squelchy wrote:

Hi John firstly thank you for your advice can you please answer these
questions for me -

Can you please let me know how these calculations are done so I can
calulate the correct loads with different materials and wood thickness
as I like knowing these things for future referance?

The how (as in mathematically) is quite complex - not because the sums
are that difficult in themselves, but because there are lots of
different ones you need for dealing with point loads or uniform loads,
bending, and shear forces etc. If you want that level of detail then I
suggest some of the books I have linked to he

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

The practical answer (and the way that most architects etc are going to
produce the calculations) is using a software package designed for the
task.

You can download a demo version of Superbeam (the one my architect used)
he

http://www.sda.co.uk/sbw.htm

Note however that software is not a total solution. If you don't know
what data to feed into it, you will simply end up with a potentially
dangerous design faster! With plenty of research and a book like:

http://www.amazon.co.uk/exec/obidos/...ternodeltdcomp

You can probably get a good deal of the source data you would need to
produce unsable data for the program.

The more practical alternative is to insert 8x3" beams in between and

parallel to the existing ceiling joists and remove the tie beams
altogether. You could then insert a row of noggings between the new
floor beams which you fix to the ceiling joists.


sounds like a good plan as this would give me a higher cealing it is
quite large already though with a middle hight of around 3m so quite
allot to work with.

how would I go about this i.e how to support the cealing before the tie
beams are removed I guess you need to remove these before you put in
the 4.5m sections from the outer house walls to the center wall ? would
I attach the cealing jiosts to the perlins with metal ties and cut the
tie beams into sections to remove them ?

First let me state again I have not seen your loft - so there may be
some fundamental deign point I am missing. Also while I am an engineer,
I am not a structural one. In other words don't go hacking lumps out of
your roof until you have verified what I am saying!

If you have a close look at the first two photo's on this page you can
see me doing exactly this:

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

The tie beams were in my case only 4x2" like the other loft joists. They
ran across the loft and were skew nailed to each of the joists. Hence
their main function was to prevent latteral movement of the joists, and
provide a little coupling and load sharing to the adjacent joists. Note
however they strength of this coupling was limited by the relatively low
forces that would have been required to pull the nails out[1].

To allow the joist to be inserted, we prepared *three* lengths of 4x1"
to use as temporary straps. You can nail these to the purlin[2], and the
to the tie itself. We used one either side of the section to be removed.
After these were in place a section of the tie was cut out. To insert
the next joist you nail up the third one up to the side of the next cut,
and then when that is in place, take out the middle one (that way you
never "let go" of the tie beam and alow a bit of the ceiling to sag).


[1] You would need to look carfully at you larger cross beam and see how
it is fixed to the joists to understand if it is simply doing the same
as my ones were, or if it also performs some other function.

[2] Leave the heads sticking out so you can pullem out and reuse the
next time!

I am guessing this would pass the preasure to the middle wall and the
frount and back walls of our house the floor tie beam looks quite
large, is it not doing that much that it can be easyley removed as you
sirjest? (sorry my spellings not very good)

If it is doing as I susspect, then it can be removed in the way
desribed. Once you have at least two new big joists in place you can
stick a 2x2" noggin across between them and nail them to the old ceiling
joist and the sides of the new floor joists. That will then duplicate
the function of the tie beam.

I have been informed that I could also hang 8"x3" jiost on the party
walls at 400mm centres using jiost hangers with the morter of the
current brick walls grinded out and then placing the hangers in the
wall and cementing them in is this a practical way of doing it ? and
would it give me the same amount of structual stregth i.e is it better
to hang jiost on the frount and back of the house or the two party
walls ?

You could, but it is harder work, takes longer, is more expensive, and
you loose 4" extra headroom.

if I do hang the jiost over the fround and back walls how would I
attach them to the walls just lay them on or what part should they be
succed to ?

The tops of the load bearing walls will probably already have a "wall
plate" on them (i.e. timber beam running along the inner course of
brickwork). This will normally be fixed to top of the wall, and each of
the rafters will be fixed to it by cutting a "birdsmouth joint" in the
rafter, and nailing it to the wall plate. To add your floor, you first
nail a packing piece to the wall plate between all the existing joists
(this gives clearance between the underside of the new floor and the
ceiling below). The new joists themselves are then skew nailed to the
packer. There is not much structural purpose to this fixing - the beams
are designed to carry the load simply resting on the wall plate, they
are not held in tension - but it does serve to stop them sliding about!

--
Cheers,

John.

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