Blower door before internal plastering...

dos29

Has anyone done the above, and if so, what was your result please?
Recently had this done to check airtight membranes and taping before slabbing goes ahead. Exterior of house is plastered, but not interior. 8 inch cavity pumped with bonded bead.
Only got a rating of 7.5 on a positive test(dont know anymore technical details then that). Really hoping for a result below 1.5 at the end, so slightly worried about this. There was some leaks into the cavity which are being addressed, but nothing too severe.
Thanks in advance for any replies.

MicktheMan

Bare block walls are porous to air so am not surprised with the poor result.
Why was the test only a positive one. In my experience of testing, a depressurisation test is a lot more informative on where the weaknesses are especially at the stage your build is at.
What advice did the tester give you?

fclauson

you will need to parge coat the WHOLE of the inside of the house BEFORE you slab

As mentioned block is porus - we have also seen sockets being a real problem - each one needs to be parged coated before fitting

Plus any conduit which goes outside the envelope will need blocking
and any U bends

dos29

Only positive test as tester was afraid negative might damage areas of exposed membrane which was only held by staples until its slabbed over.
Advice from tester was apart from the leaks listed which are in hand, the windows, doors and roofing performed brilliant, so just have to see what difference the plastering makes. He hadnt done a house pre plastering before so nothing to compare result with really.
As for parge coating, I'm not sure I'm following?
Its story and a half with slopes membraned and taped from wall up to peak. Slabbing, along with insulating, is next on ceilings and stud walls upstairs. Then all block walls getting plastered with sand/cement and skim finish.
I knew block was porous, just wondering how porous and what kind of result might somone expect from the way the house is at the moment.
Maybe its a bit like how long is a piece of string in that it depends on quality of blockwork too, cos of gaps in mortar.

BryanF

You need to put on the scud coat ( base coat of plaster on to block), and retest. Forget drylining until then. You do appreciate that 7.5 ach doesn't meet the regs!

You haven't by any chance got a performance clause in the contract with the builder?

MicktheMan

Tester could have protected the membrane using 2 by 1 battons temperarly screwed across membrane to prevent it from moving (temporary screw holes sealed later with tape).
Notwithstanding the porous block walls at the moment, 7.5 is poor. If the membrane/tapes is good then go ahead and slab the roof and plaster the walls and then have a proper test (both +ve, -ve). Use the -ve test to find weaknesses and fix.

dos29

BryanF wrote: »

You need to put on the scud coat ( base coat of plaster on to block), and retest. Forget drylining until then. You do appreciate that 7.5 ach doesn't meet the regs!

You haven't by any chance got a performance clause in the contract with the builder?

Scudding is done, but scudding doesn't cover much of the blockwork to be fair, so I dont think would make much difference either way.
Building covered by older regs of having to be below 10 ach but thats a non issue anyway as HRV is being installed so I'm looking for MUCH lower!
Self build so no builder as such.

MicktheMan wrote: »

Tester could have protected the membrane using 2 by 1 battons temperarly screwed across membrane to prevent it from moving (temporary screw holes sealed later with tape).
Notwithstanding the porous block walls at the moment, 7.5 is poor. If the membrane/tapes is good then go ahead and slab the roof and plaster the walls and then have a proper test (both +ve, -ve). Use the -ve test to find weaknesses and fix

Lot of membrane has been used and its on some awkward roofing so good chance battening wouldnt have worked as straight forward as might think.
I was fairly resigned to only course now is slab, plaster and proper test now, but was curious as to whether anyone else had a figure for a similar test.
Thanks for replies folks.

MicktheMan

dos29 wrote: »

but was curious as to whether anyone else had a figure for a similar test.
Thanks for replies folks.

From top of head, large house tested before internal sand/cement 3.5, after internal plaster 2.0. Note, walls in this case were poroton, not concrete block.

BryanF

dos29 wrote: »

Scudding is done, but scudding doesn't cover much of the blockwork to be fair, so I dont think would make much difference either way.
Building covered by older regs of having to be below 10 ach but thats a non issue anyway as HRV is being installed so I'm looking for MUCH lower!
Self build so no builder as such.


Lot of membrane has been used

you installed the air-tightness yourself didn't you

its on some awkward roofing so good chance battening wouldnt have worked as straight forward as might think.
I was fairly resigned to only course now is slab, plaster and proper test now, but was curious as to whether anyone else had a figure for a similar test.
Thanks for replies folks.

my two cents:
if it were me I'd employ a good air-tightness installer, or if moneys tight forget the HRV and do the air-tightness & put in DCMEV