Insulation under the roof tile boards?

[aj]

We had the roof replaced a few years ago. Terracotta pan tiles, wooden boards underneath and resting on new wooden beams. We would have liked a 'membrane' sheet under the tiles, but "you don't get what you don't ask for".

We're not having a ceiling, just leaving the beams exposed with insulation? and plasterboard.

There are gaps of up to an inch between some of the boards. Should I fill the gaps and seal the boards with membrane? Can anyone tell me what I can put under the boards, between the beams, before I plasterboard.  

Thank you

 

[Quillan]

I butted battens up to the boards and to the beams, fixed them with screws then used plasterboard with polystyrene foam stuck to it (you buy it like that). I then screwed the sheets to the battens, taped the joints and filled in the edges. My beams are rough, not smooth so filling and painting the plasterboard is grief because you don't want to get anything white on the beams because it is so difficult to get off as the beams absorb the stuff. Shed loads of masking tap was used.

If I had smooth beams I would varnish them first as this will stop the beams from absorbing the filler and paint If rough give them a coat to seal them a bit then paint them again afterwards. It's not a bad job to do, I used a hand ripsaw to cut the plaster board and trim off enough polystyrene along the edges so I could crew them to the battens. Loads of screws and a good electric screwdriver with a good clutch on it is a must.

I used the semi adhesive fabric tape for the joints and cut all the plasterboard width ways. Although this makes smaller sections they are more easy to handle and as the boards were feathered edged I got away with just jointing, light sand, another coat of jointing filler then painted. Once you have twenty or so joints you can actually do it in one go. I bought pre mixed joint compound because it is exactly the right consistency and you don't get any lumps at in it.

It looks really good when finished and makes the room warmer. We actually use an office desk fan in the winter on its lowest setting. This stirs up the air else all the hot air goes up to the highest point and the room feels colder. The benefit in summer is that the hot air rises and keeps the room cooler. The only thing I would do different is fit two or four velux windows in the roof. Electric opening ones with electric blinds and open them late evening in the summer to let the hot air out.

Hope that helps and good luck.

PS. If you want to put ceiling lights up then do that after you install the battens but before you put the plaster board up. You can drill a hole through the battens and beams to put the cable in then make a small mark on the beam so you know where the cables are so as not to put a screw through the cable.

[Frederick]

I have this sort of insulation stapled to the boards between the beams then covered by plaster board ,  Its cool in summer warm in winter...There must be plenty of other material  also available to you ...

http://www.superquilt-insulation.com/index.php

[ericd]

[quote user="Frederick"]I have this sort of insulation stapled to the boards between the beams then covered by plaster board ,  Its cool in summer warm in winter...    http://www.superquilt-insulation.com/index.php

[/quote]

Frederick, you must be the only person I know who is happy with the comfort of the thin "superquilt" insulation material. These "should" work if a 20mm gap of still air is ensured on both sides of the thin insulation.

[Frederick]

The stuff was already in place under a new roof as I bought a not completed renovation . l just added battons and the plasterboard .I have no experience of anyother kind to compare how good it is We just find the house keeps comfortably warm when the heating is needed and cool in the summer

[woolybanana]

[quote user="ericd"]

[quote user="Frederick"]I have this sort of insulation stapled to the boards between the beams then covered by plaster board ,  Its cool in summer warm in winter...    http://www.superquilt-insulation.com/index.php

[/quote]

Frederick, you must be the only person I know who is happy with the comfort of the thin "superquilt" insulation material. These "should" work if a 20mm gap of still air is ensured on both sides of the thin insulation.

[/quote]

Tell us more svp ericd as I was thinking of putting some on.

[ericd]

Happy to do so.

None of the French DIY forum I visit (futura science for example) have positive comments about what is known as "multicouches". The R values given by the manufacturers were achieved in extremely controlled conditions and rarely admitted. For the "superquilt Multicouche" foil to work effectively, one has to ensure a still air gap on both sides of the foil. In the loft, one of the sides will be in constant draft (roof side) and the foil won't work correctly. The foil is good for the summer heat as it will reflect back out any heat that penetrates the tiles/slates etc. hence Frederick's room feeling nice and cool in summer.

