Extension Roof Types

kev1234

Hi,
I have recently purchased a 3 bed semi detached house in North Dublin and am in the initial design stages for an extension. I am not sure about what type of roof I can put on my rear and side extensions. In particular in the extension at the rear of the house I am looking to have as high a ceiling as I can without impacting/colliding with the second floor windows. I had looked at both 'lean to' and 'gable' roofs but cannot get the required pitch without going over the upstairs windows.
Could I put up some form of 'mansard roof' with a lean to on either side and flat in the middle? Or can a standard flat roof be elevated to a high level to give a higher internal ceiling? I suppose this is a question for an architect but I have not yet engaged one and was just wondering if others here had any ideas?
Thanks,
Kev

jmBuildExt

The trend seems to be towards flat roofs alot these days. Apparently they are more reliable now, than they used to be, but i think insurance industry mightnt have caught up with that fact - I think a common question is how much (as a percentage of floor space) of your roof is less than a certain angle.
For that reason we are going with what would usually be flat roof material on an actual sloped roof. I wont go into whether its lean to or not (its not) its an odd shape extension with 2 separate slopes.

In your case you could go with something different, e.g. slope back into the house as they did on an episode of room to improve in the last series.
Most architects would be good at working out this type of detail and coming up with alternatives to the norm.

kev1234

Thanks for that. I don't think I seen that episode, I will have a look to see if I can find it. 
See attached some draft images of options I was considering:
http://imageshack.com/a/img924/4433/gVSasw.png
http://imageshack.com/a/img923/6243/BEaYr7.png
http://imageshack.com/a/img924/5009/y2RPKe.png

jmBuildExt

kev1234 wrote: »

Thanks for that. I don't think I seen that episode, I will have a look to see if I can find it. 
See attached some draft images of options I was considering:
http://imageshack.com/a/img924/4433/gVSasw.png
http://imageshack.com/a/img923/6243/BEaYr7.png
http://imageshack.com/a/img924/5009/y2RPKe.png

it was one of the first few episodes in the series. it was a couple in templeogue.

Metric Tensor

I second the above. Ask your designer to consider a low pitched roof with a flat roof product applied.

1. Insurance companies have a degree value below which they count as flat. Make the pitch greater than this.

2. When you are building this type of roof you can do a good job or a cheap job. There is no way of doing both with this type of roof so be prepared to pay more than you expect for a good product and installation.

Your designer may have other good roofing ideas too. This is a very common issue.

Gumbo

kev1234 wrote: »

Thanks for that. I don't think I seen that episode, I will have a look to see if I can find it. 
See attached some draft images of options I was considering:
http://imageshack.com/a/img924/4433/gVSasw.png
http://imageshack.com/a/img923/6243/BEaYr7.png
http://imageshack.com/a/img924/5009/y2RPKe.png

I think they look really bad. Why go through all that hassle and still be left with a flat roof. I would just design for the flat roof from the start.

A nice dark coloured fiberglass roof, contrasting render and dark Mateo CSO on top of the parapet wall.

Put in some large flat roof windows too.

mrsWhippy

I don't think any of those roof options look nice, they look dated already tbh.

I'd go with a flat roof but a really large roof light, you could go almost the entire width of the extension if you wanted and go quite high with the ceiling level too. Also, the simpler the roof, the cheaper it will be to build most likely.

kev1234

kceire wrote: »

I think they look really bad. Why go through all that hassle and still be left with a flat roof. I would just design for the flat roof from the start.

A nice dark coloured fiberglass roof, contrasting render and dark Mateo CSO on top of the parapet wall.

Put in some large flat roof windows too.

Ok, but with the flat roof I can't have any openable velux windows can I? Just a fixed roof light?

Can the height of the flat roof be raised higher than normal so that the ceiling in that part of the extension is higher than the rest of the house? I am looking to have greater ceiling height in that room to make it feel more open.

BryanF

kev1234 wrote: »

Ok, but with the flat roof I can't have any openable velux windows can I? Just a fixed roof light?

Can the height of the flat roof be raised higher than normal so that the ceiling in that part of the extension is higher than the rest of the house? I am looking to have greater ceiling height in that room to make it feel more open.

yes

You put the rooflights on an upstand and locate to avoid existing upstairs windows

<Edit>

Gumbo

kev1234 wrote: »

Ok, but with the flat roof I can't have any openable velux windows can I? Just a fixed roof light?

