1930s Semi Refurb - Part 4 of ... (Edition: Loft Insulation)

[dlockers]

Hi folks,

Me again - given the turn in weather, the boiler man being booked for early November, and a Christmas visit from my mum planned - I am thinking I may hold off on any major progress on the bathroom until the new year. Cue the perfect opportunity for a low effort (lol), high impact (lol) job - loft insulation.

At the moment I have a lath and plaster ceiling, and about 60% of the loft boarded. The roof is the original 1930s clay tiles on wood (no felt). It is cold up there, and I think the lathe and plaster ceilings offer little to nothing in terms of insulation. There is some fibreglass looking stuff up there in places at the moment, but not very much and clearly a half job (maybe just for one of the bedrooms).

I have seen a few products that suggest raising the joists to pack in (but not squash) rockwool type stuff, and silver barriers stapled to the roof interior. I also found this chap who goes into detail on the theory and provides some tips, so this'll be my default guide.

What's the general craic on doing this job? Where do I begin? What systems have you used and is there a way to do this inexpensively?

Thanks!

 

[dlockers]

Top man, thank you! Did you do anything special around wiring/services?

Are the loft legs solid?

Did you do anything about the roof itself? I have seen a few images pop up of a lady stapling some kind of foil to the roof rafters?

 

[dlockers]

Thanks chaps - RE: Cold/Warm loft, who decides?

I have a roof as pictured here, so I am unsure I have traditional soffits that I can vent:

Improving the Thermal Performance of UK 1930s Semi Detached Houses

Sharing the experience of improving the thermal performance of a UK 1930s semi detached house and suggestions for what could be done…

peter-wurmsdobler.medium.com

Loft may be a living space in many years time but not yet.

 

[dlockers]

I'll have a proper look up there in due course. I think I'd stick to cold roof.

First job, I need to swap the dodgy lightbulb for some LED lighting as well as it is really too dark to do anything at the moment.

Thankfully its full of old carpet which I think was used to cover the rafters and avoid boarding out the rest of it ! I guess with the 300sqft workshop it was low down the priority list.

 

[dlockers]

Hi guys,

As per man jobs thread - I have made a crack at the loft today (minor) and took some measurements. Roughly, excluded the very front with the funky roof, I have about 28m2 - or 4.2m * 6.6m.

The hatch itself is a nightmare as it opens out into the bathroom of all places.

I'm thinking
1) Order a tonne of bin bags and clear out the mess
2) Vacuum the entire thing
3) Get a decent quantity of framing timber to add noggins to what are presumably, just basic ceiling joists? (will these support my weight?!)
4) Buy some loft legs
5) Board
6) (in the wrong order) - put some PIR down the hips of the roof (is that what they are called?)

My only concern is I may need to get to the lighting circuit of the rooms beneath, so I am a little turned off by the thought of tongue and groove. I guess the obvious answer is to do any light wiring beforehand, but I am a million miles off getting my head in gear about that.

Can anyone coach me on an easy way to get this all nice

https://i.imgur.com/KxQ9L7p.mp4

 

[dlockers]

Appreciate the replies chaps, thank you.

Will certainly be clearing the lot out. If 2x4 framing timber is still the same cost, it will actually be cheaper than loft legs so I am tempted to go that way. Some of the timbers are already twisted so I can't imagine loft legs will be straight forwards in any case.

I have lathe and plaster ceilings and the one room is battered to heck, so also noted on being careful. I need to overboard and plaster (in due course).

You've probably put the nail in the coffin for me W.R.T swapping the loft hatch for a proper modern sealed unit.

My biggest concern is ventilation - if I insulated the "hips" of the roof (still unsure if this terminology is correct) - then I won't have much natural airflow. Other than the funky bit of my roof, I don't really have "eaves" as the roof comes down so low to the walls. Potentially I can put vents in what I have, but it won't be "back to front" ventilation like what may be required.

Wiring looks legit - but worried about losing access. Maybe I'll batten + board in squares so I can lift up entire sections without issue.

Will dream on it for a few weeks (y)

 

[dlockers]

Would that sort of loft suit a warm loft system instead? i.e. insulate directly onto the roof rather than the floor? Means he could board up the floor with less insulation and generally I think it allows for better air flow?

I'm just nervous that the wood will rot through as there is no felt...

 

[dlockers]

Subject to someone telling me to stop... I'm thinking of starting with 8 rolls of this stuff.

https://www.diy.com/departments/knauf-eko-roll-loft-insulation-roll-l-4-83m-w-1-14m-t-200mm/182147_BQ.prd

The first job may be to move the hatch though so I can get the 2.4m x 600m boards up there... I bet they weigh a tonne as well.

 

[dlockers]

Where will you be moving the hatch to? We are currently in the position of moving ours from the bathroom to the back bedroom.

Also a 1930s semi.

Probably front bedroom, but trying to forecast where the bed/wardrobes will be so it is super accessible. Alternatively, the hallway if I can avoid the beams.

 

[dlockers]

Really struggling to find clarity on what to do with the sloping bits of the roof - to maintain what I guess is a required air gap?



This chap reckons 50mm Rockwool but that'd stop any ventilation (assuming it comes from the soffits?)

 

[dlockers]

You may have reviewed this, but are you leaving a gap between the insulation and the loft boards? I understand you need a gap to avoid damp.
@Mason- doesn’t look like you have a gap? Did you get different advice?

I really want to increase my insulation but don’t want to raise my boards so I haven’t bothered.

