Do I really need a ventilated ridge?

[epsilonGreedy]

I have been delaying trying to get my head around roof space ventilation.

 

There seems to be a prevailing assumption that a modern house requires a ventilated ridge but I do not see these on some new builds near me. Digging deeper I have read that my 30 degree pitch slate roof with hipped ends can meet building regs with just eave ventilation.

 

https://www.wienerberger.co.uk/content/dam/wienerberger/united-kingdom/marketing/documents-magazines/technical/UK_MKT_DOC_TEC_ROF_SAN_Dr_John_notes_roof_space_vent_001.pdf

 

If a put some effort into meeting the "well sealed ceiling" criteria, is a ventilated ridge an avoidable complication?

 

p.s. I am likely to end up with wooden boxed eaves with a 9" to 12" overhang.

 

p.s. The underlay will be conventional felt and battens.

 

[Mr Punter]

The dry ridge systems are ventilated and allow the ridge tiles to be mechanically fixed, which is more secure and simpler than mortar bedding.

[Temp]

Depends where the roof insulation is. If it's on the floor of the loft you only need eaves ventilation and tunnels to keep it open. If its between the rafters you might need ridge ventilation if the membrane isn't vapour permeable (I think if the membrane is vapour permeable you dont need any ventilation).

 

Edited August 25, 2020 by Temp

[Onoff]

Think I asked elsewhere but can anyone recommend a dry ridge / hip system? Only for my garage but I don't know which make to avoid!

[epsilonGreedy]

14 minutes ago, Temp said:

Depends where the roof insulation is. If it's on the floor of the loft you only need eaves ventilation and tunnels to keep it open. If its between the rafters you might need ridge ventilation if the membrane isn't vapour permeable (I think if the membrane is vapour permeable you dont need any ventilation).

 

 

Thanks it is a cold attic space with insulation at ceiling joist level.

 

I have not made a decision in vapour permeable felt yet. Depending on slater availability the felt might be exposed to the elements for a month or two. I assume an old fashioned impermeable felt is tougher?  

[Declan52]

The new roof felts are much much stronger. Having them exposed for a month or 2 is fine as well. 

Do you really want to be getting up onto the roof in 10/15 years to redo motar than has came loose?? 

Plus if you ever need to remove a few tiles it's only a screw that has to come out and go back in again to expose the top row.

[Temp]

26 minutes ago, epsilonGreedy said:

Thanks it is a cold attic space with insulation at ceiling joist level.

 

 

So the main thing to avoid is insulation blocking the ventilation at the eaves. There are products like this Roll Panel designed to prevent it..

https://www.google.com/search?q=eaves+ventilation+roll+panel&client=tablet-android-samsung-nf-rev1&prmd=sinv&sxsrf=ALeKk02fV26W0P4UCVa6FKBEdZmYUStI2Q:1598367385098&source=lnms&tbm=isch&sa=X&ved=2ahUKEwj9-NXBzrbrAhUCQEEAHThkBGQQ_AUoAnoECAsQAg&biw=1280&bih=800&dpr=1.5

 

Edited August 25, 2020 by Temp

[Temp]

27 minutes ago, epsilonGreedy said:

 

Thanks it is a cold attic space with insulation at ceiling joist level.

 

I have not made a decision in vapour permeable felt yet. Depending on slater availability the felt might be exposed to the elements for a month or two. I assume an old fashioned impermeable felt is tougher?  

 

Think I used VP400 and it was exposed at least 6 months, much longer than recommended with no problems.

[PeterW]

5 minutes ago, epsilonGreedy said:

 

Thanks it is a cold attic space with insulation at ceiling joist level.

 

I have not made a decision in vapour permeable felt yet. Depending on slater availability the felt might be exposed to the elements for a month or two. I assume an old fashioned impermeable felt is tougher?  

From memory you can’t get a BS under felt any more suitable for new build. The breathable ones are much nicer to work with and they are cheap as chips. Nothing wrong with putting two layers on either if it will be left open for a period - just buy a cheap disposable one to go over the top of the first tacked down with a few counter battens. 
 

52 minutes ago, Mr Punter said:

The dry ridge systems are ventilated and allow the ridge tiles to be mechanically fixed, which is more secure and simpler than mortar bedding.

 

+1 to that - they are simple to use and not expensive.  
 

28 minutes ago, Onoff said:

Think I asked elsewhere but can anyone recommend a dry ridge / hip system? Only for my garage but I don't know which make to avoid!

 

Timloc Easy Ridge system are good - they need a timber up stand in the centre of the ridge but nothing too complex. 

[wozza]

4 hours ago, Onoff said:

Think I asked elsewhere but can anyone recommend a dry ridge / hip system? Only for my garage but I don't know which make to avoid!

 

http://www.fix-r.co.uk/shop/tilr/dry-fix-ridge-kit/universal-dry-fix-ridge-kit/

 

@Onoff   I used this - it was cheap and easy to do - never used one before but SWMBO and I did it no problem, we got it from the local roofing place who suggested using it saying it was as good as the more expensive ones.

 

 

Edited August 25, 2020 by wozza