How do roofs work?

[AMc]

A thought occurs... how deep is the void?
If you can feed layer of wooly insulation next to the interior wall and then hold it in place away from the inside of the roof with say 25mm thickness of celotex/ecotherm/kingspan board cut as tight as you can, you might get the best of both? The wool/fibre would help to prevent ventilation losses around the board and you could maintain a ventilation layer between the insulation and the inside of the roof?

Thinking further you could put a thin layer of board in, wedge it off the inside of the roof with wood battens then inject expanding foam between the board and ceiling to seal the board against the ceiling. Remove the wedges after the foam has cured and you have insulated the internal surface and maintained an air gap under the external surface.

BUT I have to say that any method that involves solid insulation is going to prevent moisture movement a.k.a. breathability so you really need to understand where the existing damp is coming from to make sure you are stopping it coming into the house from the roof not making it worse by trapping moisture from a different source inside the room. Adding an impermeable plastic layer would also be irreversible so if those are original walls (lath and plaster/reed and plaster etc.) then I would be loathed to recommend it. If it's plasterboard then I would be considering it.

You could also look at loose fill insulation kept off the inside of the roof with mesh and capped to stop it blowing around.

Whatever you do I would remove the existing insulation then take your time to decide what's next.

 

[Lime]

The issue is with air tightness.

Precisely.
If there is any air movement/circulation between the warm ceiling and the underside of the insulation nearly all the benefit is lost.
Further, obstructing the narrow space between the roof and ceiling will reduce ventilation considerably if no gap is allowed between the felt and the insulation.

You would be much better off to remove any old insulation from out of the void and fit insulation to the ceiling within the room.

 

[vicky whitworth]

I really do appreciate all your kind advice and opinions. The void between the ceiling and the roofing felt is merely the depth of the rafters - about 3 inches. I suspect that the sloping ceiling is nailed to the rafters. The builder thought he could get the old insulation out of the void but as has been pointed out we couldn't get a good seal with solid board insulation as it would have to be slid down between the rafters into that tiny gap while at the same time allowing a 50mm gap to allow the soffit grills to function properly. I have tried to attach a pic but I'm not too good at the technology so who knows what might happen...
We can't create new ceilings in the bedrooms because we already bump our heads when getting out of bed (I have had to have emergency eye surgery for a detached retina when I bashed my head on a low beam).
The builder suggested we move...

 

[worms]

Interesting pictures. Is there something above that is allowing water to drip along the lines of the pools, something underneath that is causing condensation to form along these lines, just the camber of the floor boards or something completely different going on?

I reckon when a builder suggests you move, the answer is ...to a different builder!

 

[Lime]

Interesting pictures. Is there something above that is allowing water to drip along the lines of the pools, something underneath that is causing condensation to form along these lines, just the camber of the floor boards or something completely different going on?

I reckon when a builder suggests you move, the answer is ...to a different builder!

Perhaps the builder has a point?
The picture of the damp drips shows just how serious this situation is.
The roof is under a serious threat both from rot and rust.
Old nails rust very fast when in damp conditions.
Little else but nails hold many roof timbers up.

 

[worms]

Lime, hope all is well with you, your posts this morning (here and on the "brick plinth" thread) are fairly pessimistic!

In this case, you may be right, but I suspect that many of us are living with buildings where common sense would suggest that the best option would be to move or demolish rather than repair!

 

[Flyfisher]

Moving home because of a leaking roof seems a bit extreme. The expense involved would probably pay for a completely new roof to be built!

Worms makes a good point about the pattern of water though. If the problem is condensation then I'd expect it to be forming throughout the roofspace, so is there a particular feature we can't see in the photo that's causing it to drip along those two lines?

 

[MdB]

Just a thought. You don't have any extractor fans from the kitchen / bathroom that pass through the roof space? If a ducting pipe has failed / fallen off then that might explain the excessive moisture in your loft.

 

[Lime]

Lime, hope all is well with you, your posts this morning (here and on the "brick plinth" thread) are fairly pessimistic!

In this case, you may be right, but I suspect that many of us are living with buildings where common sense would suggest that the best option would be to move or demolish rather than repair!

I'm facing a similar but relatively very minor dilemma of my own today.
~Do I cut through existing skirting, dado and picture rail etc to install an interior porch or do I cut out the wooden porch to fit round them?
(It would make the job much easier to cut the skirting et al.)
My instinct says cut the porch.
Except my draught-excluding part of my brain then asks what about the gap that runs under and behind the skirting (it is a tall skirting).. it will let through cold air and bring in a lot of dirt.
I do have a solution to that however.

..... back to the thread.

No I'm not suggesting moving is a good idea.
Apart from the expense you know for sure that prospective purchasers are all going to look in the loft!!

But the roof does require thorough ventilation NOW.
The longer it is left the worse it will get.

 

[Flyfisher]

Is the brickwork just beyond the chimney stack an outside wall? If so, might that be a good place to insert an airbrick? Perhaps one each side of the stack?

 

[worms]

But the roof does require thorough ventilation NOW.

