Help!! Re-roof problems - Ventaflex underlay leaking

[prodigymad]

Please can somebody help me! .

I have got a local roofing contractor currently replacing the entire roof and due to the typical British weather the rain is delaying the work.

At the moment I have both the front and side elevations stripped of the original tiles and he has laid down the roofing underlay (Ventaflex) with the required battens. He has assured me that this underlay is totally waterproof for up to 3 months and will be ok as a roof covering until the rain stops.

However, I have now noticed some damp patches on the interior walls so I went into the loft area to take a look and most of the rafters are soaking wet with water running down and dripping onto the ceiling.

Does this mean the underlay has been laid in the wrong way? His argument has been that it will be fine when the tiles go on as this underlay is only to stop the wind, etc.

Am I justified in asking him to re-lay the entire underlay?

Heres just one pic:

 

[datarebal]

To be honest every breathable underlay we have ever used has a saturation point and will let small amounts of water in, eventually.

It will with out doubt be fine when the tiles go on. the guy is telling you the truth
if just one or two rafters are wet it could be he has missed with a nail and this is steering it in.. take another look over the whole roof..

Looking at the photo he has given it good laps and there is not much else anyone could do short of pulling a few sheets over the top..

personally I dont think you are justified to tell him to redo it

 

[prodigymad]

Hi, thanks for the quick reply.

The underlay has been exposed to the elements since Wednesday afternoon and I did notice a couple of rafters were wet during the week so he came back to fix that area yesterday.

However at the moment it is the majority of rafters that are wet, so wet that they are leaking through to the ceiling (see below, this wood is like a wet sponge!):

The underlay is supposed to be ok for up to 3 months, I hope that it stops raining soon!!

 

[datarebal]

Ok I know it's a real worry.. but it will be fine.. obviousy if it looks like it will cause damage you could ask him to get a couple of tarps and tie them over it.. or if it's interlocking tiles ask him to at least get it roughed in.. that will take care of most of it..

Good pic.. looking at it the vertical stud might have pierced the felt where it appears to be touching.. you could try carefully cutting the contact corner off with a saw.. (just a small bit)
then see if it stops.. better still ask the guy to take another look and ask him to do it. At least that way if it's punctured he could fix it from outside..

Fingers crossed the weather dries up!

who says it's ok for three months?

 

[^woody^]

Your roofer is wrong in terms of the underlay purpose.

The purpose of felt, or membrane in a modern roof is to keep any water getting past the tiles out of the dwelling. It is not just to seal draughts - that is just a bonus - in fact membrane roofs can be more draughty than felted roofs.

Rain will get blown under the tile laps, or perculate the runners or tile, or condensation will form on the underside of the tile.

Breathable membranes are designed to typically resist the pressure of water from a 3-5m head for a few hours - so rain should never get through the material

It may well be that driven rain is being blown under the membrane laps. Or the roofer has torn the membrane, ripped it on a nail, or miss nailed - or the membran is punctured on protuding strut or nail etc.

If the membrane is punctured, then you want any holes repaired.

If the membrane is intact and driven rain is the issue, then yes, it will be fine once the tiles are on.

If the roofer is a bit hap hazard with the membrane, then I would keep my eye on the rest of the work - especially any ridge, valley or verge mortar.

In my view, you have too much water coming through in too many places. Typically the roof should be water tight once the felt/membrane is on.

Edit

You should also ask for compensation for any damaged decorations in the rooms below.

 

[datarebal]

If the tiles are fitted at correct gauge to the correct pitch then No water will blow under the laps. All tiles produced in UK are tested non stop for months for this and other things.

The underlay has been fitted with at least 150mm laps which have been cleated down..Hardly hap hazard (see pics)

I am pretty sure the vertical stud has either pierced the underlay or is pressing hard on it causing the damp on the stud.. as stated this needs attention and should not take more than 10 mins

I think the three months comment refers to resistance to UV not rain day in day out...

"a central permeable layer ensuring high water vapour permeability and superior water tightness." (does not say waterproof)

 

[^woody^]

Rain will get under interlocking tiles in certain circumstances - via the runners, as the tiles move and settle, via the ridge etc.

