What would you do? Boarding loft......
Discussion
Hi all
Ive just insulated my loft and now i have the problem of how to get my storage back.
Sorry for my very crude drawing but this is the basic layout up there:
Where and how would any of you guys suggest i get some boarding to fit up there, i cant lay it on top of the insulation and not shown in the picture is the tank that is smack bang in the middle.
Cheers lads
Pics/Diagrams would be lovely
Ive just insulated my loft and now i have the problem of how to get my storage back.
Sorry for my very crude drawing but this is the basic layout up there:
Where and how would any of you guys suggest i get some boarding to fit up there, i cant lay it on top of the insulation and not shown in the picture is the tank that is smack bang in the middle.
Cheers lads
Pics/Diagrams would be lovely
ks' and squash the insulation a bit. I'm happy with 4" of insulation and a slab of chipboard on top. Sam_68 said:
Do a search on this forum for 'loft condensation' or 'interstitial condensation' before you make your mind up.
If you restrict air circulation over the insulation by boarding over it, you're asking for trouble.
How about drilling, say, 1/2" holes at various intervals through the board? Still strong enough to put stuff on, but some ventilation too.If you restrict air circulation over the insulation by boarding over it, you're asking for trouble.
Simpo Two said:
How about drilling, say, 1/2" holes at various intervals through the board? Still strong enough to put stuff on, but some ventilation too.
I doubt it would have much effect. The housebuilding industry is suffering severe problems with condensation in the thicker insulation we're using these days, even without boarding over it. Anything that restricts the airflow over the insulation even slightly is potentially a really bad idea.Having said which, our current research seems to suggest that there may be two mechanisms at work causing condensation problems in lofts: one is the traditional interstitial condensation (warm, moist air seeping out of the heated living space below, which cools down and dumps its moisture in the middle of the insulation), the other is dew condensation forming on surfaces from the external air that is being circulated through the unheated loft space.
If you had a really well sealed ceiling (vapour check plasterboard with a sealed perimeter, no cracks, no penetrations for light fittings, a well sealed loft hatch, etc.), it's possible that boarding over the loft insulation would actually improve things, since the surface condensation would sit on top of the boards where it easily evaporates off in the daytime when temperatures increase, rather than soaking into the insulation quilt.
The likelihood is that an existing house that's had it's insulation increased will not have a particularly vapour-tight ceiling, though, so your main problem will be the traditional interstial condensation.
nicky.mattsson said:
'Packing' to move joists upwards seems like a good idea, i had no idea you couldnt seal the insulation in though, thanks for the warning.
Another i dea i had was something like this:
Is it safe to fix something to the vertical parts of the 'W'?
Definitely not safe to fix something to the struts on the Fink truss.Another i dea i had was something like this:
Is it safe to fix something to the vertical parts of the 'W'?
Since this is a motoring forum, you might like to go off and read up on spaceframe chassis design, which uses similar principles, but the bottom line is that the relatively flimsy bits of wood making up the Fink trusses work by being triangulated, so that they are only taking pure tension and compression loads. The water tank supprts are specifically designed by the truss manufacturers to take the weight in that area.
Doing what is shown on your sketch would introduce bending loads in the struts and could cause severe distortion or even collapse of the roof structure, depending on how much weight you put up there. You would need a Structural Engineer to look at it, if you are thinking of anything fancy, like that.
Sam_68 said:
nicky.mattsson said:
'Packing' to move joists upwards seems like a good idea, i had no idea you couldnt seal the insulation in though, thanks for the warning.
Another i dea i had was something like this:
Is it safe to fix something to the vertical parts of the 'W'?
Definitely not safe to fix something to the struts on the Fink truss.Another i dea i had was something like this:
Is it safe to fix something to the vertical parts of the 'W'?
Since this is a motoring forum, you might like to go off and read up on spaceframe chassis design, which uses similar principles, but the bottom line is that the relatively flimsy bits of wood making up the Fink trusses work by being triangulated, so that they are only taking pure tension and compression loads. The water tank supprts are specifically designed by the truss manufacturers to take the weight in that area.
Doing what is shown on your sketch would introduce bending loads in the struts and could cause severe distortion or even collapse of the roof structure, depending on how much weight you put up there. You would need a Structural Engineer to look at it, if you are thinking of anything fancy, like that.
freecar said:
hearing about all this interstitial condensation it might be a good idea to raise the level of the joists to about 2" above the insulation. This would maintain an airspace above the insulation just make sure to only board up to say 12" from the roof each end.