Can the height of the flat roof be raised higher than normal so that the ceiling in that part of the extension is higher than the rest of the house? I am looking to have greater ceiling height in that room to make it feel more open.

You can have velux on an upstand that can be opened.
not a fan of these myself, id rather a larger fixed pane of glass.

Yes, the ceiling will be higher in this location.

Jamesgrace

A heavy timber truss would give you structural strength to carry the roof while opening up the room height and providing an interesting feature too.

kev1234

Sorry to bring this up again but I spoke to my insurance company and basically a flat roof over the entire rear and side extensions is a no go. I went back to the drawing board and tried the 2 below options. Are these an improvement on what was previously posted? I've left the side roof with a flat roof and parapet that should match the neighbours house exactly and then have tried a couple of lean to roofs for the rear.

Any recommendations or advice would be greatly appreciated, thanks.

http://imageshack.com/a/img923/4230/jbxgdX.jpg
http://imageshack.com/a/img922/3732/IOaZhn.jpg

kieran.

For insurance purposes any roof 10 degree of less is considered flat (Generally). I think both your current options would be classed as flat ?

JimmyMW

kev1234 wrote: »

Sorry to bring this up again but I spoke to my insurance company and basically a flat roof over the entire rear and side extensions is a no go. I went back to the drawing board and tried the 2 below options. Are these an improvement on what was previously posted? I've left the side roof with a flat roof and parapet that should match the neighbours house exactly and then have tried a couple of lean to roofs for the rear.

Any recommendations or advice would be greatly appreciated, thanks.

http://imageshack.com/a/img923/4230/jbxgdX.jpg
http://imageshack.com/a/img922/3732/IOaZhn.jpg

How about forgetting about the roof lights and have the low point of the roof starting at the existing house with the high point at the furthest part of the extension with higher glazing on the new higher part of the elevation, this way you can keep the roof pitch grater than 10degs if necessary

kev1234

kieran. wrote: »

For insurance purposes any roof 10 degree of less is considered flat (Generally). I think both your current options would be classed as flat ?

Actually both the existing images are at an 11 degree pitch so would technically be considered pitched if 10 degrees is indeed the threshold. I could lower the glazing end further by 200-400mm if necessary to increase the pitch angle but essentially we are looking to have as high a ceiling in this area as possible to make it feel spacious.

kev1234

JimmyMW wrote: »

How about forgetting about the roof lights and have the low point of the roof starting at the existing house with the high point at the furthest part of the extension with higher glazing on the new higher part of the elevation, this way you can keep the roof pitch grater than 10degs if necessary

Hi, yes this had been mentioned to me before. I will put it into the model later and post an image this evening to see how that works. I'm not sure of the aesthetics of a roof the pitches up and out from the house. Great for having more glazing and light in but externally I always think it looks a bit strange. I'll have a look.
I also would have thought that much higher glazing at the back would be more difficult to source and much more expensive? Most window/door companies I've spoken to say that 2.8m - 3m high sliding doors would be the max they do.

JimmyMW

kev1234 wrote: »

Hi, yes this had been mentioned to me before. I will put it into the model later and post an image this evening to see how that works. I'm not sure of the aesthetics of a roof the pitches up and out from the house. Great for having more glazing and light in but externally I always think it looks a bit strange. I'll have a look.
I also would have thought that much higher glazing at the back would be more difficult to source and much more expensive? Most window/door companies I've spoken to say that 2.8m - 3m high sliding doors would be the max they do.

Do see what it looks like, thats the max height of the door you can always put fixed glazing above that.

kev1234

JimmyMW wrote: »

Do see what it looks like, thats the max height of the door you can always put fixed glazing above that.

Ok, so I've done that up on the model and came out like the attached. Is this something like you were suggesting?

In one of the links I have put a glass panel at high level on the side of the house, this would be above the kitchen cabinets. Not sure how difficult or costly this would be to achieve though so would need to look into it. Let me know what you think.

http://imageshack.com/a/img924/9950/Bi5C3g.jpg
http://imageshack.com/a/img924/8130/KWxnjz.jpg

Gumbo

Much better imo

Have a look at this for a similar example.
This was done nearly 10 years ago so a more modern looking option is available with trocall, fibreglass or zinc.

Dropped pin
near 16-2 Glasnamana Rd, Ballygall, Dublin
https://goo.gl/maps/jft15aLXBCo

JimmyMW

kev1234 wrote: »

Ok, so I've done that up on the model and came out like the attached. Is this something like you were suggesting?

