I was trying to avoid membranes between the floor & wall at this junction because I don't like the way it acts as a slip membrane reducing the bracing the floor provides. Pro Clima Intello is a membrane & I could cut this into strips & use it with ORCON F adhesive, but I can't help feeling there's got to be a better solution.

At the ground floor junction, I have folded the DPM up the outer face of the inner leaf & I could seal it to the outer face of the inner leaf reducing the risk of air leakage. However, the air barrier is the plaster on the inner face of the inner leaf. So there's a risk of leakage vertically/diagonally through the blockwork.

Similarly, I could seal some strips of membrane to the outer face of the inner leaf above & below the 1st floor/wall junction, but there's the same risk of vertical/diagonal air movement through the junction.

I have thought about using Illbruck Butyl Fleece Tape & incorporating it into the wet plaster:

http://www.tremco-illbruck.co.uk/products/03254_index.html

The junction with the slab would be totally reliant on butyl adhesive, but the fleece would be held in place by the plaster on the walls. Does this look like a better solution?

David

Thanks for the feedback. I think that's a good solution. Incorporate the tape in the wet plaster & secure it to the slab/soffit with a skirting board/batten.

However, I do wonder whether the slab will be flat enough for the skirting board/batten to work & whether its better just to bond the plaster to the slab/soffit. The AECB Gold Standard detail just shows wet plaster continuous to slab/soffit.

David

Posted By: davidfreeboroughHowever, I do wonder whether the slab will be flat enough for the skirting board/batten to work & whether its better just to bond the plaster to the slab/soffit. The AECB Gold Standard detail just shows wet plaster continuous to slab/soffit.

I suppose you could level the slab as Chris suggests or by powerfloating etc. Or even compress a gasket between the batten and the tape.

But perhaps it's all overkill as the AECB detail suggests - the Passivhaus details don't seem to mention anything special in that position either. I guess a pile of blocks on concrete doesn't move very much. I'm more used to looking at details with a timber frame sitting on the slab, since that's closer to the situation with bales, I think.

Posted By: davidfreeboroughI'm using Compriband in two places: between the window frames & the inner face of the outer leaf, which is pretty standard; and between a plaster stop bead & the ground/1st floor slabs, which isn't. I did wonder about airtightness, because although they give weathertightness results, they don't give anything specific on airtightness.

My understanding is that it's not (very) airtight - it's open-celled (which is how it expands), and contains a water repellent (to stop rain driving through). There are similar products which are airtight, such as "isobloco one" I believe they achieve this by being:

1. Thicker
2. having a coating on the inner side which is more airtight

... but I could be wrong.

Posted By: Chris P Bacon

Posted By: davidfreeboroughHowever, I do wonder whether the slab will be flat enough for the skirting board/batten to work & whether its better just to bond the plaster to the slab/soffit.

I have also been concerned about how smooth my slab is in this area and whether it will adversely affect my airtightness. I am considering to apply some Ardex feather finish in this area. As the name implies it can be applied by trowel to a fine edge and is rapid drying.

I just finished taping the airtightness membrane to the slab this morning so for what it is worth I will share my experience while it is still fresh in my mind. it may be of use to someone.

We used an insulated slab which has a thermal break between the ring beam and the main slab and as a result the area of the ring beam wasn't power floated to the same finish as the main slab was. In a few places the finish was quite rough and not at all suitable for taping to.

To prepare the surface I used Ardex K14 (I think K13 is the equivalent in the UK or K15 would do just as well) and troweled it on to the area I would be taping to. It's self levelling and self smoothing so not much work involved just spread it on and break the surface tension when necessary.

After a day when it was fully hardened I went over the whole surface with a quick rub of a flat grinding stone to remove any bits of grit sticking out of the surface of the levelling compound which could puncture the membrane.

When it was time to stick down the membrane I first vacuum cleaned the entire area and then applied a band of Siga Dockskin with a 2" brush. I've never used the stuff before but it seems very much like a good quality PVA glue? I bought a 1kg tub of it and used about 75% of it applying a 2" wide band to a perimeter of about 50 linear metres.

I applied it last thing in the evening and left it overnight, by the following morning it had a nice amount of tack to hold the membrane perfectly in position. So I set it all in position first and then went around and taped it.

It really helps if you have been careful in putting up the membrane and it is cut exactly to size so that you don't have any folds to contend with. There was one short area where it wasn't falling right for me and it was a pain trying to get it sorted.

Overall I am very happy with the result and glad that I went to the trouble of using the levelling compound and Dockskin primer as I am sure that taping directly to the concrete surface would have been a disaster in comparison.

Posted By: davidfreeboroughInteresting. Glad it worked out.

What membrane did you use? Can you remind me, do you have timber frame walls? Is this membrane also the vapour barrier?

David

Thanks David, yes we have a twin wall timber frame the membrane was supplied by the TF company and I don't have much in the way of details on it, it's made by Temballage and is both airtightness and vapour barrier.

http://www.tjallden.se/sv/sidor/48/19/31/lagenergigrund.aspx

This is the one we used.