Sub floor advice please

[sambotc]

hi all,

I'm in the middle of doing some plans to show the LABC my intentions for a self built single storey rear extension. I'm also trying to gather how far I need to dig out below FFL.

Could someone confirm whether this document is still acceptable please? It's a few years old.

http://www.broxbourne.gov.uk/sites/default/files/Documents/Building_Control/Ground bearing floor and foundation Oct2010.pdf

Also, I've seen some suggest using steel reinforcement in the slab, is this a requirement or belt and braces?

Thanks in advance !

 

[sambotc]

Actually, I've just realised the insulation and slab are the opposite way around to what I'd imagined... Would it not be better to put the insulation on top of the slab and then screed on top of the insulation with a separating layer in between?

I'm used to underfloor heating where this is the case.

Thanks again

 

[oldbutnotdead]

There's a big caveat on the top of that document- 'only suitable for certain ground conditions'. That being said, it is a decent starting point (you'll need all the elements mentioned), depending on your ground, drains, trees etc. you may not have to go so deep (or you may have to go deeper).

Steel in the slab again down to ground conditions, BCO influence- if the slab is only performing as a floor (ie separate from the foundations) and you're on good ground then not really required.

So stick a print of that in your folder (you doing full plans submission I take it), go and have a chat with BCO and take it from there. You won't get laughed at with that spec

 

[sambotc]

Thanks for the reply that's great.

The ground is clay / shingle and the BCO who I've already spoken to said that it should be a ' normal' 1 metre dig based on the ground.

I think it's probably better to do a full plans so we both know where we are anyway, also saves a few quid doing so.

 

[oldbutnotdead]

Very good idea (full plans) if you're self-building- with luck the BCO will guide you round the beartraps at paper stage. Have fun