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.

[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.

[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

[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.

[King Herald]

bennno said:

King Herald said:

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

This is a garage you are building? is there not vehicular access ?

bennno

Yes, but funnily enough, access is through the existing garage, of which I knocked the back wall out a couple of months ago.

Them brown doors in the distance go to the garage.

[King Herald]

sparkythecat said:

About 10yrs ago, I built a single storey extension on my last house a 1960's semi. IIRC the extension footings were about 30ins deep. I thought that seemed excessive at the time as the existing house footings were only about 15 ins deep.

I guess it all depends on the local soil. If you live in a swamp you're going to need the 3 metre footings mentioned earlier, but if you have clay just below the surface I'd think you have to dig a lot less. Mine was into clay type stuff some 18" down, and it got reeaal hard work digging then.

sparkythecat said:

..............I reckon they'll both still be there when I'm eventually dropped into a 6ft hole

Actually, 3ft deep would be ample, depending on the soil....

ferrisbueller said:

You're going to kill that bush aren't you??

Murderer.

May transplant it, if possible, but that area will be block paved to lead gently down the slop into the garage, as there is about a 12/18 inch gradient. With a drain/soakaway to lose the rain water before it floods the garage.

[King Herald]

johnniem said:

Don't want to worry you but this "I can do what I want" stuff relates only to planning consent, not to building regulations. If you build without getting the building control officer to sign the works off (at their various stages - foundations being a very critical one!), when you come to sell the house and you can't produce a completion certificate from the local authority you will then have to try to get retrospective approval which may mean digging out to expose the depth of foundations. Don't take my word for it thought, why not just give the local building control department a call; it will clarify your responsibilities. Just because you don't need planning consent this has nothing to do with building control approval. Under new regulations you will also need to have any new electrics installed and certified by a qualified NIC IEE sparks.

Hope it all works out geez!

I've done all the checking business, spoke to planning permission people and they said okay, and they told me that it doesn't come under building regulations as it is less than 30sq metres. I have the printed council paperwork here verifying the local regulations, and it states no regs required.

I've requested a letter stating that in writing too, as ten years down the track people will say "who the hell told you you could build that in your garden???"

My bro in law is a licensed electrician, who is able to sign off and certify the electric work, and he lives just two doors away

[King Herald]

danielgray said:

King Herald said:

sparkythecat said:

About 10yrs ago, I built a single storey extension on my last house a 1960's semi. IIRC the extension footings were about 30ins deep. I thought that seemed excessive at the time as the existing house footings were only about 15 ins deep.

I guess it all depends on the local soil. If you live in a swamp you're going to need the 3 metre footings mentioned earlier, but if you have clay just below the surface I'd think you have to dig a lot less. Mine was into clay type stuff some 18" down, and it got reeaal hard work digging then.

The 3 metre footings were in clay, dad had 14 redimix lorry's that day to fill it all and it cost a fortune.

But why would you go 3 metres deep??

Humour me here, but I'm pretty sure it was not because you're dad liked digging. There has to be a reason for such monumental footings.

I recently watched them build some two storey flats near my house, and they dug down maybe 5 or 6 feet.

autonotiv said:

hard clay or soft?
I can picture this, King herald will be posting a pic of his new garage, then a week later he will be posting a pic of his flat garage! lol

good luck

And if my garage sinks like that, I'll just build another on top and say, yes, I have footings 12' deep y'know.

And a basement