Can you lay concrete in the rain?

[King Herald]

My mixings arrived after dark tonight, and the plan is/was to start mixing and laying the footing for my new garage at first light tomorrow. But now it is persisting down with rain, and the forecast is much the same for tomorrow. Will this ruin the concrete after I've laid it? Can I just cover it over with plastic or tarps?

This is just the footings, not the actual floor bit.

Bit late at night to start asking I suppose, seeing as I want to start in the am tomorrow. Doh.

[speedy_thrills]

Cover the area you are laying (once down) and make sure that there is no water in the hole when you are pouring.

[bennno]

footings should be about 1.2M deep, biggest risk is them caving in if you try to do it in the wet. plus it will be a bugger to mix and the rain may wash the cement out. better to wait for it to stop raining

most get ready mix delivered as its rapid set and consistent....

bennno

[r39s1]

Concrete will set under water. A lot of people think that concrete drys and sets but in fact it is a chemical reaction that takes place to set the concrete. The problem will be getting a good finish on top. I had the over site done on an extension and it started raining that evening left tht suface a bit bobbly, didn't matter as it was being given a another layer later.

[Ed450]

Shouldn't be a problem - in fact the concrete will set harder in the rain! The only problem might come if the area collects water - ie there is no drainage. I'd say that if it was light to moderate rain and it wasn't pooling anywhere then it wil be fine, but anything too heavy and you may not want to do the job anyway!

BTW i'm not a builder, but I did work in a concrete factory for a while

[King Herald]

bennno said:

footings should be about 1.2M deep, biggest risk is them caving in if you try to do it in the wet. plus it will be a bugger to mix and the rain may wash the cement out. better to wait for it to stop raining

most get ready mix delivered as its rapid set and consistent....

bennno

1.2m??? It's only a simple breeze block double garage I'm building, not the Taj Mahal

Ready mix would come in a huge and very fast lump, dumped in a pile, so I'm doing the footings myself, building a two block high wall, whacking the centre flat and hard with rubble/ballast then getting the ready mix man in to fill it up. Should be about four/five cubes for that. The footings won't be more than a cube and a half at most.

[King Herald]

r39s1 said:

Concrete will set under water. A lot of people think that concrete drys and sets but in fact it is a chemical reaction that takes place to set the concrete. The problem will be getting a good finish on top. I had the over site done on an extension and it started raining that evening left tht suface a bit bobbly, didn't matter as it was being given a another layer later.

The finish isn't a problem as it will all be underground when the wall is built and the main floor poured, and all filled in around it. I was worried I might have a large slit trench full of wet concrete, even after a week or so.

[danielgray]

King Herald said:

bennno said:

footings should be about 1.2M deep, biggest risk is them caving in if you try to do it in the wet. plus it will be a bugger to mix and the rain may wash the cement out. better to wait for it to stop raining

most get ready mix delivered as its rapid set and consistent....

bennno

1.2m??? It's only a simple breeze block double garage I'm building, not the Taj Mahal

I know of a bungalow which has 3m under it, nothing seems to be less than 1.2 by 0.6m now.

[Parrot of Doom]

I remember something on telly about 2 gay blokes, 1 of them shoved some wet concrete up the other's arse, I don't know, some kind of 'lets make it a perfect fit' adventure.

Only the concrete set.

And it wouldn't come back out.

And they had to go to the hospital and explain how it got there.

[bennno]

King Herald said:

bennno said:

footings should be about 1.2M deep, biggest risk is them caving in if you try to do it in the wet. plus it will be a bugger to mix and the rain may wash the cement out. better to wait for it to stop raining

most get ready mix delivered as its rapid set and consistent....

bennno

1.2m??? It's only a simple breeze block double garage I'm building, not the Taj Mahal

Ready mix would come in a huge and very fast lump, dumped in a pile, so I'm doing the footings myself, building a two block high wall, whacking the centre flat and hard with rubble/ballast then getting the ready mix man in to fill it up. Should be about four/five cubes for that. The footings won't be more than a cube and a half at most.

