Insulating around window support bars

The airtightness tape must be fitted to the window, across the insulation and onto the block on all four reveals. Make sure to remove the foil from the frames first.

Seen a lot of people just dob tape over the bar, making no allowance for the fact it is raised, leading to corners not sealing.

As for can tape go directly, i think there are ways to do both, but remember the block is not airtight.

And as for the suggestion of rough plastering the blockwork, with the greatest respect to BryanF - that's creating another physical intervention for the block-layer/plasterer, requires time to dry and also adds a small amount of build-up of the thickness of the reveals; so it's adding cost and complexity to something that already seen as somewhat as a costly nuisance (those tapes aren't cheap). I'd much rather just roll on some approved primer to the block and have it ready within hours.

Possibly nothing as it's behind the air tightness layer, but I would suppose any packing such as low expansion foam would be suitable and then cut-back slightly to maintain allignment at the edge of the support?

I assume it will be plastered with sand and cement first and then plasterboad followed by skim - though I am not sure why the plasterboard would be necessary (except under the window board maybe) as couldn't the plaster be just skimmed over? It says plasterboard on reveals in one place on the plans and sand and cement in another so that's why I was confused - will be confirming with him anyway.

As an aside would plasterboard which would be sealed with skim not be airtight?

Hi All, sorry to drag up an old thread but its very relevant to my previous conversation above. Airtightness taping was done on windows with the plasterable tape and I was working of the assumption that the reveals would be sand and cemented but with slabbers working in the house now they have said they will be slabbing the reveals once finised the ceilings - I questioned it and they said that's how its done in every house. Asked the plasterer and he said he never puts sand and cement on reveals anymore and would not be willing to plaster over airtightness tape as he doesnt trust it not to crack.

So half my revel is covered with the tape but the the other half will be bare blockwork and a slab will be going straight over it. I know its not the absolute best practice for airtightness but my feeling is that it shouldn't cause major issues either or am I wrong?

There wont be time unfortunately I am already racing against time to get the strip painted on the blocks that will be left between airtight membrane and plaster upstairs due to the thickness of the insulated slab on the ceilings (if you get where I mean). I will just about get that done this evening ahead of upstairs slabbing tomorrow - it would be probably a full days work minimum to paint all the reveals and that's not going to happen between now and Thursday.

Does the slab and skim coat not do a fairly good job in sealing it up? the slab will be stuck to the wall in my understanding. I have spoken to two different people since (a carpenter and my blocklayer) and both said this is how they see it done in every house they work on (including their own recently built house in the case of one of them).