RC30 concrete foundation levelling

[Vijay]

Hopefully gonna be finally pouring the foundations by next week and I need to have a pretty accurate finished level as I’m building in ICF, so how self levelling is RC30 concrete? . Do I need to have markers in the footings to see my levels as it’s poured? Would vibrating the concrete be a good idea to help the level?

 

Cheers

 

Vijay

[PeterW]

Get a decent slump on it to start with. Go round the trenches with a can of marker spray and put a line every 6ft where the level should be and work to that too 

[Vijay]

Don't think marker spray will cut it. According to the ICF installation paperwork, foundations should be within a 6mm tolerance  It would be difference in traditional blocks cos the mortar could take up any bigger gaps. The Polarwall system does have some allowance as I can cut the panels to fit, but it would make life far easier if I was able to get the concrete level bang on.

 

I did see something where a guy suggested tapping in markers like nails or I was thinking something like wooden biscuits (like you use with a biscuit joiner)?

Edited April 23, 2017 by Vijay

[PeterW]

If you put a marker at the height you want and spray along it the line will be where the straight edge is. 

 

Given the  tolerance on most laser levels is 0.5mm in 5m, you will be 6mm out over 30m anyway so I would not worry too much. Last ICF build I saw they cut the bottom off the units and spray foamed them to the founds anyway so not sure why polar need that tolerance. 

[Brickie]

Do you have a laser level with the beeping receiver? My mate (a basement contractor) creates an upside down t in 4x2 & atteches the receiver to it,so the bottom of the it is set at the desired height. I'd say you'd want to vibrate the concrete anyway,& the answer to 'how self-levelling...' is 'not very!'

[Alexphd1]

Do you have you much rebar coming out of the footings? if not how about using rails (usually overkill for strip foundations but 8mm tolerance is very low) ? We are planning on using http://www.acrascreed.com/index.html on the next build but its a eps raft slab. If you do have rebar cant you just pre mark the rebar say 30cm up and measure back during the pour. Does the polar wall have a starting strip for the 1st course to sit on? the nudara icf is pretty forgiving for poor levels.

Edited April 23, 2017 by Alexphd1

[ProDave]

Another vote for a rotating laser level and measuring staff with laser detector.  This is what my builders used, checking the level about every foot or so as they went along with a rake leveling it.

[Vijay]

2 hours ago, PeterW said:

If you put a marker at the height you want and spray along it the line will be where the straight edge is. 

 

Given the  tolerance on most laser levels is 0.5mm in 5m, you will be 6mm out over 30m anyway so I would not worry too much. Last ICF build I saw they cut the bottom off the units and spray foamed them to the founds anyway so not sure why polar need that tolerance. 

Good point, I think it's more the manual has to say what it should be but in reality, a builder would probably never get it to that tolerance and then do what you said with cutting things to fit

[Vijay]

2 hours ago, Brickie said:

Do you have a laser level with the beeping receiver? My mate (a basement contractor) creates an upside down t in 4x2 & atteches the receiver to it,so the bottom of the it is set at the desired height. I'd say you'd want to vibrate the concrete anyway,& the answer to 'how self-levelling...' is 'not very!'

Yes I have and will do that. I have 80 odd cube of concrete going in so it would have been useful for an easy visual marker too

[Vijay]

2 hours ago, Alexphd1 said:

Do you have you much rebar coming out of the footings? if not how about using rails (usually overkill for strip foundations but 8mm tolerance is very low) ? We are planning on using http://www.acrascreed.com/index.html on the next build but its a eps raft slab. If you do have rebar cant you just pre mark the rebar say 30cm up and measure back during the pour. Does the polar wall have a starting strip for the 1st course to sit on? the nudara icf is pretty forgiving for poor levels.

The rebar is going in to the semi wet concrete as it's only shorter lengths of straight bar.

 

Polarwall uses a rail system, so there is a U rail that is fixed to the concrete and then the polystyrene panel is inserted into the U

[jamiehamy]

4 hours ago, Vijay said:

The rebar is going in to the semi wet concrete as it's only shorter lengths of straight bar.

 

Polarwall uses a rail system, so there is a U rail that is fixed to the concrete and then the polystyrene panel is inserted into the U

I initially used my power drill to make holes to fix the u-rails into - and discovered the wonders of an SDS drill! Although foaming them on first could be a good idea to stop any moving off line.   

[Vijay]

Hello bud,

 

How did you find getting levels of concrete vs first layer of Polarwall?  I just don't want to spend ages cutting down the first row of panels...............................

 

 

[jamiehamy]

9 minutes ago, Vijay said:

Hello bud,

 

How did you find getting levels of concrete vs first layer of Polarwall?  I just don't want to spend ages cutting down the first row of panels...............................

 

 

Ours was a bit odd because we were building inside the water tank. The end gables were perfect as they were build up in blocks with beams on top,  then the icf. Along the length of the beams,  the camber was slightly noticeable through the first courses of icf but it seemed to sort itself. 

 

In terms of windows,  nothing matched the icf courses anyway so it was never really an issue.  

 

I'd you've got a rotary level and staff in centre of house you'll be fine. 

 

If the levels go a bit wonky it's not the end of the world - you'll be cutting the corners anyway and have corner braces,  so not problem there. For Windows,  it will take a couple of mins to trim the sill if not level and at the wall head you'll be measuring the concrete with the staff anyway to ensure its. 

I think Polarwall has to be be one of the most flexible products out there.  Can built it anyway you want and very very forgiving if you get it wrong.  

[jamiehamy]

BTW I'm getting ready to order the garage walls soonish - 100 XPS +250 core +100xps. Should be warm and bomb proof! 

[Vijay]

Hi Jamie,

 

I think I might be going overboard and worrying about things most builders wouldn't - but I've never built anything with ICF so am just trying to look at any potential problems as early as I can

 

Polarwall does look very flexible but hopefully I won't create extra work if I can get the concrete spot on

 

250mm core - why??????????????????????????? lol   I'll be doing my garage in ICF too but 155mm core the same as the house.

[Mr Punter]

You are better off getting the concrete right.  If you can't you could chock up the starter U channel with packers to suit and screw some 2 x 2 timber down around the perimeters where the footing is low to stop the concrete spilling out and the bottom of the formwork moving.

[Vijay]

Yeah that's my exact logic. Good idea about packing where I need to, I think with the suggestions on here, any concrete that's out won't really be a huge issue but I will obviously aim to get the concrete as good as I can to save work.