Re: fixing gaps and splits in roofing felt in loft
NT
> There are a few splits and some missing piece of roofing felt in our
> loft. The bitumen stuff I have for felt doesn't really work upside dow
> - as I found to my cost! I have found some "liquid rubber" from the
> might B&Q and this claims to stick felt. It does. However it takes at
> least 12 hours to set. Standing in the loft holding a felt patch on
> for 12 hours does not appeal to me so I wonder if anyone has some
> clever way to hold the felt in place which the rubber adhesice cures?
> My thinking stops at wedging pieces of hardboard etc between the roof
> joists - but that doens't really work as only "hold" in one spot.
> Any ideas?
> Thanks
>
> ps The felt in the loft is 40 years old. The above excepted, of looks
> in good condition. The new felts I see in B&Q etc seem a different
> type of thing. For starters the new stuff has "grains" which fall off
> all the time whereas the old stuff is dry and dust free and black -
> not "almost black". So - perhaps I am using the wrong type of felt?
> Your help would be appreciated.
It sounds like you're referring to the layer under tiles or slates on
a sloping roof. If so, this is a backup only, and its not normally
necessary to repair it where broken. Plenty of roofs have no such
lining.
NT
Harry Bloomfield
> There are a few splits and some missing piece of roofing felt in our
> loft. The bitumen stuff I have for felt doesn't really work upside dow
> - as I found to my cost! I have found some "liquid rubber" from the
> might B&Q and this claims to stick felt.
The stuff you found at B&Q is intended for hut roofs, roofs with no
tiles on top. The felt you need is nothing like that. If it is only
torn, just repair it with gaffa tape, making sure that any water which
might get blown under the tiles would be channelled down onto the next
level of felt.
--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
Dave Liquorice
> So - perhaps I am using the wrong type of felt?
Yes, you want "sarking" and really needs to be inserted through the
splits/tears such that any water running down the top of the old
surface hits the top of the new and is carried down below the hole
before being put back onto the top of the old. Bits stuck on will
just catch the water and hold it there...
o
o
no
no
nHn
on
on
on
o
o
o - old felt
n - new felt
H - Hole
Tuck the top end of the new behind a lath and the bottom end under a
lath and you don't need any glue. It can be tricky near rafters and
it might not be possible to produce a 100% leak proof section.
--
Cheers
Dave.
gunsmith
wrote:
If its 40 years old and split the chances are its life expired and
needs replacing. A non-trivial job.
Kipper at sea
> loft. The bitumen stuff I have for felt doesn't really work upside dow
> - as I found to my cost! I have found some "liquid rubber" from the
> least 12 hours to set. Standing in the loft holding a felt patch on
> for 12 hours does not appeal to me so I wonder if anyone has some
> clever way to hold the felt in place which the rubber adhesice cures?
> My thinking stops at wedging pieces of hardboard etc between the roof
> joists - but that doens't really work as only "hold" in one spot.
> Any ideas?
> Thanks
>
> ps The felt in the loft is 40 years old. The above excepted, of looks
> in good condition. The new felts I see in B&Q etc seem a different
> type of thing. For starters the new stuff has "grains" which fall off
> all the time whereas the old stuff is dry and dust free and black -
> not "almost black". So - perhaps I am using the wrong type of felt?
> Your help would be appreciated.
The type of underlay felt you need is " type 1f “, doubt if you will
be able to get the bitumen stuff and its heavy but the newer underlay
is light weight. Marley TX breather felt or a none breather 1f none
bitumen stuff is ok. To hold it in place you can staple it to the back
of the slate or tile lath. Down fall is that all the rolls of
underlay felts come in 45 or 50 mtrs rolls, approx £60 to £120 a roll.
Jules
> Down fall is that all the rolls of
> underlay felts come in 45 or 50 mtrs rolls, approx £60 to £120 a roll.
Freecycle list, source some offcuts...
John Rumm
> There are a few splits and some missing piece of roofing felt in our
> loft. The bitumen stuff I have for felt doesn't really work upside dow
> - as I found to my cost! I have found some "liquid rubber" from the
> might B&Q and this claims to stick felt. It does. However it takes at
> least 12 hours to set. Standing in the loft holding a felt patch on
> for 12 hours does not appeal to me so I wonder if anyone has some
> clever way to hold the felt in place which the rubber adhesice cures?
