Re-Installing Loft Flooring and Fixing the Errors of the Past

[Mysterae_]

I previously posted some images of my loft flooring project and the issues I found in the man jobs thread and thought I’d make this thread to keep it all together. So here we are!

The loft always had issues.

1. Shortly after moving in a few years ago the ceiling below the loft started to show cracks at the taped joints of the plasterboard. There were tell-tale signs of a previous repair so I knew it would just happen again if I repaired them – the cause had to be found and fixed first.
2. Similar to above, there were some cracks between the coving and ceiling in some rooms that would open in the winter and close in the summer. I filled these cracks previously with caulk but they just came back. This led me to think it may be caused by truss uplift.
3. It never felt particularly dry in the loft either and this was made worse when the soffits were replaced as this sealed it up and insulation placed over the soffit restricted any airflow in and out of the loft. Any moisture was trapped.
4. The flooring was uneven and seemed “soft” between the joists and creaked when I walked over it, suggesting the floorboards were compromised and had some movement in general.
5. I discovered that whoever installed the extractor fan for the ensuite thought that it was acceptable to just vent in to the insulation! Really?!
6. To fix the ensuite extractor fan issue I installed a new fan and ducting to the outside but the fan always leaked condensate despite the ducting being insulated. I need a permanent solution.

To mitigate those issue this is what I’m planning:

Issues 1 & 2 – When the previous owners floored the loft they only floored one third of it, right down the spine of the house. The floorboards were nailed straight to the joists compressing the insulation and causing a cold bridge from the 18mm flooring through the joists to the ceiling below. Not the most ideal thermal solution. Cleared the loft of everything but the spiders and measured things up.

I mentioned truss uplift earlier - I searched on seasonal cracks appearing and that’s what popped up more often than not. My surmising is that in the winter the joists to the left and to the right of the loft flooring are all cosey and warm around the 325mm of insulation but the centre of the joists are connected to a massive block of cold flooring. This disparity across the span of the joists causes them to contract in the centre and lift. We’re talking only a millimetre or two of uplift in my case but I’ve seen some examples of it being over 10mm!

This is an exaggerated interpretation of what I mean:

The solution is simple – remove the cold bridging and insulate the length of the joist spans to the same degree by removing the existing floor and laying more insulation down, making sure the new floor doesn’t compress the insulation. I’m going to lay 200mm insulation which matches that of the insulation to the right and left.

Issues 3 & 4 – A couple of things can be done for this. Firstly, is to make sure all the soffit vents are clear of insulation so that air can flow freely. Secondly is to make the new loft floor high enough so that air can flow under the floor and any cold bridging between the flooring and the ceiling is removed as best as it can be.

I looked at the options for raising the loft floor and decided on the system from LoftZone. The supports/legs are 279mm tall so with 200mm of insulation underneath these would give plenty of separation between the insulation and the flooring. I also decided on 22mm thick flooring rather than the 18mm fitted previously.

I just needed to work out how many uni-supports, tri-supports and crossbeams I’d need, not forgetting the floorboards. To the SketchUp!

I also used the SketchUp model for the best positioning of the LED battens which I increased from three to five. Light is good.

That looks like quite a lot of supports....

So I'd need:

• 70x Uni-supports
• 40x Tri-supports
• 35x Crossbeams (1.8m long)
• 21x floorboards (2.4m x 600mm x 22mm)
• And a lot of screws. Not nails. Definitely not nails. Nope.

And lastly Issues 5 & 6 - the extractor fan and ducting. This is what I found after I lifted the flooring adjacent to where the previously fitted in-ceiling extractor was fitted:

Yuck.

The plan here is to reroute the fan ducting so that it's length is under and in the insulation and the fan is to be mounted on the gable end wall with a condensation trap fitted to vent it out a pipe in the wall. A bit like this:

Rather than go out through the roof the exhaust will use the pre-existing hole I made for it a while back. The pipe on the right of the image close to the floor is what I'll use to expel the condensate.

So that's the plan. I've done some already but still waiting on certain items, deliveries can take ages where I live.

 

[Mysterae_]

How'd you like your loft insulation sir?

The Battenberg Cake look please!

 

[Mysterae_]

I've used the loftzone system before its quite good. I'd just use the existing 18mm floor unless it's mouldy. You'll still have point loads in the ceiling where it's tied to the truss.

I'm glad you think well of the loftzone stuff, hopefully it's cost is justified. I considered reusing the 18mm board but it was a bit warped from being damp I think.

It also got a bit wrecked when taking the nails out, especially when the damn head break off. Then I have to dig them out with the multi-tool. I swear this has happens in about 1 in every 5 nail.

I decided that the existing flooring was of no use to anyone and I needed to get them down from the loft. They are much more manageable at 800mm long rather than 2.4m lengths so used my new toy (I mean tool, every project requires a new tool right?!) and ripped 3 boards at a time in to thirds. This circular saw is a beast!

