Basement Concrete Pour - Thoughts on this...

[Internet Know How]

To pour the walls in one, or to not pour in one.....thats the question.

 

We have a basement in the process of construction, and wondering if we should pour the walls in one or split it up into two pours. My installer has reservations about the potential of introducing cold joints if the concrete goes off too quickly before they get around to the next part of the pour to reduce the risk of any cold joints appearing in the walls due to concrete going off too quick. Although we have a construction joint where the wall meets the kicker,

 

- outline plan of walls attached

- basement wall height is 3410mm plus a 300mm reveal to the top

- Sika waterproofing in the slab and wall concrete, using a c32/40 mix

- Walls are to be constructed using H16-H20 rebar

- Aluminium formwork panels will be used, panel height will be 3.9m, but the wall itself will pour as per above

- Walls are 72 linear meters in total, and at 393mm thick we have about 100m3 to pour in the walls

- We are in the water table

- Will install a kicker, cast as part of the slab

- We are using external sika tanking under the slab and down all walls

- Pouring 1m section around the entire perimeter at a time, pokered, before going round for the next pass until the pour is complete. 1 perimeter pass will take 4 concrete wagons. In total in the 1 day we would need 13-16 wagon loads if each deploys 7.6m3. 

- The concrete yard is ten minutes down the road, and we can have multiple wagons on rotation.

 

I personally want a single wall pour, and technically we meet the wall height to width pour ratios. I don't really like the idea of splitting the basement in half vertically for the pour and having sikaswell water bar up two sections of wall. What if there is ever any future movement, even slightly could open up a joint. I prefer a single pour, tied together completely with rebar.

 

Would welcome your thoughts on this.

 

Cheers

 

 

[Thorfun]

Ours was multiple pours with water bar strip. they basically built 2 corners diagonally opposite and then struck the formwork and rotated it to do the other 2 corners to make the rectangular box. 
 

details here. 
 

 

No leaks so far but it’s only been 6 months. 
 

 

[Ronan 1]

It's a bad idea, it's way to much for a wall pours in a single pour, doesn't matter how good of service you have you have a massive risk of cold jointing I wouldn't even contemplate it and I do RC frames for a living.

 

It may be new to you but it's really a very common standard piece of work and I can't see any reason a day joint if done properly would give any problems.

[Internet Know How]

9 hours ago, Ronan 1 said:

It's a bad idea, it's way to much for a wall pours in a single pour, doesn't matter how good of service you have you have a massive risk of cold jointing I wouldn't even contemplate it and I do RC frames for a living.

 

It may be new to you but it's really a very common standard piece of work and I can't see any reason a day joint if done properly would give any problems.

I'm no expert, I just think its better to have the one pour if possible. I do know of one other basement build who had walls at 2.7m high and probably 100m3 concrete pour...they did it in one with Sika. That doesn't mean my one will go smoothly though so I appreciate your knowledge and advice

[Internet Know How]

9 hours ago, Thorfun said:

Ours was multiple pours with water bar strip. they basically built 2 corners diagonally opposite and then struck the formwork and rotated it to do the other 2 corners to make the rectangular box. 
 

details here. 
 

 

No leaks so far but it’s only been 6 months. 
 

 

The video looks great, did you hire the time lapse camera or buy one?

[Thorfun]

9 minutes ago, Internet Know How said:

The video looks great, did you hire the time lapse camera or buy one?

Thanks. It’s a GoPro that I already owned. 

[Mr Punter]

You have got 24 corners in that basement.  That must make the formwork and reinforcement a challenge!

 

I would leave it to the contractor / designer to decide on how many pours are required.

[Internet Know How]

On 09/05/2022 at 22:06, Ronan 1 said:

It's a bad idea, it's way to much for a wall pours in a single pour, doesn't matter how good of service you have you have a massive risk of cold jointing I wouldn't even contemplate it and I do RC frames for a living.

 

It may be new to you but it's really a very common standard piece of work and I can't see any reason a day joint if done properly would give any problems.

Hi Ronan, what are your thoughts if we were to put 2 pumping wagons on this and 4 concrete wagons serving them half and half of the diagram I shared? We pumped a 97m3 slab last week with one pumping wagon and 3 concrete wagons on rotation in 5 hours start to flat float finish on the slab. We would probably need 6 men, 3 on each half, plus 2 guys moving the pump boom. 

[Bitpipe]

We had multiple pours just like @Thorfun with rotating form work. Sika swell bar horizontal between kicker and wall and vertical between walls.

 

The contractor built in a recess for the swell bar in the concrete and it was held in place with the sika mastic. Worked well - if installed correctly the swell bar will easily cope with the tiny amount of movement you will get - it expands to multiple times its original volume when wet.

 

We had a warranty from Sika for the system which gave me peace of mind. Leave it to the experts.

[Internet Know How]

Hi All,

 

We poured this in one in the end. I had 4 concrete wagons on rotation, and 2 pumping wagons, one on standby just incase we hit any problems. Flow rate was fine followed by multiple pokers....weather perfect. Whilst it probably cost me more in formwork, we didnt have to move this stuff around. My only joint is where the slab meets the walls as well as the tie rod holes, since sealed with Sika X plugs and tanking membrane, which we protected with moisture resistant kingspan, which was also to meet EPC requirements.

