Reparing pitched roof internal felt - from the inside?

[JakeD]

A section of the felt is missing from the inside of my pitched, tiled roof.
It's about a 2 mtr length, and two rafter-spaces wide. The tiles are the
fairly common large concrete type and the roof has 4"x2" rafters and
standard 1" battens. Is it feasable to restore the missing felt from the
inside, without removing roof tiles? Alternatively, is there another way to
affect a repair (expanding foam, perhaps)? I mainly just want to keep cold
wind from entering the loft between the tiles in that area.

Thanks,

Jake

[Cash]

JakeD wrote:
> A section of the felt is missing from the inside of my pitched, tiled
> roof. It's about a 2 mtr length, and two rafter-spaces wide. The
> tiles are the fairly common large concrete type and the roof has
> 4"x2" rafters and standard 1" battens. Is it feasable to restore the
> missing felt from the inside, without removing roof tiles?
> Alternatively, is there another way to affect a repair (expanding
> foam, perhaps)?

A temporary patch yes, by tacking the felt (or even a plastic sheet) to the
underside of the tiling battens (which will let in the rain in the event of
tile damage) - but a permanent repair will require the
lifting of tiles and battens in the affected area.

> I mainly just want to keep cold wind from entering
> the loft between the tiles in that area.

Even if you carry out a permanent repair, you won't stop the wind blowing
into the attic - simply because of the way the roof is constructed -
besides, some 'draught' in the roof space is required to prevent the
build-up of interstitial condensation on the underside of the roof felt.

If you are trying to keep the heat in the property, then you would be far
better off filling the roof space with around 280mm of loft insulation and
insulating any pipes and tanks there against freezing.

Cash

[JakeD]

"Cash" <.............\\@...............//.com> wrote in
news:9i3a55...@mid.individual.net:

> If you are trying to keep the heat in the property, then you would be
> far better off filling the roof space with around 280mm of loft
> insulation and insulating any pipes and tanks there against freezing.

Thanks... I've already got the pipes lagged - and 280mm of loft insulation,
thanks to B&Q offering the stuff for £3 for 3 rolls at present. But it does
seem extremely drafty up there, when the wind is blowing, which must be
leeching warmth from the house, despite the insulation.

Al

[Cash]

Not really Al. As long as the attic trap door also has the same thickness
of insulation fixed on top of it - and draught strips to seal the trap door
where it sits on the frame.

Also, it really is a good thing to have an airlow in the attic - hence the
soffit and roof vents that are fitted to many houses these days that have
good loft insulation.

As a matter of information: My wall cavities are filled [1], my loft is
fully insulated, the trap door covered and sealed with a draught strip and
all roof sarking felt intact - yet there can be what appears to be a force
10 gale blowing around up there, with the temperature at or below freezing,
yet the bedroom that I now use as computer room-come office, is a nice
comfortable 65� without the C/H on and around 74�when SWMBO turns the
heating on.

All bedrooms, landing and bathroom are the same - and all bedroom rads have
thermostatic rad valves fitted.

[1] As an old builder, this was done against my better judgement, but
retirement and increased heating costs sort of forced the issue - and I must
admit, the job has certainly cut my heating costs. All I'm waiting for now,
is for my old Baxi wall boiler to pack up, which because of the shortage of
some spares, will force me to replace it with a new condensing boiler.

(It's not cost effective to replace it now just to 'save' some money on gas,
because of the length of time it takes to recover the capital outlay of the
boiler in energy saving costs).


Cash

[Jim K]

On Nov 11, 12:56 am, "Cash" <.............\\@...............//.com>
wrote:

<snip>

> Even if you carry out a permanent repair, you won't stop the wind blowing
> into the attic - simply because of the way the roof is constructed -
> besides, some 'draught' in the roof space is required to prevent the
> build-up of interstitial condensation on the underside of the roof felt.

<snip>

<nitpick on>

it's not really *interstitial* condensation on the underside of
roofing felt, just plain old common garden condensation ...

