How long should fibre cement slate roof last?

d2ww

Hi all,
I have a bungalow thats around 30 years old, and the slates could best be described as furry and weaker than new ones. I plan to add on some rooms, which would involve extending the roof.
My question is, should I be expecting at least another 20 years from these slates, or I should I just get new felt/battens and slates put on as I will have the builders in anyway?
Thanks in advance,
d2ww

Slates

d2ww wrote: »

Hi all,
I have a bungalow thats around 30 years old, and the slates could best be described as furry and weaker than new ones. I plan to add on some rooms, which would involve extending the roof.
My question is, should I be expecting at least another 20 years from these slates, or I should I just get new felt/battens and slates put on as I will have the builders in anyway?
Thanks in advance,
d2ww

It depends on the condition of the slates, there is a building in Rathcoole, Co.Dublin that has AC slates on it since 1913,

If the slates are in good condition you can get them repainted to match the new slates, there should be at least another 20 years life in your AC slates

d2ww

Thanks Slates for the reply.
Unfortunately, the orginal builders didn't bring the felt all the way down to the gutter, it stops over the cavity in the wall!!!So it leaks from the top of two of the window frames on the west side of the house. Also,the previous owner had some cowboys install 5 velux windows, all of which have caused problems.
The main worry I have though is the idea of rain forcing its way up the slates in the wind(there's a 30 degree pitch on the roof). I live on a west facing hillside in Wicklow, and it can really blow a gale here.
I was thinking that for a given pitch, tiles are better than slates for stopping this capillary(?) action, is this right?
d2ww

Slates

d2ww wrote: »

Thanks Slates for the reply.
Unfortunately, the orginal builders didn't bring the felt all the way down to the gutter, it stops over the cavity in the wall!!!So it leaks from the top of two of the window frames on the west side of the house. Also,the previous owner had some cowboys install 5 velux windows, all of which have caused problems.
The main worry I have though is the idea of rain forcing its way up the slates in the wind(there's a 30 degree pitch on the roof). I live on a west facing hillside in Wicklow, and it can really blow a gale here.
I was thinking that for a given pitch, tiles are better than slates for stopping this capillary(?) action, is this right?
d2ww

The Min pitch for 600x300mm Fibre cement slates is 25°

A quick outline spec for your job would be
600x300mm Fiber cement slates fixed with 2 copper nails and 1 copper crampion laid with a 110mm heaplap
on 50x25mm battens ( for rafters @ 400cc )
on HP underlay with 150mm laps
on rafters

Mellor

d2ww wrote: »

I was thinking that for a given pitch, tiles are better than slates for stopping this capillary(?) action, is this right?
d2ww

I think most slates actually perform better tan tiles, see Slates guidlines above, the min for most tiles is 30-35 deg, depending on manufacturer

d2ww

You are probably right about the tiles Mellor, I did spot tegral's Melbourne slate(tile?) http://www.tegral.ie/Tegralbp/products/spec/melbourn_spec/mel_spec.htm and Capro's PV10 tile, but both seem to only nailed at the top which makes me a little worried about uplift on windy days. They claim a min pitch of 15 and 17.5 degrees repectively, but only in sheltered areas.
I think slates with 110mm headlap, as per Slates suggestion, is the way to go.

Slates

d2ww wrote: »

You are probably right about the tiles Mellor, I did spot tegral's Melbourne slate(tile?) http://www.tegral.ie/Tegralbp/products/spec/melbourn_spec/mel_spec.htm and Capro's PV10 tile, but both seem to only nailed at the top which makes me a little worried about uplift on windy days. They claim a min pitch of 15 and 17.5 degrees repectively, but only in sheltered areas.
I think slates with 110mm headlap, as per Slates suggestion, is the way to go.

The Melbourn slate will work down to a 15° pitch, with a maximum 5.5m rafter length, at pitches below 20° the Melbourn slate is fixed with 2 stainless steel nails to negate wind up-lift

roofer

hi all
the old fibre cement slates go like glass after a few years so the less you touch them the better. i would like to think that you would get another few years from them, but if you are going to extend it might be worth replacing them at this stage.on the other hand if its not broken dont fix it. if it is leaking where the felt stops you have a problem. this means the water is getting in higher up the roof,not a good sign.slates perform very well in the wind. i would however suggest using an aluminium trim from tegral on the verge as this is where the wind will cause the most problems. tiles, because of their weight also perform well in the wind but i would also suggest a dry verge system for tiles. the less cement the better, as cement absorbs alot of water.if your worried about the pitch (which sounds fine)you could opt to tighten your batton centres from 10 in to 8 in giving you an extra 2 in cover which means you will have 6 in headlap, more than enough