I wasn't planning on a gap there but I will need to consider how I insulate the slopey bit whilst maintaining airflow.

 

[dlockers]

I need to sort this too, I have a hipped roof too. In all the bedrooms the ceilings slope in. My plan was to replaster those rooms and when I do that, rip off the existing plaster and insulate. But I agree that is a ventilation space and if you stuff it with insulation it might cause problems.

In that scenario though you can alleviate it by felt lap vents and roof tile vents.

I'm wondering if some PIR stuff down there with a noggin to keep it spaced will work. I could then put a full length soffit vent. Hmmm... Too cold and wet for all this messing with insulation and roofing.

 

[dlockers]

Thinking about it more I’d probably leave the ventilation gap in the hip and insulate ‘inside the slope’ if you see what I mean. Don’t insulate in the gap between tiles and wall, but on the side of the wall in the room. Lose a little bit of the room space (tiny really, 50mm insulation + 12mm plasterboard?). But you keep the ventilation gap on the hip.

Hmm yeah that might be a better idea actually. One room is the bathroom so less bothered, but the other room will be a bedroom. The roof loss won't be the end of the world either, and actually removes a complicated curvy part of the roof for future plastering/painting needs...

 

[dlockers]

Yeah spot on. I think that is very much achievable. That also kicks that job down the road a bit

 

[dlockers]

Had another peak earlier:

There is zero ventilation. I don't think the loft is vented anywhere other than a few bricks removed into next doors loft (lol, I can see their stuff).



Just a dead-end:


And some off cuts of lathe to deal with



Not sure what this means. Maybe 50mm PIR and wedge it close to the roof? Other bits of the loft have fibreglass stuff just wedged in there.

 

[dlockers]

I managed it.... But I'm probably somewhat stronger than the average person!

However yes it's far more sensible to get some help. I found the toughest bit was manoeuvring them whilst crouching in the tight loft space!

Do you have someone to help or are you relatively stocky? @dLockers

Pics of diameter? . I'm a brute force and ignorance lad so I'm sure I'll suss out a means to get them up there, so yes entirely solo on this job.

I think going with mason's idea of insulation on the inside makes more sense. You do need some airflow in the loft regardless of warm/cold loft design.

Do you not reckon I can get away with 50mm PIR and leave 50mm gap to the rafters? There is no vents in the hip at all, maybe I'll add vents into the soffits.

 

[dlockers]

I had 5 of these to take up to the loft. Probably the same as what you've bought? They're just bulky rather than anything - I just "threw" them up to the loft and hoped it didn't land on anything fragile! (I exaggerate a little).

50mm gap is generally what is needed for airflow - so if you can leave a 50mm gap then you should be all good.

Yeah that's the stuff. Although I think I've got the 200mm stuff in the basket at the moment. I'm trying to work out the best value by m2 but it's like a GCSE maths problem as they're all different thicknesses and lengths lol.

 

[dlockers]

I already had 170-200mm so only needed it to top up and/or plug the gaps that was needed. If you have nothing then 200mm is bare minimum.

Just plug the values in excel and work out £ /sqm for each roll, and then multiply it by the number of sqm.

Yeah I was planning on 200m + 100m, but couldn't work out if 3x 100m was cheaper initially (will do the Excel as you said).

Do you need to sink the insulation into the gap between the ceiling joists? Or can it sit "as it falls?"

 

[dlockers]

I would push some into the gap between the joists, 100mm is probably good. Then run a 200mm on top of that going perpendicularly to your joists. Are you definitely going to use timber instead of loft legs? Seems like it would be a lot more work using timber. And does it really need to be super level?

That's a good shout.

I'm still not sure about loft legs...but I'm equally unsure without buying a forest's worth of timber how to baton it out sensibly. Or use noggins and have something even more unstable lol.

Edit: They also say no more than 25kg per square meter which is just LOL?

 

[dlockers]

I used this, far better than loft legs IMO since it creates a decent platform thats linked. Its quite quick once you get the first couple in place to act as a working platform

Raised Loft Boarding For Your Home | LoftZone UK

Our BBA-Approved raised loft boarding system saves money, helps the environment and increases safety, without invalidating new build warranties.

www.loftzone.co.uk

This looks awesome. Need to do some man maths.

If I read the spec correctly they’re covering their arse. The legs can support more, but the joists are probably more likely to fail before the legs if you overload them. So to save themselves from litigation “you said your legs could take 500kg but when I tried to store my car in my loft the roof caved in!!! Give me money!!!”.



They say most engineers say you shouldn’t put more than 25kg per square metre in your loft. I suspect our over engineered old houses could support more, but again it’s an arse covering exercise from them.

I’ve used them and they are really solid, surprisingly so, I was sceptical too, how solid can plastic be? But they are plenty strong.


Up to you at the end of the day. But using timber will likely be more costly, more time consuming. And it adds weight more so than the plastic legs. It would most likely be stronger but how strong does it need to be. It’s going to rarely be under a dynamic load and unless you plan to put a home gym up there I highly doubt you’ll have problems with weight.

Yeah that's a fair shout, I hadn't read the wording as closely as I should have.

I think my order is shaping up as:
* Bunch of cheap framing timber to add noggins to ceiling joists/avoid twisting
* Loft legs or loftzone (need to do man maths)
* New hatch
* New ladder
* 21 big boards
* Insulation
* 50MM PIR

Not sure how I get into this mess. My job at hand was the dining room