As a general rule of thumb, is it more cost effective to trench fill at the way to the top with concrete, or use interlocking trench blocks for the top 450mm? Assuming both methods meet all the requirements necessary.
Cost of trench blocks, vs more concrete.....
- Thread starter williamglossop
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I don't think there's much in it.
Most builders I know always go for trench fill.....they finish founds about 1 block and 1 engineering brick below ground level.....depending on if there's a slope, then 2 courses of face brickwork up to damp.
For builders it means foundation pour in one day, then upto damp in one day and no bending down in a muddy trench.
Most builders I know always go for trench fill.....they finish founds about 1 block and 1 engineering brick below ground level.....depending on if there's a slope, then 2 courses of face brickwork up to damp.
For builders it means foundation pour in one day, then upto damp in one day and no bending down in a muddy trench.
If the conditions are scientifically perfect for each then if just assuming a m run of trench, a masonry foundation can be cheaper than a m run of concrete. But this can be just a matter of a few pounds per m run, so not significant for a small extension
But when you factor in all the other influences, you can find that one is more economical or beneficial than the other. Especially the knock-on costs - extra skip and loading spoil for concrete foundations, or cost of a pump for concrete foundations. And then you may find that the cost could be say £50 per m run difference, so its worth while
So you need to do the calculations, based on the material labour and site conditions.
Then there is the difference between trench blocks and normal block cavity foundations.
But when you factor in all the other influences, you can find that one is more economical or beneficial than the other. Especially the knock-on costs - extra skip and loading spoil for concrete foundations, or cost of a pump for concrete foundations. And then you may find that the cost could be say £50 per m run difference, so its worth while
So you need to do the calculations, based on the material labour and site conditions.
Then there is the difference between trench blocks and normal block cavity foundations.
Bricky I work with always uses minimum concrete and builds most of his founds 14” solid concrete block to do away with the cavity fill.
If it is upto me though I’d spend the money on the extra concrete to avoid tight founds with heavy blocks.
If it is upto me though I’d spend the money on the extra concrete to avoid tight founds with heavy blocks.
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I've seen a firm locally that do quite a few builds. They mass fill to 300 mm below ground, then use one trench block and 3 bricks up to damp. Seems like the worst or best of both worlds..... mass fill to a level that means u barely have to get in the trench and don't have to mess about in filling cavity.
That’s what most people do now I reckon, although not necessarily with trench blocks. It’s what I do. It’s a no brainer imho, if you’re getting a concrete truck out in the first place, just carry on filling it up to 450mm below dpc vs days of laying blocks underground
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