Foundation choices

[vivienz]

There's been some miscommunication re. my piled foundation design with the result that I now have 2 options:

 

1. The piles are tied to the ring beam with the result that there is what MBC describe as a 'minor thermal bridge' for each pile.  The upside of this design is that I don't need to spend approx £5k on cellcore for anti-heave and perinsul blocks for the load points of the superstructure to sit on.

 

2. The thermal bridge is broken by not tying the piles into the ringbeam; I will need to have cellcore and perinsul blocks.  I don't know the cost of the latter but it's unlikely to be cheap.

 

MBC haven't specified what they mean by a 'minor thermal bridge' so it's hard to make an assessment.  Obviously, saving £££ on the anti-heave and additional insulation is attractive, but I don't know if it's a good long term decision.

 

Any thoughts from the hive mind?

[mvincentd]

23 hours ago, vivienz said:

haven't specified what they mean by a 'minor thermal bridge' so it's hard to make an assessment.

Strikes me you need to see a drawing in order to make a decision.

[PeterW]

23 hours ago, vivienz said:

The thermal bridge is broken by not tying the piles into the ringbeam; I will need to have cellcore and perinsul blocks.  I don't know the cost of the latter but it's unlikely to be cheap.

 

Can't see an SE signing that off as the ring beam is structural and tying it to the piles is usually how they create integrity

 

minor bridge probably means the square area of each pile will conduct heat from the slab - with 30 piles at 300mm on a 90sqm slab would be 3% of the total area - not a big issue !

[vivienz]

Here's the design - for the pile and its attachment to the ringbeam.  There are 34 of these, 25 of which are in the thermal envelope (the remaining 9 are in the uninsulated garage).

 

The alternative design is from the same SE - I have both options from them.