John W

Slates wrote: »

The Melbourn slate will work down to a 15° pitch, with a maximum 5.5m rafter length, at pitches below 20° the Melbourn slate is fixed with 2 stainless steel nails to negate wind up-lift

Sounds like you know a good bit about slates. I live in Wexford and have a south to south west elevation. I am trying to get someone to build a sunroom for me, but nobody will touch it. Problem is, I have an existing roof it needs to attach to at the pitch is 45o, to increase my problems there are 2 valux windows about 4 feet up from the gutter. The proposed room would be about 13X13 (already have foundation in from when I built the house).problem is everyone says to get the roof to attach to the other roof the only angle or pitch that would work would be 15o anything above that would hit the valux windows. second problem is, nobody will do it with slate (that is what is on the existing dormer room). So do you think your Melbourne tiles would do the job? Where can they be purchased, and is there anything else I can do to "guarantee" it won't leak? As you can probably tell, I am not a builder, so answers in terms I can understand would be great.
Thanks in advance for your help, John.

Slates

John W wrote: »

Sounds like you know a good bit about slates. I live in Wexford and have a south to south west elevation. I am trying to get someone to build a sunroom for me, but nobody will touch it. Problem is, I have an existing roof it needs to attach to at the pitch is 45o, to increase my problems there are 2 valux windows about 4 feet up from the gutter. The proposed room would be about 13X13 (already have foundation in from when I built the house).problem is everyone says to get the roof to attach to the other roof the only angle or pitch that would work would be 15o anything above that would hit the valux windows. second problem is, nobody will do it with slate (that is what is on the existing dormer room). So do you think your Melbourne tiles would do the job? Where can they be purchased, and is there anything else I can do to "guarantee" it won't leak? As you can probably tell, I am not a builder, so answers in terms I can understand would be great.
Thanks in advance for your help, John.

Do you have a sketch of what you are trying to do , it's way more helpful to see whats going on that describing it

John W

I do have a few - now these are just rough, but I did try get the correct dimensions - the windows are placed in the roof exactly 4'9ft from the bottom edge and 4ft from the side of the roof as they actually are etc. The size of the sunroom is 13x13 (as I said these are governed by the fact that I have the foundations down already and there is a corner window on one side, you can see this in the last picture "15oRoof_Side.gif"

here are the links, I have put in the different pitches so you can see why i think it won't work, but maybe something can be done with the way it is attached?

http://www.rathronan.com/45oRoof.gif
http://www.rathronan.com/30oRoof.gif
http://www.rathronan.com/15oRoof.gif
http://www.rathronan.com/15oRoof_Side.gif

Thanks for your help.

Slates

John W wrote: »

I do have a few - now these are just rough, but I did try get the correct dimensions - the windows are placed in the roof exactly 4'9ft from the bottom edge and 4ft from the side of the roof as they actually are etc. The size of the sunroom is 13x13 (as I said these are governed by the fact that I have the foundations down already and there is a corner window on one side, you can see this in the last picture "15oRoof_Side.gif"

here are the links, I have put in the different pitches so you can see why i think it won't work, but maybe something can be done with the way it is attached?

http://www.rathronan.com/45oRoof.gif
http://www.rathronan.com/30oRoof.gif
http://www.rathronan.com/15oRoof.gif
http://www.rathronan.com/15oRoof_Side.gif

Thanks for your help.

You should have no problem constructing this roof with Melbourn slates, the velux roof windows will require a flat conc. tile flashing and you will have to do some careful detailing of the pitched metal valley to prevent surcharging of water from the 45° pitch onto the 15° pitch slope

John W

Slates wrote: »

You should have no problem constructing this roof with Melbourn slates, the velux roof windows will require a flat conc. tile flashing and you will have to do some careful detailing of the pitched metal valley to prevent surcharging of water from the 45° pitch onto the 15° pitch slope

Thanks for your help - I assume from seeing the pictures that the 15 degree option is the only way around this, you can't think of another can you?

Mellor

John W wrote: »

Thanks for your help - I assume from seeing the pictures that the 15 degree option is the only way around this, you can't think of another can you?

The other option is to remove one of the velux windows. In my opinion, this is the better looking off your option externally. You will need an accurate survey to get the exact max pitch. With an accurate survey it may be possible to get the pitch close to 20. There are things to help here.

• Bring the new ridge as close as possible to the velux, but no closer than 150mm, flash over
• Drop the eaves of the new roof below the existing eaves, This is common but might not be wanted.
• Have a minimum soffit overhang, its small but the difference between a 300mm and 100mm soffit at 15 deg is over 50mm.

ircoha

Could also consider full/half hip at each end or at least at house end.