One of the biggest concerns we are most often asked about is the impact of tree roots on the foundations of new buildings and extensions, particularly when a tree could be retained if it is significant in the landscape, or it may be in a Conservation Area or it could be covered by a Tree Preservation Order (TPO).
The development might be delayed for further planning, be perceived as too difficult because the tree is too close and shelved, or a risk may be taken about removing the tree which will potentially come under scrutiny by the planning authorities.
But none of these options are necessary if one or more of the following steps are taken:
- The tree may appear outwardly sound and worthy of retention but a detailed inspection may reveal significant defects which could render the tree dangerous or not worth designing around. Under these conditions the tree could be removed and replaced in another part of the property allowing the development to go ahead as planned.
- Assessing the rooting area of the tree to see how far it extends towards the foundations, and depending on the tolerance of the tree species, the proposed root loss may be acceptable
- As tree roots are normally only found in the top 600mm to 1m of soil, small bore pile and beam foundations can be designed to retain the majority of the rooting environment of the retained tree while supporting the building way below the rooting system. This is achieved by drilling holes into the soil or driving piles into the ground.
Once in position, the piles support ground beams, which in turn hold up the building. The beams are placed above existing ground level to avoid damage to the rooting systems of the trees. This method of foundation construction may affect the height of the internal floor levels of the proposed building. The use of pile and beam foundations offers an effective way of constructing the building whilst minimising root disturbance to the retained trees.
A rain water collection system can be designed which re-directs run off to the area beneath the foundation, therefore providing the water necessary for tree root survival and growth.