Hello there,

I’ve just been informed by building control that the garage re-build currently underway will need a new floor slab.

Work required:
Remove existing slab and hardcore. Slab c. 75mm about the same hardcore, and excavate to foundation depth, 200mm below exising.
100mm stone.
sand blinding.
DPM
100mm concrete.

Access is great, maybe 2m to the road. Job is in Lancaster.

The builder presently on site has quoted £1,200! Seems a bit rich to me. What do you guys think?

As always all advice very much appreciated.

Alex

If that includes all materials and clearing the rubbish then that sounds pretty cheap. I’m guessing it’s pretty big if building control are involved.

I spent about half that doing mine and I DIYed it all and got the sand and hardcore free.

What’s the square meterage? You don’t get much for £1200 these days, including plant hire.

ditto above. that sounds reasonable.

As above you really need to give us a size.

There is a fair amount of hard labour involved plus matterials. Sounds initially like a good price. Does it include disposal for all the rubble? I guess not..

Eyup all, since this seems to be the thread for building works does this quote for drainage works seem to be in the ballpark? (I’ve a horrible feeling that the answer will be ‘yes’)

Repair: Sonar trace 4.9m downstream of manhole, excavate and replace 2m section of pipe work including junction and pipe section upstream of junction.

Jet pipe to clear debris, re-survey in preparation for lining.

Reline from manhole downstream for a distance of 2m, insert patch liner at 9m downstream of manhole 1. Replace vertical pipe from junction to existing soil pipe. Remove all excavated material from site, reinstate area of excavation.

Depth of excavation is between 1.5 and 2m. Pipe is 100mm diameter and obviously knackered.

Quote was £1650+VAT E.mids

I don’t really understand that quote for drainage as I can’t work out what’s damaged and what’s not. Where in East Midlands are you? At 2m operatives need to know their shizzle. Who’s quoted? A builder or by the sounds of it a jetting company?

That was ANSA, I’m in Notts.

The answer to what’s damaged is ‘most of it’. From the survey, which I have the video of.

0.3m Joint Displaced (Medium)
0.5m Longitudinal Crack @ 10 o’clock
1.2m Circumferential crack (10 to 2 o’clock)
4.9m Broken pipe (2 to 4 o’clock)
5.1m Multiple fractures
5.1m Pipe deformed 20%
5.2m Defective Junction @ 9 o’clock, broken pipework on junction
5.5m Broken pipe (8 to 2 o’clock)
6.6m Circumferential crack (12 to 12 o’clock)
9.0m Circumferential crack (10 to 4 o’clock)
12.8m Water lever @ 30% (Attached solids below water)
14.0m Boundary (woo bloody hoo!)

All distances are from the Manhole.

Are you blocked as we speak? It’s got to be worth another quote. I’m presuming they’re digging for the damaged pipe at approx 5m as it can’t be lined. Notts has some sketchy areas of ground and at 2m they can’t just be sending a man down in an open trench, check there are no loadable extras for shoring etc as it could get well out of hand. Presume they’re happy with the last section even though it’s holding 30 percent water/solids, what is it down there?

Cheers, soil is clay, I’ll be getting a full cost breakdown of all the works by item, and a couple of other quotes too. I’m already a little concerned about what happens if the post repair/pre-lining jet buggers up some of the crack sections to beyond lineable…

They’re pretty sure that the section holding water is due to chunks of concrete coming away from a previous bodge job (nothing to do with me a hasten to add!). I’ve learnt a lesson about buying a house from a tradesman, the last few years have been a bodgetastic voyage of discovery!

Edit: not blocked at the moment.

Jetters in the wrong hands can cause all kind of problems especially on old salt glaze clay drainage etc. It may be a better option to pull a new trench entirely then you have no bodge at all. This may also allow you to come out of the groind quicker as you head upstream away fron the sewer connrction. Hard to say without seeing the job. Good luck.

OP, what’s building controls’ reason that it need to be replaced?

Balls! I thought I’d put all the info.
Thanks for all the replies so far, it’s around 15m2

BC want existing replacing as it’s in pretty lousy shape, and not up to standard for a structure attached to a house.

APF

Unfortunately I occasionally have to break up concrete floors at work. The price sounds reasonable. It’s a sugar of a job.

RE: conc slab – I wouldn’t think that would be massively far off if they are removing the spoil as well. How many days have they quoted?

The stock GEN1 concrete in ready mix will be ~£150 for 1.5cu/m however with small loads depending on how its delivered you end up paying a surcharge for empty space.

If they are using a machine I would say that is best part of a day to break out and excavate the material and remove to a skip or stock pile if the are removing it with a grabber truck.

Based on your depths of material removed and assuming a similar sized slab currently that’s approx 5.25cu/m of material to dispose of, at approx 2.3g/cm3 so 12 tonnes ish of material to dispose of which depending on where they dispose of it / who they know will be inert / non-haz waste, so half half load probably another £100-200 to dispose of the material.

This is assuming you are building on natural or relatively clean ground and don’t need particularly sulphate resistant concrete or need to dispose of nasty made ground from beneath the slab. .

APF, sounds pretty cheap to me. How deep are the foundations? Could end up being a very deep hole!

We paid a grand for additional foundation depth (going down another 2m, cos a sewer was vaguely close by 😯 . Literally felt like throwing money down a pit! It was an impressively deep hole though

OK guys, just wanted to check I wasn’t being burned.

I’ll talk to the contractor today and give the go ahead.

Charitable donation forthcoming as good karma for the advice.

Good luck to the drainage guy too.

Cheers,

Alex

Apf, what levels are you working to? Could it be over laid with 75mm reinforced screed. Im presuming you arent building off the slab and have put new founds around the outside. Absolutely no issues with going over the existing.

Thanks again Wrightyson and APF, ideally I’d have the lot up and replace, but the drain runs under my garage, and the manhole is the lowest point on the surface, it’s uphill to the location of the main sewer in the road from my garden…

As a guide we did same for our new garage and that was about 1600 quid so in the ballpark.

Curiously my builder, who started to lose control somewhat of his job, then claimed the outside slab was “a 10 grand slab” when he started demanding more money. It was exactly the same as the inside one and couldn;t explain the difference. Anyway, all dealt with by me providing a detailed breakdown of his own costs and refuting his quite bizarre assertions. My lawyers after him now for the money he owes us now having looked at what he didn’t do. And breathe.