Should i wait or start building on slab asap.

[maza]

Hi everybody.

The guy who is doing my concrete/formwork etc for my ground slab for my new home recommends that i wait 28 days till i start building on it so it doesnt crack.

Now in reality, dont think anybody is going to wait 28 days to start building.

He then says to me just wait atleast a week then do the framework.

Is it really necessary to wait for the concrete to fully dry or can i start buidling few days after the slab is laid?

Im doing a brick vaneer home, what kind of damage can be done if i started within a week of being laid?

Is there any real science or research articles that show the longer the slab is left alone the better?

I though cracking was caused by the heat/cool process.

 

[craigb]

should be ok if you load up the frams one at a time , if they place the frames and trusses in the center in packs it might crack, some times they crack any way and theres nothing you can do about it , so i would proceed if it was my place .

 

[laurencei]

Why dont you trust the person who you are paying $$$ for the job their sound advice?

Concrete slabs need time to cure. The longer you leave it, the better the result.

 

[Jase H]

It is true that concrete needs 28 days to cure fully. The first 7 days of this process is quite vital. If it were my place I would wait a minimum of 7.

p.s. whilst i'm not in the building game, my old man has been a licenced builder for 40 odd years and he advised me same when we had concrete poured.

 

[DaveM]

The general rule of thumb is 1 day per mm of slab thickness.

 

[BuildingBlocks]

The general rule of thumb is 1 day per mm of slab thickness.

For every 1mm or every 1cm?

 

[craigb]

should be ok if you load up the frams one at a time , if they place the frames and trusses in the center in packs it might crack, some times they crack any way and theres nothing you can do about it , so i would proceed if it was my place .

each to there own i am a licenced builder though?

 

[DaveM]

Per 1mm for curing. Unless the slab is particularly thick, 1 month is the usual minimum before doing any work on top of the slab. If it is thicker, leave more time again.

 

[jeffb5ltr]

A Lot depends on they type of concrete, if you paid a cheap price then you most likely got a cheap mix, which usually takes longer to come up to strength.

I would wait at least 7 days and don't forget keep it wet if the days get hot and windy otherwise you get faster shrinkage which cause cracks.

 

[Ocean Architect]

one of the guys in my building course was in charge of a block making factory and was expert in all things concrete (and reminded the rest of us frequently)

anyway apparently concrete reaches 90% or so of full strength in 4 weeks, but is suitable for work to be done on it after about a week. the only thing that youd really worry about (if at all) is if you, say, had a suspended slab on a multi story building or carpark and wanted to start driving large machinery on it. In that case, you might have structural failure/collapse.

in the case of a house slab on the ground (the ground supports it, obviously) youre not going to have anything heavy that moves on the slab, just a few workmen shuffling around with toolboxes etc. so long as your crane operator doesnt start dropping paletts full of bricks or all your roofing trusses on it youre okay

it is absolutely standard practice up here to wait a week or so and then keep going. Ive been watching a multi story complex go up and these guys went up 4 levels in 3 or 4 weeks, and thats with 200mm suspended slabs.

i really wouldnt worry at all, but to be on the safe side have a chat to your builder and ask him to keep the concrete as wet as possible during that week. some builders cover the slab in sand and put a sprinkler or something on it to keep the water in, then wash the sand off after a week and get stuck into it - but for the most part (in my experience) most dont even do that

 

[craigb]

one of the guys in my building course was in charge of a block making factory and was expert in all things concrete (and reminded the rest of us frequently)

anyway apparently concrete reaches 90% or so of full strength in 4 weeks, but is suitable for work to be done on it after about a week. the only thing that youd really worry about (if at all) is if you, say, had a suspended slab on a multi story building or carpark and wanted to start driving large machinery on it. In that case, you might have structural failure/collapse.

in the case of a house slab on the ground (the ground supports it, obviously) youre not going to have anything heavy that moves on the slab, just a few workmen shuffling around with toolboxes etc. so long as your crane operator doesnt start dropping paletts full of bricks or all your roofing trusses on it youre okay

it is absolutely standard practice up here to wait a week or so and then keep going. Ive been watching a multi story complex go up and these guys went up 4 levels in 3 or 4 weeks, and thats with 200mm suspended slabs.

i really wouldnt worry at all, but to be on the safe side have a chat to your builder and ask him to keep the concrete as wet as possible during that week. some builders cover the slab in sand and put a sprinkler or something on it to keep the water in, then wash the sand off after a week and get stuck into it - but for the most part (in my experience) most dont even do that

yes that what i said , don't load the frames on the slab , drag them on one at a time and all should be ok, suspended slabs i have done this also but the scaffolding stayed a month untill they started creaking ( drying out)

 

[Ocean Architect]

yes that what i said , don't load the frames on the slab , drag them on one at a time and all should be ok, suspended slabs i have done this also but the scaffolding stayed a month untill they started creaking ( drying out)

complete agreeance. not to be too blase but stressing about a ground slab with the engineering we use these days plus a geotech report is a little silly to me unless youre dropping a few tons of material via crane from half a metre up. If a builder told me that I had to wait a month for 200mm thick rio concrete to cure, copping time delay/interest for that month, because he didnt want to start laying on a 600mm deep footing (plus 200mm slab, total depth 800mm of concrete and steel to hold up a few hundred kilos of brick per metre) i would have no confidence in that builder and slap myself for being so foolish as to contract him

 

[RenoTeam]

complete agreeance. not to be too blase but stressing about a ground slab with the engineering we use these days plus a geotech report is a little silly to me unless youre dropping a few tons of material via crane from half a metre up. If a builder told me that I had to wait a month for 200mm thick rio concrete to cure, copping time delay/interest for that month, because he didnt want to start laying on a 600mm deep footing (plus 200mm slab, total depth 800mm of concrete and steel to hold up a few hundred kilos of brick per metre) i would have no confidence in that builder and slap myself for being so foolish as to contract him

Hit the nail on the head... completely agree here