Frederick's experience of a warm feeling in winter doesn't mean anything. Yes he can feel warm but his radiators are may be working overtime and the heat getting lost to the outside. This he can confirm.

In a loft I would hesitate using the multicouche on its own for winter usage. If it were used in parallel with another insulater (Rockwool etc. ) then it could work if fitted correctly.

Against a wall this is different. Batten the wall with 30mm/25mm and stapple the foil in place to the battens. Then batten the same way again on the room side. Ensure all foil perimeters are stuck to wall and ceilings using continuous bids of squirty mastic. Use strong masking tape (sold with the rolls of foil) to stick sheets of foil together, remember you are doing this to ensure no air moves from one side of the foil to the other. Plasterboard on battens as you would (watch out for screws as threads tend to bite into man-made fibers inside foil insulation). Nails would be better.

I hope this helps.

 

[woolybanana]

Thank you, eric. What about the insulation made from sheeps' wool, any good?

[ericd]

[quote user="woolybanana"]Thank you, eric. What about the insulation made from sheeps' wool, any good?[/quote]

Sheep wool is an excellent insulator but the worry concerns its lifetime performances. For roof insulation, sheep wool should be stappled to the beams or it will collapse in time. The jury is still out on life expectancy. Sheep wool can be attacked by mites (although manufacturers deep it in "Sel de Bore" to stop this happening, it's not mite-proof 100%) you won't be noticing the day you are (if you are) being attacked and as the material is relatively "new" in loft/roof insulation, the same jury is still debating. Mice & Co. would also love nesting in the giant jumper.

After having read a lot and asked many questions, we have decided to go for 280mm (80mm between rafters and 200mm above across)of  "Laine de Bois". This is mainly due to us having our house in Tarn & Garonne where summers can be particularly hot. Had the house been in a more temperate region (ie. not so hot in summer), we would have gone for Rockwool or similar of the same thickness of Laine de Bois and Rockwool have similar insulation properties to keep the heat inside.

Laine de Bois is the best for "dephasage" or worst heat transfer characteristics on a very hot day. With our 280mm thickness, it will take around 10h/12h for the afternoon heat to reach the inside of the room. The same could be had with rockwool but for a much greater thickness of insulation.

I hope this helps.

[Frederick]

Hi Eric    I don't have a loft    These old Vendee houses are bungalows with a shallow roof . The insulation is like ice cream in a wafer between the underside of  the roof boards that but up tight to each other  fixed between the beams and the plaster board ceiling went over it ... It seems to work OK for me .  

[woolybanana]

Thank you eric, I shall consider to look and read and see what is best. or I might get fed up and move instead. Norman has offered me the barrel next, to his cheap!

[andyh4]

[quote user="ericd"]

. Use strong masking tape (sold with the rolls of foil) to stick sheets of foil together, remember you are doing this to ensure no air moves from one side of the foil to the other.

[/quote]

Any views on the lifetime of the tape?  Personal experience is that any tape looses its tack within 5 years and will just peel away.

I am sure we have all see the bottom of a packing case fall out after the old tape has just disintegrated.

[ericd]

Correct Andy, it's not your bulk standard brown packing tape. Even Duck-tape would not have my vote for long term usage (20 years +). It's a "special" tape they sell along with their rolls of multicouche.

http://www.vipso.fr/accessoires-isolation/89-adhesifs-aluminises-100mm-x-25ml.html

 

[BIG MAC]

Serving suggestion,

Use visqueen type plastic (Bin liners even) stapled to rough timber to protect it,

 Install battens along the side of the rafters (chevrons) further securing the masking plastic

Install Kingspan type rigid board insulation between battens allowing air to circulate behind.

Fit one layer of foil bubblewrap to go over the kingspan and battens.

Cut and fit foil backed plasterboard - tape and joint the joins (using lengthways these should be few and possibly hidden behind half purlins.

Fill and decorate

Run round edges of masking plastic with a craft knife.

Remove plastic exposing the timber to the room while that enclosed in the roof structure remains wrapped behind the finishes.

Stand back and admire.

