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PostPosted: Thu Oct 12, 2017 7:49 am 
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Hello

I have been involved with several installs of steels, and there always seems to be some confusion over what is best practice, what building control want and what is the reasoning behind certain things. I'm talking specifically packing above the steel.
So I gather that most building control officers don't approve of slate because it can crack, especially assuming builders are using bits of old slate. So I'm assuming steel shims are the direct replacement. But then the question arises, why bother to use them at all. If dry pack is properly installed i.e. packed, and made to a good consistency and mix of 3:1 sharp sand : cement, what is the point of packers? The dry pack will surely spread the load of the RSJ. Does it depend on the height of the gap?

Appreciate any clarification.

Many thanks guys


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PostPosted: Thu Oct 12, 2017 8:17 am 
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This is not something that I've done much of and is only really my personal opinion, (but initially I must have been following directions from someone more knowledgeable than me): I'd use slate or steel shims underneath and dry pack on top. The dry pack has to be done right, a bit of shuttering needs installing so the dry pack can be rammed home, it's not the same as pointing a brick joint.

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PostPosted: Thu Oct 12, 2017 9:31 am 
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even new slate is very old so unless the slate has turned to mush i dont see how it would be a problem tbh.

never had an issue in the past


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PostPosted: Thu Oct 12, 2017 3:06 pm 
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Dry packing?ramming (Engineers known to refer to it as Dry compacted fill.) is fine for gaps above installed RSJ's up to 50mm or so.
Anything over this and you would be best advised to insert a course of brick splits with the top joint tightly pointed with a 3:1 mortar mix.

We often used 'Dry Packing in underpin situations where the gap may be up to 100mm deep. If access was available from both sides, one side would be shuttered as mentioned above.

Davyp1


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PostPosted: Thu Oct 12, 2017 5:50 pm 
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davyp1 wrote:
Dry packing?ramming (Engineers known to refer to it as Dry compacted fill.) is fine for gaps above installed RSJ's up to 50mm or so.
Anything over this and you would be best advised to insert a course of brick splits with the top joint tightly pointed with a 3:1 mortar mix.

We often used 'Dry Packing in underpin situations where the gap may be up to 100mm deep. If access was available from both sides, one side would be shuttered as mentioned above.

Davyp1


After posting I realised that there are a couple of points I should make.
The first is that I would not advocate the use of steel shims to pack the masonry above a steel RSJ. Even if they were used, mortar would aso need to be used in conjunction with them to ensure they remained in place!
Use of Dry Packing would be far superior.
But I would also like to add a point regarding the mixing of the dry-packing. As mentioned previously, the Sharp Sand / Cement mix is 3:1. The important aspect is the amount of water used in the mix. You need to add the water in small amounts, it is ready and correct when a handful of the mix when squeezed in the hand retains its shape. As you will gather, this is in reality a "semi-dry mix".
The mix is literally pushed into the hole or void being filled and rammed in using a suitable piece of 2x2 or similar. The final visible surface may then be rubbed up with a plastic float.


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PostPosted: Thu Oct 12, 2017 6:32 pm 
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we use semi-dry first an then drive in slips of slate an then touch upbut its dead rare to have a large gap for shimming in residential work, brick or block.
we fix joist tails in wall pockets roughly the same way.


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PostPosted: Sat Oct 14, 2017 8:00 am 
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Hi

Thanks everyone for your valid points. But no-one has answered my main question directly, which does make me wonder if anyone truly knows because I've searched the web and can't find an answer. So my main question again is, why use steel shims or slate spaced out at intervals when dry pack alone is obviously strong enough? What does the slate/metal shim actually do?

Thanks


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PostPosted: Sat Oct 14, 2017 9:40 am 
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Dry pack alone is strong enough, shims/slate does wedge up and tighten any loose/dropped masonry.

It all boils down to what the young over eager building inspector asks for.


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PostPosted: Sat Oct 14, 2017 11:04 am 
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JT101 wrote:
Hi

Thanks everyone for your valid points. But no-one has answered my main question directly, which does make me wonder if anyone truly knows because I've searched the web and can't find an answer. So my main question again is, why use steel shims or slate spaced out at intervals when dry pack alone is obviously strong enough? What does the slate/metal shim actually do?

Thanks


If you're talking about underneath the RSJ, a steel shim or slate packer allows for any temporary support for the RSJ (i.e. Genie lift or Acrow props) to be removed immediately. If you dry pack underneath you'd have to allow time for the dry pack to harden.

This may or may not be relevant, each job will differ, but in some circumstances it will allow progress to be made that would otherwise be held up.

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PostPosted: Wed Oct 18, 2017 11:12 pm 
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Actually meant above the beam. Still don't understand the purpose of them when you can use dry pack. But useful to know why they're used underneath thanks


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PostPosted: Thu Oct 19, 2017 6:28 pm 
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Dry pack is never going to lift/ tighten up any loose/dropped masonry above.

Theres a post on here from Chez ( Ultimate Handyman ) regarding fox wedges, just imagine firing some of those in, which would lift a house, similar principle.

If done right, ie mortared and well packed/wedged up you wont see any dropped, settlement cracks.

So what is it that you don't understand.


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