Refurbishing an Existing Terrace Area

An increasing number of flat roof owners are discovering that their flat roof can with some planning and thought become a valuable outdoor space, adding that wow factor to any home and of course additional space as a garden or a refurbished terrace roof, this is not of course to be confused with a green roof.

To find out how to refurbish a terrace roof simply call us today Freephone 0800 098 8271 for a no-obligation free survey and quotation, or complete the form below. There are of course a number of points you’ll need to consider before you can refurbish a terrace roof into a patio or garden terrace as follows:

Balcony with External Steps & timber decking

Timber decking and wrought iron railings


May be required for any railings that are considered permanent* a simple phone call to your local planning office will be well worth the time before spending any more time or money to refurbish a terrace roof.


Of your existing flat roof sub structure, I would strongly recommend engaging the services of a local structural engineer to asses the load bearing capability of the existing structure. A few hundred pounds invested at this point could save you thousands later on, we’ve seen many horror stories around this type of conversion so please don’t become one of them.


Conservation of Fuel and Power in existing dwellings: assuming your flat roof is over a living area and you’re refurbishing more than 25% of the flat roof, you’ll be required to upgrade the insulation to meet a target U value of 0.18. You can find out more about the most efficient way to do this by reading our section on insulation.


Sarnafil membrane with smooth lightweight pendle


Natural patio slabs on pads with pebble border


As a general rule it’s not recommended to try and use your existing felt roof surface as one to put anything weight bearing on, this is because a lot of the older types of felt are oil based and the surface melts in the summer and can become brittle in the winter, imagine having to then remove your new timber deck or paving slabs to repair or replace the failed roof.


A great deal of care and consideration should be applied to this part of your project as picking the wrong type of waterproofing system can cost you dearly in years to come as removing the roof terrace to solve a leaking roof is expensive and time consuming.


Your water proofing layer needs to ideally be tough and at the same time flexible and resilient to anything the British weather has to throw at it.


We would strongly recommend using a polymeric PVC Single Ply Membrane such as Sarnafil, Danosa or Alwitra-Evalon as these membranes have many years of successfully being used both for commercial roof gardens and in many smaller applications without failure and as such you wont compromise your system guarantee by creating a new patio or roof garden on top of them provided the approved installer has completed the whole project or supervised any third party.



This is without doubt the most contentious part of your flat roof conversion as it requires planning permission to erect any type of permanent type of handrail around your flat roof so you should always check with your local planning office first.


The most popular type of handrails tend to be wrought iron or stainless steel and glass, although there are now options in powder coated aluminium available.


Wrought Iron Railings


Stainless Steel and Glass

Consideration needs to be given to the best way to fix your handrails in order to both comply with building regulations by being at least 1100mm high but also how they can be fixed into the flat roof and still remain water proof.

Finished Surface

The two most popular finishes are lightweight slabs or decking, the correct way to install either of these options is to first place a loose laid protection layer on top of your membrane then the slabs or decking should be placed on top of some type of simple support. We tend to use 8mm plastic or rubber paving support pads, one big advantage is the fact that any water will simply drain away under the slabs.

Rubber Support pads supplied by Wallbarn

Paving Slabs

There are an increasing number of paving slabs you can use however you need to be aware of the weight loading you’ll be placing on your roof if the sub structure is timber rather than say block and beam or concrete slab.


The type of paving slab should be 450mm x 450mm and no more than 32mm to 35mm thick, this makes them lightweight and still strong enough to be supported on the corners. The main benefit of this type of finish is that simple and fast to do has very little ongoing maintenance and this means it represents very good value for money.


Pendle buff paving riven finish


Pendle natural riven finish


Your decking can be either softwood, hardwood or now there a number of low maintenance composite decking systems that will give you a 25 year guarantee.


Composite decking by TimberTech from their Floorizon range

End your flat roof worries today by calling Freephone 0800 098 8271 for a no-obligation free survey and quotation, or completing the form below.