Hi, after years of preparing for our new build, finally just after Christmas it started.
We've had some problems with our ground workers who either seriously underestimated or didn't work very efficiently; in reality I think it was a combination of both. In the end they came to us and told us they were projecting such a financial overspend at their cost (fixed price quote) they simply could not afford to continue, and have now left the site.
I know we can go to court here for breach of contract etc but to be honest I don't want to hold things up and have the expense of court fees etc, I'd rather just move on. We'd lost trust in both the ability and the scrupulousness.


The final thing the ground worker did was to lay the foundation slab; we've got floating raft foundations, which will seat a timber frame on top. Where as the slab should be level to a tolerance of + / - 10mm, the timber frame company says ""The spot levels demonstrate +/- 26mm i.e.: a lowest point which is 52mm below the highest point""

They go on to say:
"We suggest that you construct 225mm high (the depth of the floor make-up) sleeper walls underneath all of the timber frame super structure walls which will give you the opportunity to remedy the difference in levels. In that way, after the timber frame super structure is complete and immediately prior to installing the floor make-up you can apply the horizontal membrane to the slab, over painted where it extends beyond the sleeper walls and install the floors straight away to protect the membranes."

Have had a brief email conversation with building control about this idea and they say they cannot simply approve this idea without us going back to the structural engineer and/or architect for new plans.

"The proposal of sleeper walls could be an option but this would be to an engineerĂ¢â‚¬â„¢s design and consideration will need to be given with regard to the damp proofing over the floor slab (must ensure the damp proofing method is fully continuous; using a cementious tanking system). Once the design or proposal has been drawn up please can you submit the details to me prior to carrying out the works on-site, from this I can assess the proposals and there implications on the Building Regulations."

Obviously there's going to be further expense in getting around this which ever way we choose. At the moment I'd be quite glad to not have to go back through structural engineers costs plus the costs of remedial work though I accept we may have to.
Are there other (reasonable) ways to level a slab?

Help!

Thanks
Richard.

Surely there's some high-strength thin pour-screed-like product - cant be an unusual problem, to be solved quickly, in modern fast-track projects?

like dis

Then make up the difference for the interior floor finish using a screed.

I would leave a 100mm gap at the lowest point to let the water out and I would also remove the shims as I went along too.

That is truly amazing - revoultionary - to see you not in smart/office clothes, Mike! No, seriously, it's a dream isn't it. Can it do everything that ordinary conc can do e.g. if it's a reinf slab or even a rigid structural raft, with downstands etc? What if upstands are needed, cast over starter bars later? Wd ordinary conc be used for that, bonding to this stuff, or more of the same?

Just don't tell you know who...

The concrete comes in at 700 [yes 700] slump. When it is poured it is just like watching the tide come in. A quick walk around in wellies and it is virtually flat. The delivery truck brought the tapping bar with them.

Some important points though.

Insulation must be BELOW the DPM or it will float
Also there must be no gaps in the membrane or you will be needing a second delivery...

Not so off topic Mark- I genuinely think this may solve Rich's problem

Re, datums, I don't know about the chemistry but there is no discernable shrinkage on the floor I did. Also very level - I was at the job today and ran a 3m aliminium straight edge over it - as good as any screed I have seen [and better than many].

Hi RT

Sitting the TF directly on a cold slab may not be the best idea. It creates a temperature diferential in the timber frame which could cause condensation and decay. The Scandinavians stopped pouring secondary screeds in the early 90's because there were a number of court cases over this issue. It can also be problematic having the TF lower than the floor if you get a leak in your kitchen, utility or bathroom.
My first instict would be to try and sit your TF walls on a layer of structural EPS or XPS. This can be cut in wedge shapes using a hot wire at the production plant.
You could also put shimms under the Timber Frame at 400-600mm centres and fill in between the shimms with PU foam.

I'd go with Mikes suggestion. Set up new form work accurately with a laser level so you have at least the minimium thickness everywhere. I'm not familiar with agelia but I wouldn't rely on ordinary self levelling screed being self levelling, make sure you have people on hand to do it.