Which Heating System???

If I may, an example:

A strip foundation, and a raft foundation. Taken inside the last month on two sites 100m apart, in Co Galway.

Strip foundation:



Raft foundation (also note quality of ground works - grass still intact.....)





Groundworks for the strip founds started 1 month before the raft. In the length of time it took to excavate, pour strips, lay blocks in the photo, backfill & pour subfloor, the entire raft, AND HOUSE - including roof - were excavated, poured and building erected.

The raft house is currently being first-fixed services......the other house is only 4 rows of blocks high on one end.........

.....whichever way you crack a nut, if you can finish a house 3 or 4 months earlier, you'll save money.

...ok, gotta go - off to the Energy Show tomorrow to see what's what :)
 
baldyman27 said:
Re: raft vs strip (sorry, don't have the patience to dissect your post!), can you explain why raft foundations are not the norm if they are so much faster, easier and cheaper? They are obviously more structurally sound which makes it even more intriguing.
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For the same reason that the hollow concrete block is still in existence in the East........you have strip foundations. " cos that's the way we always do them 'round here" :)

This side of the Shannon is almost exclusively rafts, for the reasons above.


NoIdentity said:
I had planned on strip foundations. However, I just got a call this minute from the earth mover saying that they've hit rock and will require a rock breaker. Does this mean I will have to go with a raft foundation?
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No, not necessarily. Don't panic. Someone - or you - needs to get a look and see how much is involved. If it's a huge mass of rock, then yes a raft may be a better option. But for one rock, it's not a deal breaker (pun, sorry...:) )

On my own house, I had the big mass of rock thing, and the breaker was there for 4 full days........... :( Nope, didn't like the bill, either...:eek:
 
galwaytt said:
This side of the Shannon is almost exclusively rafts, for the reasons above.
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Nothing to do with prevailing ground conditions west of the Shannon I suppose?




galwaytt said:
Someone - or you - needs to get a look and see how much is involved.
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Specifically your engineer. He is ultimately responsible for the structural integrity of the house. Solid bearing will have to be found all around, even if this involves finding the rock under all areas and bringing back up to level with leanmix. Could be costly but hopefully not the case.

Galwaytt, you seem to be giving out biased and possibly self-serving advice re raft foundations and misleading advice re the presence of rock. I hope for his/her sake, that the OP isn't too impressionable.
 
galwaytt - I am amused that you think a raft foundation is cheaper than strip foundations.It may be able to compete in terms of cost if you uncover a reaonably level rock platform to build off.Surely as you discovered on your own house there was a rock breaker required for four days to create a decent platform.
NoIdentity - in your case it may well be cheaper to do a raft if your groundworker has uncovered rock as the entire area below the house will have to cleared down to clean rock - assuming that this is not an isolated pocket of rock - further site investigation will conclude this.On a previous project - a v. large private house ,there was significant rock (granite) breaking required.There were strip foundations called up on that project, the architect thought that we could rock break to underside of hardcore and then locally rock break for the strip foundations.We were allowed to reduce the rising blockwork to 450mm (2 blocks) high thus reducing the depth of rock breaking on the high side by 225mm.We shuttered the strip foundations and then laid the rising blockwork on top.The reason that this was more cost effective as that we had 450mm of rising block on the high side and 2.475m (11 courses) on the low side - that was the profile of the rock.In fairness that was a particularly large house and the underlying rock strata at a particularly steep gradient.
On a separate standard private house the rock was shale.The strip foundations went ahead with rock breaking using a JCB required in certain areas to achieve the depth.
I would imagine in your case that the difference in rock level across your house will be alot less and I hope that you have no rock-breaking at all.

Once your groundworker has cleared off the rock under the house you will know more.You haven't mentioned if you have an engineer on board.You will need one to design the raft (if required) and to generally advise on the suitability of the rock platform.
 
galwaytt - have just looked at your photos , that's just blatant advertising.Have you no batter shots of the raft that could be blockwork for all you can see there
 
galwaytt said:
Raft foundation (also note quality of ground works - grass still intact.....)
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What are you trying to suggest here? That strip foundations automatically lead to more site clearance? This has nothing whatsoever to do with whether a strip or raft foundation is called up, all to do with the contractor, the site conditions, etc. Get real man and stop pushing your own agenda. You are unfairly leading people astray here.
 
Engineer & builder recommended a raft foundaton for my self-build. The reason they agreed on this was due to the changeable nature of the soil across the site. In our case the raft foundation is the better option & will reduce settlement cracks etc. Will cost approx. 1k more than strip but we believe it is money well spent in our case.
 
kemosabe said:
Engineer & builder recommended a raft foundaton for my self-build. The reason they agreed on this was due to the changeable nature of the soil across the site. In our case the raft foundation is the better option & will reduce settlement cracks etc. Will cost approx. 1k more than strip but we believe it is money well spent in our case.
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1000 more is incredible.... you must have been getting roasted on strip foundation prices..

raft foundations increase concrete demand of about 150-200%
steel reinforcement increases on average about the same....

in my area (midlands) the difference between cost of strip founds and raft founds can be as much as 100%.... that 'may' be because they are not as popular here as they are in the west due to the wests vast underlying rock topography....

whether or not they are better is relative....

all foundations should be designed to suit their ground conditions... a raft in an area where strip is sufficient is a kin to breaking a nut with a hammer...
 
Im based in the midlands also, I dont work in the area so I wont attempt to contradict your figures except to say that both engineer & the builder stated that the price of raft foundations has narrowed dramatically in comparison to strip. Engineer stated that the only disadvantage to using a raft is the price, every other aspect is an advantage.
With regard to which one is better I would agree it is completely relative but I know which one I would prefer in my build & that is raft due to the soil type.
 
interesting.... i wonder what the reason is for the narrowing of the price difference???
steel certainly isnt getting cheaper.... so i wonder if its the abilities of the builders which are getting better???
 
Syd, I've found the price of steel has come down dramatically from the highs of c. E1000 not too long ago. Haven't had cause to buy cut and bent steel lately, but A393 mesh is literally half the price I paid a year ago. What it could possibly also be is the chippies labour rates for the formwork which they might price on time now rather than M2.
 
baldyman27 said:
Syd, I've found the price of steel has come down dramatically from the highs of c. E1000 not too long ago. Haven't had cause to buy cut and bent steel lately, but A393 mesh is literally half the price I paid a year ago. What it could possibly also be is the chippies labour rates for the formwork which they might price on time now rather than M2.
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makes a lot of sense...

just adds to the realisation of how we were screwed during the 'good' times!!!


just checked and see steel hit a high around july 2008, and is now down to about 50% of that price!!!
 
The reason steel was so high was because of China's demand. Believe it or not (I know most won't) I knew guys in 2007/2008 who lost money on jobs that they had priced before steel started to go crazy. These would have been jobs with a fair amount of re-inforcing and structural steel. Crazy but true.
 
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