Trench Fill or Trench Blocks...Block & Beam or Slab Floo

[ahhwoodrow]

Hi, Planning a new extension and hoping to do a lot of the work myself. Father in law has Digger and space to put soil so digging and disposal of soil isn't an issue but I'm trying to decide on the best way to go.

Extension will be 8m x 5m on the back of an existing bungalow, if we need to do a 1m deep foundation all the way round the 3 sides would I be better of financially to fill with concrete or to do the minimum required and lay trench blocks myself?

Following on, would it be cheaper to dig out the 0.5m across the whole site to do a full slab, or dig out less and install a block and beam floor insead.

Laying the trench blocks and fitting the beams I would do myself.

 

[noseall]

Depends what value you put on time.

A builder would usually go for mass fill with solid floors because time is money.

 

[r896neo]

would it be cheaper to dig out the 0.5m across the whole site to do a full slab, or dig out less and install a block and beam floor instead

This doesn't make sense? you would have to dig out more for a B&B floor?

If the natural ground level is a good deal lower than the existing house floor then you might want to use a block and beam to save having to fill a large depth if you wanted a normal slab.

Unless you talking about a raft footing?

Generally speaking if you have lots of time then footings in block will be cheaper material wise than a trenchfill.

Also material wise a slab is cheaper than block and beam. Also a lot less fiddly

 

[limerockconstruction]

Like noseall says - as a builder I would generally prefer the mass fill option, if you can only leave yourself 1 or 2 courses of blocks in the ground its a damn site easier when the top of the footings are higher, but make sure you get your concrete nice and level because there is less scope to get your levels back by the time you get to DPC. We tend to pump a lot of our footings (because its easier on my body!), we can mass fill 8cu/m in about half an hour, measure that in time against an inexperienced brickie setting out an extension - could take a lot longer! But do whatever you feel comfortable with.

As for floors again, we would look at the slab option, B&B are great, but fidly and a bit more costly, great for covering massive holes or ground subject to heave - also bear in mind that, a B&B floor will traditionally be quite thick anyway

Screed 75
Insulation 100-125
Beams - 150
Air gap underneath floor 150 minimum depending on ground
Some authorities may well also want an oversight slab in or maybe a 150mm type 1 base anyway

So this could be up to 650 anyway!

Go for the slab every time. If yer old mans any good on a digger he'll grade back for a slab in about an hour, so wont take long.

Have fun....