Also, any existing roof is most likely to have settled somewhat, and the tiles will not be perfectly flat and interlocking - there will be gaps - large or small there will be rain penetration of the tiles to some degree

An interlocking tiled roof is not as resistant as a traditional clay tiled roof - which never used to have any underlay at all. Therefore the underlay/membrane is an intergral part of the waterproofing.

As indictated in the OP's photos, there are several places where the water is coming in, and to me, that is unacceptable and indicates a lack of care/ability - it is hap hazard - if the cause is not driven rain under the laps.

That strut, if it is above the rafter line would be clearly visible, and would take 10 seconds to trim flush, rather than chance it and lay the membrane over it.

Membranes are weather resistant in use as an underlay . They will yeild under prolonged high pressure exposure, but they will never get that on a roof

Membranes which are BBA certified and installed to BS 5534 are for all intents waterproof in use

 

[datarebal]

Sorry but you are very incorrect prolong rain eventually seeps through breathable underlays as then state they are water resistant ..it does not say water proof....BBA or not
but obviously not when the roof covering is in place

A concrete interlocking tiles is more water resistant than say a clay double roman

 

[prodigymad]

Just slightly off topic:-

After reading a few other articles on the forum I have seen a few talking about roof spread.

I am concerned that the new tiles are going to be too heavy for the current roof support. The old tiles were asbestos slate and were very thin.

The new ones are Marley Eternit slates and look very thick and heavy in comparsion.

Should my roofing contractor inform me if this needs extra supports and would it be covered under the guarantee if this new roof starts pushing the walls apart.

 

[^woody^]

Sorry but you are very incorrect prolong rain eventually seeps through breathable underlays as then state they are water resistant ..it does not say water proof....BBA or not
but obviously not when the roof covering is in place

Isn't that what I said?

"They will yeild under prolonged high pressure exposure, but they will never get that on a roof

Membranes ..... are for all intents waterproof in use"

A concrete interlocking tiles is more water resistant than say a clay double roman

Maybe, but only for the first few years while the protective coating is intact. Then the resistance reduces.

Also the runners are very easily broken as the tile ages - and these are generally not noticeable from just looking at the tiles.

Clay tends to perfom much better over its lifecycle

 

[^woody^]

Just slightly off topic:-

After reading a few other articles on the forum I have seen a few talking about roof spread.

... .

The difference in weight between your new and old tiles is not that significant.

Roof spread is a different situation and is not likely to be related to any change of tiles.

If the roof is braced correctly now, then heavier tiles will not cause it to spread.

If it is not braced correctly now, then it will have spread already

 

[GuyProos]

This is a bit of an old thread, but am new to the forums and was just having a nose around so thought i'd throw my thoughts in.

Datarebels, completley right in what he's saying. Brethable felt does "leak".

I would however disagree with woody.

The purpose of felt, or membrane in a modern roof is to keep any water getting past the tiles out of the dwelling. It is not just to seal draughts - that is just a bonus - in fact membrane roofs can be more draughty than felted roofs.

The purpose of modern felts is to prevent wind uplift. Tiles are not "blown" off a roof, they're "sucked" off. Oh to be a roof tile...

There secondry purpose is to prevent water ingress, i.e act as a "backup" for if/when the tiles fail.

 

[noseall]

we lathed (tile battened) a roof on friday using breathable membrane and not a drop soaked through. i have never seen water even so much as seep through breathable membrane, even when ponding at the eaves trough.

woody's spot on.

do you honestly believe a company would make a product so that it will leak, the main purpose of that product, to keep the roof dry?

 

[^woody^]

Will that be cash or cheque matey?

 

[GuyProos]

To quote from Tyvek Literature

"Tyvek Surpo is an extremley water-resistant, airtight... etc etc"

and

"Provides temporary weather protection..."

However, saying this, I wouldnt expect a roof covered with this or similar to actually leak, unless it was prolonged in severe exposure, or pooling at the eaves.

And, ina ll fairness, another manufacturers literature (Marley) claims their brathable membrane (RoofTX) to be watertight. However, the list of what the felt is designed to do starts with:

"provide a barrier to minimize the wind uplift load acting on the slatyes or tiles"

If you ask any manufacturer, that is felt/membranes main purpose.