MBC passive slab. Quick answer needed

[dogman]

Morning all.

 

How far did your compacted hardcore go beyond the slab.

 

I could go to MBC but i was hoping someone on here with the MBC slab could give me an indication.

 

I have a ground worker coming today and was going to ask for 1m but looking at photos of others this maybe too much.

 

It will make a difference in muck away costs.

 

MBC have yet to specify the slab as we found some issues when we removed the old house.

 

Thanks 

[Mikey_1980]

Ours was one metre as specified by the Hilliard the MBC SE, perhaps drop him an email to confirm, do you know the depths that Hilliard has specified yet?

Edited December 19, 2016 by Mikey_1980

[dogman]

Mike 

 

we have only just got the old house down. ( we cleaned and stacked 7000 old stock bricks as we took them down so took a while)

 

The survey is this week to see what is under the old house. So far found a old courtyard with bricks and gully still intact and a foul chamber we did not know about.

 

Trial pits hit solid chalk at 600mm with 300mm hard hogging on top so looks good.

 

Issue is that the drains we want to keep are closer to the structure than we had hoped. And the old foundation walls go down to the chalk so have asked if they can stay to prevent the ground being dug under the slab. 

 

Martin

 

I sent a question to MBC asking but i think they are in the XMAS slow down.

[jack]

I was sure that we had 1 metre specified too, but looking at the drawings, all I can see is a perimeter land drain 600mm out.  

 

 

Maybe assume the worst (1m) and ask him to be ready to quote differently if you can get away with less once you've spoken with MBC?

 

Also, have you tried Hilliard Tanner (MBC's consultant engineer) directly?  I found him very approachable and helpful when we had a couple of issues along the way.   His details are here: http://www.tsd.ie/aboutus.html  Maybe he hasn't knocked off for Christmas yet!

[dogman]

Thanks Jack and Mike. I will go with 1m. 

 

Interestingly, had an email from MBC just now. (are you on here ? MBC )

[jack]

32 minutes ago, dogman said:

Interestingly, had an email from MBC just now. (are you on here ? MBC )

 

I think they do keep an occasional eye on the forum, as they know they get discussed a fair bit.  Suspect they don't get involved because they don't want to be seen to be touting their wares.

[DavidFrancis]

They've got a fairly prominent link to this forum on their UK web site!

[TerryE]

@dogman, Ditto 1m.  We actually got MBC to include laying the hardcore and doing the compacting in their price.  The crew were very particular in doing this in 50mm layers, whacking down each before laying the next.  They went to some lengths to get each layer flat to within 5mm or so and the last one to a better tolerance than that. 

 

I asked the crew boss why since it was going to be covered by the slab, and his answer was: the risk of differential settlement.  Doing it in 5cm layers ensured that the compaction was thorough and uniform.  He said the last thing that you wanted when you came to the concrete pour was some part of the slab to drop a cm, say, relative to the rest as this could bugger up the mould and the pour.

 

Incidentally  this is the reason why they often specify a land drain and a course (no fines) hardcore -- to ensure uniform drainage for the same reason.

 

@DavidFrancis David, we don't mind them advertising our site, and we'd love other suppliers and related sites to do the same.  This is very different from allowing any supplier to openly advertise here.  On the other hand we do want members to give open and honest opinions of supplier performance, when based on personal experience -- so long as they declare any financial interest before doing so. (E.g. Jeremy Harris wrote up some excellent stuff on his SunAmp installation, but openly stated that he'd got a discount on his kit if he agreed to write it up.   The moderators were entirely happy with this because we were sure that JSH would be honest in what he wrote, whatever.)

[DavidFrancis]

Terry - I wasn't questioning the ethics of their link to here.  It's just that BuildHub is the only "external" link in their list of links, so they must consider this forum as fairly important.

[Ferdinand]

12 minutes ago, DavidFrancis said:

Terry - I wasn't questioning the ethics of their link to here.  It's just that BuildHub is the only "external" link in their list of links, so they must consider this forum as fairly important.

 

Excellent that they think we are the only forum worth a link :-).

 

F

 

[dogman]

Quick up date------he did not turn up. spent all morning painting lines on mud so he could see the footprint and sorting levels so he could estimate how much muck is to be removed.

Hopefully paint will last till Wednesday when next one comes to have a look.

[Declan52]

Go at least 1m out and you will have a great base already there to put a path round the house.

[TerryE]

BTW we've mentioned this before but its well worth while pegging in some rebar spikes at least 2m out from the footprint of the slab so that you can quickly put in sight-lines / taut lines for the main and side elevations of the slab so you can be sure of the exact position of the slab at all stages of the groundworks.  There's no point in pegging out the corners themselves because you'll lose these pegs as soon as anyone does anything!