1.2x0.6 wide is the current UK standard. We did a 4.5x3m single story extension and the footings took 7m2

how deep have you dug for the footings?

bennno

bennno

[RobDickinson]

As said concrete is a chemical reaction, its acutaly sprayed with water in hot countries whilst setting otherwise it drys out and cracks.

Romans used it under water to make docks...

[mybrainhurts]

Parrot of Doom said:

I remember something on telly about 2 gay blokes, 1 of them shoved some wet concrete up the other's arse, I don't know, some kind of 'lets make it a perfect fit' adventure.

Only the concrete set.

And it wouldn't come back out.

And they had to go to the hospital and explain how it got there.

Thanks for that little anecdote...

I'll use it next time the vicar drops in.....

[FourWheelDrift]

RobDickinson said:

Romans used it under water to make docks...

The Romans added volcanic ash to make their concrete set underwater. Not all concrete will react and set underwater though. Modern concrete that uses Portland cement will set underwater as Portland is a hydraulic cement, this means that it sets and hardens due to a chemical reaction.

[King Herald]

bennno said:

King Herald said:

bennno said:

footings should be about 1.2M deep, biggest risk is them caving in if you try to do it in the wet. plus it will be a bugger to mix and the rain may wash the cement out. better to wait for it to stop raining

most get ready mix delivered as its rapid set and consistent....

bennno

1.2m??? It's only a simple breeze block double garage I'm building, not the Taj Mahal

Ready mix would come in a huge and very fast lump, dumped in a pile, so I'm doing the footings myself, building a two block high wall, whacking the centre flat and hard with rubble/ballast then getting the ready mix man in to fill it up. Should be about four/five cubes for that. The footings won't be more than a cube and a half at most.

1.2x0.6 wide is the current UK standard. We did a 4.5x3m single story extension and the footings took 7m2

how deep have you dug for the footings?

bennno

bennno

I've gone down 2', by about 16" wide. I think actual dwellings have to have far more strict building regs, in case they fall down and squish folk, hence the mahoosive footings. Most garages this size I've researched have a foot or two at the most, so should be okay. I hope

[Dogwatch]

King Herald said:

I've gone down 2', by about 16" wide. I think actual dwellings have to have far more strict building regs, in case they fall down and squish folk, hence the mahoosive footings. Most garages this size I've researched have a foot or two at the most, so should be okay. I hope

This all sounds a bit iffy. Are you sure some bloke from the council isn't going to roll up and tell you to re-do the footings as they don't meet the regs? A bit of research might save a lot of money in the end.

[smilerbaker]

Dogwatch said:

King Herald said:

I've gone down 2', by about 16" wide. I think actual dwellings have to have far more strict building regs, in case they fall down and squish folk, hence the mahoosive footings. Most garages this size I've researched have a foot or two at the most, so should be okay. I hope

This all sounds a bit iffy. Are you sure some bloke from the council isn't going to roll up and tell you to re-do the footings as they don't meet the regs? A bit of research might save a lot of money in the end.

Yes check the building regs, if you go over your councils m2 floor space for building regs they will make you dig the foundations up to prove the depth. I got caught out by building regs and it took a lot of time and money to sort out

Also be careful with ready mix companies, I used one for my foundations, but we had some left over. No problems we'll take it back no charge.

Mrs smiler goes out an hour or so later and the b****ds had dumped it in the road outside my house!!!! not fun moving a ton or so of hardning concreate with buckets.

[swilly]

RobDickinson said:

As said concrete is a chemical reaction, its acutaly sprayed with water in hot countries whilst setting otherwise it drys out and cracks.

Romans used it under water to make docks...

The Romans used a volcanic pozzolanic ash in concrete for water-related structures, which was not effected by being submerged in water.

[swilly]

Dogwatch said:

King Herald said:

I've gone down 2', by about 16" wide. I think actual dwellings have to have far more strict building regs, in case they fall down and squish folk, hence the mahoosive footings. Most garages this size I've researched have a foot or two at the most, so should be okay. I hope

This all sounds a bit iffy. Are you sure some bloke from the council isn't going to roll up and tell you to re-do the footings as they don't meet the regs? A bit of research might save a lot of money in the end.

