Shez Posted September 21, 2021 Share Posted September 21, 2021 Please could anyone advise me about the depth footings should be for a permitted planning, brick porch, 3 metres square floor and no higher than 3 metres to the top of the roof / built on slightly clayey ground Link to comment Share on other sites More sharing options...
bassanclan Posted September 21, 2021 Share Posted September 21, 2021 Depth of footings is nothing to with planning permission, it is to do with building regulations. A small porch like that is exempt from building regulations. Assuming you aren't in a conservation zone or listed building you can do what you want. Having said that, it makes sense to do it properly, there are nhbc tables which give you a guide for foundation depth depending on soil type etc Link to comment Share on other sites More sharing options...
Temp Posted September 21, 2021 Share Posted September 21, 2021 55 minutes ago, Shez said: Please could anyone advise me about the depth footings should be for a permitted planning, brick porch, 3 metres square floor and no higher than 3 metres to the top of the roof / built on slightly clayey ground Welcome to the forum. Can be a bit tricky with clay. An extension that small isn't putting a lot of load on the foundations so that's not really the issue its how the clay may move as it expands and contracts. Probably the best advice is to make them similar to those of your house in terms of depth. Perhaps also line the sides of the trenches with insulation boards before pouring concrete to prevent movement causing an issue. That might well be overkill but its hard to know what you can get away with. Link to comment Share on other sites More sharing options...
Mr Punter Posted September 21, 2021 Share Posted September 21, 2021 My brother has a large detached house high up on a hill but with highly shrinkable clay soil. The foundations are piled 25m depth. They wanted to have an orangery but did not want to pay to match the piled foundations so went for a raft. The orangery looked fantastic and for the first 12 months all was fine, but then some of the doors would not open and eventually it started to part company with the house. He has now had the orangery demolished and is left with a patch of uneven ground and some scars on the walls where flashings etc were. For @Shez, if the clay is not too bad 600mm deep would probably do. Link to comment Share on other sites More sharing options...
Shez Posted September 21, 2021 Author Share Posted September 21, 2021 (edited) Thankyou for your help, I was thinking of maybe going 30 inches, I believe the house is built on a concrete raft Edited September 21, 2021 by Shez Link to comment Share on other sites More sharing options...
Mr Punter Posted September 21, 2021 Share Posted September 21, 2021 It might be good to debonding wall starters and some compressible material where you join to the house. Link to comment Share on other sites More sharing options...
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