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#1
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Under Slate felt , whats the story?
Looking at getting late 1880`s 4 storey tenement re-slated, exposed
position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Seems to be varying opinions on covering bleow new slates though, some say use a breathable fabric and no additional slate vents, others appear to be advsing non breathable and ` a few ` slate vents. Seen loft to habitable conversions and BC seem very keen on lots of slate vents. Whole of this roof is above habitated space. Whats anyones experience of undertile fabrics and the pros and cons? Thanks Adam |
#2
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Under Slate felt , whats the story?
On 13 Aug, 04:14, Adam Aglionby wrote:
Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Seems to be varying opinions on covering bleow new slates though, some say use a breathable fabric and no additional slate vents, others appear to be advsing non breathable *and ` a few ` slate vents. Seen loft to habitable conversions and BC seem very keen on lots of slate vents. Whole of this roof is above habitated space. Whats anyones experience of undertile fabrics and the pros and cons? Thanks Adam The reason for istalling fabric is it makes the building weather proof quickly & if there is a faultly tile/slate it keeps the waterout. Keeps draughts and driving rain out too. Years ago they used reinforced bitumous felt. But it was easily damaged and a fire hazard. Then they used plastic & there were problems with condensation and rot. So vents were installed to limit this. (They sometimes don't work well) The latest thing (last ten years) is the breathable membrane which is "vapour permeable" but still waterproof. Its claimed this doesn't need vents. Early days yet. The stuff is very tough. The main thing about installation is to leave "droops" beween the rafters so water can drain away and the battens stay dry underneath them and air can circulate. |
#3
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Under Slate felt , whats the story?
On 13 Aug, 08:56, harry wrote:
On 13 Aug, 04:14, Adam Aglionby wrote: Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Seems to be varying opinions on covering bleow new slates though, some say use a breathable fabric and no additional slate vents, others appear to be advsing non breathable *and ` a few ` slate vents. Seen loft to habitable conversions and BC seem very keen on lots of slate vents. Whole of this roof is above habitated space. Whats anyones experience of undertile fabrics and the pros and cons? Thanks Adam The reason for istalling fabric is it makes the building weather proof quickly & if there is a faultly tile/slate it keeps the waterout. Keeps draughts and driving rain out too. Years ago they used reinforced bitumous felt. But it was easily damaged and a fire hazard. Then they used plastic & there were problems with condensation and rot. So vents were installed to limit this. (They sometimes don't work well) The latest thing (last ten years) is the breathable membrane which is "vapour permeable" but still waterproof. *Its claimed this doesn't need vents. *Early days yet. *The stuff is very tough. * The main thing about installation is to leave "droops" beween the rafters so water can drain away and the battens stay dry underneath them and air can circulate.- Hide quoted text - - Show quoted text - Oh and you will need eves ventilation (behind the gutters) and consider ridge ventilators too. |
#4
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Under Slate felt , whats the story?
On 13 Aug, 08:59, harry wrote:
On 13 Aug, 08:56, harry wrote: On 13 Aug, 04:14, Adam Aglionby wrote: Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Seems to be varying opinions on covering bleow new slates though, some say use a breathable fabric and no additional slate vents, others appear to be advsing non breathable and ` a few ` slate vents. Seen loft to habitable conversions and BC seem very keen on lots of slate vents. Whole of this roof is above habitated space. Whats anyones experience of undertile fabrics and the pros and cons? Thanks Adam The reason for istalling fabric is it makes the building weather proof quickly & if there is a faultly tile/slate it keeps the waterout. Keeps draughts and driving rain out too. Years ago they used reinforced bitumous felt. But it was easily damaged and a fire hazard. Then they used plastic & there were problems with condensation and rot. So vents were installed to limit this. (They sometimes don't work well) The latest thing (last ten years) is the breathable membrane which is "vapour permeable" but still waterproof. Its claimed this doesn't need vents. Early days yet. The stuff is very tough. The main thing about installation is to leave "droops" beween the rafters so water can drain away and the battens stay dry underneath them and air can circulate.- Hide quoted text - - Show quoted text - Oh and you will need eves ventilation (behind the gutters) and consider ridge ventilators too. not part of trad. roof construction tho are they? why would they be needed in this instance? underfelts should also allow water to drain off them over the eaves (usually lapped into troughings) and not allow water to pool or "pond" behind the fascia boards... and rot the underfelts and drain on/into the walls... Jim K |
#5
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Under Slate felt , whats the story?
