How are flat roofs being constructed these days?

ircoha

Client wants a 5.2 metre deep by 3.5 metre wide lean-to extension.

Max slope I can achieve due to window in gable is 9 degrees.

Any suggestions please for roofing, she wants to use roof tiles to match existing, so any thoughts on what can be used underneath.

Could counter-batten for tiles to ensure drainage.
As an alternative
am I asking for trouble by going for an A roof across the 3.5 as the extension is between two walls for the whole 5.2m on one side and 2.6m on the other

Thanks.

AckwelFoley

Jesus 9 degrees is awfully flat for tiles. i wouldnt recommend it myself... at all.

There are products from marley on the market. They are designed for 15 deg You will certainley need to double the felt and use Marine grade ply..

Id normally think anything other than 20 or under is too low a pitch.

A flat roof is difficult to do, particularly because to flash the roof into where it meets the wall is commenly done incorrectly and causes for future problems and a bad rep.
Im sorry im not providing any assistance .. ill have a browse of the internet.

On edit: Is the extension between 2 buildings? If you had a sketch you could email or upload that i could have a look at?

ardara1

Minimum pitch for roof tile I've ever come across was 12.5 degree - check with tile manufacturer.

You're looking at a flat roof - hows about traditional lead over fleece over ply - vented over insulation on rafters

smashey

A long shot here, but what about the kingspan rooftile panel?

Mellor

I think ircoha was suggesting that the tiles be used for show only. To match existing, but not be the actual water proofing layer, the min pitch for tegral tiles (used as intended) is 35 deg. FC Slates can go to 25 deg. It varies alot from manufacturer.


The situation above appear tricky . 9 deg is a flat roof. The main problem I see with using the tiles as an aestheic finished material is that battens used to fix the tiles to will break the water-proofing layer on the flat roof. (If a trocal or similat was used)

I can think of two solutions.

1. Build up a flat roof as normal, then build a grid of battens on top, crossed and fixed to each other but not the roof. Fix tiles yo these, max lap and fixings. The weight of the tiles should keep the grid in place. The only concern is that the tiles will blow loose in heavy wind, not the grid but single tiles, this applies to any solution. Contact tegrals technical department and see if tiles will be ok here. Highlight that they are not a water proofing layer.
   
2. The other option is to highlight to the client that at such a low pitch the surface of the roof won't be very visable, it will be completely hidden from view if you are within 6m of the extension.

AckwelFoley

crossed and fixed to each other but not the roof. Fix tiles yo these, max lap and fixings. The weight of the tiles should keep the grid in place. The only concern is that the tiles will blow loose in heavy wind, not the grid but single tiles, this applies to any solution

Has this been done?.

Personally i dont or wouldnt put anything up similar to what you describe unless i could fix it in place, and while you are correct, that the weight of the tiles would probably be more than suficent considering the angle, i always lean to over kill.

Edit: Yea, the weight of the tiles would be fine to hold in place in my opinion

sydthebeat

what about using Nordman tilesheets.

http://www.nordman.ie/spec.htm

Tilesheets are an Irish made product with a 20 year Guarantee, subject to fitting in accordance with Nordman's installation instructions. Our product is the first approved Tilesheet and the only roofing tile in Ireland or the UK with agreement certification for use down to 4°.

Im not involved with this company in anyway.

smashey

sydthebeat wrote: »

what about using Nordman tilesheets.

http://www.nordman.ie/spec.htm

Tilesheets are an Irish made product with a 20 year Guarantee, subject to fitting in accordance with Nordman's installation instructions. Our product is the first approved Tilesheet and the only roofing tile in Ireland or the UK with agreement certification for use down to 4°.Im not involved with this company in anyway.

I've used them before. Good idea.

AckwelFoley

Those sheets are like the Profile Ridge Capping (3m) ppl are using now instead of the regular truetone / supercem ridge capping.

Wonder what the lifespan of these are considering what they are made of...

2 stroke

Your client probably cannot visualise the finished project, or the longterm problems she will have with this roof.

Mellor

As far I can remember they are polymer based, so they should have a very long lifespan. As longs as a building anyway.

Personally i dont or wouldnt put anything up similar to what you describe unless i could fix it in place, and while you are correct, that the weight of the tiles would probably be more than suficent considering the angle, i always lean to over kill.

Well, personally I would do it either.
But I certainly wouldn't fix the battons through the flat roof.
I'd be sure the whole grid would lift, but in strong winds single tiles might, if battons are fixed to roof or not (due to low incline).

If 9 deg is defo required, I'd feel safer with a sheet profile material.


Would it be an option to fall the roof as a mono pitch accross the 3.5m length? This would increase the pitch to 13.5 deg (for same height), Even greater if the window in gable wasn't full width of 3.5m.
I know you were concerned about building either side, but you could change the overhanging eaves to a parapet and drain behind here. I did this on a very restricted site during the summer, This could also be regular pitched (A roof). Reaching about 25 deg, approaching a decent range for tiles/slates now

smashey

2 stroke wrote: »

Wimmin have no spatial awareness,

Wtf?

Infraction given.

AckwelFoley

id like to see some sort of sketch or plan of the original buildings and the extension, im useless at making a decision without plans BUT if it was me there would be no question on what id do, if the layout is as i imagine it, i would cut an "A" roof for it.

AckwelFoley

OFFTOPIC:

smashey wrote: »

Wtf?

Infraction given.

Actually, it is a scientific fact, believe it or not.


