Tony K Posted October 15, 2018 Share Posted October 15, 2018 Hi, The base /slab of my selfbuild bungalow has to bridge over the roots of a large protected tree which is in close proximity. I will probably use mini piles and a raft, but the top of the roots may be higher than I thought, which in turn may push the FFL up and perhaps leave me having to go back in for planning if that affects the rest of it. Does anyone have any experience or knowledge of clever ways to minimise the depth of the slab / base and perhaps the floor insulation etc? That may save me a lot of bother if I can get the total thickness down enough to compensate for raising the underside of the base. Thanks Link to comment Share on other sites More sharing options...
the_r_sole Posted October 15, 2018 Share Posted October 15, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Mr Punter Posted October 15, 2018 Share Posted October 15, 2018 Hmm this is just one tree so unless it is of national importance I cannot see why it can't be worked around. Otherwise you can bridge over it. Don't do an application where you are short of available height as it may come back to bite you. Link to comment Share on other sites More sharing options...
Tony K Posted October 15, 2018 Author Share Posted October 15, 2018 1 hour ago, the_r_sole said: what's your current build up and what kind of uvalue are you looking for? how much do you want to lose? do you have a strict ridge height set by planning that is tied to ordnance survey height data? I'm working on the basis of a 200mm reinforced slab, then insulation plus screed to bury underfloor heating. The U value doesn't have to do anything more than meet Building Regs, so 0.3 overall. As a planner myself I should probably stress that the ridge height is always strictly set! The approved drawings are to scale, and show the overall height of the building relative to external ground, so yes I do have a fixed point I cannot exceed, though only in a way which is true of nearly all permissions. Link to comment Share on other sites More sharing options...
PeterW Posted October 16, 2018 Share Posted October 16, 2018 How close is the tree..? What species..? What age..? Link to comment Share on other sites More sharing options...
Russell griffiths Posted October 16, 2018 Share Posted October 16, 2018 We have just piled so did a fair bit of research on the subject, we found a good few of the mini piling companies are developing methods of spanning from pile to pile, with either concrete beams or steel sections. However these are all suspended systems, not ground bearing so will not help you lower your build height it may be you will need to go back to planning and discuss ridge height, because of the build system necessary to accommodate the tree. I cannot see you getting a thinner slab as they should be insisting on some sort of root protection,shrinkage, heave product under the slab to accommodate any movement check out ROGER BULLIVANT PILING some interesting solutions to ground problems. Link to comment Share on other sites More sharing options...
the_r_sole Posted October 16, 2018 Share Posted October 16, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 5 hours ago, PeterW said: How close is the tree..? What species..? What age..? Its ridiculously close (nature of the plot I'm afraid). Probably about ten inches away from my new wall if measure five feet up at the main trunk. Its a Robinia, and I think it must be about thirty years or so. Link to comment Share on other sites More sharing options...
Tyke2 Posted October 16, 2018 Share Posted October 16, 2018 Be careful with the tree whilst in construction. The company I worked for employed tree surgeons to fell 3 trees in a conservation area. The workmen cut the right ones down , but then for some inexplicable reason felled a further three trees. It cost £9000 in fines plus legal fees. I think now it would ne £20,000 or even unlimited if it was thought to be to the benefit of a new development! Link to comment Share on other sites More sharing options...
bassanclan Posted October 16, 2018 Share Posted October 16, 2018 Is it worth trying to get the TPO revoked/permission to remove? I can't see a 30yr old Robinia having such a positive impact on the street scene to warrant a TPO? 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 16, 2018 Share Posted October 16, 2018 Get a mitigation strategy in place demonstrating the planting of new trees in a quantity that should offset the impact of losing that one. Deffo try appealing against the TPO. Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 The tree belongs to the neighbouring landowner, an absent landlord who can be uncooperative at times, and is a very nice backdrop to the new house anyway. Even if I can convince the council to let me fell it, I'd then have to deal with the neighbour and lose the benefit of the tree, none of which I fancy particularly. I can of course go back to planning for a redesign, but if there is a way to engineer a solution outside of that then I'd certainly explore it. Link to comment Share on other sites More sharing options...
bassanclan Posted October 16, 2018 Share Posted October 16, 2018 Any problem can be overcome, it just depends how much you want to spend overcoming a problem which is actually caused by your neighbour's "trespass" 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 16, 2018 Share Posted October 16, 2018 Fell that and plant something that will root locally. Conifers for eg. You can then put a ground barrier in also to train new roots and stop them becoming problematic in the future. I think running ring beams either side of the root could work, and just have insulation there not concrete. An SE should come up with a solution if they are the type that engage and enjoy a challenge. As said, how much will you spend / compromise for a tree? If it were me I’d have just chopped it down on day one and pretended that I don’t speak english. “Que?” Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 Ta for the suggestions all. I am of course considering all options including removing the tree, but as I said, I like it and want it to stay if possible. Presuming the slab can't be made slimmer than 200mm, does anyone know how little I can get away with in terms of insulation and screed etc? Link to comment Share on other sites More sharing options...