On Thu, 12 Aug 2010 20:14:29 -0700 (PDT), Adam Aglionby wrote:
Whats anyones experience of undertile fabrics and the pros and cons? Had the modern breathable membrane stuff put in when we had our slate roofs redone a few years back on the basis that the normal sarking rots eventually and doesn't withstand exposure at all well. ie you loose a slate and the sarking fails where day light (and water) can get in between the slates... Along the gutter line our roofers put 18" (maybe 2') wide DPM with the membrane stopping 6" or so short of the slate edge on top of it. DPM doesn't degrade... Inside the roof it is dry, there is occasional condensation but it does dry out no vents as such but it's still pretty drafty up there... The lofts is much brighter as well, membrane is a light colour rather than dark. -- Cheers Dave. |
#6
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Under Slate felt , whats the story?
harry wrote:
On 13 Aug, 04:14, Adam Aglionby wrote: Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Seems to be varying opinions on covering bleow new slates though, some say use a breathable fabric and no additional slate vents, others appear to be advsing non breathable and ` a few ` slate vents. Seen loft to habitable conversions and BC seem very keen on lots of slate vents. Whole of this roof is above habitated space. Whats anyones experience of undertile fabrics and the pros and cons? Thanks Adam The reason for istalling fabric is it makes the building weather proof quickly & if there is a faultly tile/slate it keeps the waterout. Keeps draughts and driving rain out too. Years ago they used reinforced bitumous felt. But it was easily damaged and a fire hazard. Then they used plastic & there were problems with condensation and rot. So vents were installed to limit this. (They sometimes don't work well) The latest thing (last ten years) is the breathable membrane which is "vapour permeable" but still waterproof. Its claimed this doesn't need vents. Early days yet. The stuff is very tough. The main thing about installation is to leave "droops" beween the rafters so water can drain away and the battens stay dry underneath them and air can circulate. The reason for felt below slates is not to make them rainproof, although there is a grain of truth about driving drain. Salates overlap, and an overlappped roof is rainproof. It takes a lot to drive rain UP a slope. The function of the fabric is to make the roof WIND proof. There are three reasons to do that, and the most important is to prevent suction tearing the slates of or working them loose. The second was to reduce heat loss from the loft..but see below The third and least important is to slow airflow down and thereby prevent rain crawling UP the slates. But with a double overlap, it has to crawl 2/3rds of the way up a slate to get to the top, and in general, it wont. The air is pretty dead behind slates even without sarking. The fabric should never get wet, and a well laid slate roof without it is perfectly rainproof. I've lived under some. Once it was used, it was discovered that (especially in uninsulated houses) it led to rot, because it acted to trap the house moisture under it. That condensed on the cold sarking, and beams, and dripped around. So controlled air movement, by vents, eave and ridge, and/or by breathable membranes was introduced. Personally I think its way overkill, because you are likely also to have a deal of insulation these days and that implies a vapour barrier in the ceiling (foil backed plasterboard) anyway, so there is virtually no humidity escaping into a loft, ergo it really needs a lot less ventilation than the regulations call for. However some houses still have water header tanks and so on up there, so it is still useful to ensure ventilation. If you have e.g. a modern CH system without a header, and better still if you have a mains pressure hot water supply, and loft insulation, you won't have water in the loft. So my instinct is to use as little ventilation as the BCO will allow. If you are thinking of converting to living space you will necessarily be using something like foil backed Kingspan to insulate the rafters with an air gap at the top anyway. Its almost arguable you need no sarking at all in this case.. Anyway the point of this all is to show that airtightness is what you want, and breath-ability or venting is slightly a hangover from 'days before insulation'. With a vapour barrier at the boundary of the habitable space, there is much less need for it. I would personally go therefore for breathable, and as few vents as the BCO will let you get away with. |
#7
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Under Slate felt , whats the story?