Im not worried about going all the way across, i just want the area arund the hatch done. dibbers006 said:
Everything people have said is correct and logical but take into consideration the tolerances of homes. I they could no cope with a bit of moisture, twisting, weight etc the first rain storm would take us all out!
I may be being excessively cautious, but my advice - having seen plenty of major defects cause by these sorts of modifications - is simply don't do it!The design of modern roof structures is a lot more marginal than some people think, and as far as insulation/condensation problems are concerned, we've already gone way beyond having any tolerance at all. You might find it scary to contemplate that from the information I have, anything up to 20% (1 in 5) of new houses currently being built could be suffering from serious seasonal loft condensation problems even when they've been designed and built 'properly'.
The OP doesn't say what thickness of insulation he's just added, but up to 450mm (ie. a foot and a half) is not unusual these days and I think you might be underestimating how difficult it is to dry that sort of thickness of fibreglass quilt out, once it gets piss wet through.
After the recent cold snap, I've seen houses with no obvious ventilation or airtightness defects that were so wet in the loft that the water actually tipped out on your head when you opened the loft hatch.
We're still researching this, but a big part of the problem would seem to be simply that the increased insulation thickness' being used these days makes houses so efficient in terms of heat loss that the air space above the insulation is basically at external air temperature, whereas in previous years the heat loss would have kept it a few degrees warmer and hence prevented the issue occurring.
We don't yet have a complete grasp of the problem and it's possible that we never will, because changes in construction specifications (particularly widespread implementation of MVHR to meet ever increasing Part L Regs) may mean that it ceases to be an issue on new houses and to be frank, nobody cares about problems with older housing stock - it's not covered by NHBC warranty, so the builders, NHBC and BRE don't really give a toss.
Roughly 8" (20cm). Only reason we bothered is cos the missus is currently unemployed so we thought we would take advantage of some free insulation. I never knew it would open a can of worms like this.
What would happen if i told you lot that we were also getting the cavities done. Good, bad?
What would happen if i told you lot that we were also getting the cavities done. Good, bad?
Screw some 2" x 2" battens down on top of the original joists, or 2" x 4" if you need the extra height to clear your insulation, and lay your boarding on them. Leave some gaps to allow air flow, and forget all this about interstitial condensation, as you're only putting some shelving over the existing insulation. You're not boarding out the whole loft, just a small area.
Chances are you have internal walls that are actually supporting the existing roof joists, just like our house has. You could try to make sure you only add extra load above where they are, rather than in the middle of a large bedrooms ceiling area. Make sure your 'battens' overlap a support wall at each end so they lend some support.
Or maybe you live in a modern 'cardboard' house, in which case I'd advise against even going into the loft for fear it all come tumbling down.
Chances are you have internal walls that are actually supporting the existing roof joists, just like our house has. You could try to make sure you only add extra load above where they are, rather than in the middle of a large bedrooms ceiling area. Make sure your 'battens' overlap a support wall at each end so they lend some support.
Or maybe you live in a modern 'cardboard' house, in which case I'd advise against even going into the loft for fear it all come tumbling down.
nicky.mattsson said:
What would happen if i told you lot that we were also getting the cavities done. Good, bad?
Cavity insulation is fine, by and large - very few defects arise from cavity fill insulation, these days, if it's done right.It can exacerbate problems with damp penetration if the original build quality was a bit shoddy (eg. mortar snots on wall ties) but generally you don't get too many problems.
King Herald said:
Leave some gaps to allow air flow, and forget all this about interstitial condensation, as you're only putting some shelving over the existing insulation. You're not boarding out the whole loft, just a small area.
Your call whose advice you'd rather take, if anybody's, Mr Mattsson; FWIIW I'm head of Design and Tech for a Region of a major housebuilder (with access to all the defects data that affords me) and (scarily for me) have over a quarter of a century's experience in the housebuilding industry...It isn't a matter of 'cardboard' houses. The problem is down to vapour and temperature control. The vapour control on older houses is considerably worse than on modern houses (we have the air pressure test results to prove it), so if you create the same temperature profile by using modern levels of loft insulation, logic says that there is potential for the problem to be worse on an older house.
My company is now taking a real 'belt-and-braces' approach: vapour check plasterboard ceilings, additional eaves ventilation, ridge vents and breathable roofing felt (in theory the breathable felt should be able to do the job on its own), and the air tightness build quality of our houses is amongst the best in the industry. You can be assured that we wouldn't be making such costly efforts in the current, difficult market conditions if we didn't think it was absolutely necessary.