I do believe the council inspector has to inspect your footings and give approval BEFORE you put any concrete in.

As far as the concrete itself is concerned, free water in your footing should be avoided, but this can be simply displaced by the concrete itself so long as you ensure there is a route for the water to be displaced to.

Free water wont naturally mix in with the concrete. The specific gravity of the concrete being greater than the water will prevent this.

What you should avoid is just dumping concrete squarely onto water, as it is likely you will trap the water and prevent it being displaced.

The result being you will have water-filled voids in and under your concrete.

These voids will weaken your footings, leading to a degree of failure as you build your structure on top and eventually you could suffer all sorts of damage to your structure if the footing collapses.

Try to avoid allowing any depth of water to sit on the top surface as well, as you will find the top 10mm or so doesnt cure properly. When the concrete has cured, you will find the top 10mm or so of the surface will be without integrity and crumble.

Cover up with plastic in cold weather. If the weather is very hot allow the concrete to cure so that it is hard to touch then cover in damp hessian blankets.

[King Herald]

Dogwatch said:

King Herald said:

I've gone down 2', by about 16" wide. I think actual dwellings have to have far more strict building regs, in case they fall down and squish folk, hence the mahoosive footings. Most garages this size I've researched have a foot or two at the most, so should be okay. I hope

This all sounds a bit iffy. Are you sure some bloke from the council isn't going to roll up and tell you to re-do the footings as they don't meet the regs? A bit of research might save a lot of money in the end.

I did my research, and the max floor space is 30 sq metres, below which I was told I can basically build what I like, how I like. I am currently awaiting a letter of confirmation to this effect, though I have had it verbally that I can go ahead. My garage is 16' x 20' so it falls within the 'do what you like' category. he said hopefully

swilly said:

Dogwatch said:

King Herald said:

I've gone down 2', by about 16" wide. I think actual dwellings have to have far more strict building regs, in case they fall down and squish folk, hence the mahoosive footings. Most garages this size I've researched have a foot or two at the most, so should be okay. I hope

This all sounds a bit iffy. Are you sure some bloke from the council isn't going to roll up and tell you to re-do the footings as they don't meet the regs? A bit of research might save a lot of money in the end.

I do believe the council inspector has to inspect your footings and give approval BEFORE you put any concrete in.

As far as the concrete itself is concerned, free water in your footing should be avoided, but this can be simply displaced by the concrete itself so long as you ensure there is a route for the water to be displaced to.

Free water wont naturally mix in with the concrete. The specific gravity of the concrete being greater than the water will prevent this.

What you should avoid is just dumping concrete squarely onto water, as it is likely you will trap the water and prevent it being displaced.

The result being you will have water-filled voids in and under your concrete.

These voids will weaken your footings, leading to a degree of failure as you build your structure on top and eventually you could suffer all sorts of damage to your structure if the footing collapses.

Try to avoid allowing any depth of water to sit on the top surface as well, as you will find the top 10mm or so doesnt cure properly. When the concrete has cured, you will find the top 10mm or so of the surface will be without integrity and crumble.

Cover up with plastic in cold weather. If the weather is very hot allow the concrete to cure so that it is hard to touch then cover in damp hessian blankets.

Thanks for the info. I started laying this morning, and there was but a couple of tiny puddles in the footings, saucer sized. The sun is out too, so I'm working like a navvy to get it done before the weather gets cacky. Concrete is mixing as we speak, so I'm off right now to tip another load and spread it about

[King Herald]

And now I'm just about to pour the last mixer load out.

I thought it would take a lot longer, but once I got 'into the groove' I only had the mixer stopped when I was pouring it out. Next load was ready to go in and away it went churning away again.

I used 2 1/4 tons of mixed ballast, and about 12 or 14 bags of cement, so about a cube and a bit of concrete went in, less than I thought I'd need. I bought enough stuff to make two cubes, just in case.

Hardest part was carrying all the stuff 25 metres from the front drive to the back garden.