Post posting note: If the make up (depth) of the chevrons / rafters is not sufficient I would place rigid insulation between rafters before counter battenning (or metal framing) then board as a conventional ceiling...If you want the look of rough timber chevrons then some rough sawn douglas fir could be fastened verically to create the impression. Need to mark out where the good fixings are while assembling the ceiling.

[aj]

All very interesting replies, thanks.

Can I go back to my original question. I have a new pan tiled roof , the tiles lie on wooden boards and the boards rest on new wooden beams, there's no loft and there wont be a ceiling.

Some of the boards have gaps of up to an inch between them exposing the underside of the tiles. Should I fill in the gaps? Can I cover the boards with waterproof membrane?

I'm going to fit plasterboard half way down the beams, what should I put in the void? Some say fill it with insulation, some say insulate but leave a gap under the boards.  

Thanks

[ericd]

Hi aj, we get talking and talking and the OP never gets the right answer.

If your roof is new (as you say), there should be an "membrane flexible de toiture" below your tiles (that stops water and insect ingress).

If not, it is up to you to decide if you need one or not. If the tiles get displaced during a storm, water can get in the loft area and rot the wood away so I would advice to fit some membrane between rafters to give you "some" protection.

The gaps between boards have no importance whatsoever (they will actually add to the "ventilation" of the loft). but be sure to leave 20mm air gap between your membrane and the (called Volige in French) and insulation in order to avoid moisture settling there (point of dew issues etc...) and damage your wood and insulation unnoticed.

 

You can "easily" do this by fitting battens at angles between rafters nailed into what you call planks holding your tiles (the french term is Volige).

[BIG MAC]

Apologies for not giving the 'right answer'

I didn't go into detail but you wouldn't neccessarily see a breather membrane on top of the boards and may not need one..Its the tiles that keep the weather out and a breather membrane just acts as a 'back up'

The spec I gave you considers the protection of the framing and considers the sarking boards (where you see gaps) to be to an extent expendable ...(they should last as long as the tile battens)

The rigid insulation is foil faced and can be cut to fit snugly while leaving an optimum air gap to allow condensation and any slight weep to run down the face of the insulation. the boards can extend down into the soffit / eaves and allow cross ventilation which will further help to protect the wooden parts.

The gaps in the sarking would have (back in the day) been filled with pitch if you were in wet or snowy climes and the gaps would allow some expansion and contraction.

There are many chateau which will not as yet have breather membranes yet manage to shed water quite adequately. Why strip a roof you are happy with to counter batten and membrane?

There is no such thing as 'The right answer' just a number of options...

Hopefully this helps

[aj]

Hello all,

 

There's no apologies needed, all your solutions looked good, and I'm grateful for your help.

 

I expected a waterproof membrane to be fitted under the tiles, but was told there wasn't one fitted because I didn't ask for one. One of the drawbacks of not being there.

 

The beams run right to left in line with the front and back walls, the boards run from the top of the roof to the gutters, and the tiles lie on top of the boards. As far as I know there are no tile battens, the top and bottom tiles are bedded in mortar.

 

After reading all your replies I think I'll fit membrane in the space between the beams and staple it on with a gun then fit chevrons (arris rail?) as Big Mac suggests

 

Then I'll fit some battens on the beams, leaving enough space for the rigid insulation board (3"?) (foil side up?) and the 20mm air gap, then fit plasterboard.

 

Does this seem about right?

 

Thanks again.

 

Ps. We don’t have lofts or ceilings in the reconditioned rooms.

[BIG MAC]

You are about 3 and a half hourse south of us so weather isn't likely to be massively different . Our roofs are slate and tingles (Ardoise et crochet I guess)

I recovered one of our hangar roof slopes a couple of years ago and will do the other soon, in this case as the area may end up being occupied I used breather membrane however the rest of the property hasn't got membrane and doesn't need it.

I don't think yours will neccesarily need a membrane either if the covering has sufficient laps and is secure.

Our Hangar Roof was relatively simple to do but as one can see the opposite face needs doing (I patched it up llasty year as time was tight)

The main roofs will just get the insulation and board treatment...not bothering with membrane until I absolutely need to re slate.

