Strengthening a tie beam

In my house is a 6 metre inserted tie beam which needs strengthening
so I'm planning to fix two 3 metre timbers to it by bolting with
threaded rod
The tie beam is slightly arched in the centre. I'm inclined to think
that I dont need to cut the ends of the timbers so they butt, nor do I
need to bolt the two timbers together
but I could be wrong?
Anna
Reply to
Anna Kettle
What is the purpose of the strengthening?
If it's to hold the eaves together, then your proposal wont help.
If it's to stop sag, then some ply or OSB board can be nailed and glued to the sides of the beam.
dg
Reply to
pwooding
Anna I am confused Can you send a picture or explain what you mean? If you want to strengthen a 6 m beam that can be done several ways a) put 6 m of steel alongside and connect it to the timber eg an RSC or RSA This is normally connected to the timber with single side tooth plate connectors at appropriate centres or more to the point connected to the rafters associated with the tie beam by appropriate connecting steels b) supplement the timber with timber as you suggest but to do that the timber must also be 6 m long OR two 3 m bits connected longitudinally which would need overlaps with a third bit probably of 1.5 m length - not very elegant! c) put an inverted T beam down a slot in the beam or a T beam down in a slot in the top and connect with bolts and resin (not needed in this case from what I can see) Chris
Reply to
mail
Why does the tie need strengthening?
If it is to restrain the eaves/truss, then your proposal will not work
If it is to prevent sag, then this can be done by nailing and gluing ply or OSB to the sides of the beam.
dg
Reply to
dg
Yes to stop sag. I cant imagine that the timber sags much but at some stage a prop was put in the middle which I want to remove. Glueing wont work, the timber is too uneven. Nailing would probably work but I thought I'd bolt it to get a better fixing
I was planning to put the new timber above the old one, nostly because it is easier to get at than the side. Is that a mistake?
Anna
Reply to
Anna Kettle
I'll try. Its a beam which runs front to back (north to south) of the house and was inserted to provide support for a bedroom ceiling to the east side. Dunno when but I will guess it was done in 1720. About 1m below this inserted timber is the original tie beam which holds the house together. Between these two beams (and looking ugly in the bedroom) is a vertical post. The post could have been inserted at the same time as the ceiling support beam or soon afterwards and I want shot of it
Another possibility is to replace the one post with two posts at the 'one third' positions. Fixing them would be non trivial but they could be hidden and so not offend my eye
I cant get 6m in to the space without taking the roof off. Probably couldnt a get 3m timber into the space now but I am a girl guide
Elegance is not important as its in the attic. The beam is not very under strength (6" by 4") but it is propped in the centre so someone must have thought it looked saggy
Would it help for me to just strengthen the middle 3m of the beam?
Anna
Reply to
Anna Kettle
The message from snipped-for-privacy@freeukisp.co.uk (Anna Kettle) contains these words:
I could be barking up the wrong tree (woof, woof) but are you sure that the purpose of this strut is just to support the centre of the ceiling beam? Could it perhaps be the stub end of a kingpost that was cut when the ceiling went in? In which case there may be a continuation above that is still an important part of the roof structure.
FWIW I have a gut feeling that a 6" x 4" beam with a span of 20' should require a prop if it carries a significant load. No doubt someone with superbeam can put some figures to it's potential strength.
Reply to
Roger
A wood beam is effectively a very stiff spring. So if you infinitely strengthened 3m out of 6m of its length, you might see half the sag, which sounds insufficient here. If you used 2x 3m lenths, most of it would be stiffened, but not the patch around the centre where they joined. You can make a 6m beam from 2x 3m beams by using a finger joint and glue, which could be done once the timbers had been brought to final use location. Alternatively if you butt the ends up you'd get quite a lot of the stiffening but not the full amount.
To be effective the new wood needs to be glued and screwed every 6", using a glue suitable for the job, so not pva or similar.
Timber above will have much more stiffening effect than to the side.
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Reply to
meow2222
Dear Anna I am a bear with very little brain and am still confused but here goes I cannot understand the purpose of the beam if it is to support the ceiling of a room to the east. In my mind it can only support a ceiling immediately underneath it.