On 13 Aug, 09:30, The Natural Philosopher
wrote: harry wrote: On 13 Aug, 04:14, Adam Aglionby wrote: Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Seems to be varying opinions on covering bleow new slates though, some say use a breathable fabric and no additional slate vents, others appear to be advsing non breathable and ` a few ` slate vents. Seen loft to habitable conversions and BC seem very keen on lots of slate vents. Whole of this roof is above habitated space. Whats anyones experience of undertile fabrics and the pros and cons? Thanks Adam The reason for istalling fabric is it makes the building weather proof quickly & if there is a faultly tile/slate it keeps the waterout. Keeps draughts and driving rain out too. Years ago they used reinforced bitumous felt. But it was easily damaged and a fire hazard. Then they used plastic & there were problems with condensation and rot. So vents were installed to limit this. (They sometimes don't work well) The latest thing (last ten years) is the breathable membrane which is "vapour permeable" but still waterproof. Its claimed this doesn't need vents. Early days yet. The stuff is very tough. The main thing about installation is to leave "droops" beween the rafters so water can drain away and the battens stay dry underneath them and air can circulate. The reason for felt below slates is not to make them rainproof, although there is a grain of truth about driving drain. Salates overlap, and an overlappped roof is rainproof. It takes a lot to drive rain UP a slope. The function of the fabric is to make the roof WIND proof. There are three reasons to do that, and the most important is to prevent suction tearing the slates of or working them loose. ?? it was a 60s invention to make life easier for re-roofers Jim K |
#8
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Under Slate felt , whats the story?
Had the modern breathable membrane stuff put in when we had our slate roofs redone a few years back on the basis that the normal sarking rots eventually and doesn't withstand exposure at all well. ie you loose a slate and the sarking fails where day light (and water) can get in between the slates... Along the gutter line our roofers put 18" (maybe 2') wide DPM with the membrane stopping 6" or so short of the slate edge on top of it. DPM doesn't degrade... Had my roof reslated 2 years ago, with hand-finished Spanish slate - very happy with it all round. Similarly had Tyvek throughout the whole roof, with additional waterproof felt/DPM on the lowest 18-24" and lapped into the gutters. Inside the roof it is dry, there is occasional condensation but it does dry out no vents as such but it's still pretty drafty up there... The lofts is much brighter as well, membrane is a light colour rather than dark. My roofspace is bone dry, all year round, no condensation. No roof vents, though there is an original (1873) arrow-slit type vent in the brickwork on one gable end. My additional tip would be don't skimp on the detailing - leadwork, chimney & other flashings, chimney maintainence, gutters, fascias & soffits etc - get the lot done at the same time. Get it all specified in the contract, and accept there may be cost overruns if it becomes apparent additional remedial work is required. Swallow the cost and get it all done. |
#9
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Under Slate felt , whats the story?
"Adam Aglionby" wrote in message ... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... and no carbon offset bringing across Europe. |
#10
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Under Slate felt , whats the story?
On 13 Aug, 15:25, "Rick Hughes"
wrote: "Adam Aglionby" wrote in message ... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... *and no carbon offset bringing across Europe. Welsh slate IS the best. You can have thinner slates and a lighter roof and they weather significantly better, better appearance and last longer. The trouble is the Taffs don't work as cheap as the spics, the chinks or the portuguese. |
#11
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Under Slate felt , whats the story?
