There have been at least 3 possibly 4 different re-wires of my house, none
of the old wiring has ever been removed and the joists are full of holes.
Can I use a wood filler from something like a mastic gun to fill the holes
and restore some strength? The closest I have found so far is
which looks a bit pricey given the quantity of holes I need to fill. There
is also this stuff
much cheaper would it be OK??
Agreed. Epoxy resin used in conjunction with stainless steel tie rods can
restore a good amount of strength to a beam, but it's a specialist job
suited to the restoration of old oak beams, and not the material advertised
on these links.
If the holes are at mid-height of the joists then they're not significantly
weakening them, especially if they're not at centre span or right against
the end bearings. The top edge of a beam is in compression, the bottom edge
in tension, so along the centre (called the "neutral axis") there is a line
where there is virtually no stress. Deep notches in the top or bottom edges
weaken joists much more than holes.
Posted via a free Usenet account from http://www.teranews.com
Sorry, squirting stuff in the holes will fill them up but will never restore
any strength. Wood is good as a structural material becasue of the
continuous grain running through it. Forming joints properly, using wood
glue and clamping can create very strong joints as the (designed for
purpose) glue penetrates the fibres over a large mating area (large in
relation to the beam cross section). A filled hole is just a filled hole -
all the stress goes round it (increasing the stress in those areas)and will
continue to do so. Don't waste your money!
Yes, try knocking a piece up your left nostril and see what happens - either
your face will become solid or your nose will explode into a ball of snot
and blood, my money is on the latter.
Seriously George, *you* must know what happens if you force an object into
wood? - especially if you force two in, one from each side as you have
As long as their diameters are less than 20% of the joists depth and they
aren't on top of each other they should not be a problem.
If the floor is sagging or there are any other structural failure symptoms
then you need some help to fix it as you don't understand the properties of
This may involve fitting reinforcing (steel, plywood, etc.) to the sides of
the joists or even replacing them.
You (and other respondees) are right about not understanding timber, hence
I merely wanted to try to rectify a bodge while it was easy to do it.
I get the message though, nothing is sagging so leave alone.
Disagree, having had this problem.
Leaving alone might be OK if the holes are within the zones given in
the B Regs, but my joists had nasty large holes for CH pipes knocked
through close up to the support wall. My prediction was a collapse
waiting to happen.
I filled the holes with timber rounds turned to size on a lathe and
glued them in place with a PVA glue (Evostik W waterproof version).
(Tight fit but not forced) Then I faced both sides of each joist with
12mm WPB plywood glued with PVA and screwed on with 25mm gauge 6 screws
and clamped whilst the glue set. Note: ordinary PVA glue *may* be
susceptible over the years to weakening due to absorbation of
Joist span was longer than the plywood so the plywood butt joiints are
staggered on each side & run diagonally down at around 30deg to the
vertical. In a few cases where the joist wall sockets looked dobtful,
I hacked out the wall and ran the plywood into the wall, but mostly I
stopped at the wall edge.
If it is just a short length of joist peppered with holes it is
proabably Ok to face over the holed zone plus say 300mm at each end.
Method produces extremely strong joists which should give no future
problem. Slight snag is increased thickness & decreased inter joist
gap which can make for more difficult drilling.
I treated the joists with Cuprinol (Green) before fixing the plywood to
guard against future rot or worm problems. Incidentally it rather
appeared from setting times that Green Cuprinol is a catalyst (or
similar) for PVA glue, ie it speeds up setting.
Result is a good solid floor with far less bounce than ordinary joists
sized to the B Regs give.
In some parts of the world, eg N America where wood is plentiful,
composite beams formed in a similar way are widely used, for instance
to provide long ceiling spans.
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