Lets go back to first prinicples
What do you want to do? A Get rid of a post in a room below supporting an ORIGIAL alleged tie beam but is it a tie beam as you do not mention any associate rafters for the truss ( a tie beam is usually the bottom chord of a truss) so it may just be a normal beam "spanning" between two walls and tieing them together If so there is another beam (resting on what?) 1 m above it in a roof void Where is the ceiling plaster relative to the two ? Hopefully along in under by the lower of the two beams The top beam at 6 x$ spanning 20! is a liablity and not of much help Why not just stenthen the beam below and get rid of the post You can use steels in small sections eg RSCs and RSAs as previously described BUT and here is an idea IF I have the situation correctly understood you can make a proper truss beam using the two togther and linking htem with ply bits It will need a bit of design input but small sections of ply an appropriate centres and angles will make a whole truss 1 m high and very very strong Use 10mm ply and UF or Phenolic F gluelam beam glue and screws nails at 100 mm ccs etc come back to me if this is feasible Chris
Reply to
mail
Hi Chris
Sorry, I probably could do a picture, but just one more try to see if words are enough ...
The ceiling joists span between this (upper) beam and the gable end
All beams are staying where they are
Its just a single beam. I dont think the truss had been invented when my house was built. I think I had better do a drawing after all ...
I hope that
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a useful drawing. Let me know if not
Yes, pinned to the rafters
From the underside of the upper beam, over to the gable end, which is about 10 feet away
Yes but its only supporting a ceiling
Because it is visible and old and beautiful and strong and doesnt need strengthening. This is the one that ties the house together and its fine. Its the upper beam I'm concerned about
Yes thats what I want to do
That should be a good idea but in this house doing it is tricky in part and impossible in part because there is an old vertical plaster wall and an old pargeted panel filling in the gap already. It would be possible (though not easy) to fix a 6 inch piece of ply or a couple of stout timbers vertically at the 1/3 and the 2/3 positions to replace the vertical timber at the 1/2 position
Thanks for your time and effort. Hopefully you will help me find a good solution :-)
Anna
Reply to
Anna Kettle
On Tue, 4 Dec 2007 08:17:24 GMT, Roger wrote:
Yes I'm pretty confident that I'm right, but I think I have managed to confuse you :-) The ceiling joists span between this beam and the gable end. Originally there was no ceiling other than the underside of the roof ie it was a vaulted ceiling. This ceiling may have been inserted 350 years ago at the same time as the room was given a fireplace
Hopefully! The load is a lath and plaster ceiling
Anna
Reply to
Anna Kettle
Hi NT
I see. So anything I do to stiffen it will help and I (just?) have to work out what is the most effective and simplest thing to do
I dont think gluing will be possible. Its just a tree with bark removed, not planed and square. I could screw it every 6" and presumably that is better than nothing ... and do you think better than my original idea of six rod fixings?
========= It is not essential to use full length timber. Using cut timber finger jointed gives almost the same rigidity. Square cut wood butted firmly end to end also gives a lot of additional rigidity, if not as much as continuous or finger jointed timber. Use a mallet to prevent gaps between ends. =========
Thats interesting, it looks like there must be good contact between the two new 3m timbers if I put them end to end
Anna
Reply to
Anna Kettle
Yes: They will be in compression, and need to be butted up HARD. This WILL put a stress conentrartion on the beam below: consider a steel jointing plate let into the upper beam to hold the two bits together. This should go underneath the new beam, but on top of the old.
I did manage to buy a 6 meter length of 12x12 oak from Whippletree Hardwoods, in Duxford area - if you feel like making a real feature of it.
Probably have a few 3meter lengths of scrap in teh back garden of very old hard oak..need a sandblast though.
The advantage of coach screws is they wont show below. The advantage of bolts is they never pull out...even if existing timber is a bit rotten.
Reply to
The Natural Philosopher
The message from snipped-for-privacy@freeukisp.co.uk (Anna Kettle) contains these words:
If the only purpose of the centre strut is to provide support to the otherwise inadequate ceiling support beam then the alternative proposal you put forward earlier of replacing it with two supports at one and two thirds would seem to be the simplest solution. They together will give the ceiling support beam more support than the single centre strut but being in different places there might be some slight initial settlement.
As I see it there is considerable scope for the length of the newly supported centre span at least right up to half the original 6m but the closer together they are the less chance of settlement. I am not sure how it is that the centre support is visible but the ones at one and two thirds wouldn't be but the obvious position to fix the new props would be the point at which they become hidden.