On Aug 13, 4:39*pm, harry wrote:
On 13 Aug, 15:25, "Rick Hughes" wrote: "Adam Aglionby" wrote in message ... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... *and no carbon offset bringing across Europe. Welsh slate IS the best. You can have thinner slates and a lighter roof and they weather significantly better, better appearance and last longer. *The trouble is the Taffs don't work as cheap as the spics, the chinks or the portuguese. Wrong.. The reason Welsh slates are more expensive is the amout of waste in selection of quality and yes apart from Westmoreland slate Welsh are second to none. |
#12
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Under Slate felt , whats the story?
On 13 Aug, 12:11, " wrote:
Had the modern breathable membrane stuff put in when we had our slate roofs redone a few years back on the basis that the normal sarking rots eventually and doesn't withstand exposure at all well. ie you loose a slate and the sarking fails where day light (and water) can get in between the slates... Along the gutter line our roofers put 18" (maybe 2') wide DPM with the membrane stopping 6" or so short of the slate edge on top of it. DPM doesn't degrade... Had my roof reslated 2 years ago, with hand-finished Spanish slate - very happy with it all round. Similarly had Tyvek throughout the whole roof, with additional waterproof felt/DPM on the lowest 18-24" and lapped into the gutters. Tyvek seems to be one product mentioned, but its non breathable? Inside the roof it is dry, there is occasional condensation but it does dry out no vents as such but it's still pretty drafty up there... As long as it stays draughty guess is good, rot needs still air in general.at least dreaded dry rot does to get started,. The lofts is much brighter as well, membrane is a light colour rather than dark. My roofspace is bone dry, all year round, no condensation. No roof vents, though there is an original (1873) arrow-slit type vent in the brickwork on one gable end. This is a terrace , so am concerned that ventilation is maintained.Yes, thre is sarking, hopefully in reasonable nick... Something local BC seems very keen on as well, as say seen habitable loft conversions where BC wanted dozen or more vents installed in each slope in a large semi. My additional tip would be don't skimp on the detailing - leadwork, chimney & other flashings, chimney maintainence, gutters, fascias & soffits etc - get the lot done at the same time. Oh thats the other half, re-render chimney stalks, properely, some of the neighbours do show that cement work is a skill and one quite possible to get very wrong. Mortar ` water gates` slump mortar at join of chimney and slates and hope water stays out, they have to go and get replaced with proper lead/zinc ones. Get it all specified in the contract, and accept there may be cost overruns if it becomes apparent additional remedial work is required. Swallow the cost and get it all done. Its getting 8 individuals to swallow the cost and realise another patch up is a waste of money, its about 10 grand + Vodka And Tonic just for scaffolding , really don`t want a biennial roof patch up scheme. Cheers Adam |
#13
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Under Slate felt , whats the story?
Tyvek seems to be one product mentioned, but its non breathable? Breathable. http://en.wikipedia.org/wiki/Tyvek |
#14
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Under Slate felt , whats the story?
On 13 Aug, 21:02, Kipper at sea wrote:
On Aug 13, 4:39*pm, harry wrote: On 13 Aug, 15:25, "Rick Hughes" wrote: "Adam Aglionby" wrote in message .... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... *and no carbon offset bringing across Europe. Welsh slate IS the best. You can have thinner slates and a lighter roof and they weather significantly better, better appearance and last longer. *The trouble is the Taffs don't work as cheap as the spics, the chinks or the portuguese. Wrong.. The reason Welsh slates are more expensive is the amout of waste in selection of quality and yes apart from Westmoreland slate Welsh are second to none. Looking at cost, Welsh seems to come inat around double cost of Spanish, one company tried to sell us on Canadian!? which sems a bit of a carbon cost. Is there a Euro/BS/BBA someat spec should ask for the slates to meet? Thanks Adam |
#15
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Under Slate felt , whats the story?
