Gaps between insulation in cavity wall

letape

Would appreciate views on this. I'm not a building expert but assumed that insulation like this (Xtratherm) being put into newly built cavity wall should tightly fit together by the tongue & groove system. Please see attached picture - they are definitely not tight together. I am concerned that the insulation will not be effective so I think this is a big deal & requires remediation (reconstruction or other?). Thanks for your thoughts.

darragh_haven

letape wrote: »

Would appreciate views on this. I'm not a building expert but assumed that insulation like this (Xtratherm) being put into newly built cavity wall should tightly fit together by the tongue & groove system. Please see attached picture - they are definitely not tight together. I am concerned that the insulation will not be effective so I think this is a big deal & requires remediation (reconstruction or other?). Thanks for your thoughts.

They should fit tightly together. And be tight against tge inner leaf. Your wall ties are covered in mortar too. They need to be clean.

masonchat

Could be cleaner indeed, again it is mortar droppings keeping those sheets apart

letape

Thanks for the above. Yes, I noticed that in some cases there is mortar between the insulation boards. Presumably, whether it is air or mortar between them, the insulation won't function properly.

Is there anyway to make this good, other than reconstructing the wall?

Bluesky008

I have similar issue would be interested in answer to your question if reconstruction is only solution

MicktheMan

letape wrote: »

Would appreciate views on this. I'm not a building expert but assumed that insulation like this (Xtratherm) being put into newly built cavity wall should tightly fit together by the tongue & groove system. Please see attached picture - they are definitely not tight together. I am concerned that the insulation will not be effective so I think this is a big deal & requires remediation (reconstruction or other?). Thanks for your thoughts.

Would you accept a hole in a new wool jumper? Why then accept a "hole" in your insulation?

This is why, imo, insulation boards should not be specified in a new build unless proper attention is given to the installation. By proper attention, I mean, the inner leaf is constructed first ensuring no mortar snots, then insulation is installed tight to the innerleaf (gap free) with boards butted tightly and joints taped (again no gaps), then outer leaf is constructed. As this doesn't get done too often, pumping the empty cavity with bonded bead is the superior solution by far based on normal building practice in Ireland.

Who is supervising your build?

I assume your builder is contracted to build according to the building regulations. Then the following will be of use to you -

From TGD Part L:
Installation guidelines and precautions
Insulation should be tight against the inner
leaf. Any excess mortar should be cleaned
off before fixing insulation. The insulation
layer should be continuous and without gaps.
Insulation batts should butt tightly against
each other. Mortar droppings on batts should
be avoided. Batts should be cut and trimmed
to fit tightly around openings, cavity trays,
lintels, sleeved vents and other components
bridging the cavity, and should be adequately
supported in position. BRE “Good Building
Guide 68 Part 2 Installing thermal insulation:
Good site practice” provides further guidance
on installing insulation in cavity walls.
Critical locations where care should be taken
to limit thermal bridging include lintels, jambs,
sills, roof/wall junctions and wall/floor
junctions. The method of cavity closure used
should not cause thermal bridge at the
roof/wall junction (see Acceptable
Construction Details, section 1 details).

MicktheMan

Bluesky008 wrote: »

I have similar issue would be interested in answer to your question if reconstruction is only solution

Of course it is, it should have been done properly in the first place. Why hasn't your architect / engineer pickup up on this?

masonchat

What is the building going to be used for ? it looks like an outdoor structure if that is the case i.e not a living area i wouldnt bother just point it out to the builder ask he keeps cavitys and wall ties cleaner ensuring sheets sit flush.

AS the cavity is open you could pull out the sheets , take off the pastic crosses from the wall ties.

At this stage you will want to clean off any mortor snots that you can , reinsert first clean sheet , as you dont want to remove the male strip on top of sheet put it in at an angle i.e bottom in against inner leaf while the top of sheet is resting against outer leaf, then start to straighrten the sheet , the wallties will slice through the aero board, if you cant apply enough pressure you can stick something down the cavity , like a lenght of 3*2 cut into a wedge at one end, place between aero and outter leaf and tap tap tap your way along.

Now you want to ensure it stays in place , get a walltie bend it in half and put that between aeroboard and outter leaf, pointy end in first you want a tight fit you can push it down halfway with a level , place these 5inch in from either end of sheet.

AND repeat

letape

Thanks masonchat - the wall is the external rear wall of our house, unfortunately. We are having out house renovated and this wall is the only one that is being rebuilt, the other existing walls are just been insulated / dry lined on the inside.

Would it be easier to take the wall down and start again? The wall is about 5 foot high and 20 foot long (although there are large openings for sliding doors).

To be honest, the level of building quality demonstrated here gives me concern and we are only 3 weeks into a 16 week project.

DOCARCH

letape wrote: »

To be honest, the level if building quality demonstrated here gives me concern SD we are only 3 weeks into a 16 week project.

...just to add...the lower wall tie in that picture appears to have been bent in some way to fit, so that wall tie is falling back in, possibly due to coursing of outer leaf being higher than inner leaf?

In addition, mortar joints look a little big?

_Brian

This has forever been the problem with boarded wall insulation.
Can you imagine how the bad the fit is in areas where it's not visable.

And in fairness it's often a result of block layer being paid by the block laid.

Seeing dirty wall ties in this day is just madness.

If I were OP I'd be having serious conversations with the block layer. The poorly fitted insulation could be repaired by pumping insulation. But the dirty wall ties are liable to cause damp issues down the road and would make pumping insulation risky too.

masonchat

The reason i gave the above advise is it didnt look too long a wall , now if it doesnt have sections that are too long (preventing access to the aeroboar) then the above is doable.

