How long to leave acros under new lintel?

[goosebump]

Just a quickie - Ive tried a search and cant find the answer:

New lintel gone in between two stone walls, and is supporting part of the first floor external wall. The builders have poured concrete shuttering (with padstones on top) to support both ends of the lintel, and tie it in to the stone walls. How long do the acros need to stay before we can safely remove them? There is talk of leaving them for 48hrs but Im not sure thats long enough?

 

[PrenticeBoyofDerry]

If the location is warm and dry, 48hrs is plenty long enough.
Out of interest, what are the dimensions of lintel and padstones?

 

[goosebump]

Thanks for the reply. Its not warm and dry, our house has no central heating (yet) its effing freezin

The lintel is actually 3 x 3.2m steels side by side with spacers, resting on padstones that are 25cm deep x wall width (45cm) x 35cm. If you can imagine a house that a kid would draw, 4 windows with a door in the middle, well we have knocked out the bit between one window and door downstairs. There is a crappy single storey flat roof extension hitched on to the back of the house whcih we have opened into giving us a good sized kitchen dining room. We hope!

 

[PrenticeBoyofDerry]

I'd be concerned they had been built in, in this weather. Was or is there any frost protection.
I assume the pour was not structural, but just a tidy up job.

Normally 48 hrs would be plenty, but the weather has not been kind and frost and concrete are not great friends.

 

[goosebump]

It is structural work, being done in two stages so poured to half height at present.

We are close enough to the sea that so far the innards of the house havent frozen, but I imagine we are only a degree or three above 0. Met office say its 3 degrees anyway.

No frost protection on the concrete. I have a tiddly plug in radiator (750W) I could stick in the room overnight, but I cant imagine itll make much odds to the temperature. Is it worth a go anyway?

 

[r896neo]

If its done now then definately put your heater on. Mortar is relatively useless at these temperatures and does not set but stays crumbly forever and would need re-done. Its hard to know as we can't feel what its like there but indoors you should be ok with the concrete especially if it has decent depth/thinckness. I'd certainly do anything you can to be on the safeside though.

I wouldn't put it right at the face or anything but generally heating the room a little would be good.

 

[PrenticeBoyofDerry]

I agree, but you should not be pouring concrete in condition that cold,
3 degrees c and below you stop.
4 c and rising is the guildeline.
If not it's quite possible as r896neo mentioned it will be a waste of time, no matter how long you leave the concrete will never cure correctly.

edited missed not out

 

[hotrod]

The builders have poured concrete shuttering (with padstones on top)

It is structural work, being done in two stages so poured to half height at present.

I'm slightly confused as to what the builders are doing. I assume the acros are supporting the shuttering, into which the concrete is being poured? Is that correct? If so what are they pouring that's structural? Are they pouring padstones / casting a lintel etc? And why is it being done in 2 separate pours?

 

[goosebump]

Hello,
My posts are confusing - sorry! The first one was written as if the builders had dont eh job, when in fact they were half way through.
Acros are supporting the steel lintels.
The builders are pouring an "end" to one of the stone walls, effectively a column that butts up and ties into the stone structure. It was half poured yesterday, the rest is going in today. Then the padstone will go on top, and any shims needed between the padstone and the steel lintels above.
Hope thats clearer?

 

[PrenticeBoyofDerry]

very much so
The concrete still needs to cure and these condition are not at all friendly.
Ideal conditions are dry and 4c or above or you may have problems.
If concrete pour is frost effected it will never be right and not fit for this purpose.
If you do decide to pour get some anti-frost admixtures in pour wrap pour in frost blanket or at least hessian cloth and best of all get some warmth in to the location.
That will also apply to sitting the lintel on it's bearers.

 

[goosebump]

Thanks, and sorry for rubbish confusing posts. The pour is done - it went in in two lots, half yesterday along with some rebar, half today. Ive got a 2kW plug in rad in the room which is definitely keeping the chill off, but not baking the concrete. The builders come back on Monday to remove the forms from the top half, and fit the padstone.
I still reckon the lintels should be supported for a day or so after the padstone has gone in, and to let the concrete cure. But Im no authority on this - is it an good idea and if so how long should they stay in place?

 

[PrenticeBoyofDerry]

Indeed it is a good idea to support the lintel, for a period of time whilst the compo sets.
If condition are in your favour 3 or 4c 48hrs is plenty enough.
If it was summer, I'd be happy removing them the next day.
Your brickie will most likely us packers on the joints, which will keep the joint and stop the compo from spreading out of joint, when taking the weight of lintel when wet.
But I'd still use props (acros)

 

[goosebump]

Thanks - your views and advice much appreciated

 

[alittlerespect]

7 days - remove the acrow props on the eighth day!

Would be my advice!

Regards