 

[Mysterae_]

Have you considered doing a proper conversion even if only for storage?

Very nice size and looks like those trusses could be removed.

I did think about it because it would make an awesome space but the cost of it was prohibitive, somewhere between £50k to £100k. It probably wouldn't add anything to the value of the house either.

 

[Mysterae_]

Wtf is all that stuff? Vacuum, ear AND eye protection? And your tools are neatly laid out?


>Negative 10,000 points for what looks like a £ stretcher tape measure tho<

Safety first!

B&Q Value tape measure my friend! I've got an expensive 12 incher but as a rule I don't use it .

 

[Mysterae_]

are you upgrading 18->22 just for stepping around / dynamic load ?
otherwise, do the underlying ceiling joists and their strength/span justify it from a pov of weight of stuff you might store/m2

To be honest I saw the state of the existing 18mm flooring with it's bowing and warping that I decided to replace it with thicker boards. Perhaps overkill and wasteful but I wanted it to be right and never done again.

You mention the strength of the ceiling joists and the weight of stuff that will be stored there. I was concerned about the weight of the supports, beams and boards with their total weight of 556kg although some should be deducted for cutting boards around the chimney, loft hatch etc. Given there will be 110 points of contact, the size and spans of the joists, I feel it's sufficiently spread out and will be far lower than the 25kg/m2 standard for permanent loads in loft floors. Ironically, since clearing the crap out of the loft and binning a significant amount of it a lot less is going back up there - but you never know what'll go up there in the future.

The joists aren't exactly equidistant but I plan to space the crossbeams equally.

Has the insulation significantly bounded as the top is removed

The existing insulation has certainly started to decompress (is the word uncompress? bound? lol) as the old boards are removed without any "fluffing" by me. With the 200mm going on top of this it should be a noticeable improvement.

 

[Mysterae_]

its a loft used for storage, I would use any old chipboard I could.
The only reason I would dispose of the chipboard you have is where it has got mold on it.

I had to buy chipboard for our loft as I didn't have much, but i defo wasn't happy about it, I go up there once every 2 or 3 months for 10/15 minutes max (usually for 2 minutes or less) anything i put up there is almost wasted money in my eyes.

I totally understand.

 

[Mysterae_]

A little update while I wiat.

There are so instances of this where whoever laid the previous loft board notched the joists for the cable but then used screws to hold them in place. Did they not think?

I'll be careful removing these and checking for any damage to the insulation (of the cables).

Next little job is to make sure all the eaves and soffit vents are clear of insulation as most of them are not.

Now I'm just waiting on the LoftZone delivery as I can't progress any further. I'm a bit annoyed as I ordered the stuff first thing Monday morning this week and today being Friday means if it's not here today it'll probably be next week.

 

[Mysterae_]

Wow that screw vs cable is bonkers

Indeed. If that had shorted and tripped a breaker (best case) it would have been a nightmare to diagnose and find. It would probably have meant pulling up the loft floor or cutting in to the ceiling to find it.

 

[Mysterae_]

On the up side though you would have been halfway through with the job you are now starting

It was meant to be!

 

[Mysterae_]

what is their dimensions - do you attach the legs to them first, and then upturn and screw it all down onto joist.
if they are 4x2 laying on their sides , then is that really optimising height and strength versus a grid of 2 levels of 4x2 stacked to 8" (which would weigh more)

was wondering about using material like we have on office floors https://www.buildingmaterials.co.uk/caf600-office-grade-panel-598mm-x-598mm-x-30mm-pack-of-10-3-58m2

The crossbeams are thin galvanised sheet metal that's bent in a C shape that slides over the supports. The idea is to fix the tri-supports (or uni-supports if it's not possible) to the joists first then slide the crossbeams in to position, then screw the beams in to the supports.

If you have 30 minutes to burn here's their training video that explains it and more.

presumably you wacked nails from the other side too, too remove them - seems a lot of damage

No, all the nails were taken out from above, the ones which their heads broke were then dug out with the multi-tool and yes, it did make quit the mess getting them out!

 

[Mysterae_]

I get nails out like that with a Priory PRI150 nail puller as it doesn't even need the head on the nail. The speed you can remove nails from floorboards with these is impressive once you get the knack perfected.

That's a nice bit of kit and I did see it when looking for a nail puller. I probably should have got it as it would have saved me from cutting in to the board when the heads broke! Instead I went for this DeWalt tool:

It has hollow end that you put over the nail that's below the surface and hammer you down to expose the head. It's alright, but after a while I found myself just using the short claw end and digging down while hammering but makes a right mess of the board. As mentioned before sometimes the head of the nails break.

That's where a traditional pinch type nail remover would have been better. I'll admit that once the board was up any remaining nails in the joist were cut down with the multitool and the rest left in the joist!

