Hey friends,

I'll start with a quick retraction - I said a couple of weeks back that VAT on insulation products was being removed but I got that wrong, it's only VAT on professionally installation that is going, which is a shame for us DIYers but I did think at the time that it would be too much of a giveaway to the big developers. Sorry if I got your hopes up and thanks to Greg for pointing it out.

Some good news to replace it though, DIY waste charges at recycling centres might get scrapped. Apparently councils have finally cottoned on that the charges provoke fly-tipping. Not all councils charge right now but around me they do so I'm really hoping this gets past the consultation stage to become law.

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I've always thought that the doing of DIY isn't the hard bit. There are four other factors that stand in our way:

• Time
• Money
• Knowledge
• Order

With the bathroom I've been finding order one of the trickiest aspects - what sequence should the tasks be done in? To gain some clarity, I made an order-of-works. I've done the green and in today's NL I'll cover the yellow:

🔌 Sockets

First job on the list was to deal with the plug sockets as you can't have them in a bathroom unless they're 3 metres away from Zone 1 and our bathroom isn't big enough for that. The same goes for the light switch which will need to be outside.

I followed the cables linking the four sockets and found they all traced back to two cables coming from the landing.

With the power turned off at the mains I unscrewed the sockets from their back-boxes, released the cables and pulled them through to the floor. I discarded 3 sockets and the superfluous cables and for a temporary solution have reconnected the two remaining cables to a socket under the floor in the landing.

I managed to trace one of these cables to a socket in the second bedroom but I can't yet work out where the other one goes. I have 4 options:

1. Remove these cables completely if they're not needed (I need to trace that second cable)
2. Add a maintenance free junction box under the floor (+ cut & tidy up cables).
3. Install this socket (or a nicer, newer one) on a wall somewhere (+ cut & tidy up cables).
4. Use them for the underfloor heating ✅

Having done some reading on the topic you can also power a shaver socket from the socket supply but more common is to have it running off the lighting circuit. I'm going for the latter as it means I can have all the electrics done at the same time.

🪚 Noggins

I then moved onto the floor noggins. The stud wall which will be against this wall will benefit from more support than just the chipboard so I installed noggins, avoiding the waste pipe from the sink. Fortunately I'm not short of timber offcuts.

Having no long screws to hand I resorted to using my first-fix nailer with 90mm nails (these nails work well, the gas is not required for my battery powered gun of course) to attach the noggins on the near side through the joist. The nail gun is designed to fit between 400mm on centre joists/studs but here they're around 360mm which made it a little tricky. On the far side I used some 60mm screws at an angle from above into the joist.

These noggins will give me something to attach the bottom plate of the stud wall into for sturdiness. Later on, when the floor was down I did the same in the ceiling.

🐑 Acoustic Wool

Next up was soundproofing the floor. The joists are a true 170mm deep. My options were:

• Source 170mm insulation. I'm sure it exists but I couldn't find any.
• Go with 200mm wool and compress it a bit (you wouldn't want to do this with thermal insulation but with acoustic it's likely okay - what you lose in absorption you gain in reflection of sound)
• Go for 100mm or so and leave a gap (might cause amplification so not my preference)
• Put some 70mm on top of 100mm which is what I decided on. I got the 100mm from Wickes and 70mm delivered by Selco.

The joists are spaced ~355mm on centre. They're a true 50mm wide so the space between is ~305mm. Therefore I went for the 600mm wide wool batts and cut them in half. Any little gaps on the sides I filled with bits I tore from offcuts. For some reason the 600mm batts are a lower cost per square metre than the 400mm batts so unless the 400mm fits your voids perfectly, it's more economic to go with the 600mm.

On my insulating a suspended timber floor video I cut the wool with a box-knife but had a few comments recommending a serrated knife instead. This time I tried my plasterboard saw but the teeth were a bit too big so even with back and forth cuts (rather than just long backward cuts) the teeth would clog with wool. Next I tried my handsaw which worked best. I might compare it with a bread knife in future as that would likely work well too.

This is it with the 100mm in...

..and fully filled. I've also filled up some of the walls with 100mm but need the electrical work complete before filling the rest of the voids.

The difference in acoustics is immediately clear. All the echo has been taken out of the room and I couldn't hear the boy playing below. On the downside it does mean that heat from the future wood-burner won't rise to the upstairs so easily. This is in part why I didn't add acoustic insulation to the main bedroom even having soundproofed the party wall - because it's directly above the sitting room where the wood-burner will be.

• The rockwool is fire resistant which is a nice bonus.
• This Rockwool sound insulation looked and felt exactly the same as the Rockwool thermal insulation I used for the office floor, so I looked into it. The thermal rockwool has a thermal conductivity of 0.037 W/mK and the acoustic rockwool 0.038 W/mK. Practically identical! So if you're using rockwool for thermal insulation use whichever is cheapest or fits your voids best. What a jip!
• As for the sound absorption of each, it states 'no performance determined'. Helpful. If you know more, get in touch.
• I think it's a good idea to put lagging around your hot water pipes because in summer your heating will be turned off but you'll still be having hot showers and those hot pipes will have the effect of heating up your house when you want it stay cool. Because of the insulation I felt it wasn't necessary here. I guess that the pipes being plastic, and therefore less conductive than copper, helps as well.
• The reason I haven't put in downlights for the room below at this stage is that it will be part of the rear extension and I don't know where or how many lights we'll need so that work will have to be done from below when the time comes.

