Midona Posted June 27, 2019 Share Posted June 27, 2019 Hi, Our plot was excavated down to the bed rock before we bought it. Personally, I can't think of anything better than building foundations on rock that has been in-situ for nigh on half a billion years. However, our Quantity Surveyor in quoting for an Outline Cost Plan said that in his experience engineers can get very nervous about founding on rock. Can anyone enlighten me on the problems of founding on rock please? I just want to be fore-armed with some information when I next talk to him. Thanks. Link to comment Share on other sites More sharing options...
jamieled Posted June 27, 2019 Share Posted June 27, 2019 Whilst rock can be strong in terms of its bearing capacity, the nervousness might come in the form of the interface between the foundation and the rock. It requires quite careful consideration of how the foundation is keyed in. I'm aware of examples using concrete pads supported by steels drilled into the rock, but there will be other options. It will be worth getting advice from an engineer with decent experience of this type of foundation, otherwise they may take quite a risk averse approach which may not be the most economical. Link to comment Share on other sites More sharing options...
ProDave Posted June 27, 2019 Share Posted June 27, 2019 You mean the whole site has been stripped to rock? If there was still some (thin) top soil then you could dig trenches down to the bedrock and pour concrete strip founds. But if the whole site is stripped I would say that makes things awkward? Do you have mains drainage? Link to comment Share on other sites More sharing options...
Triassic Posted June 27, 2019 Share Posted June 27, 2019 My insulated raft foundation sits directly on rock, the engineer I used to design it didn’t raise the rock as a problem! Link to comment Share on other sites More sharing options...
Midona Posted June 28, 2019 Author Share Posted June 28, 2019 15 hours ago, ProDave said: You mean the whole site has been stripped to rock? If there was still some (thin) top soil then you could dig trenches down to the bedrock and pour concrete strip founds. But if the whole site is stripped I would say that makes things awkward? Do you have mains drainage? Yes the whole site has been carved out of the hillside with all topsoil removed. There is mains drainage at the site boundary but, due to the topology, all water/sewage from the bottom/basement floor will have to be pumped. Link to comment Share on other sites More sharing options...
Midona Posted June 28, 2019 Author Share Posted June 28, 2019 14 hours ago, Triassic said: My insulated raft foundation sits directly on rock, the engineer I used to design it didn’t raise the rock as a problem! That's good to know. I'm not sure if rock type makes a difference. I assume you're on granite...we're on quartzite. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now