Johnny Jekyll

May I ask how you properly seal the cavity at the top?

Thanks guys. Project was well planned. SAP passes on paper without any insulated plasterboard (did 7 different assessments during planning). Using Cavity Therm (great science behind the product and seems superb if installed correctly). The ties cut through the ridges and jamb the insulation in place. It won't move let alone slip. I've spoken with them. They say insulated plasterboard should help with this. I'm just a bit of a perfectionist. Quite funny really how things turn out. We're gonna live in it so I just want it warm for myself. Think I'll stuff some rockwool down the backs where possible, and be very diligent from this point up. Insulated plasterboard is the answer for me.

I guess sand could act as a bridge for damp so maybe that's not the best idea. Please correct me if I'm wrong on this. I have tons of it on site. I guess grey EPS insulation beads would help but just can't find them anywhere (except installers). Could buy bean bag beads from ebay or amazon but believe they're a fire hazard. Photos attached, you can see the space behind the boards to the blocks (medium dense, not thermalite). Insulated plasterboard is at the top of my list at the moment.

It's a long story, I won't bore you with it. It's messy all over. So I'm going to install the insulated plasterboard all over the inside perimeter. It costs what it costs. I'm just furious about the whole thing...!

Do you think the insulated plasterboard will do a good job in solving the cold bridge problem? Common sense says yes but you're a lot more experienced on this than me.

Yes I understand your question. Problem is we are 17 blocks up, so near the top. And the brickies didn't do the best job of cleaning the mortar in the cavities on the way up. Some sections are not too bad. Other sections definitely need filling behind. Can't find where to buy EPS beads (in the next 2 days as we are laying again on Monday)? Thinking of ways to fill the gaps? Insulation manufacturer says using insulated plasterboard inside will help. Do you agree with that?

QUICK QUESTION GUYS. Looking at my insulation gaps today, what about pouring sand down the back of the insulation where the gaps are? Would that at least fill some of the gaps, and help with the thermal looping?

Valinor, my walls are going up as we speak, I'm using full fill PIR insulation, cost me a fortune. The whole thing has been a complete and utter nightmare. My first self-build, 3 years in planning, bought into the science of everything, had multiple site meetings in the months running up to the build, had everything on site ready, colour coded notes for everyone. My architect said in 50 years he's not seen anyone better prepared. Totally pointless. It just doesn't work practically with the way the trades work, and they will not adapt to you. For example if brickies are on price work, all they want to do is lay brick, and QUICK. Air gaps, mess, thermal looping, you'll get the lot, even if you try to do the insulation yourself (I've been fitting my PIR myself around them since the first row). If you have the time, sell your PIR, at a loss if necessary. Get the brickies to concentrate on laying brick straight and accurate, lay the wall ties properly, wipe mortar away on all sides. Once they're off site, pour EPS beads in from the top ensuring all gaps are filled. I've debated and been advised by our knowledgeable friends on here to take mine down and start again. Not an option for me, so I've paid fortunes for full fill PIR, now I'm going to have to pay lots more and install insulated plasterboard on the inside to reduce the cold bridge effect, and lose internal space for the pleasure. EPS beads all the way.

Thanks everyone, very helpful and honest feedback. I researched and planned so much but practical application is another animal altogether. I would love to take down and start again, but family and other circumstances mean it's just not an option. I'll do my best to fill gaps where possible. Moving forward. The house will be pretty airtight once I'm finished on the inside. And we are using an MVHR. Considering this may I ask 2 questions: 1 ) Surely using insulated plasterboard, thermal liner, or battens with thin PIR / wool / foil insulation on the inside will help? Form a barrier against the blocks from the inside? 2 ) Our plan is for underfloor heating. Should we continue with this or move to radiators? Thanks very much.

Thanks for the reply, but taking down isn't an option. This full fill doesn't require the wall ties with retaining discs (I know the ones you mean). Need to solve this retrospectively.

ADVICE NEEDED PLEASE..! The walls on our detached 3 bed new build are made up of (from in to out): 100mm medium dense blocks, 100mm cavity with full fill PIR insulation (cavities are more like 115/120mm wide), 100mm medium dense blocks (no thermalite has been used). We are at block course 14 of 23, so already towards the top of the house. The problem is the insulation has not been fitted tight to the inner leaf. We have a 10mm gap behind the insulation to the inner leaf in numerous areas. This will likely cause a cold bridge. I of course wish we could start again, and use wider cavities with EPS beads but we are where we are. Any ideas to stop the potential cold bridges? The options I see are: 1 ) Try and spray foam filler or EPS beads down the back of the insulation already installed, although I don't think this will get very far down. 2 ) Fit the full fill insulation tight to the inner leave from this point up (of course). 3 ) Insulate internally using some sort of insulated plasterboard / PIR / wool / thermal liner / foil insulation (we don't have much room internally though). 4 ) Insulate externally using some sort of external wall insulation (although this may require planning permission - and lots more money I don't have). Any help / advice you can offer is much appreciated please. Freaking out...!

I have 4 steels on my project (2 x UC23 and 2 x UC30). The UC23's are at mid-floor level. The UC30's are at eaves roof level. I purchased them with oxide paint already applied, about a month ago. The plan is to install them and then cover in the 30 mins fire proof paint in situ (all specified and agreed). I am noticing bits of rust coming through the oxide paint (see photo). I presume this is where they were perhaps a little rusty and just painted over before being delivered. Do I need to strip them back completely to bare metal and start again? Thanks.

Just read all of the feedback, thanks everyone. Hope this will be good for others who investigate resin anchors in future.

Have just donated £20 to [Note new PayPay account from early October 2025: @buildhubforum] Thanks guys.

Yes this is the one I watched when I first started looking at them.

Thanks guys. I will use all your info and proceed very carefully as always. Gonna donate to the forum now. This is a great place.

Perfect thanks.

Great advice thanks. I've watched videos on it and I'm pretty confident. I'm all about the detail.

I'm looking at this one. HIT-HY 200-A ADHESIVE ANCHOR

Thanks Tony, I'm looking at the Hilti website. There are numerous different options. Is there a specific one I should be looking at? these resin anchors (M12 in pairs @ 400 centres) are to hold the mid-floor wall plate, to hold the posi-joist hangers.

We are installing a wall plate to hang posi-joists. The structural engineer has specified M12 Resin Anchors. I know what resin bolts are and I know the mixture mixes as it travels down the tube. I'd like any recommendations for which resin to purchase? Thanks very much.

Moonshine, I have a nearly identical set-up to your walls (only difference is a 100mm cavity). May I ask, have you decided where you're getting your premade cavity closers from? And also your cut to length ones? And are they checked fit or flanged fit? Thanks very much.

Thanks everyone. I can see how this is installed with the expansion bead. Makes perfect sense now.

Any recommendations for a good quality sealant to finish off the expansion joints on our house please? The walls are 100mm block, 100mm cavity, 100mm block, white render finish. The expansion joints are 10mm thick. We have the movement ties and the foam filler. Just need a nice long lasting sealant to finish them off. Many thanks.

Good photo and info thanks cwr