> My thinking stops at wedging pieces of hardboard etc between the roof
> joists - but that doens't really work as only "hold" in one spot.
> Any ideas?
> Thanks
I suspect you are worrying about it a bit too much. The felt is there as
a backup to prevent water ingress should a tile break or slip, and to
catch any fine snow that blows up the roof slope and hence under the
tiles. While routinely fitted on modern builds, it was not usually used
on older properties. So the likelihood is your roof will continue to
function just fine even with a split in the felt. The secondary problem
is that to replace a section is difficult - you would really need to
remove the tiles, and the battens, then refelt, batten and tile.
If you really want to patch it, then I would suggest an offcut of "torch
on" underfelt and a hot air paint stripper. Wearing thick leather
gloves, heat the end until it goes wet and glossy looking, and apply
this at the end of the split. Press it down and hold it til it cools and
sticks. Then fold the felt back so the underside is facing you. Now heat
the edge of that, and then slide it along and press it into position -
keep going to the end of the patch. The felt will "set" and achieve full
bond strength in the space of time it takes to cool.
--
Cheers,
John.
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Dave Liquorice
> If its 40 years old and split the chances are its life expired and
> needs replacing. A non-trivial job.
If the roof is in otherwise good condition, no slipped/missing
tiles/slates then patching up the torn sarking is worth it if only to
keep the powder snow out. I've taken half a dozen bucket fulls of
powder snow from one of our roof spaces before now and it all came
through a very small hole and it doesn't need to be a direct
straight, as in you can see light, route from the outside to insdie
for powder snow to find it's way in.
--
Cheers
Dave.
Kipper at sea
gun, on old type 1f felt. The reinforcing webbing will act like a wick
in a candle with the bitumen
John Rumm
> Don�t even try to use heat in a confined space, even from a hot air
> gun, on old type 1f felt. The reinforcing webbing will act like a wick
> in a candle with the bitumen
Your concern being what exactly? Given you won't be getting it close to
ignition temperature.
Kipper at sea
> Kipper at sea wrote:
> > Don’t even try to use heat in a confined space, even from a hot air
> > gun, on old type 1f felt. The reinforcing webbing will act like a wick
> > in a candle with the bitumen
>
> Your concern being what exactly? Given you won't be getting it close to
> ignition temperature.
>
> --
> Cheers,
>
> John.
>
Just caution, hot air guns melt paint, I’ve no idea what temperature
they heat to. But I've seen them ignite dried grass in eaves that
birds have used. You only need one strand to ignite in a loft.
If bitumen isn’t melted hot enough it won’t stick. It as to be hot
enough to soften the old felt to adhere.
John Rumm
> On Aug 22, 11:31 am, John Rumm <see.my.signat...@nowhere.null> wrote:
>> Kipper at sea wrote:
>>> gun, on old type 1f felt. The reinforcing webbing will act like a wick
>>> in a candle with the bitumen
>> Your concern being what exactly? Given you won't be getting it close to
>> ignition temperature.
>>
>> --
>> Cheers,
>>
>> John.
>>
>
> they heat to. But I've seen them ignite dried grass in eaves that
They can get hot certainly (over 300 deg C, which would ignite paper)...
Much depends on hte heat setting you use, and the amount of time you
allow it to dwell on a surface.
However you only need reach about 150 deg C to start melting most SBS or
APP felts.
> birds have used. You only need one strand to ignite in a loft.
> If bitumen isn�t melted hot enough it won�t stick. It as to be hot
> enough to soften the old felt to adhere.
Not really - as long as you melt the torch on felt, it tends to stick
like STAB. You usually arrange it such that the surface you are heating
is folled up or folded back on itself so that the substrate you are
sticking it to is protected from the heat.
Obviously, I am not suggesting one does not need to take care - but if
one is careful, the risks are fairly small and you get very fast and
lasting results in a situation where applying patches via other means is
difficult.