Just re-read your previous post and it seems the additional supports could be hidden, not would be hidden so you might want to space these as far apart as possible. I don't suppose the ceiling support beam would be loaded as heavily as a floor joist and a 6" x 2" floor joist can have an allowable clear span marginally in excess of 10 feet. Assuming there isn't any defects in the timber (at 6 x 4 twice as strong) you might be able to place the new props at least as far apart as 12 feet (guestimate). The closer the supports get to the beams junction with the rafters the greater will be the change in loading at the ends. I can't see why reducing the load should make a significant difference but there would come a point where the ends would actually get lift when the original support is removed which might be problematical.
Reply to
Roger
The message from snipped-for-privacy@freeukisp.co.uk (Anna Kettle) contains these words:
Ah the vagaries of Usenet. I initially got your reply to Chris but not the others.
Your original post did confuse but by the time I replied your follow-up had opened my eyes to all but the possibility of a king post.
And presumably the ceiling joists as well.
Seeing no one has so far I downloaded the demo version of Superbeam but what with the cryptic designations and the alien metric system I didn't get an answer. And alas my theory is far too old and rusty to be trusted to get the right answer the old fashioned way I was taught 45 or more years ago.
If your beam is a largely undressed tree trunk then it might not be quite as strong as the nominal dimensions suggest and it might also be significantly tapered which means that the spans I suggested in my previous reply might be suspect. OTOH old oak is tough (or at least the bit left after woodworm has removed the sapwood :-)) so a 6m span might have been acceptable and the prop was put in because the wood was bent and might have a tendency to reverse without it.
FWIW the purlins visible in my bedroom are tree trunk shaped and tapered with some bark still remaining on the ends buried in the walls. They span over 13 feet and the visible section (lath and plaster ceiling between the purlins hides a bit) is about 5" x 6" in the centre of the span and I have several inches of stone on my roof above.
Reply to
Roger
On 6 Dec,
Why not tie the upper beam to the apex of the roof, as in modern trusses? You could hang the centre off it, or two at an angle to the thirds.
Is the lower beam supported at all? It seems long not to be.
Reply to
<me9
Well done that man! Why not indeed. It would be much simpler to do it that way than either of my other ideas and the best ideas are always simple
No its not supportedexcept for the post which I want to remove . I've revised my estimate of the dimensions when I realised that a tree shaped bit of wood was unlikely to be 6" by 4" so I went and had a look. Its now 6" by 6"
Anna
Reply to
Anna Kettle
Dear Anna Your sketch was useful in that I now understand that you have a tie beam running at waist or shoulder height on your first floor rooms. That the ceiling joist beam needs mid span "support" allegedly from the 6" square tie beam and presumably your first floor is an inserted floor that is relatively modern (ie post-dates the timber frame)
Laudible tho the idea of tieing into the roof is (and it is good in theory) you need to check that the connections of the rafters are ok first as they are notoriously unreliable in old TF houses due to decay and settlement
One idea that you could consider is as follows;
the function of the ceiling beam is dual (1) a supplementary tie for rafters mid rafter 2) support the ceiling plaster (?)
This beam can simply be beefed up with ply - or the need for it eliminated with a new ply beam use say 1/2" in 8' lengths by cutting up a sheet of ply in four longitudinal bits each nearly 300 deep and lapping them together At the ends you could put in a gusset that is much larger to the rafter next to the beam Connections would be with whatever suits the timber - bolts - and double sided tooth plates and BIG washers - glue and nail ( high withdrawl resistance ) coach screws - studding - whatever "fits" the odd shapes of old timbers
Once beefed up the beam can have the post removed The new beam canbe part of or above the old
How do you get from place to place in the room? duck?
Lastly connections connections connections - ,make sure all rafters are connected to plates and to ridge beam (if present - usually rafters butt at top
Chris
Reply to
mail
The ceiling beam is 6" square, the original tie beam is more like 12" or 14" square
The first floor is original, its the floor of the parlour /solar
I will do that in the morning and report back. It might be useful that there are actually two sets of rafters at this point, both the old ones and over them new (1960) rafters which support the new concrete roof tiles
Yes thats possible, I will look
It would be decidedly difficult and expensive to introduce a new beam so the 'beefed up' idea sounds better to me
I dont understand this. I think a picture would help but I will get up into the attic and inspect the timbers and the connections and report back first
??
Yes. The tie beam is about 5ft off the floor
Will do. Thanks again for your help
Anna
Reply to
Anna Kettle
On Mon, 10 Dec 2007 20:49:01 GMT, snipped-for-privacy@freeukisp.co.uk (Anna
More precisely, it is the original floor on one side of the tie beam - on the side below the ceiling I have been discussing. It is an inserted floor on the other side of the tie beam
Anna
Reply to
Anna Kettle

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