I have a lintol to fit in an interior wall that is marginally too long for the hole I have made for it. Next stock size down is much too short.
Is it wise to just trim a lump off one end with an angle grinder?
I currently have a diamond blade in the angle grinder. Will this go through the reinforcing rods as well as the concrete or do I need something different?
There are specialist discs for this like the Multi-Slysa Premium universal, here:
I've used a cheap Aldi masonary disc on a reinforced Lintel and cut through the steel rods as well as the concrete.
The message
from clangers snipped-for-privacy@yahoo.co.uk contains these words:
Thanks but I couldn't get the link to work (end missing) and couldn't work out which disc you were recommending.
Try unwrapping the link:
Blow that,I'd rather ruin two cheap disc for the sake of cutting a one off concrete lintel.
It will cut through like butter
Alex
The message from John Rumm contains these words:
that didn't work for some reason.
Ouch. I think I will switch to an abrasive stone cutting disc and see how that gets on with the steel bars. I think I have a couple of part used discs somewhere, one for metal, one for stone, but unfortunately I can't tell which is which. If the worst comes to the worst there is always the hacksaw. :-)
Believe me when I say this...these multi purpose disc will cut through it,I have used them on the same Lintels youre doing. Takes a bit longer but if you cut all four sides equally towards the middle with one then use another new one or metal disc they will suffice.
Aren't these prestressed? I've got visions of something nasty happening when you cut away all the concrete in compression and are left with the bar in tension...
If you're greatly in doubt? suggest you buy a steel lintel. What you holding up a church spire?
In message , Roger writes
As another poster has indicated, you absolutely should not cut or alter the lintel. The reinforcing inside is arranged in such a manner to transfer the stresses to compression of the concrete (ie, the steel is shaped). Someone
The message from snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) contains these words:
Not sure but I don't think so. Big stuff certainly is but is there enough meat to give a good grip?
Anyway trimming 3" off one end isn't going to give much much movement if the stress in the end is relieved.
I don't know how close to the ends of the lintel the reinforcing comes but perhaps it might be better to trim 1.5" off both ends.
Actually I need to cut a 1.5" to 3" taper across the lintel so how much should I cut off the square end to minimise cutting the reinforcing rods?
Even if they are pre-stressed, cutting a small piece off the end won't cause a problem.
A pre-stressed lintel is kept in compression by stressed wires which are passing through the concrete. The stressed wires are carrying zero load at the cut ends. The stress gradually increases to its full designed value over a length of just a few centimetres from each end. If you cut off a centimetre, you merely move the point at which the wire reaches its full stress inwards by another centimetre.
The lintels are made in multiple, in a single pour, end-to-end in long moulds with the already-stressed wires passing through. The concrete for all the lintels is cast in one single unit and steadily gains strength. After the concrete has sufficiently cured, the lintels are sliced into the required lengths with a diamond saw.
A DIY-er cutting one of these lintels *in the middle* is not a good idea, though! In controlled conditions in the factory, it is a different matter.
Nonsense. They are routinely cut in the factory. See my other post which describes how they are made. There is no harm cutting a little off one end, but they should not have a significant amount cut off or be cut in half, because that could be dangerous.
If it is a pre-stressed lintel, cutting a 1.5" to 3" taper off one end will be fine. See my other message explaining how pre-stressed lintels are manufactured.
Unless your x-ray vision can see into the lintel to confirm the placement of any reinforcing you have no idea what the nature of the reinforcing is - ergo where it is likely to be and in what form. The OP refers to a 'reinforced' concrete lintel, not pre-stressed as you describe. See a typical reinforced lintel below....
- Removing or weakening one of the hooked ends {____) of the bar which transfers the stresses to the concrete under compression.
- Having less concrete between any steel and the atmosphere. Concrete reinforcing recommendations for external use is something like 50mm cover, I don't know internal use but wouldn't fancy risking it myself.
Someone
The OP is just a DIYer who bought a concrete lintel. The lintel is almost certainly pre-stressed.
Funny how you had to go to a German web site to find an ordinary reinforced (rather than pre-stressed) concrete lintel ... That's probably because ordinary reinforced lintels have become rare in the UK since the development of more modern casting methods for pre-stressed lintels and, in particular, the publication of BS5977: part 2:1983.
The vast majority of pre-cast companies no longer offer reinforced lintels because the pre-stressed variety are more structurally efficient (they are smaller for the same load capacity) and highly cost-effective due to the streamlined manufacturing process. The standard lintels offered by builders merchants are almost certainly all pre-stressed by now, although the might still be imprecisely described as "reinforced". It is quite a few years since I have seen an ordinary reinforced lintel, and that was custom-made to order for a specific project.
Those considerations simply do not apply to the mass-produced pre-stressed lintels that we are discussing. Ill-informed scaremongering helps no-one on here.
As for 50mm cover, some pre-stressed lintels have overall dimensions as small as 65mm to 70mm. It is physically impossible to provide 50mm cover for a lintel of that size. That should tell you that 50mm cover is actually not required. The very high quality concrete mix used, which has extremely low permeability, and the highly controlled curing of the finished lintels means that much less cover is needed.
For the original poster, it is easy to identify whether it is a pre-stressed lintel. The pre-stressing wires will be easy to spot:
Most prestressed lintels are made on the long line system: they cast one very long lintel and then cut it into lengths. If you can see the prestressing cable when looking at the end of the lintel it's almost certainly made this way, and cutting it will not be problematic.
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