 

Backfill now complete too, which was only started after all internal walls had been build and the block and beam floors installed

 

Very happy with the end result so far. Thanks for all the responses, really good hearing from others who have been there

[Mr Punter]

Nice. Did you organise this yourself or did a contractor do it?  Pics?

[Internet Know How]

2 hours ago, Mr Punter said:

Nice. Did you organise this yourself or did a contractor do it?  Pics?

I organised everything and  brought a contractor in to do all the labour elements. They provided the man power supported by workers I have onsite too, and I sorted all materials inc formwork designs and co-ordination so it went according to plan.

[Mr Punter]

That looks better than most professional sites.  Quite an achievement!  How come you have beam and block in the basement when there is already a slab?

[Thorfun]

Great job! I bet you’re over the moon. 

[Russell griffiths]

That is a stunning job, well done. 

 

[Pocster]

12 hours ago, Mr Punter said:

That looks better than most professional sites.  Quite an achievement!

That’s what you said about mine 

[Internet Know How]

23 hours ago, Mr Punter said:

That looks better than most professional sites.  Quite an achievement!  How come you have beam and block in the basement when there is already a slab?

Thanks! Its been logistically challenging with just a single ramp in and out and no extra storage space. To avoid a split level slab i wanted a full void under the entire building to accommodate pool equipment but also basement accessible drainage. Its been easier doing it like this than split slab and partial void. 

[Internet Know How]

23 hours ago, Thorfun said:

Great job! I bet you’re over the moon. 

Yeah its turned out well, you’d never know it was there now we’ve backfilled

[Thorfun]

19 minutes ago, Internet Know How said:

Yeah its turned out well, you’d never know it was there now we’ve backfilled

Yep. I remember that feeling!

[Trw144]

8 hours ago, Internet Know How said:

Thanks! Its been logistically challenging with just a single ramp in and out and no extra storage space. To avoid a split level slab i wanted a full void under the entire building to accommodate pool equipment but also basement accessible drainage. Its been easier doing it like this than split slab and partial void. 

Hi

 

Would you have any drawings to share on your drainage scheme under the beam and block? I have similar basement and pool to build (albeit in a bank so basement on three sides).

[Internet Know How]

On 26/09/2022 at 22:52, Mr Punter said:

That looks better than most professional sites.  Quite an achievement!  How come you have beam and block in the basement when there is already a slab?

Rather than have a split level slab to accommodate the pool and area around it for heating and ventilation pipes we excavated the entire plot to the one level. So we have a void now beneath the B&B floor in the basement to slab level.

[Internet Know How]

On 28/09/2022 at 06:54, Trw144 said:

Hi

 

Would you have any drawings to share on your drainage scheme under the beam and block? I have similar basement and pool to build (albeit in a bank so basement on three sides).

I dont have any, but we are going to install a sump pump. Something along these lines: https://www.tanks-direct.co.uk/waste-water-tanks/sewage-pump-stations/single-pump-sewage-pump-stations/c1050     

 

We already have a void to accomodate the the sump pump, but if you dont you need to cash this into the slab so it sits flush and then you have proper flow into it. The web has lots of useful bits about but often websites such as this wiill give you a good idea. End of day its just a few pipes in and then another out to ground level to take the waste up. 

[Internet Know How]

On 26/09/2022 at 22:52, Thorfun said:

Great job! I bet you’re over the moon. 

Yeah I am, its been well worth the effort. All backfilled now and on with the ground floor brickworks.

[Thorfun]

1 hour ago, Internet Know How said:

I dont have any, but we are going to install a sump pump. Something along these lines: https://www.tanks-direct.co.uk/waste-water-tanks/sewage-pump-stations/single-pump-sewage-pump-stations/c1050     

 

We already have a void to accomodate the the sump pump, but if you dont you need to cash this into the slab so it sits flush and then you have proper flow into it. The web has lots of useful bits about but often websites such as this wiill give you a good idea. End of day its just a few pipes in and then another out to ground level to take the waste up. 

our civil engineer specified one of these for our foul water to all flow out of the basement and in to the sump and then pumped to the STP. when I looked in to costs for a 4m - 5m deep one at £5k I decided to ask them to design the foul water to use gravity and if we ever fit a toilet in the basement we'd use a saniflo! obviously a little different for you with a pool as I'm sure you'll have more need for foul/waste water to be dealt with in your basement.

[Internet Know How]

1 hour ago, Thorfun said:

our civil engineer specified one of these for our foul water to all flow out of the basement and in to the sump and then pumped to the STP. when I looked in to costs for a 4m - 5m deep one at £5k I decided to ask them to design the foul water to use gravity and if we ever fit a toilet in the basement we'd use a saniflo! obviously a little different for you with a pool as I'm sure you'll have more need for foul/waste water to be dealt with in your basement.

Yeah good idea if it works! £5k is expensive isnt it. Im going to look into saniflo too as it may just do the job for the 2 toilets we have down there, and then maybe just a clean water sump pump instead to manage the shower room/sinks