Concrete slab query......

[merlecollins]

Broken slate is alright for sub tbh. If you're still at 260mm, you can just chuck a couple of bags of mot down as is. I wouldn't want to blind off over slate as it may still puncture the dpm, you've probably just about stopped digging in the right place.

If you've a whacker plate then this is on the way to being a top notch job. You getting concrete delivered?

Yes mate, the original floor was approx 200years old Caithness slate flagstones, with whats known locally as 'sea scrapings'(sand and shells) as a sub base, as we've been digging this out we have hit loads of slate pieces (and bones!!) that must have been thrown in to give a more substantial base.

The base is still quite sandy although stable enough (200 years in the making).

What do you think??

 

[Deluks]

All good! Although I'd personally be wanting to dig down a bit more, in case there's any buried pirate treasure!

One other point, lay polythene over the insulation before laying concrete, doesn't have to DPM thickness but reasonably tough. Concrete can have a negative effect on the foil backing on the inso.

Of course if you've bought a massive roll of dpm then this will ensure it doesn't end up taking space in the shed.

 

[merlecollins]

All good! Although I'd personally be wanting to dig down a bit more, in case there's any buried pirate treasure!

One other point, lay polythene over the insulation before laying concrete, doesn't have to DPM thickness but reasonably tough. Concrete can have a negative effect on the foil backing on the inso.

Of course if you've bought a massive roll of dpm then this will ensure it doesn't end up taking space in the shed.

Thanks for all that Deluks mate

So, just to re-cap....

100mm Type 1 sub base
20mm sand blinding
1200 Grade Visqueen
80mm Quinntherm
1200 Grade Visqueen (I'll still have loads left over!!)
100mm Concrete

Then cover the slab with a sheet of the Visqueen for a couple of days..

Would you still put the mesh in?

 

[Deluks]

Yes, I would personally. Overlap by 400mm and tie.

 

[merlecollins]

Yes, I would personally. Overlap by 400mm and tie.

Thanks again!!

What do you normally tie the mesh with?

 

[Deluks]

Annealed wire, or coat hanger wire and a big pair of pliers! Basically any wire than can be twisted without it breaking. It's only to hold it while concreting, once it's set, it's going nowhere.

If you order the steel direct from a steel supplier they sometimes throw the wire in for free.

 

[merlecollins]

Whats the easiest way to space the mesh 50mm up?

 

[Deluks]

Get spacers from the supplier. Or a 50mm paver smashed up and spread out. Or simply dollop some pads of stiffly mixed concrete down every 18", an hour or so prior to the main pour, tamp down to 50mm and rest the mesh on that.