Women tend to be poorer in this area, where as 3 in 5 men are colour blind and the same amount of women - 3 in 5 cannot tell left from right when asked on an "instant"

So although its a general statment made there is some truth to it :O

smashey

snyper wrote: »

OFFTOPIC:




Actually, it is a scientific fact, believe it or not.


Women tend to be poorer in this area, where as 3 in 5 men are colour blind and the same amount of women - 3 in 5 cannot tell left from right when asked on an "instant"

So although its a general statment made there is some truth to it :O

It has nothing to do with the question.

AckwelFoley

True. You are correct.

But i would advise that he fully consult said client and show her plans of what he intends to proceed with for the simple reason that i find that a contractor always needs to be very clear as to what the final result will be and to its appearance, so as to avoid any disagreement on job completion.

2 stroke

O.k. To answer the question properly.

How are flat roofs being constructed these days?

Generally fairly poorly, such that they usualy leak or cause dampness problems within 5 years.

AckwelFoley

The biggest problem with flat roofs is that they have a shorter lifespan than conventional A roofs.

The problem is that firstly the flashing is quite often poorly fitted, and on top of that many times because it is in theory easier to do a flat roof, the work is not carried out by compitent and expierenced tradesmen. The key to a flat roof is the flashing and the proper application of the felt.

Also, because felt is a bitumen based product it has a limited lifespan. Granted the felt used today is much better than the god awful mineral felt that was widely used in the 70's and 80's

Mellor

snyper wrote: »

The biggest problem with flat roofs is that they have a shorter lifespan than conventional A roofs.

The problem is that firstly the flashing is quite often poorly fitted, and on top of that many times because it is in theory easier to do a flat roof, the work is not carried out by compitent and expierenced tradesmen. The key to a flat roof is the flashing and the proper application of the felt.

Also, because felt is a bitumen based product it has a limited lifespan. Granted the felt used today is much better than the god awful mineral felt that was widely used in the 70's and 80's

I wouldn't agree that flat roofs are designed to be of a shorter lifespan. Think outside domestic extension, outside domestic altogether.

Mellor

snyper wrote: »

OFFTOPIC:
Women tend to be poorer in this area, where as 3 in 5 men are colour blind and the same amount of women - 3 in 5 cannot tell left from right when asked on an "instant"

also, the basis for your statement is true. But you are grossly exaggerating.
3 in 5 men are not colour blind. It is about 8% in men, and <1% in women. This is for common red/green colour blindness, for more extreme types it is much lower and more equal.

Men do have better spatial awareness than women on average. Note better and average are highlighted, men are better, this does not mean women have none. The male advantage is about 1 standard diviation, not a huge amount.
The 3 out of 5 left and right is nonsense. Firstly 3 out of 5 is way too high, and secondly, left and right isn't a really spatial awareness.



Anyway, less nonsense and thread on topic please.

2 stroke

Mellor wrote: »

I wouldn't agree that flat roofs are designed to be of a shorter lifespan.

Not designed to be of a shorter lifespan but poorly built in general though I would not expect a well built roof to outlast an A roof.

muffler

2 stroke wrote: »

Not designed to be of a shorter lifespan but poorly built in general though I would not expect a well built roof to outlast an a roof.

Re. colour blindness. Women see and can describe to each other more shades of each colour than men can. Though I suspect they have a problem with shades of white, eg. white pvc windows and doors aren't actualy white, more like a shade of grey but few women spot it.

Thats twice now you have gone off topic in the same thread - yellow card. Any repeat and it will be a red one.

Infraction also for this.

ircoha

Many thanks to you all for the input, much appreciated.

Mellor

2 stroke wrote: »

Not designed to be of a shorter lifespan but poorly built in general though I would not expect a well built roof to outlast an A roof.

As I said previous, think outside domestic. Large buildings in dublin city etc.


Ircoha, best of luck with this. Maybe keep updated with the option you go for and outcome. If it has to be tiles I think an "A" roof is best.

250882

I know the client wants tiles but Really the only option(except cnventional flat roof is a zinc or copper roof,

VillageIdiot

Apologies for hijacking the thread. How do you guys recommend the flashing should be carried out where a flat roof meets a wall?

muffler

VillageIdiot wrote: »

Apologies for hijacking the thread. How do you guys recommend the flashing should be carried out where a flat roof meets a wall?

There are details for that and the best I can think of (for want of a link to something online) is look up the Homebond House Building manual.

ircoha

Mellor wrote: »

As I said previous, think outside domestic. Large buildings in dublin city etc.


Ircoha, best of luck with this. Maybe keep updated with the option you go for and outcome. If it has to be tiles I think an "A" roof is best.

Mellor: As requested, am coming back with what the final solution is in this case:

we reconfigured to get an A roof at about 17 degrees and are using Tegral melbourn slates [aka resonstituted slate] which work down to 15 degrees, http://www.tegral.com/Tegralbp/index.asp

The downside is that they are only available in blue/black.

Am using top abutment ventilation system from http://www.glidevale.com/

Richmond carry the product here.

Mellor

Thanks for the update.
Glad to hear it worked out.
Will be a decent reference for other low pitch slate/tile roofs, we;ve have a few roof threads lately

sinnerboy

Sorry for entering late on this one . OP what about means of escape / rescue from the existing first floor windows adjacent to the roof ? what worked out well for me in a similar situation was to raise the newly created ""hidden valley" horizontal bearers up the slope to achieve a 600mm wide gutter sole . not wide enough for every day traffic but you would be glad of it if you needed it in case of fire . lined with a torch on felt with factory applied stone chippings .