Home > Extension Options > Putting the Roof on Your Extension

Putting the Roof on Your Extension

By: Chris Hogan MSc - Updated: 10 Sep 2012 | comments*Discuss
 
Extension Build Plan Building

Once the walls have reached the relevant height it's time to top off with the roof and begin to get the build watertight, so that work can go on inside the extension, something that's crucial with the unpredictable nature of the weather in the United Kingdom. Having said that, note that it's usual to put the doors and windows in after the roof, but that's a relatively quick job once the roof is on.

The process will depend on the type of roof that is being put on the extension, but they will all demand that the walls and other supporting structures are able to take the weight the roof that is going to be erected. The vast majority of extensions roofs will be either pitched, with tiles of one kind or another, or flat, with a waterproof membrane. How to choose between them and some of the other alternatives is covered in our article on roofs in our 'Extension Options' section.

Flat Roofs

Of course the weight of a flat roof will be a lot less than that of a pitched roof. The materials are lighter in the first place, and the area to cover is a lot less, sometimes as little as half the area of a pitched roof. This means that the supporting beams can be probably be laid across the walls with little in the way of extra support as long as the span isn’t too great.

A timber 'deck' is then laid across the supporting steel or timber and the waterproof layer applied on top of the deck. The deck can be of concrete too, although this will need more support. Its worth noting that the previous habit of putting insulation below the deck is now frowned upon in England and Wales and actually outlawed in Scotland. Insulation must now be laid on top of the decking and below the waterproof layer.

Pitched Roofs

A pitched roof will usually have a timber frame to which battens and then tiles are added. Constructing the frame on site may be necessary for an unusually shaped extension but it's a lot cheaper if you can get pre-constructed A-frames delivered and erected on site. This will also be a lot faster, meaning the building will be weatherproof that much sooner.

Once the A-frames are in place the additional in-filling timbers or steel members can be added. These brace the trusses together and provide the support for the roof covering. The various purlins, spars, collar ties and hip and valley trees needed for the size and shape of the roof really need to be calculated by an expert to make sure they can take the weight of the roof and the battering of the weather.

When all the intermediate support is in place a layer of waterproof underlay sheeting (solid boarding in Scotland) is laid down, and the battens that the tiles or slates will be nailed to are put in place. Once the tiles or slates have been attached its important to make sure that adequate ventilation has been left at the eaves to prevent condensation build up and associated damp problems.

Safety First

It should go without saying that if you are at all uneasy about building the right structure to support your roof, regardless of which type you have chosen, then get the professionals in. It's not worth scrimping on this as it's your family that could be at risk if the construction is not up to scratch.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

Title:
(never shown)
Firstname:
(never shown)
Surname:
(never shown)
Email:
(never shown)
Nickname:
(shown)
Comment:
Validate:
Enter word:
Topics
Latest Comments
  • Lizzy
    Re: When is an Annexe Not an Annexe?
    Hi, My husband and I bought a 3 bedroom house which already had and annex extension built above the garage attached to the…
    7 September 2018
  • Mermanda
    Re: Planning Issues for Self Contained Annexes
    Hi, My partner's mother has agreed that we can build a 2 bed wooden cabin in her garden. It will be a single…
    31 August 2018
  • Broady
    Re: Keeping in With the Neighbours
    My neighbour has had a porch built and we were going to do the same and with the neighbours permission, join the porches.…
    20 August 2018
  • AJ120
    Re: Planning Issues for Self Contained Annexes
    Hi, I have been reading through all the questions and answers which is very interesting and useful. We are in…
    18 August 2018
  • ExtensionBuild
    Re: Keeping in With the Neighbours
    NewishOwner - Your Question:We have a small detached property with a side return - one wall of which is our neighbours house.…
    8 August 2018
  • NewishOwner
    Re: Keeping in With the Neighbours
    We have a small detached property with a side return - one wall of which is our neighbours house. They built a single storey…
    7 August 2018
  • felttip
    Re: When is an Annexe Not an Annexe?
    Hi, It's me again, sorry to be so needy. The stables we wish to convert into a self contained granny annex was built by me…
    19 June 2018
  • felttip
    Re: When is an Annexe Not an Annexe?
    Hi We have some stables that are now redundant because the Council are going to build on the fields we rent to graze the…
    19 June 2018
  • ExtensionBuild
    Re: Keeping in With the Neighbours
    Si - Your Question:We have plans approved for a single storey rear extension to our semi detached home. Our neighbours have…
    15 June 2018
  • ExtensionBuild
    Re: When is an Annexe Not an Annexe?
    Louloubelle - Your Question:My father has detached barn which he has converted into an Annexe with relevant permissions an…
    15 June 2018
Further Reading...
Our Most Popular...
Add to my Yahoo!
Add to Google
Stumble this
Add to Twitter
Add To Facebook
RSS feed
You should seek independent professional advice before acting upon any information on the ExtensionBuild website. Please read our Disclaimer.