low pitch extension roof

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Hi all,

we are planing to build an extension to the rear, 5m wide, 4.5 meters deep

The original idea was to build 4.5 meters deep extension in the roof style similar to the neighbouring properties (see attached picture and "extension variant 2" plan, btw already 12' pitch), ie. tiles + roof windows flush to the roof surface (not protruding). However, our architects are proposing to build a lower pitch "flat" roof instead, arguing that 2m door height will look too low (extension variant #3 attachment + top view for both variants)

Any comments welcome, specific questions I am considering:

1. General comments on tiles/roof windows on low pitch roofs (12.5', first version)

2. Materials and costs comparison for the two options (total roof area about 25 sq m)

Thanks,
D

[original post edited, question shortened and simplified ]
 

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  • extension - top view.png
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Hi I build extension like this regularly with this same problem. I don’t like low doorways and I hate your architects option. There are other options if your interested then I will look out for your response. Fred.
 
Hi I build extension like this regularly with this same problem. I don’t like low doorways and I hate your architects option. There are other options if your interested then I will look out for your response. Fred.

Hi Fred, what are other options you are mentioning?

At the moment I have checked the standard height of folding doors and they all seem to be 2.1 meters, so we are going to have 'classic' low pitch tiles and a bit shorter extension, say 4.2 meter deep and 2.1 m door opening at the end.
 
Are these proper designers? Their design skills in general is lacking and drawings fancy but poor architecturally.

Anyway, who designs a 2m external door? Seriously. That's about 1.9 and 1.95 door opening by the time the frame head is taken into account.

The desinger needs to have another look at the options, as unless you have specifically asked for that design, he is costing you money unecessarily with bad design choices and it is looking poor in to the bargain.
 
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How about like this with a peak over the doors:

IMG_5049.jpg


(Looking at the house from the back garden)
 
Ha ha ha!!! Mine when I read the general chat section:

IMG_5057.jpg
 
The things you have to be aware of is the fact that velux windows have a minimum pitch of 15 deg. And you have very limited tile options lower than that as well. The simple answer is to have a flat roof section between the main house and the pinched roof that faces the garden. This is simple to achieve with a steel beam running from one side wall to the other. You can then run your 15deg tiled roof at the right hight for the doors etc. I’ve built 3 extensions like this now. They look great and give you the space you are looking for.
 

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  • 95E184A9-623D-416E-8036-00E4CDB8B8BD.jpeg
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The things you have to be aware of is the fact that velux windows have a minimum pitch of 15 deg. And you have very limited tile options lower than that as well. The simple answer is to have a flat roof section between the main house and the pinched roof that faces the garden. This is simple to achieve with a steel beam running from one side wall to the other. You can then run your 15deg tiled roof at the right hight for the doors etc. I’ve built 3 extensions like this now. They look great and give you the space you are looking for.

Thanks Fred, seems to be a good idea indeed. We are going to discuss it with the architects, not sure why it has not been risen earlier.

Few questions that I have:
- What is the typical construction & materials for the flat section? How it is joined with the pitched roof? Is it more costly/more complicated to build?
- What is the door frame height in the extension in the picture? Is 2.1m really a "standard", what people are usually going for?
- Any thoughts on 3 small vs 2 (larger) roof windows?

One very technical question - we have been told that in order to properly insulate the roof and the beam above the patio doors, the beam should be effectively under the roof, so this is why doors in the original design (version 2) became so low, b/c there's a beam above the door frame (23-25cm) + the roof itself (30-35cm thick). Is it the typical construction way, or the structural beam can be somehow incorporated into the roof structure reducing the overall thickness of structure above the patio doors?

Thanks,
D

P.S. Woody - don't be so critical on the designers : ) After all they did not let us build 1.9 height doors in version 2 : ) I think they know their stuff overall, although in some places the answers I am getting are not too concise
 
There is little extra cost with regards the flat roof section. You will need a structural calculation for the steel. The flat roof joists and the pinched roof rafters both pocket in the the steel. You will need to strap some of the joists to some of the rafters to prevent them from separating over time. But your structural engineer will advise on the amount needed.
With regards the door hight 2.1 is considered to be a standard now. However there is no regulation on this hight. Depending on the patio door size will you will either need another steel with an under plate welded on it or you may be able to use a standard lintel. Fred.
 
What will be the material for the flat section, felt, grp, zinc?
 
Hi there, just an update to anyone who may be still reading this

Thanks to Fred for pointing out and explanations about the possibility of combo flat+pitched roof. We currently do think that this is probably the best option in our case. However, our architects are refusing almost point-blank to draw it, citing difficulties with design, waterproofing etc. So we are currently looking for London-based design bureaus who are experienced in designing such a roof. Your pointers are welcome.

Current options are attached:
- combo roof sketch, 1.5 meters flat section, and then 3 meters of 16'-18' degree pitched roof. 4.5 meter deep extension (prefered)
- low pitch (13') roof, 4.2 deep extension (second option, in case we will not find designer/builder to build option #1)

Thanks and happy holiday season,
Dmitry
 

Attachments

  • extension variant - combo roof, 4.5m deep.png
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  • extension variant - low pitch 4.2m deep.png
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I would try and avoid the WC adjacent/opening onto the dining area. Can you have it opening into the hall/where the cupboard is situated?
 

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