I'd assumed he was jemmying the boards ... so would mainly get them from behind ... but, on reflection, did i see a jemmy.
I normally put biggest screwdriver over some kind of fulcrum ... another screwdriver

e: thought these were interesting

Tekwarm Insulated Loft Deck | 1200mm x 600mm (All Sizes)

Transform your loft with Tekwarm Insulated Loft Deck, blending superior insulation with practical storage solutions. Enjoy a safer, more efficient loft space with our high-quality, easy-to-install decking boards.

www.insulationuk.co.uk

(yes - no air gap)

Jemmying a long run of nailed and heavy T&G boards would have been fun . Once the nails were out the boards were jemmied to break the tongue and grove and get the boards up. Sometimes I'd cut along the joints with the multitool or circular saw for the stubborn ones; when you know you're not reusing the boards you can be as destructive as you want to be .

Obviously haven't discovered just mashing them back in

been there done that!

problem is you can pop nails or even drop a plasterboard or lath and plaster in some cases

Popped nails and cracks in the ceiling underneath were inevitable but I wanted to minimise the damage. That's the reason why I used a combi-drill on a low torque setting to drive the screws of the legs in to the joists rather than use an impact driver. There is some damage to the ceilings underneath but most of it existing before .

 

[Mysterae_]

Ah, someone else who watches that Welsh chap on youtube who does snagging on new homes

Yeah, he's great. After seeing some of his critiques I think I've gotten off lightly. Shocking!

 

[Mysterae_]

I've been a bit on and off with this over the weekend but have some progress and plenty of images. Words are of course optional .

I went a bit MacGyver and fabricated a tool from extension poles, a tree felling wedge and plenty of duct tape so that I could reach the eaves to clear the soffits of insulation. I really didn't want to clear or crawl over all that insulation! Worked a treat .

The MacGyver'ing continues - ripped a length of old board to make my Stick Of Support. Obligatory power tool image . I'm such a Makita tart.

First few uni-supports in their place.

Then ran a datum line (using strimmer line pulled taught as I'd ran out of string!) and the tri-supports in place, the Stick Of Support guiding the way.

Then some more supports and then crossbeams fitted.

Next section, skipping the uni-supports as these can be placed under the crossbeams later, saves marking out all the joists.

Some more crossbeams fitted...

...and some more.

The previously compressed insulation is really starting to lift now.

Taking of insulation....

The part nobody likes. One roll down.

This insulation has cuts semi-made so makes placement over the crossbeams a lot easier.

The third roll of insulation down.

That's half of the loft done like this but I'll be putting the boards that this section first before moving on.

It's pretty easy stuff, just takes time and feeling like Tarzan going from one truss to another keeping your feet on the joists.

Itchy.

 

[Mysterae_]

Braver than me stepping over the rafters! I was worried about falling through so I did it more it iteratively.

I can recomend a hatch like below I made

Nicely done! That'll definitely help access and prevent anybody falling down the hatch. Funny that you mention it as it's the one area that I've not finalised yet.

The additional height of the legs will raise the loft flooring by 300mm so it'll be quite a big step from the loft ladders so will need a handle or support to aid access. Additionally the loft hatch door has the ladders integral to it and it's not insulated and I'm sure leaks a bit. Seems a bit silly to go to such lengths to insulate the loft and leave this obvious weak spot.

I'm wanting to make something that will seal the loft from the house but still allow air to flow over the hatch, eave to eave and under the loft flooring. I'm thinking something along the lines of a piece of insulation board that I can pull down in place before folding the ladders and closing the hatch. It'll then need lifting and pushed out the way when access is required. There's a few videos on youtube where they've done something similar.

 

[Mysterae_]

Ive gone all itchy just looking at these

how much roughly to do the entire loft?

I'm hoping I can do away with some of the new build chaos bracing in the loft

Oddly enough the new insulation I used wasn't as itchy as the stuff that was already down, easy enough to cut or tear too.

To do this section of loft at an area of 30sqm it was £1,366 rounding the pennies (LoftZone stuff - £659, flooring - £452 and the insulation - £255). It wasn't until after the ordering that I found out I could have got a discount on the flooring and insulation if I had bought it in person so perhaps £150 cheaper. I worked out if I wanted to floor the entire loft rather than just this section it would cost around £3k as the insulation is fine in the other areas and the boards would be smaller, but I thought that it was a bit of diminishing returns. The area floored is ample already.

You mention new build - the insulation should already be at least 270mm already so are you just looking at flooring it?

 

[Mysterae_]

Looks good! That loft zone equipment is much more expensive than the plastic loft legs I used.

Indeed, it took some justification to go down the loft zone route. B&Q sell the XL loft legs at £130 for 72 of them, two packs would have been enough. I could have used thinner insulation and 18mm boards (or attempted to reuse the old bent and stinky ones) for an even bigger saving.