i'm in the process of renovating a cafe/gallery. the building is 1
1/2 storeys and the upstairs is vacant at present but ultimately we
hope to open it up (coombed ceilings). however we are installing
heating downstairs and so i want to insulate the roof. i was planning
using rigid insulation above and beneath the rafters so i got in touch
with my local BC re ventilation. i was surprised to find out because
this is a commercial building the ventilation rules do not apply and I
am not obliged to install any. however I tend to think that these
guidelines are put in place for a reason and of course condensation
would be an issue so I DO WANT to ventilate but am just wondering what
a sensible solution would be. the rafters are at ~400mm (although
they do vary) centres and venting every bay seems excessive. There is
no soffit, I would get a vented ridge placed on the top so ventilation
would be required at the bottom of the roof.

there are probably 60 bays so i was thinking perhaps venting every
third and providing ventilation to the ones either side by drilling
holes through the rafters - would this work?

or because there is no soffit maybe removing stones (stone wall
exterior) from the top of of the wall.

any recommendations greatly appreciated?

On 16 Feb 2007 03:25:25 -0800, wrote:

|!i'm in the process of renovating a cafe/gallery. the building is 1
|!1/2 storeys and the upstairs is vacant at present but ultimately we
|!hope to open it up (coombed ceilings). however we are installing
|!heating downstairs and so i want to insulate the roof. i was planning
|!using rigid insulation above and beneath the rafters so i got in touch
|!with my local BC re ventilation. i was surprised to find out because
|!this is a commercial building the ventilation rules do not apply and I
|!am not obliged to install any. however I tend to think that these
|!guidelines are put in place for a reason and of course condensation
|!would be an issue so I DO WANT to ventilate but am just wondering what
|!a sensible solution would be. the rafters are at ~400mm (although
|!they do vary) centres and venting every bay seems excessive. There is
|!no soffit, I would get a vented ridge placed on the top so ventilation
|!would be required at the bottom of the roof.
|!
|!there are probably 60 bays so i was thinking perhaps venting every
|!third and providing ventilation to the ones either side by drilling
|!holes through the rafters - would this work?
|!
|!or because there is no soffit maybe removing stones (stone wall
|!exterior) from the top of of the wall.
|!
|!any recommendations greatly appreciated?

You will be covered by the Health and Safety at Work Act.
Why not contact the Health and Safety Executive?
http://www.hse.gov.uk/

As you are intending to use the premises as a cafe, you will have to
satisfy the local Environmental Health Officers eventually, why not contact
them first and gain a few brownie points.
--
Dave Fawthrop dave hyphenologist co uk
20,000 free e-books at Project Gutenberg! http://www.gutenberg.org
For Yorkshire Dialect go to www.hyphenologist.co.uk/songs/
http://www.gutenberg.org/author/John_Hartley
http://www.gutenberg.org/author/F_W_Moorman

On 16 Feb, 11:56, Dave Fawthrop
wrote:
On 16 Feb 2007 03:25:25 -0800, wrote:

|!i'm in the process of renovating a cafe/gallery. the building is 1
|!1/2 storeys and the upstairs is vacant at present but ultimately we
|!hope to open it up (coombed ceilings). however we are installing
|!heating downstairs and so i want to insulate the roof. i was planning
|!using rigid insulation above and beneath the rafters so i got in touch
|!with my local BC re ventilation. i was surprised to find out because
|!this is a commercial building the ventilation rules do not apply and I
|!am not obliged to install any. however I tend to think that these
|!guidelines are put in place for a reason and of course condensation
|!would be an issue so I DO WANT to ventilate but am just wondering what
|!a sensible solution would be. the rafters are at ~400mm (although
|!they do vary) centres and venting every bay seems excessive. There is
|!no soffit, I would get a vented ridge placed on the top so ventilation
|!would be required at the bottom of the roof.
|!
|!there are probably 60 bays so i was thinking perhaps venting every
|!third and providing ventilation to the ones either side by drilling
|!holes through the rafters - would this work?
|!
|!or because there is no soffit maybe removing stones (stone wall
|!exterior) from the top of of the wall.
|!
|!any recommendations greatly appreciated?

You will be covered by the Health and Safety at Work Act.
Why not contact the Health and Safety Executive?http://www.hse.gov.uk/

As you are intending to use the premises as a cafe, you will have to
satisfy the local Environmental Health Officers eventually, why not contact
them first and gain a few brownie points.
--
Dave Fawthrop dave hyphenologist co uk
20,000 free e-books at Project Gutenberg!http://www.gutenberg.org
For Yorkshire Dialect go towww.hyphenologist.co.uk/songs/http://www.gutenberg.org/author/John_Hartleyhttp://www.gutenberg.org/author/F_W_Moorman

i have already been in touch with environmental health - they are
satisfied with how we are proposing to refit the kitchen - upstairs
will be a gallery i just want to make sure i put in place measures to
minimise condensation risks while maximising insulation.

building regs require a 50mm ventilated space above any insulation added to
rafters,and this needs to be fixed so that the space can not be
compromised,this is done by adding battens,to prevent the insulation moving

are you saying that rafters are open at soffit,if so I would add a facia and
soffit then ventilate this space difficult without pictures.

all the above is for residential,

wrote:

there are probably 60 bays so i was thinking perhaps venting every
third and providing ventilation to the ones either side by drilling
holes through the rafters - would this work?

First question is does the roof have any sarking under the tiles? If not
then job done!



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 17 Feb, 00:25, John Rumm wrote:
wrote:
there are probably 60 bays so i was thinking perhaps venting every
third and providing ventilation to the ones either side by drilling
holes through the rafters - would this work?

First question is does the roof have any sarking under the tiles? If not
then job done!

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

yes there is sarking, its actually 3 roofs because historically its
been added to over the years (long time ago)
the first section and mid section has what seems to be tongue and
groove sarking, probably with tar based felt on top of that. the end
section newset has sarking through which i can poke a key and touch
the slate so this part may not need ventilating.
its the first two sections i'm concerned about ventilating - just
wondering if there is a way without venting every bay - leaving a 50
mm airgap but then venting between the bays by drilling holes through
the rafters?

On 16 Feb 2007 03:25:25 -0800, a particular chimpanzee,
randomly hit the keyboard and produced:

i was planning
using rigid insulation above and beneath the rafters so i got in touch
with my local BC re ventilation. i was surprised to find out because
this is a commercial building the ventilation rules do not apply and I
am not obliged to install any.

I must say I'm mystified by this statement. Requirement C2 (and
before it F2) has applied to all buildings since 1990, as the primary
concern is not the health of the occupants, but the damage to the
structure and performance of the building.

It could be that you are merely installing additional insulation to an
existing vaulted ceiling. You would not be carrying out a material
alteration (ie, making the ventilation any worse than it was before),
therefore you are not _required_ to install any additional
ventilation. Although, as you will be 'renovating' the roof over more
than 25% of its area (by replacing the plaster), you are required to
insulate the roof to a minimum standard.

A few solutions present themselves:
1. As pointed out elsewhere, if you don't have roofing felt, it most
likely that there will be sufficient ventilation to begin with. If
you do have felt, then you can wedge the laps open slightly.
2. If you don't have an overhanging soffit, but you have a fascia, you
may be able to lift up the bottom row of tiles and insert a continuous
over-fascia vent strip.
3. If the wall is built up to the underside of the tiles, you could
remove the top mortar bed and insert some vents in there.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"