"DjB" wrote in message
...
We're in the process of renovating one of our ground floor rooms and when
we
removed the ceiling we discovered one of the joists in the floor above has
been heavily damaged over the years by woodworm (which has been recently
treated). I can wiggle the joist around and it has the consistency of
cork.
Two other joists are also damaged but still seem to have strength. My
first
plan was to remove the damaged joist and install a new one but I've
realised
this is going to be difficult since one end is imbedded into the exterior
wall and the other end imbedded into the sleeper (is that what it's
called?)
running across the fireplace hearth. Would my best bet be to run new
joists
in parallel with the existing ones using joist hangers? I've not used
joist
hangers before, is there a write-up somewhere on the Internet on how to
use
them? Thanks for any help. The link below is to some pictures of the
problem.

http://myweb.tiscali.co.uk/dbecker/joists.htm

As suggested elsewhere, you need to confirm that the only problem is
woodworm, not some form of rot which may have spread into other parts of the
house; use a specialist firm for this.
Also confirm that the other damaged joists are still suitable - 'seem to
have strength' may not be enough of a test as they will be braced by the
floorboards above which are nailed into them.

Joist hangers are pretty easy - obvious when you look at them.
You should be able to replace your joists with new joists in the same
position if you use joist hangers.
You need the kind which fit flat to the wall/beam and are secured by
rawlbolts or similar.
The more common type has a hook at the top to fit over a cross beam or into
a brick/block wall and is (I think) intended more for use when you are
building a new structure..

Couldn't find an Internet site with instructions with Google, but didn't try
very hard.

As a rough guide - and with no warranty attached:

Supporting the floor via props under other joists (for belt and braces) then
remove the dodgy joist.
You will then have to fill in the hole in the wall with brick.
Depending on how the other end is fixed to the fireplace you may have to
fill a hole there as well; on the other hand it may just be skew nailed to
the cross beam.
Prop your new joist into place, then secure with a joist hanger at either
end, bolted to the wood or brick.
AFAIK you secure the joist to the joist hanger with nails - at least there
are loads of nail shaped holes in the sides of the hangers :-) Before you do
this you may need to knock small wedges between the bottom of the hanger and
the end of the joist to ensure the joist is tight up against the floorboards
above.
Oh, and you will have to remove and replace the nails which are through the
floorboards into the joist - this may be all that is holding the old joist
together :-)
This assumes you have confirmed the type of infection and treated
surrounding areas and the replacement joist accordingly.
You main challenge may be to find a joist and hangers to match the size of
your existing joists.

There is no reason why you can't put a joist either side of the damaged one
instead of replacing it directly - putting just one joist in alongside the
old joist might weaken your floor as it would give you:
Joistsmall gapNew JoistLarge gapJoist
Ignoring the shaky breaky part you are replacing.

One problem I see from the pictures is that you have cables running through
your joists somewhere near the middle.
Without re-running your cables you are going to have to find enough slack to
lift the cables up into a notch on your new joist(s).
However there does look to be a reasonable amount of slack (but check before
you start).
If you have to replace more than one joist then this can become a problem.

One other thought - if the joist is damaged in the middle only it is
possible to replace part of the joist by joining in a new piece and
reinforcing the joins.

I would recommend the purchase of a good DIY book (e.g. Collins or Readers
Digest) after first checking that it gives you the information required. The
cost is not much compare with the cost of getting this wrong, or employing
someone to do this for you.

As stated before, there is no warranty with these suggestions - they may be
totally wrong so you take your chances!

HTH
Dave R