<nitpick off>

Jim K

[Cash]

If it 'hangs' on the sarking felt. it's technically interstitial
condensation - or at least that was what I was told by the 'experts' way
back when I was attending the local building college for five years as a
snotty nosed apprentice - see:

http://www.sispecificationandsupport.co.uk/ica.asp

Cash

[Cash]

Jim K,

Just re-read the post and apologies if the tone of it sounds a 'bit testy' -
been having a bad day, even SWMBO, who has just gone to bed calling me a
"grumpy old b*****d" thinks so - (and it really is unusual for her to use
such language - so...).

Cash

[Dave Liquorice]

On Fri, 11 Nov 2011 00:56:06 -0000, Cash wrote:

>> Is it feasable to restore the missing felt from the inside,
without
>> removing roof tiles?
>

> A temporary patch yes, by tacking the felt (or even a plastic sheet) to
> the underside of the tiling battens

Such a temporary patch can be pretty effective at keeping any wet out
though. The weak points are the holes you need where a batten crosses
a rafter. Everything else can be lapped such that any water that does
get onto the felt can find its way to the gutter.

The lapping is a bit complex to explain but essentially the top of
the new bit over laps on the loft side of the old at the top and
sides. The sides need to be formed so that water will tend to stay on
or move to the middle of the new. The bottom needs to be over lapped
with the old on the roof side. you should able to push it down the
gap between a batten and the old felt. Each rafter gap will have to
be dealt with individually, think about how the joins at the rafters
over lap.

--
Cheers
Dave.

[Cash]

Dave Liquorice wrote:
> On Fri, 11 Nov 2011 00:56:06 -0000, Cash wrote:
>
>>> Is it feasable to restore the missing felt from the inside,
> without
>>> removing roof tiles?
>>
>> A temporary patch yes, by tacking the felt (or even a plastic sheet)
>> to the underside of the tiling battens
>
> Such a temporary patch can be pretty effective at keeping any wet out
> though. The weak points are the holes you need where a batten crosses
> a rafter. Everything else can be lapped such that any water that does
> get onto the felt can find its way to the gutter.

I concur with that Dave - I've done it many times after storm damage, and I
used to form a trough in the "felt patch" and aim this into a rather large
container below to catch any 'loose' water until a 'proper' repair could be
done, rather than try and re-direct it down to the gutter.

Cash

[Dave Liquorice]

On Sat, 12 Nov 2011 00:33:50 -0000, Cash wrote:

>> Such a temporary patch can be pretty effective at keeping any wet
out
>> though. The weak points are the holes you need where a batten
crosses
>> a rafter. Everything else can be lapped such that any water that
does
>> get onto the felt can find its way to the gutter.
>
> I concur with that Dave - I've done it many times after storm damage,
> and I used to form a trough in the "felt patch" and aim this into a
> rather large container below to catch any 'loose' water until a 'proper'
> repair could be done, rather than try and re-direct it down to the
> gutter.

Once the water is on the new felt with the bottom of that slipped
between the old felt and batten at the bottom it should find it's way
to the gutter, just as any other water on the felt would. As you say
form the new felt into a shallow trough so water will flow down the
middle rather than the edges where it might find the holes required
at the batten/rafter intersections and it will be almost as good as
contigious felt.

I had to work all this out during a storm when the only roofing was
the old felt. the slates where all off as the roof was in the middle
of being relaid by others. The wind got under the old felt and
started ripping it off, fortunately the new battens had arrived and I
had some long enough nails to "batten down the hatches" but not
before there where a number of rips/tears in the felt.

--
Cheers
Dave.

[Jim K]

On Nov 11, 11:32 pm, "Cash" <.............\\@...............//.com>
wrote:

No probs fella - still not interstitial if you can see it ;>)

e.g. google interstice :-

amongst others:-

interstice (plural interstices)

1. A small opening or space between objects, especially adjacent
objects or objects set closely together, as between cords in a rope or
components of a multiconductor electrical cable or between atoms in a
crystal.

the underside of roofing felt is open (hence you can observe and touch
any condensation) so by definition it's not interstitial...

Jim K