entire weight of the ceiling, the
loft ladder (and people on the loft ladder), the contents of the loft
and potentially the king post would be supported by the bits marked
'A' on plan.gif. Should I extend the 'Blue' supports out further (to
the next set of joists either way) to spread the load?

Personally, I would say that you would need to replace your "blue" beams
with sufficiently strong ones hung from structural brickwork at both ends.
Simply tying the cut joists together when they are already worse than
marginal probably won't do. An alternative would be to strengthen the next
uncut beam either side to hang your "blue" beams off, either using a very
deep wooden beam or a steel beam sufficiently protected against fire, which
may fit within the existing joist height.

Either get a structural engineer to design the thing, or have a play with
SuperBeam, if you've got enough mechanical knowledge to make safe use of it.

Personally, if I was doing structural alterations of this sort, I would
design a whole new structure based on standard floor loadings. That way you
can be sure that (a) you're laughing if you decide to convert the loft and
(b) you can use the loft for much heavier storage without breaking the
ceiling.

Christian.

In an earlier contribution to this discussion,
pecanfan wrote:

Hi - I'm after some structural joist cutting type advice and figured
this would probably be a good starting point! :-)

First of all, I'm very confused by the structure of our 1900's
terraced flat so I've taken some pictures to accompany this post which
I hope will help!

Basically, I want to fit some (rather substantial) loft ladders
however I'm a bit stuck when it comes to locations for them and am
left with little alternative but to run them perpendicular to the
joists. The opening required for the ladders is 120 x 70cm (47 1/4" x
27 1/2") and the ceiling joists are 12" apart (12" gap that is). The
joists are 2 1/2" x 2 1/4" by the way.

Unfortunately this means cutting 3 joists in order to fit them in!
(see http://www.pciq.co.uk/pics/newopening.jpg - new hole marked in
red). Now that wouldn't bother me too much if it wasn't for two
things:-

1. Our ceiling joists appear to be held up by 1x1" bits of wood
nailed to 1x4" bits of wood which are somehow attached to the walls
(see http://www.pciq.co.uk/pics/joistends.jpg - I'm sure I'm missing
something here but see for yourself!)

2. There would appear to be a large king post (11' high) supported by
two 2x7" joists held together in the middle somehow which look like
they're resting on our ceiling joists (see
http://www.pciq.co.uk/pics/kingpost.jpg)

There are NO load bearing walls in our flat (other than the outside
walls of course) so can anyone explain the structure of our house?

Anyway, my plan was to basically cut the three joists to create the
opening and install some new 2 1/2" x 4" joists to support the cut
joists - these would be morticed and screwed together for extra
strength. This is much easier explained if you look at this:-

http://www.pciq.co.uk/pics/plan.gif

Yellow = new opening
Black = ceiling joists
Blue = new 2 1/2 x 4" joists
Brown = 2x7" joists (spanning 30')
Red = King post (11' high)

So basically, the profile of the new joists (shown in blue) would be
like this: http://www.pciq.co.uk/pics/profile.gif

My only concern here is that the entire weight of the ceiling, the
loft ladder (and people on the loft ladder), the contents of the loft
and potentially the king post would be supported by the bits marked
'A' on plan.gif. Should I extend the 'Blue' supports out further (to
the next set of joists either way) to spread the load? My only
concern is that it would potentially weaken even more joists by
morticing into them.

Should I be concerned? Should I employ the services of a structural
engineer? Should I sell my loft ladders?

As a side note to all this, does anyone know why we appear to have
ready made joist holes in our walls above the ceiling joists? (see
http://www.pciq.co.uk/pics/joistholes.jpg and
http://www.pciq.co.uk/pics/joisthole.jpg)

Thanks for taking the time to read this epic - I look forward to ANY
responses!!

Cheers,

Andy

I'm confused by your structure, and feel that you need to get expert advice
before doing anything.

If your joists are only a bit bigger than 2 x 2, they're only capable of
holding themselves plus the ceiling up - and I certainly wouldn't want to
store anything other than empty cardboard boxes on top of them!

Ceiling joists are often an integral part of the roof structure - and are in
tension to stop the ends of the rafters from spreading. If you cut them, you
can have problems with the roof. [Yours may not be like that, because they
appear to be at right angles to the rafters - so I can't work out what's
going on! - all the more reason for getting expert advice].

Some of your pictures seem to suggest that the joists are not all at the
same level - implying that the ceilings slope. Is this the case?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

pecanfan wrote:

1. Our ceiling joists appear to be held up by 1x1" bits of wood
nailed to 1x4" bits of wood which are somehow attached to the walls
(see http://www.pciq.co.uk/pics/joistends.jpg - I'm sure I'm missing
something here but see for yourself!)

What depth are the current ceiling joists?

2. There would appear to be a large king post (11' high) supported by
two 2x7" joists held together in the middle somehow which look like
they're resting on our ceiling joists (see
http://www.pciq.co.uk/pics/kingpost.jpg)

THe way in which the post meets the joists and the two ends of the
ceiling joists "fly past" each other would suggest there is a supporting
wall or some other load bearing structure under there.

It is quite common to have a load bearing wall in the middle of the
property which has the effect of splitting the ceiling joists into two
sides (or front and back).

There are NO load bearing walls in our flat (other than the outside
walls of course) so can anyone explain the structure of our house?

How do you know the wall are not load bearing? (a stud wall can be load
bearing as well - it does not need to be brick / block).

If there really is no load bearing wall, is there a substantial joist at
the apex of the roof? If so it may be that the king beam you see is
actually under tension and carries the horizontal joists rather than
being supported on them or a wall.

Anyway, my plan was to basically cut the three joists to create the
opening and install some new 2 1/2" x 4" joists to support the cut
joists - these would be morticed and screwed together for extra
strength. This is much easier explained if you look at this:-

http://www.pciq.co.uk/pics/plan.gif

Where you add stringer beams like this that span a few joists, it is
quite common to strengthen the ones at the end which are now taking the
load of several joists (i.e. the black beams at the points marked A in
your photo). This would often be done by running one or two extra beams
beside the existing ones and bolting them together.

My only concern here is that the entire weight of the ceiling, the
loft ladder (and people on the loft ladder), the contents of the loft
and potentially the king post would be supported by the bits marked

I doubt the king post comes into the equation directly here since it
must either be supported from beneath, or is doing the supporting.

I would be more concerned with the depth of the existing ceiling joists.
They look a little shallow from your photos. If there are less than 4"
deep I would be wary of placing much load on them at all (in addition to
their own weight and that of the ceilings).


--
Cheers,

John.

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