[aj]

Hello again Big Mac,

I've just read your reply, thanks. The areas with the new roof will be lived in.

Re: 'I don't think yours will neccesarily need a membrane either if the covering has sufficient laps and is secure'. Are you referring to the pan tile overlap?The pan tiles have stops on the sides, they just overlap and are pushed down to the stops.

During very high winds & heavy rain there's been some water leaking in, in different parts of the roof, I don't know how often as I'm only there in the Summer at the moment. Maybe just for that reason it may be beneficial to have a liner.

Thanks

[BIG MAC]

The principle is that pan tile roofs existed long before membranes and if properly installed shouldn't let in. Equally one needs to have confidence in the roof covering before doing decs so without seeing it its difficult to advise further.

Even without membrane, water shouldn't penetrate so worth playing a hose on a small area at a time (trying not to shoot under the tiles) better to aim high and let the water fall mimicing rain. You may be able to use an endoscope through the gaps in the boards to see exactly where the penetration is.

 

[Quillan]

[quote user="aj"]

During very high winds & heavy rain there's been some water leaking in, in different parts of the roof, I don't know how often as I'm only there in the Summer at the moment. Maybe just for that reason it may be beneficial to have a liner.

[/quote]

I don't want to sound alarmist but if you have water coming through then you have a problem and you really need to get that fixed before you think about lining the roof. If you line the roof now for example with a membrane how will you know that it is not getting worse? It might just be slipped tiles so you may be lucky as that is what normally happens but do yourself a favour and get it sorted before doing anything else

[Théière]

[quote user="BIG MAC"]

The principle is that pan tile roofs existed long before membranes and if properly installed shouldn't let in. Equally one needs to have confidence in the roof covering before doing decs so without seeing it its difficult to advise further.

Even without membrane, water shouldn't penetrate so worth playing a hose on a small area at a time (trying not to shoot under the tiles) better to aim high and let the water fall mimicing rain. You may be able to use an endoscope through the gaps in the boards to see exactly where the penetration is.

[/quote]

That's not strictly true, old hand made tiles had different and varied curves (2 dimensions) compared to modern machine made ones so they don't lay as flat as a modern roof and with a bit of wind (depending on the direction etc) it can and does blow in.  That is of course dependent on them being used correctly in the first place (tile overlap and roof angle within spec)

In the UK we have under felted for much longer than in France so haven't noticed so many leaks.  The UK tends to use more flashing's than in France who rely on flaunching which doesn't stay attached due to movement. 

A thermal imaging camera is one of the best ways to find leaks if you can hire one.

That doesn't of course mean you shouldn't as the spirit of the posts says get it fixed as it could cause rot in the timbers which would entail a lot of work to put right afterwards. 

[aj]

It's rained quite a few times since it leaked and I haven't noticed any more. One leak seemed to be in the vicinity of a Velux and the other leak ran down the inside of the back wall. I checked out both areas but couldn't see any reason why there were leaks. Will it happen again? Who knows? It's a pity I haven't been there for the last few months, I'd certainly know the score then.

I'll carry on with the recommendations of membrane, air gap, insulation and plasterboard.

aj

 

 

[BIG MAC]

Oh dear, I wasn't planning on writing a thesis..

1) If the tiles are irregular it should become apparent using methods described

2) Thermal imagery will show you the area getting wettest and consequently getting some evaporative cooling...this is likely to be the point where water gets past the sarking board...the leak may be 20ft further up the roof or in a ridge or flashing.

3) Velux kits dont tend to be too great with pan tiles and flashing details need to be executed properly

4) A membrane below the timbers will be expensive and wont achieve much more than the foil backed rigid insulation board which would conduct a minor ingress to the eaves.

5) I suspect the problem to be in the velux which I think often  assumes the presence of underfelt. If the head gutter or side flashing details arent executed well then water can simply spill off them. It may be the case that its worthwhile whipping the tiles off round the window and checking the flashins are set up properly...Not a bad idea to felt below the flashings for a short way.

Without seeing - difficult to help more but a pragmatic approach is way to go.