Edited by Sam_68 on Sunday 14th February 17:14
Sam_68 said:
Your call whose advice you'd rather take, if anybody's, Mr Mattsson; FWIIW I'm head of Design and Tech for a Region of a major housebuilder (with access to all the defects data that affords me) and (scarily for me) have over a quarter of a century's experience in the housebuilding industry...
It isn't a matter of 'cardboard' houses. The problem is down to vapour and temperature control. The vapour control on older houses is considerably worse than on modern houses (we have the air pressure test results to prove it), so if you create the same temperature profile by using modern levels of loft insulation, logic says that there is potential for the problem to be worse on an older house.
My company is now taking a real 'belt-and-braces' approach: vapour check plasterboard ceilings, additional eaves ventilation, ridge vents and breathable roofing felt (in theory the breathable felt should be able to do the job on its own), and the air tightness build quality of our houses is amongst the best in the industry. You can be assured that we wouldn't be making such costly efforts in the current, difficult market conditions if we didn't think it was absolutely necessary.
Quite WTF all the above has to do with suspending a few well ventilated sheets of chipboard above the current insulation, is beyond me. Will it really magically produce gallons of condensate? Why, there would be no shortage of drinking water during our long hot summer droughts if producing water were so simple and easy.It isn't a matter of 'cardboard' houses. The problem is down to vapour and temperature control. The vapour control on older houses is considerably worse than on modern houses (we have the air pressure test results to prove it), so if you create the same temperature profile by using modern levels of loft insulation, logic says that there is potential for the problem to be worse on an older house.
My company is now taking a real 'belt-and-braces' approach: vapour check plasterboard ceilings, additional eaves ventilation, ridge vents and breathable roofing felt (in theory the breathable felt should be able to do the job on its own), and the air tightness build quality of our houses is amongst the best in the industry. You can be assured that we wouldn't be making such costly efforts in the current, difficult market conditions if we didn't think it was absolutely necessary.
If all the combined technology of modern science can't work out how to stop condensation in the loft of a modern built house, then I fear somebody is not doing their job properly.
ps. I'm just yanking your chain, before you go off on one.
King Herald said:
Quite WTF all the above has to do with suspending a few well ventilated sheets of chipboard above the current insulation, is beyond me.
Do you want a serious answer?The problem mainly reccurs during cold spells each winter.
Airflow through lofts is at very limited velocity, anyway: if it wasn't you'd hear the wind roaring through every time the wind got up on a night. It doesn't take much to restrict this gentle circulation of air still further, and it doesn't take much of a change to turn a marginal situation into a serious problem.
Even without leakage of air causing additional interstitial condensation from within the house, my best estimate so far is that we're typically experiencing periods of several weeks at a time each winter when you're getting a couple of pints of water settling out onto the insulation of a typical loft space as condensation every night. You're relying on the temperatures rising and the relative humidity dropping off sufficiently to dry this off each day, otherwise it just accumulates.
Even under normal circumstances, the situation is marginal at best (as I said, for about 1 in 5 modern houses it's worse than marginal and causes actual, real problems each year); it doesn't take much to tip the balance on a roof that's just functioning acceptably into one where the moisture begins to accumulate and causes problems.
We have seen situations where a few lightweight boxes of Christmas decorations reduced air circulation enough to cause moisture to accumulate and cause problems throughout the loft (not just in the area the boxes were placed), which went away when the boxes were cleared out.
The difference between no problem and problem really can be that sensitive, honestly...
Sam_68 said:
dibbers006 said:
Everything people have said is correct and logical but take into consideration the tolerances of homes. I they could no cope with a bit of moisture, twisting, weight etc the first rain storm would take us all out!
I may be being excessively cautious, but my advice - having seen plenty of major defects cause by these sorts of modifications - is simply don't do it!The design of modern roof structures is a lot more marginal than some people think,...
We've just had our 1890's roof stripped, felted and the original tiles put back. In the course of doing this we found that the house originally had 2 dormer windows at the front, that match the 2 that still exist at the rear (2nd floor). We determined that they'd been removed fairly early on in the buildings history (age of wood, lath and plaster over void etc). But couldn't wok out why they'd been removed. So we decided to reinstate them. Planning application submitted and approved. Builder assigned to crack on.
2 days in, and we needed a structural engineer, building control, and a set of stress diagrams that indicated some massive roof strengthening required. £3k worth of steel reinformed timbers went into that roof space to transmit the load of the dormers evenly.
It was at this point we then realised why the dormers were originally removed - the original roof timbers couldn't take it!
So when someone says "they don't build 'em like they used to" in our case I'd glad that is now the case
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