Is this cracked base ok to build on?

Discussion in 'Builders' Talk' started by thereddevil, Oct 25, 2021.

  1. thereddevil

    thereddevil New Member

    Photo:
    https://imgur.com/cwOw8TG

    Looking to take down the concrete garage and build a timber framed outbuilding (6x5m) on the same base. It's about 200mm thick and had a car inspection pit that was filled in. It looks like the gap for the pit caused a crack from the corner all the way along the base. There is another crack on the left side not shown that's almost identical. It'll have been like this for a long time. Can it be fixed by cleaning and filling the gap, then levelling?
     
  2. Wayners

    Wayners Screwfix Select

    [​IMG]

    Cut the cracks out with grinder and epoxy concrete repair
     
  3. FlyByNight

    FlyByNight Screwfix Select

    What is outside?

    It it level or a big drop off where the cracks are?
     
  4. thereddevil

    thereddevil New Member

    The whole base isn't particularly level from when it was built. There is a slight drop off nothing major though. Outside is surrounded with soil.

    Do you have a product you can suggest for the epoxy filler?

    The other crack (not shown) makes it look like this:
    upload_2021-10-25_10-4-42.png
    You can see the damp coarse bricks dropping and mortar cracking:
    upload_2021-10-25_10-7-9.png
     
  5. rogerk101

    rogerk101 Screwfix Select

    If it were mine, I'd rip it all out and start afresh ... and that's uncharacteristic for me to recommend rip and replace!
    Yes it might seem wasteful upfront, but if you're starting from scratch, you can choose exactly what size (footprint), without being dictated by the existing ... you can do foundations to the latest specs, making the whole project that much more future-proof ... you can insulate the entire slab, so that you won't be losing heat downwards and you'll be a whole lot more comfortable ... you can do a perfect job of damp-proofing ... etc. etc. ... the list goes on.
    The only thing you'd be saving by using what's there now is the cost of a skip to remove it all, and a few materials, which is unlikely to be more than a grand tops.
     
  6. thereddevil

    thereddevil New Member

    Yes I agree a new slab would be best. And having the insulated floor flush with ground level is appealing.

    Would you have any idea on costs to remove? It could be DIY but it's a big job to break all that concrete. The slab is 6.5x7m and at 200mm thick that's about 9m3!!
     
  7. rogerk101

    rogerk101 Screwfix Select

    You're already having to get rid of the concrete structure which is going to take at least one 12m3 skip. Just add in the cost of another 12m3 skip and you'll get rid of the whole lot. Two 12m3 skips will cost you about £500.
     
  8. Wayners

    Wayners Screwfix Select

    Buy ready mixed mortar and point up the bricks although looks white ish so order some lime mortar.

    Just duck tape either side of cracks after grinding out a bit and get epoxy concrete repair in it. Any you can pick up at sensible money will do. Pouring stuff maybe more money so stick to trowel stuff I think.

    Sinking and moving slab so may move some more so just repair and see now it goes.

    Other way as above. Remove and start again. Worth it though?
     
  9. thereddevil

    thereddevil New Member

    The garage is being removed for free and not worried about the cost of removal. It's more the labour to break and remove the slab tbh.
     
  10. stevie22

    stevie22 Screwfix Select

    Skips are getting very expensive, and you will be limited to 8yds for concrete in a conventional one unless you get the demountable body style. I just sent one away last week: £260. You will be pushing towards 20 yards so 3 skips.

    Cracks will always run to a corner as it acts as a stress raiser so that of itself is not such a worry.

    If you go down the diy route then I thoroughly recommend the McAlister £150 breaker from our hosts. I had a wall to be removed and the brickie asked me to hire a breaker but I opted to buy this as I also had bits of drive to remove. It is as animal!!
     
    rogerk101 likes this.
  11. thereddevil

    thereddevil New Member

    I'm now thinking an insulated slab would be best since it reduces the overall height. I believe I'm allowed up to 2.5m with a flat roof?

    Separate question. Would it be within planning permission to knock down this garage and build a new one (less than 30m2)? Could it be argued that since the existing building is higher, the new building could be above the 2.5m2 stated by building control?
     
  12. rogerk101

    rogerk101 Screwfix Select

    You shouldn't even ask for planning permission, unless you're really changing the size by more than, say 10% ... you could probably even sneak in 20% unless you think your neighbours might complain.
    'Repairing' an old garage, or 'updating' an old garage are perfectly reasonable things to do, and as long as you're not overdoing it, who would notice? who would care?
     

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