In one of the links I have put a glass panel at high level on the side of the house, this would be above the kitchen cabinets. Not sure how difficult or costly this would be to achieve though so would need to look into it. Let me know what you think.

http://imageshack.com/a/img924/9950/Bi5C3g.jpg
http://imageshack.com/a/img924/8130/KWxnjz.jpg

Yeah thats what i was talking about, i would not have the flat bit returning by the garage thou, i would start the lowest point of your slope in at this return, Additionally I would put a nice deep overhang on this roof to make it look right. The side light will be expensive but could be very nice.

kev1234

Thanks for the advice kceire and Jimmy, I'm now strongly favouring the roof that pitches up away from the house.
However I have read that a pitch of less than 20^o is not recommended for a lean to roof due to potential damage long term from wind/rain etc. or leaking through the roof. Is this true? My pitch would likely be approx. 12^o so should I be using flat roof construction and materials at this pitch? 

JimmyMW

kev1234 wrote: »

Thanks for the advice kceire and Jimmy, I'm now strongly favouring the roof that pitches up away from the house.
However I have read that a pitch of less than 20^o is not recommended for a lean to roof due to potential damage long term from wind/rain etc. or leaking through the roof. Is this true? My pitch would likely be approx. 12^o so should I be using flat roof construction and materials at this pitch? 

Just ensure you meet the minimum pitch for the selected materials, I think man made slate is around 15degs unless in exposed areas, check with your suppliers

kev1234

Hi, I am looking at putting a low pitched lean to roof on a side and rear extension to a 3 bed semi detached in Dublin. I had considered other roof options (flat, butterfly, inverted pitch) but for various reasons I have been advised against them. See attached sketch of the potential lean-to I'd be looking at.
Can anyone advise on what type of roof structure I could go for at a 12 degree pitch? I know that slate is out of the question. I've found a Centurion roof tile that can go to as low as 12.5degrees, which is a possibility. An architect recommended that I could go with a PVC/metal roof such as Nordman roof tiles but I cannot find their website. Would a metal roof be advisable? What are the pros/cons compared to a tile roof?
http://imageshack.com/a/img922/9596/1mnOi4.png
http://imageshack.com/a/img923/2251/Nw0QMv.png

DOCARCH

Mod Note: @kev1234 Moved your recent post into your recent thread. At least your recent post/query can be seen in context.

kev1234

I've been looking into potential options for a low pitched roof and found the following suggestions:
PVC single membrane roof.
Fibreglass
Zinc
Copper
Centurion Roof Tiles - 12.5 degrees down to 10 degrees in certain circumstances
Decra Lightweight Roof Tiles -
Tapcometal Roman Tiles - 12 degrees
Metrotile Roman Tile - 10 degrees
Eco Slate - 10 degrees
Would anyone have familiarity with these low pitched options in terms of performance, cost relative to each other, workability and ease of installing rooflights etc.? I spoke to a couple of roofing contractors, one suggested fibreglass suggesting it was far more durable than others with a 30year guarantee but roughly double the price of torch on felt. The second contractor emailed saying 'high performance felt is the best system, pvc has a short life span, and metal roofing and low pitched tiles are not suitable'. Though didn't specify why they were unsuitable. Anyone have knowledge of these roof systems?

Metric Tensor

Good quality single ply membranes are what we use for most low pitched roofs (there are a lot a sh!t ones and only a handful of good ones). They usually come with a 15-20 year guarantee but you need a skilled installer and they aren't usually interested in smaller jobs/roofs.

I wouldn't put torch on felt on a chicken shed.

BryanF

Metric Tensor wrote: »

Good quality single ply membranes are what we use for most low pitched roofs (there are a lot a sh!t ones and only a handful of good ones). They usually come with a 15-20 year guarantee but you need a skilled installer and they aren't usually interested in smaller jobs/roofs.

I wouldn't put torch on felt on a chicken shed.

Depends on what you classify as torch on felt. There are bitumen systems that will have the same guarantees, are safer to walk-on, don’t break down etc

Metric Tensor

Definitely Bryan and we've used them successfully. I mean the colloquial use of the term used to sell rolls of cheap crap to the unsuspecting punter - seen adorning many a 1970s 4 inch block rickity extension housing the washing machine and the tumble dryer! ;-)

kev1234

Metric Tensor wrote: »

Good quality single ply membranes are what we use for most low pitched roofs (there are a lot a sh!t ones and only a handful of good ones). They usually come with a 15-20 year guarantee but you need a skilled installer and they aren't usually interested in smaller jobs/roofs.

