Insulation above tounge and groove

[AndrewB]

Hey guys!

A while back I posted for some advice regarding loft insulation in my 1888 home. I now have 3 lovely pallets of rockwool sitting in my front garden ready to go in and have spent the last two weekends pulling out dusty dusty dusty damp damp fibreglass. I even hoovered the place. Henry earned his keep this week!

Anyway, a large area of the upper floor ceilings are tounge and groove ceilings in the rooms below, straight onto the joists. Some of these are sagging just a little and I plan to nail them back up and make good a few loose corners and whatnot.

Even where the tongue and groove is good, there are some gaps up to about 2 or 3mm. In the not-so-bad spots there are still small gaps enough for the dust to fall through when I was cleaning.

Between all the joists was 1938 newspaper sheets, presumably to protect from dust and act as some sort of breathable membrane? Should I be replacing with something similar? Or should I just put the rockwool directly between my nice clean joists on top of the tounge and groove?

(photo isnt necessary of a gap)

 

[Toby Newell]

My skin is currently crawling off into the next room...

Use a flexible caulk, not a cheap hard setting one and fill the gaps, glass fibre is a class H hazard (same catagory as asbestos, and mould) I would not walk into that room knowingly.

 

[AndrewB]

Oh, good idea. So run caulk along the joins from above the put rockwool straight on?

To be clear, I was thinking about sealing the gaps more from an airtightness point of view. I know airtightness is a joke in an 1888 property, but I don't exactly like the sound of nice warm air just billowing up through the cracks. May as well at least sort the bigger gaps?

I wouldn't be expecting a whole lot of dust now that I've cleaned and after adding 300mm rockwool on top. Right?

The fibreglass was a nightmare to get out. 60 rubble sacks worth over 3 days! Mask, goggles, head torch.... Nightmare! The only thing that kept me going was finding the old newspaper!

 

[Toby Newell]

I forgot to ask! How many pages did you get? I did a freebie for an old neighbour and the universe awarded me 18 pages of The Business Observer in pristine condition lining the drawers from 1971 and the day of my birth! As I recall, middle east tensions and high oil prices, what goes around...

yup. fill from above with flexible, glass wool is evil, the only reason they dont ban it is climate change, its so cheap, all health and safety is arbitary and political, its a class one carcinogen depending on the type, not as lethal as asbestos but still deposits razor shards of silica deep into your lungs, Im sensitive to it, my skin blows up like a red wotsit.

and no your idea is sensible, most heat is lost through roof as heat rises so reducing airflow up there is good idea too.

just within reason, I just lost a job because I told a customer his recently spray foamed wooden floor was a very bad idea...

 

[AndrewB]

I forgot to ask! How many pages did you get? I did a freebie for an old neighbour and the universe awarded me 18 pages of The Business Observer in pristine condition lining the drawers from 1971 and the day of my birth! As I recall, middle east tensions and high oil prices, what goes around...

yup. fill from above with flexible, glass wool is evil, the only reason they dont ban it is climate change, its so cheap, all health and safety is arbitary and political, its a class one carcinogen depending on the type, not as lethal as asbestos but still deposits razor shards of silica deep into your lungs, Im sensitive to it, my skin blows up like a red wotsit.

and no your idea is sensible, most heat is lost through roof as heat rises so reducing airflow up there is good idea too.

just within reason, I just lost a job because I told a customer his recently spray foamed wooden floor was a very bad idea...

Thanks Toby. Would you reccomend a particular product?

The 1938 newspaper is very dusty. Must have at least 100 sheets. Most was single sheet thick so bad condition both sides. Don't think I have even a single full page without damage or dirt. Think il get them scanned and print a collage of the interesting headlines and adverts After that, il box them up and leave them in the attic... Belong to the house, not me

 

[Toby Newell]

Not really, look for 'high modulus' stuff, something flexible, you want the boards to be able to move a little.

You could try MultiStick glue, its what I use, well one of the adhesives, its a hybrid PUR / MS polymer, a bit like the sole of a trainer, more of a glue but works as a sealer, very strong but remains flexible, I have used 100's of tubes. You can get it in Toolstation.

That page mentions Hitler, so that's very interesting.

 

[Toby Newell]

 

[Toby Newell]

you want to allow movement as roof spaces get warm and moist, you don't want rafting, ie gkued rigid and fails at weak point leading to a few very wide gaps or cracks.

Ive used hundreds of kilos of this type of adhesive since 2014 when it came out, a couple of years ago I predicted it would be everywhere abd now it is lol.

Was designed for flooring industry but all adhesives and sealants are moving over to it, wherever you see solvent free, hybrid, ms, pur, modified silane, thats the stuff, CT1 have big marketing spend, ergo theirs is £13 a tube, same as Everbuild (owned by Sika, UK company) multistick at £5.50. Or 3C sealants, or wakol ms262 sausages... moisture cures, incredible strength, low sag and permanently flexible. Ive used several £k worth.

 

[Toby Newell]

or... any silicone!

 

[AndrewB]

I've used the ob1 hybrid stuff before to seal in a shower. It's great stuff, much nicer to work with than silicone.

Wild expensive though!

This stuff seems to be silimar. Anything hybrid/polymer is what we're looking for right? It's also brown. Multistick only white.

Thanks for the help!

 

[Toby Newell]

yep, silicone works just as well, as long as its flexible. Lol you middle class types and your money allocation issues.

£18 for 3 isnt wildly expensive, its very cheap.

 

[Toby Newell]

Its a super hyper performqnce polymer technology similar to the stuff that holds your windscreen glass in, its cheap as chips.

I dont get it any cheaper in bulk, there are only 7 factories that make the bulk binder and all are in China.

Its literally only double the price of solvent gripfill which is a totally rubbish ancient 1960s technology 5500 type adhesive that sets rock hard and goes brittle.

Using it can save you thousands, thats why I was a very early adopter.

 

[AndrewB]

Lol cheers. Stuff is apparently a little harder to get here in NI (for a reasonable price)... Delivery prices high too. It's not so much that the product is expensive, I agree, it's great stuff.... It's paying screwfix £12 when same thing is £6 on another site/shop

 

[Toby Newell]

I see, not so small island syndrome, yes its cheaper to buy in bulk. Do you not have Toolstation over there? I hardly every go to screwfix.

Multistick is the cheapest I found, I spent 3 months researching the properties and comparing which was painful, Everbuild and Sika are rubbish at giving out information.

I worked out is is better than average and 40% the price of some.

3C sealants max bond is probably the best performance for an adhesive.

 

[AndrewB]

Nope, no toolstation! Let's not get into politics but easy to feel left out here anything you guys can get delivered for free by DHL or similar on the mainland often is like £25 delivery surcharge here. So leaves us with Screwfix mainly for that type of stuff, or amazon if shopping online... Or B+Q (but expensive).

Ordered this off amazon in the end... Hope 4 tubes will do it

 

[Toby Newell]

yes, when I worked in Guernsey same deal. That stuff is made by everbuild aka sila too so should be good

 

[AndrewB]

@Toby Newell this worked a treat. Filled the holes in the dark lol. Kept putting filler untill I stopped all the light getting up through the tounge and groove.

Decided to update the newspaper from 1938 to 2023 and put a single sheet as some sort of additional soft protection for warm air 'rushing' up there through the smallest cracks. If its worked for 80+ years so why not now...

Got about half of my rockwool laid. It's brilliant stuff. Much better than the evil fibreglass.