[Craig McGibbon Ltd]

Hi,

Been asked by a client on the feasibility of putting a deck on a flat roof – we have had a brief discussion regarding the need to get a structural analysis regarding the ability to support the weight and the benefits of composite decks like SAIGE or Millboard.

One of my main concerns is the roof is felt covered.

– Is it feasibly to place a deck on a felt roof terrace without puncturing the felt in not so much in construction but from the general use of a deck.  Personally l think the answer in No…

– Is there any methods available to protect the felt from damage – suitable standoff to support the foundation?

or should the felt be replaced with another roofing substrate before a deck is constructed.

Any advice gratefully received – thanks

[Karl Harrison Landscapes Ltd]

In the first instance one should consult a structural engineer. This will ensure a certified answer to what can and can’t be constructed, it will also indemnify you against any future issues if anything should go wrong with the roof or indeed the deck structure.

In short, to keep the point loading of the decking structure to an absolute minimum and to reduce the impact of the structure and how it interfaces with the roof materials you should use pedestals to spread the load.

Pedestals every 500mm and joists every 400mm centre will suffice for most applications, this way every square metre of decking including the structure will have the dead load divided my 6.5, thus a 45kg/sq/m load will be adequately  spread.

Be aware that should there be any issues with the roof one must remove the decking or at least part of it to gain access to the roof. Also consider creating access panels for maintenance near water outlets.

look forward to your thoughts…

[Craig McGibbon Ltd]

Hi Karl,

Thanks for the comments.

We will be getting advice from a structural engineer prior to any decisions.

Thanks for the pedestal lead – will investigate.

With respect to access and maintenance l was considering making sections that could be de-constructed with a few bolts and moved to one side.

[Karl Harrison Landscapes Ltd]

You’re welcome Craig

Pedestals are available from here http://www.exteriordecking.co.uk/shop/products.php?catid=78&hrcy=6

Karl

Craig McGibbon said:

Hi Karl,

Thanks for the comments.

We will be getting advice from a structural engineer prior to any decisions.

Thanks for the pedestal lead – will investigate.

With respect to access and maintenance l was considering making sections that could be de-constructed with a few bolts and moved to one side.

[Craig McGibbon Ltd]

Thanks Karl,

Will keep you and the network posted…

Craig

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