On 14 Aug, 14:00, Adam Aglionby wrote:
On 13 Aug, 21:02, Kipper at sea wrote: On Aug 13, 4:39*pm, harry wrote: On 13 Aug, 15:25, "Rick Hughes" wrote: "Adam Aglionby" wrote in message ... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... *and no carbon offset bringing across Europe. Welsh slate IS the best. You can have thinner slates and a lighter roof and they weather significantly better, better appearance and last longer. *The trouble is the Taffs don't work as cheap as the spics, the chinks or the portuguese. Wrong.. The reason Welsh slates are more expensive is the amout of waste in selection of quality and yes apart from Westmoreland slate Welsh are second to none. Looking at cost, Welsh seems to come inat around double cost of Spanish, one company tried to sell us on Canadian!? which sems a bit of a carbon cost. Is there a Euro/BS/BBA someat spec should ask for the slates to meet? Thanks Adam I believe there's a BSxxxx, but practically the roofing company you select will be used to using certain suppliers. Get a recommendation, look at their work, and talk to some recent customers. |
#16
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Under Slate felt , whats the story?
On Sat, 14 Aug 2010 06:00:44 -0700 (PDT), Adam Aglionby wrote:
Is there a Euro/BS/BBA someat spec should ask for the slates to meet? Just bought a handful of (spanish) slates and the crates in the builders merchant had labels that detailed grades for weathering, carbonate content, and a couple of other things. So there is a spec or at least things they measure out there, google? -- Cheers Dave. |
#17
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Under Slate felt , whats the story?
On 14 Aug, 14:50, " wrote:
On 14 Aug, 14:00, Adam Aglionby wrote: On 13 Aug, 21:02, Kipper at sea wrote: On Aug 13, 4:39*pm, harry wrote: On 13 Aug, 15:25, "Rick Hughes" wrote: "Adam Aglionby" wrote in message ... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... *and no carbon offset bringing across Europe. Welsh slate IS the best. You can have thinner slates and a lighter roof and they weather significantly better, better appearance and last longer. *The trouble is the Taffs don't work as cheap as the spics, the chinks or the portuguese. Wrong.. The reason Welsh slates are more expensive is the amout of waste in selection of quality and yes apart from Westmoreland slate Welsh are second to none. Looking at cost, Welsh seems to come inat around double cost of Spanish, one company tried to sell us on Canadian!? which sems a bit of a carbon cost. Is there a Euro/BS/BBA someat spec should ask for the slates to meet? Thanks Adam I believe there's a BSxxxx, but practically the roofing company you select will be used to using certain suppliers. Get a recommendation, look at their work, and talk to some recent customers. 27 roofers, lot dont` phone back or don`t turn up to quote, 11 quotes for wildly varying levels of works at wildly varying prices in very differnt levels of detail. Now have preferred bidder just wabnt to make sure we agree on a spec as its been open to some debate, not having to buy a football pitch of reclaimed Scotch slate was bit of a relief though. Spanish slate from quick google comes in everything from solidity of out of date sherbert to still around at next ice age, like to just make sure no questions about substitutions from spec to site. Cheers Adam |
#18
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Under Slate felt , whats the story?
"harry" wrote in message ... On 13 Aug, 15:25, "Rick Hughes" wrote: "Adam Aglionby" wrote in message ... Looking at getting late 1880`s 4 storey tenement re-slated, exposed position , scotch slates are slipping towards gutter at increasing rate, lead work evaporating etc. Flat platform in middle recovered 4 years ago. Seem to have decided on Spanish slate as against reclaimed Scotch on balance of cost and apperance, some areas would have to be Scotch, not here. Welsh Slate is the best in the world ... and no carbon offset bringing across Europe. Welsh slate IS the best. You can have thinner slates and a lighter roof and they weather significantly better, better appearance and last longer. The trouble is the Taffs don't work as cheap as the spics, the chinks or the portuguese. we worked pretty cheaply for the Romans, Normans, and most others who oppressed us |
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