🪚 Chipboard

After all my deliberation I decided that the best option was to replace the flooring with 600 x 2400 x 22mm P5 (moisture resistant) chipboard. Again this was from Wickes whom I've maybe not been the most positive about in the past but their pricing seems to have improved a lot. Of course, my recently acquired discount makes me more favourable towards them now 😁. The chipboard wouldn't fit in my car so we strapped them to Joe's roof rack which worked well.

Laying it is a lot like laying T&G laminate. The complication is I want the end of the boards to rest on the joists, not fly in the middle, but the joist spacing doesn't match the length of the board. I can get around this by making the cut side against the walls, preserving the T&G for where the boards meet. The downside is more wastage. However if the room were longer than two boards' length I'd have no choice but to remove a tongue where the board is cut or yeh, allow a floating joint - probably okay in a loft but would undermine what I'm trying do here: create a very solid floor.

On that note, I decided to go for the best of the best where floor screws were concerned - Spax chipboard flooring screws. They're oiled to help slide through the chipboard and joists and have a thread, smooth shaft and then more thread. The first thread grips the joist and even has teeth, the smooth shaft pulls in the chipboard and the last bit of thread grips it in place. I placed these every ~15cm, so 4 per board per joist. The T-star bit you can see in the pic came with the screws and was really nice to use compared with the Philips head found on most screws which can often strip making them a real bugger to remove.

But wait, that's not all. I also used glue. And not just any glue, this special foaming PU glue from Travis Perkins. Here are some other options.

This is used both in the T&G and under the chipboard. Because it's mildly foamy and expanding, it fills all the gaps between the joist and chipboard which is great if the joists aren't completely flat, which they never are. It also fills the voids in the T&G and spills out of the top if you use enough of it. Once dry the excess is easily chiselled off and it's waterproof so no water can get between the joins.

If you use this stuff, make sure you wear a mask and open windows as I think it contains the same expanding/foaming agent that instastik and similar products do which might be carcinogenic. It's fine once dried though. Also, wear gloves, otherwise you'll be picking it off your fingers for days 👀.

Doing this job also got me to try out one of my Trend Tools freebies. To make cuts to sheet materials like this I'd usually measure from the end twice and draw a line between the marks with my level but with this T-square, just one measurement and then strike the cut line.

I also used it to make sure the first board was exactly 90 degrees to the joists. Not a game changer but certainly a nice-to-have.

The floor feels rock solid so it's going to be good base for the tile (with other layers first). Given that 22mm flooring is good for up to 600mm spaced joists I probably could have gone with 18mm chipboard but I like to over engineer these things plus the rest of the upstairs is 22mm flooring so once the rest of the layers go down it will be a similar height to the carpet and underlay in the landing. I'd be tempted to do the rest of the upstairs floor like this but I guess gluing the floor down makes prying it up harder in the event of a leak or electrical fault so I'll probably just stick with screwing down the existing floorboards.

After a vacuum I used a sharpie to mark the locations of the pipes. Fingers crossed I haven't mistakenly stuck a screw in any of the pipes!

So have I changed my mind on using chipboard for a garden room timber floor? Mmm yeh, I think I have - mostly due to the cost of ply these days. Chipboard was always fine to use if either you get the roof on quickly or you install the floor after the roof but wet chipboard degrades very quickly. If you use P5 chipboard, brush some sealant on it and keep it dry then yeh, it's a decent choice. Alternatively you can get chipboard with a film on top that can be removed later once the roof is on.

💧 Vapour Barrier

For some reason whenever I've talked about cold flat roofs I've never made the obvious comparison to a house's loft. I'm not sure why that is because the principle is the same and it would have made a good explanation.

In the house's case, the loft (excluding loft extensions where the insulation is in the rafters) is the ventilation space and hence why you need vents in it to stop condensation - a future job I need to do as I noticed some condensation over the winter. A breathable membrane under the tiles can also work if you're building a roof from scratch.

This is the case even if you add insulation over the top of the joists for the recommended 270-300mm thickness.

Since this is a bathroom and there's a lot of moisture, the sensible thing to do is to add a vapour barrier which is pretty easy to do now I've removed the L&P. It's prudent to do this on every ceiling upstairs but I'm not going to go to the trouble of pulling off the ceilings elsewhere, at least not in the bedrooms.

I could use foil backed plasterboard but I couldn't find any that was also moisture resistant which I wanted for the bathroom so for this I'm using a polythene sheet. In the past I've used this one from Wickes advertised 0.125mm. This time I tried this cheaper one from Screwfix advertised at 300 gauge. This website is useful for converting the two. The Screwfix one is 0.075mm, 40% less thick, and it shows. It tears more easily so I'll go back to the Wickes one (500 gauge) when I've used this roll up. For my office floor I used a 1000 gauge DPM but that's too heavy to get up on a ceiling.

I will be poking holes in it for downlights but together with the extractor fan and future loft ventilation, it should help keep the roof rot free.

👋

So that's where I'm up to. I hope there have been some useful tit-bits here for those of you contemplating a bathroom job.

The not-fun thing I mentioned last time got postponed to this coming week so I'll be skipping another newsletter next week. I'm looking forward to getting both the bathroom and newsletter back on track after that 🙂.

Hit "reply" if you've got any comments on this week's newsletter – otherwise I'll see you next time. Have an epic week :)

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