5 reasons to call your arborist before you build your home extension

14th August 2019

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If you’re thinking of extending your home, whether up or out, you may be tempted to make your first call to a local builder or a creative architect to instruct them to get the ball rolling, but STOP, not so fast. If you have trees anywhere near the rear of your house, then there’s another professional that you should call in first or you run the risk of wasting thousands of pounds that could have otherwise been spent making your extension everything you’ve dreamed it could be.

Name that professional
When you think of a tree specialist you may think of a tree surgeon, and while they are experts in the maintenance of your trees, the professional we were referring to was an arborist, because when it comes to trees they can be considered the expert’s expert.

Though they often work alongside tree surgeons, an arborist has gained years of experience and additional arboreal qualifications, so they’ve replaced their chainsaw with consultancy as their tool of choice. Through this they have acquired a deeper understanding of how trees relate to other environmental or human factors, such as, for instance, just to pull one from the air at random – the way trees in your back garden could impact on the proposed extension you’re planning.

And, should you decide that you want to find an arborist, it makes sense to select from the best of the best, an ARB-approved contractor. The ARB is the main arboricultural association in the UK, and it’s a real accolade to be a member as approval comes only after a whole host of exceptionally tough criteria are met. We know, because our firm is one of only 300 in the country (that’s less than 2% of the tree specialists out there) that has made the grade.

Why call in an arborist?
Architects are experts in design, builders in the functional side of constructing your extension, but an arborist’s vital role is to:

  1. Identify potential issues with trees that increase the risk of planning permission being refused.
  2. Advise on how those risks can be minimised or eradicated, either by cutting back or cutting down.
  3. Assess whether surrounding tree roots could cause issues with the existing building, create obstructions for the new extension, or necessitate deeper foundations.
  4. Provide guidance on how to minimise the risk of future tree-related structural issues post-build.
  5. Prepare reports required as part of the planning application to assess the impact that trees will have on the structure of your building and to set out whether and how your trees should be protected.

In short, your friendly neighbourhood arborist has knowledge that no other professional brings to the table which could give you a better chance of getting your planning permission through first time (saving you a considerable sum in fees and costs that you would otherwise need to spend on adapting and resubmitting your application) and whose knowledge may also lead to some of your design decisions going in unimagined directions.

5 reasons why an arborist should be the first professional you call
So we’ve highlighted the fundamental role an arborist plays in your home extension journey, but here we go into a little more detail about why you should call us in first – how an arborist’s guidance could save you time and money and make your extension so much better.

  1. Light and its impact on design. When you’re planning your extension you’ll no doubt be keen to create a space with the right dimensions, cosy interior design and windows to let the light stream in. However, it’s this last point that people don’t necessarily always think all the way through.

If you have an ash, beech, oak or peach tree near to your proposed extension, would you know whether it is likely to impact on the light you will get in the new room(s)? Do you know whether this will change through the seasons in a way that could make the new room dull and dingy for months out of the year? Do you know how fast your trees will grow and, therefore, their maintenance schedule if you wish to keep the amount of light more predictable? And could this knowledge of how your trees will influence the light in your extension have an impact on the design of this new room, the location of its windows, and the plans you may have for your trees?

An arborist’s guidance could well steer aspects of the design of your extension for the better.

  1. An arborist’s role in helping you get planning permission. Architects advise on planning and technical design, engineers advise on foundations and structural design, your builder will advise you on materials, but an arborist’s advice will be useful for all of them.

Should your existing trees be left, removed or cut back, will they currently or post-remedial work impact on the stability of the soil and, therefore, the required depth of new foundations or additional support for current foundations? And, most importantly, will the trees you have give planning authorities cause for caution? Trees are one of the main factors that building control inspectors look at when determining whether or not to approve planning permission. Put in your application too soon and without speaking with an arborist first and you run the risk of rejection.

However, a free consultation from a qualified arborist could quickly and simply set out the main areas for concern and recommend relatively inexpensive work on your trees which may negate any issues an inspector might have otherwise raised.

A failed planning permission application can be an expensive mistake to make when the solution could have been something easily dealt with first.

  1. Removal, as a last resort. If it’s established that one or more of your trees could cause issues – with either planning permission or the future of your property or extension – an arborist can help you determine whether those trees need to be removed or if another course of action is feasible.

Most clients will only look to remove a tree as a last resort and that’s a sentiment we’d agree with. So, the first thing an arborist would look into is whether cutting a tree back – to slow its root growth or remove light issues – could be good enough.

However, if felling a tree is deemed necessary the next questions to be answered is whether to grind the stump down to ground level or below and whether to treat the stump or not. Stump grinding negates the need for the full extraction of stump and roots. If you fell a tree and use specialist equipment to grind it down to a certain level it will not grow again; however, fungus can colonise the stump and cause problems, so if this is a risk the stump can be treated to prevent this eventuality.

The question of grind to ground or below depends on whether you want to build over the stump or not. Ground level stumps can get in the way of foundations, so they will need to be ground down further.

  1. Prune your way to a brighter future. Pruning can be considered in two phases a) pre-construction and b) post-construction.

Pre-construction you may wish to cut back trees to stop root growth or reduce visible risks that could increase the likelihood of your planning permission application being rejected or you might thin out canopies or shape them in order to allow in more light.

Post-construction you enter the territory of protection and aesthetics. Trees near to properties will often require a strict maintenance schedule to ensure that their root systems do not suck too much water from the earth, increasing the risk of destabilising the soil under foundations. And, as we all love to look out onto a well-kept garden – pruning your trees is a large part of this.

  1. Surveys and reports. An arborist can also conduct a more detailed survey of your trees in order to identify opportunities, risks and insights. These reports include a) an Impact Assessment (a tree survey that considers how a proposed development will co-exist and interact with the trees around it), b) a BS5837 report (for anyone planning to alter a property which is close to trees), and c) a trial pit investigation (an investigation of the soil make-up around your proposed extension and surrounding trees to determine the impact those trees may have on a property).

And so, to summarise:

Trees, light and its impact on design   An arborist’s advice could lead to better design decisions around light and use of space.
Save yourself from planning permission mistakes   Planning control inspectors include tree size, species and location in their decision. Don’t give them an excuse to refuse permission.
Please the inspectors and fell that tree   An arborist can advise on trees that may impact the new extension and how best to deal with them.
Pruning, for planning and for a brighter future   An arborist’s expertise can help you determine the best maintenance schedule for your trees.
Surveys and reports so you can make informed decisions   Sometimes more detailed reports are needed for planning insights. An arborist can conduct these for you.

To book a free survey and consultation ahead of proceeding with an extension, call us on 0208 292 8992.

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