If it is as bad as you were fearing earlier, it may suddenly get way too much ventilation!

 

[vicky whitworth]

Oh, now you're scaring me. I think the water is pooling in this way because of the camber of the boards (which are chipboardy stuff). The condensation drips off the rafters. You can stand there and watch it. It's no comfort for me to say that I'm 100% sure it's not the roof leaking - the tiles and the felt are in good nick. The roof is wet everywhere. The insulation (what there is of it) is wet to touch throughout the roof. There's no extractor fan pipe work running through. I'm sure it's a straight 'we produce too much moisture in the family' problem. Several rooms replastered last year, central heating pumping away, hot kitchen. steaming baths, wet washing drying in the scullery.

Here's what I think needs doing having listened to all the advice...

• The insulation stuffed down the gaps between the sloping ceilings and the roof felt needs removing to allow the soffit grills to work.
• This void needs insulating to prevent condensation forming in the bedrooms and bedroom heat passing through the plasterboard into the loft.
• A gap needs creating (50mm?) within this void to enable the soffit grills to function.

Issues: How to get insulation out of this void without removing the tiles?
How to get a good seal with solid board insulation being slid down the gap between the rafters if the tiles are still on?
How to ensure there is a fixed gap so the soffits work? Or is it really possible to use a breathable insulation in the void that would enable the soffit grills to work effectively? I don't think so personally.

• All four loft hatches need draught excluding and three of the four could be sealed more permanently.
• There is a gap in the ceiling in the stair well where the 1990s extension joins the older part. This needs sealing. About 10mm in places.

• Ridge vents are needed along the whole length either lapvents or another unobstrusive alternative.
Issues: How many lapvents are needed?
Should we have another air brick inserted? We only have one at one end.

• Remove existing loft boarding.
• Remove rubble and tidy up.
• Smother loft floor and hatches in insulation – both between the joists and across the joists, holding it back from the edges so that the soffits grills can function. 300mm? Or is it 100mm between the joists plus 300mm across the joists?

• Leave the existing roofing felt in place unless the tiles have to come off.

The complicated bit seems to be to decide whether sliding solid board down the sloping ceiling void will actually work with the tiles on. And so the expensive bit is if the tiles have to come off...

Strikes me that it all comes down to money! So any advice on where I can find a rich Sugar Daddy?

 

[worms]

Sorry, that was a flippant remark that was not intended to scare. I'm not in the "doom and gloom" camp and I am of the opinion that one of the advantages of old properties is their resilience in the face of adverse conditions.

Unless there is an open vent from your house to the attic, I can't see how the internal humidity can be so badly affecting the loft space. One thing is clear, you need to get airflow through there as a priority.

 

[Louis Henry]

• All four loft hatches need draught excluding and three of the four could be sealed more permanently.
• There is a gap in the ceiling in the stair well where the 1990s extension joins the older part. This needs sealing. About 10mm in places.

I'm sure this is the root of the problem, plus the recent cold still weather. Fix this, which is comparatively quick easy and cheap, then work on improving the ventilation. Modern practice would be to put a sheet of plastic over the ceiling, under the insulation, to keep the water vapour out of the loft, but how this ties in to the breathability we normally go for in an old house, I would be interested to see expert opinion on. But I am sure filling those gaps in the ceiling will help a lot.

 

[Flyfisher]

Should we have another air brick inserted? We only have one at one end.

Another airbrick at the opposite end to the existing one should be a good way to introduce some though-ventilation in the attic space. I would expect that, and sealing the four loft hatches as previously mentioned, would go a long way to solving the condensation problem.

Just another thought. Since the attic space seems to be wet with condensation everywhere, would it be worth considering a portable dehumidifier as a temporary measure?

 

[Feltwell]

Just another thought. Since the attic space seems to be wet with condensation everywhere, would it be worth considering a portable dehumidifier as a temporary measure?

They don't like the cold though FF - I think it's below about 5 degrees that they cease to work. In this weather in an attic space I'm not sure one would work very well.

 

[worms]

They don't like the cold though FF - I think it's below about 5 degrees that they cease to work.

I know I've been ridiculed for saying it before, but I am still happy with the performance of my desiccant wheel dehumidifier, which claims functionality at lower temperatures than refrigerant types. Part of the benefit may simply be down to the air movement that it causes, but that in itself may also help in the attic situation. I guess also if the amount of air movement from house to attic is enough to carry all that moisture, the attic temp may stay well above the 5 degrees.

 

[skier-hughes]

litter picker is useless, I spent 15 mins and had got a handful of insulation out, as it just rips off a very small piece at a time. Besides the fact I bought one that advertised a 1.5m reach, only to find 60cm of that will be your arm length!!!!!!!!!
I've given up and will get a ladder out tomorrow and see what I can find from outside.

 

[AMc]

Perhaps you need a leaf vacuum or industrial hoover?

 

[skier-hughes]

leaf hoover won't fit, but I could try the ind. vacuum, suck up a piece to hold it and drag it up.
Just off to get ladder and look from outside to see if I can see any way of poking it upwards.