I wouldn't put torch on felt on a chicken shed.

Can you advise on what would be classified as a good quality single ply membrane as opposed to a bad one? Is this a particular type/brand/supplier or a set of technical criteria for the membrane? Also would an extension of approx 45-50sq/metres be considered too small for a skilled installer?

Dilly of a pickle

kev1234 wrote: »

Metric Tensor wrote: »

Good quality single ply membranes are what we use for most low pitched roofs (there are a lot a sh!t ones and only a handful of good ones). They usually come with a 15-20 year guarantee but you need a skilled installer and they aren't usually interested in smaller jobs/roofs.

I wouldn't put torch on felt on a chicken shed.

Can you advise on what would be classified as a good quality single ply membrane as opposed to a bad one? Is this a particular type/brand/supplier or a set of technical criteria for the membrane? Also would an extension of approx 45-50sq/metres be considered too small for a skilled installer?

The last two extensions I did single ply on in the last couple of months were approx 20m2 so I don't think that's too small but maybe that's the exception.

kev1234

Dilly of a pickle wrote: »

The last two extensions I did single ply on in the last couple of months were approx 20m2 so I don't think that's too small but maybe that's the exception.

Do you know what the cost of single ply would be roughly compared to other options such as fibreglass, lightweight tiles, eco slate? Trying to find out the pros and cons of each and the relative cost.

Dilly of a pickle

Have never used or quoted for eco slate so can't comment. If you do choose the low pitch tiles just be aware you can't fit velux tile flashing below 15 if you are thinking of putting them in. Also if your roof is cut to say 13 the effective angle of the tile is probably around 8. Cost wise I would say fibreglass and single ply are roughly the same when all materials and labour are taken into account, fibreglass is more labour intensive and has more ancillaries. To me personally I wouldn't be touching tiles or slate of any kind at low pitch. The slope back into the house looks well maybe you could carry the parapet wall all the way back? Just make sure there's an allowance made for a run off by the house. Unless you like to go swimming!

kev1234

Dilly of a pickle wrote: »

Have never used or quoted for eco slate so can't comment. If you do choose the low pitch tiles just be aware you can't fit velux tile flashing below 15 if you are thinking of putting them in. Also if your roof is cut to say 13 the effective angle of the tile is probably around 8. Cost wise I would say fibreglass and single ply are roughly the same when all materials and labour are taken into account, fibreglass is more labour intensive and has more ancillaries. To me personally I wouldn't be touching tiles or slate of any kind at low pitch. The slope back into the house looks well maybe you could carry the parapet wall all the way back? Just make sure there's an allowance made for a run off by the house. Unless you like to go swimming!

I know this is going back a bit but I think I am going to do away with the pitched roof and just go with flat roof on the back and side extensions. The choice I am trying to make now is to determine whether to go with PVC, fibreglass or rubber roof. I am going to try weigh up pro's and cons for each and get estimated costs.

Anyone on here have issues or comments about these roof types? I am leaning towards a Trocal PVC roof at present due to a strong recommendation from a Contractor I know who uses it all the time without issue apparently.

Dilly of a pickle

Yep can't argue with that it will look neater I think. Hopefully insurance won't be a issue afterwards for you.

Dilly of a pickle

Duplicate

shaydy

First off................I'm a complete amateur when it comes to building.

Building an extension on the back of our semi-d, we need to decide on a roof type. I'm a little uncertain about what to go for and having searched this forum, I was hoping someone here could give me a little feedback / help.

I like the look and finish of the flat roof however I have no idea on the reliability of flat roofs these days. The pitched roof presented looks a little off due to the L style finish of the extension, which was done to give us a little seating area.

Thoughts / feedback welcome.

Thanks

Gumbo

shaydy wrote: »

First off................I'm a complete amateur when it comes to building.

Building an extension on the back of our semi-d, we need to decide on a roof type. I'm a little uncertain about what to go for and having searched this forum, I was hoping someone here could give me a little feedback / help.

I like the look and finish of the flat roof however I have no idea on the reliability of flat roofs these days. The pitched roof presented looks a little off due to the L style finish of the extension, which was done to give us a little seating area.

Thoughts / feedback welcome.

Thanks

For your particular extension, I like the look of the pitched roof better.

shaydy

kceire wrote: »

For your particular extension, I like the look of the pitched roof better.

Would it not look / feel odd due to the partial piece on one side?

Also losing a bit of height perhaps........