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Gavin Bl

soffit vents - circular? rectangular?

It seems that I need to fit some vents to allow airflow in my loft.

The roof overhangs somewhat, and the original long soffits fitted on the underside boards were removed when it was refurbed (prior to me buying it).

It seems that circular soffits (68mm diam) are suitable for this, as I can cut the board and insert them, but they are 4 per metre, meaning I need to do 25 on each side of the house? Surprised

Anyone done this before, is there a slightly bigger, maybe rectangular, vent that I can fit at more infrequent intervals? I don't want to fit a full length soffit on the underside, if I can avoid it.

thanks alot
Gav
Gervase

How big are your soffits at the moment? There are plenty of rectangular vents that can be fitted - kober is one brand name.
Fitting the circular vents is pretty straightforward, though - just use the appropriately-sized hole-cutter on an electric drill and the plastic vents just push into place. You could fit 50 in about an hour if you've got scaffolding, or take around five minutes for each one with ladders - and the whole thing would actually be much quicker than cutting out the rectangular holes for fewer but larger vents.
I'm intrigued as to where the four-per-metre rule on soffit vents comes from. The usual practice is to put one in every rafter bay or at 600mm centres. Some vent manufacturers say to use more - but they woudl say that, wouldn't they?!
For optimum ventilation in a roof fitted with a completely impermeable vapour barrier or similar sarking, you should think about ridge vents, or some sort of ventilation near the apex. If, however, you've got a breathable sarking, like Tyvek, then you probably won't need ventilation at all.
Gavin Bl

thanks alot Gervase, the original soffits are full length of the house, but individual vents are small - maybe 30-40mm long and 5-10mm wide in a long line. These however were removed when the house was refurbished.

The underside board is reachable out of the windows - and I don't have big ladders or scaffolding.

Thanks for the tip on the 600mm spacing - funnily enough I noticed them a similar distance apart on another house on the street.

Ideally I like to have a ridge vent, but cost and tradesman hassles are off-putting to be honest.

cheers
Gav
Walda

Hi,

I am new today, so first of all hello to all those on the forum.

I have just (10 month) moved into a bungalow which needs a bit of loving.

I roved with my 9.99 moisture detector and got a reading in the loft. I noticed that there are no soffit ventelators, but there is a ridge vent (round hole about 4inches with a cap).

my question to those who hold the knowledge,

do i need to install soffit vents,

second point, i was considering installing an extractor fan to move the air out through the ridge vent,

any comments would be appreciated.

thanks,

Walda
sean

Welcome aboard. I've no idea about the answers to your questions I'm afraid but I'm sure someone else will be along soon.
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