Installing vents in an existing roof

[DeeEyeAye]

Hi- first post here.
Had a quick search but couldn't find anything that was quite the same situation.
I'm doing a loft conversion and one of the buildin warrant conditions is that I should ensure adequate ventilation to the roofspace. This includes an air gap between the sarking and the insulation (done) plus vents equivalent to a 5mm gap at eaves level (should be easy enough) plus the same at high level (either 5mm equiv along the ridge, or double that at a slightly lower level).
The roof construction is timber rafters rather than trusses, and concrete tiles. The total length of roof concerned is about 6m.
I'm wondering what will be the easiest/cheapest/most effective way forward. I'm quite wary about making holes in the roof and wonder if vented ridge tiles might be easier? The only ones I've seen didn't have much ventilation in them though so I may have to use them along the entire length of the ridge, which would not be particularly easy or cheap...
Thanks in advance.

 

[freddiemercurystwin]

For my lofty's I normally specify 3 vent tiles each side as near the ridge as is practicable, this normally satisfies Building Control. I daresay it wouldn't be too hard to do the calc to check whether this is adequate or not for your roof.

Ridge vents are not designed in the first instance as a retrofit hence why they need to be continuous along the whole length of the ridge.

Whichever is cheaper/easier for you to install will be the right route to take.

 

[DeeEyeAye]

Thanks for that, so it looks like ridge tiles are out.
Will it be hard to find vents that are compatible with my tiles- or are they pretty generic? I'm quite worried about having to make holes through the felt, but I presume the vents are well enough designed to allow me to make it all good... and if in doubt sikaflex....

 

[DeeEyeAye]

Hi again
OK, so having discounted ridge vents, I've been trying to find out what sort of tiles I have so that I can buy compatible vents. A few queries though:

- how much is it necessary to worry about the type/size of tiles that I have? I have seen reference to 'universal' tile vents.
- from a spare tile that I found, I know that I have Marley tiles. The Mendip range on their website looks identical, as far as the photos go. Is it safe to assume that this is what I have, even though the tiles date back to about 1980?
- if I buy something like this: http://www.rooftrader.co.uk/slate-tile-vents/tile-vents/marley-mendip-tile-vent.html will I need some sort of kit to go through the felt and sarking, or will this be all that I need?

Many thanks!

 

[Alastairreid]

The tile is all you will need, cut an inverted T in the felt and fold back before cutting through tha sarkin.

Or follow these instructions.

http://www.kloeber-home.de/uk/download/uk.fitting_instructions.Profile_Line_Vent.pdf

 

[datarebal]

the universal vent tile will fit the mendip

 

[RedHerring2]

I'm in the process of installing additional ridge vents. They don't come cheap, about £55 each for a vented smooth half round ridge tile.

 

[DeeEyeAye]

Yes I ruled out the ridge tiles because they were expensive and it seems that you need a continous line of them (small vent area per tile) so that puts the price even higher and more work too!

As I am retro-fitting these vents as part of a loft conversion, does anybody have any tips on placing them? Obviously I need to avoid the rafters under the roof, but until I've made a hole, how do I work out where the rafters are...

 

[freddiemercurystwin]