satumashirt
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does anybody know the process for building a raft foundation.my house is a dormer and is 140 metres, how has the site to be prepared and what are the costs like for this type of foundation.
quinno said:Cost wise, I wouldn't be 100%. I'm guessing €3k - €5k all in (depending on the house size). This is for a completed raft, with all that I've pitlned above. Get a few measurements together and get 'all-in' quotes from a builder.
Carpenter said:Based on current steel prices I doubt you buy the steel reinforcement alone for a raft of your size for much less than 2k. Add in site prep., hardcore, timber formwork, steel fixing, plumbing first fix, and concrete placement- I'd say 15k is a more realistic figure (and a conservative one at that). Rafts are also used in situations where the ground conditions are very variable- soft ground in part/ rock elsewhere for example. Any savings in rising wall blockwork etc is quickly offset by the work required to ensure services are integrated into the raft before pouring. A raft must be designed by a chartered structural engineer.
aislingkelly said:what do u mean by "A raft must be designed by a chartered structural engineer"? Also have u experience with raft foundations and if so can u give me some advice
satumashirt said:does anybody know the process for building a raft foundation.my house is a dormer and is 140 metres, how has the site to be prepared and what are the costs like for this type of foundation.
Shouldn't you really be querying this with your engineer, presumably you've paid him a fee for professional services? Anyway as a rule of thumb a strip foundation should be a minimum of 3 times the wall thickness. End bearing for hollowcore slabs is dependant on slab type, thickness, span and design but 75 to 100mm is the norm.Hi,
Can anyone tell me the strength of concrete to use in a strip foundation.
is it 25n, 35n or what??
some say 25n some say 30n. Also for a standard cavity wall 100mm block,100mm cavity,100mm block. What width should the foundation be. Note that there is 600 mm mesh also going into it. I have got specs from my engineer but do not look correct against the homebond book.
One other question, If I use hollow core how much (minimum) should be resting on an RSJ or a wall.???
Any answers would be appreciated.
Thanks.
The costs for laying a raft should be less then a strip footing. Dead walls (also called 'rising walls') are not required in a raft, so the labour in terms of excavation & blockwork is less. Don't forget you'll also have to factor in underfloor services - toilet, kitchen, ducting for electics, etc as well as DPM & a Radon barrier / sump.
Raft foundations are generally used in poorer soil conditions, such as peaty soil (hence their popularity in the west) as they distribute the load more evenly than strip foundations.
Cost wise, I wouldn't be 100%. I'm guessing €3k - €5k all in (depending on the house size). This is for a completed raft, with all that I've pitlned above. Get a few measurements together and get 'all-in' quotes from a builder.