the_r_sole Posted October 16, 2018 Share Posted October 16, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Mr Punter Posted October 16, 2018 Share Posted October 16, 2018 Very odd that consent was granted with the tree in place. Did anyone produce an arboricultural report? I think the tree has to go. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 16, 2018 Share Posted October 16, 2018 Although it may be possible to find a solution to the tree problem now, what about the future? That tree is going to carry on growing, will need maintenance, and will have to be felled at some future date when it reaches the end of its life. What will be the impact of future tree and root growth, or possible damage to your new build if the tree sheds limbs or falls over? What might be the consequences for your house from people working on the tree, or felling it at the end of its life? Finally, what might be the effect on your house of the unseen roots underneath your foundations rotting away and creating voids when the tree does die? Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 1 hour ago, the_r_sole said: To work out the uvalue of the floor you need the perimeter to area ratio... Are you going for ufh? Is the slab ground bearing or is it a suspended slab? If it's ground bearing you could go for insulation under slab and scrap the screed altogether, if you're using ufh I don't think I've seen any less than a 65mm screed 1 hour ago, the_r_sole said: To work out the uvalue of the floor you need the perimeter to area ratio... Are you going for ufh? Is the slab ground bearing or is it a suspended slab? If it's ground bearing you could go for insulation under slab and scrap the screed altogether, if you're using ufh I don't think I've seen any less than a 65mm screed Perimeter to floor ratio is 0.52 of I've calculated correctly. I am having ufh yes. The slab will probably be sat on mini piles. Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 (edited) 1 hour ago, JSHarris said: Although it may be possible to find a solution to the tree problem now, what about the future? That tree is going to carry on growing, will need maintenance, and will have to be felled at some future date when it reaches the end of its life. What will be the impact of future tree and root growth, or possible damage to your new build if the tree sheds limbs or falls over? What might be the consequences for your house from people working on the tree, or felling it at the end of its life? Finally, what might be the effect on your house of the unseen roots underneath your foundations rotting away and creating voids when the tree does die? The plot is what it is, including the tree! By using piles and bridging over the roots I am creating a build where it won't matter if the tree comes down in the future. There is to be a void former used to create space enough to accommodate future root growth. Edited October 16, 2018 by Tony K Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 16, 2018 Share Posted October 16, 2018 4 minutes ago, Tony K said: The plot is what it is, including the tree. By using piles and bridging over the roots I am creating a build where it won't matter if the tree comes down in the future. A trunk just 10 inches from a wall is pretty much guaranteed to cause future problems, I think, no matter what sort of foundation system you use. The tree could grow to around 20 to 30m high, and probably has a life in our climate of around 50 to 80 years or so. Someone is going to have to take it down at the end of it's life, without damaging your property, which sounds like a challenge. At just 10" from the wall it's going to be practically touching the gutter on that side at the size it is now, let alone when it's got a bit bigger or when it sways with the wind. Given that the canopy is going to extend a couple of metres over your roof you also run the risk of damage from falling branches and clogged gutters from all the leaves it will shed. Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 7 minutes ago, JSHarris said: A trunk just 10 inches from a wall is pretty much guaranteed to cause future problems, I think, no matter what sort of foundation system you use. The tree could grow to around 20 to 30m high, and probably has a life in our climate of around 50 to 80 years or so. Someone is going to have to take it down at the end of it's life, without damaging your property, which sounds like a challenge. At just 10" from the wall it's going to be practically touching the gutter on that side at the size it is now, let alone when it's got a bit bigger or when it sways with the wind. Given that the canopy is going to extend a couple of metres over your roof you also run the risk of damage from falling branches and clogged gutters from all the leaves it will shed. Yep, agreed, but every plot has its downsides, and mine is small with a tree too close. The upsides of the plot more than compensate in this instance, and I'm happy to work around this one issue. Link to comment Share on other sites More sharing options...
PeterW Posted October 16, 2018 Share Posted October 16, 2018 Is there any way you can shape the build around the tree ..?? I can’t see how you can build that close - not on Clay is it too..? - and also maintain the integrity of the build. I would be seriously concerned about limb shedding or worse - if it pivots over away from the property and falls, it could do serious damage. You say its and absent landlord but by building 10’’ from his boundary you will need to stand scaffold in his garden anyway and potentially need a party wall agreement if you’re doing any work that could damage the neighbouring property. I’d start with reviewing the design and then think about removing the tree - TPO was mentioned above but not by you, what’s the position with the tree in terms of removal ..? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 16, 2018 Share Posted October 16, 2018 The Party Wall Agreement is a good point, that close and it may well be required as the 45 deg rule means that the horizontal distance in from the bottom of any foundation system is going to project a fair distance over the boundary. It's a non-native species, so would a TPO have been granted on it anyway? I believe that Robinia is classed as an invasive species in some areas, isn't it? Link to comment Share on other sites More sharing options...
Tony K Posted October 16, 2018 Author Share Posted October 16, 2018 7 minutes ago, PeterW said: Is there any way you can shape the build around the tree ..?? I can’t see how you can build that close - not on Clay is it too..? - and also maintain the integrity of the build. I would be seriously concerned about limb shedding or worse - if it pivots over away from the property and falls, it could do serious damage. You say its and absent landlord but by building 10’’ from his boundary you will need to stand scaffold in his garden anyway and potentially need a party wall agreement if you’re doing any work that could damage the neighbouring property. I’d start with reviewing the design and then think about removing the tree - TPO was mentioned above but not by you, what’s the position with the tree in terms of removal ..? I may well shape the building around the tree in that the part of the house closest to the roots will have floor to ceiling cupboards anyway, so can be on a raised plinth which can be formed within the shape of the slab itself. My concern is the rest of the floor area, hence the question about slab depth minimums. It's not a tpo but is protected by condition, and as I say, I like it. Link to comment Share on other sites More sharing options...
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