Worst case he should be able to put it right by taking off the last 4/5 rows of outter leaf, fix aerobord and replace wall.

or it might be less hassel to both to have the cavity pumped with insulation at the builders expense , he wont like any of these options lol , but if you can agree on which ever suits both of you

masonchat

DOCARCH wrote: »

...just to add...the lower wall tie in that picture appears to have been bent in some way to fit, so that wall tie is falling back in, possibly due to coursing of outer leaf being higher than inner leaf?

In addition, mortar joints look a little big?

ties should fall out to run water away from inner leaf, i wouldnt worry about joint sizes if you go around measuring every joint he is likely to hit you with something lol , some times joints can vary a bit , unless finished block/brick work

masonchat

can you take a pic of the wall for me so that i can see what it actually is

DOCARCH

masonchat wrote: »

ties should fall out to run water away from inner leaf...

Ties should be level...in this case, ties (or the one I can see in the photo) are falling from outside to inside.

masonchat wrote: »

...i wouldnt worry about joint sizes...

Why not?

masonchat

DOCARCH wrote: »

Ties should be level...in this case, ties (or the one I can see in the photo) are falling from outside to inside.



Ties should fall out where possible level will do

Why not?

Why do you ? you dont want huge joints, you dont want no joints , but its quite fine that they vary , i.e if there is a gap , it can be closed by increasing the joints over a number of blocks, or the foundation may be off and you may need to raise one corner or lower another to reach parity again done over many rows. IT isnt lego you are building with , sometimes you can get a difference of 3/4 of an inch in the lenght of a block in different bales loads , thats extreme case but ive seen it

DOCARCH

All I am saying is that your statement...

masonchat wrote: »

...i wouldnt worry about joint sizes...

...is not really correct nor is it great advice...in my opinion.

The size of the mortar joint is critical to the structural integrity of the wall.

Generally mortar joists should not exceed 10mm. I say generally as I am not suggesting anybody really needs to go and measure all the joints in a wall. The odd 12mm to 15mm, or so, joint, here and there is/should generally be fine, but, if you look at the picture the OP posted, all joints look to be around 20mm...this is not good/great.

masonchat

Yeah 10mm is naturally where they will be with a stardard bed, the joints in the pic while appearing to be on the thicker end of the scale , they arent big enough for concern .

Can be deceptive viewed from there , a frontal view would be more telling , i take your point with regards to my earlier comment i should add size of joints wouldnt worry me within reason

letape

Also, I was wondering whether:

- A tray damp from inner leaf to the outer leaf should have been fitted and / or a radon barrier?

- There be a brick return on the window and door reveals?

- The joints in the insulation boards should be taped?

Thanks for all your feedback - I will post some additional and more complete pictures this evening

letape

A few more pictures below:

masonchat

FRom what i can see in the second and last photo , it looks like the cavity is blocked with mortar ? is that floor level ? the cavity should extend down 9 inch below floor lever.

there should be nothing in the cavity from damp proof down (i dont mean where dpc is visible in your pic, i mean if you have a lower floor level where the blockage is) , so aero starts at damp level , but below that you would have empty cavity 9 inch deep 4 ince wide, now some droppings down at the bottom of that is ok thats what the void is for , but to me it looks like you dont have that ? or is floor level going to be at the decking level where i can see the dpc or will there be 2 different floor levels ? ,

The wall tie i can see is dirty but its one wall till, it does look like aeroboard was poorly inserted to be fair you can see it touching outter leaf as wel.

Also by right you should have a walltie on every row where a window or door jamb is

MicktheMan

Thermal looping will reduce significantly the effectiveness of the insulation. The arrows in the pic show the movement of air due to convection in the cavity.

declan52

When bedding the wall some mortar has got pushed into the groove of the insulation that's why the tongue won't fully fit it. Its easy done but is normally wiped clean before the next sheet is put in.
I agree the wall ties look dirty from droppings.
More of a worry is how is the end being closed as there are no returns. Cavity closer?
The cavity is also not the cleanest.
See if you can reached in and unclip the sheet and clean the snots of to get a better fit.

masonchat

From the pics you pm,d me letape , its a reasonable size job you have on there and it looks very far down the line in terms of progress.

It is clear from them pics also the builder doesnt take a whole lot of pride in appearence , i wouldnt say it bad but it just looks lazy , i.e not putting window cill in when doing the wall general pointing , dirty cavitys , and the important thing ill fitting aeroboard. now the main thing is the aeroboard and if he just built that wall get him to take out wero clean cavitys and reinsert aeroboard how i suggested on page 1, it can easily be done as from what i see its only short lenghts of block work

masonchat

Declan id imagine he will run dpc down the inside of the outter leaf cuts strips of aeroboard to close cavity and plaster them up

declan52

masonchat wrote: »

Declan id imagine he will run dpc down the inside of the outter leaf cuts strips of aeroboard to close cavity and plaster them up

Yeah but you get a much better fit if its done at the time with a 100mmx100mm strip not squeezed in at the end.

masonchat

letape wrote: »

Also, I was wondering whether:

- A tray damp from inner leaf to the outer leaf should have been fitted and / or a radon barrier?

- There be a brick return on the window and door reveals?

- The joints in the insulation boards should be taped?

Thanks for all your feedback - I will post some additional and more complete pictures this evening

Only saw this post now
Damp tray from inner to outer , not normally , dpc on inner and outer leaf at floor level done from what i see , damp tray under window cill and wrapped around and damp over heads and dpc on inside of outer leaf of doors and windows .

Radon barrier would /should have gone at floor level under aeroboard and concrete , that job looks like an elevated floor or something though so i dont know what is below.

Brick return can be done not essential , an awful lot of houses were built using the method he is using , then cavity closers (l-blocks) came along . a lot use them a lot dont.

THE joints on aeroboard if he did that he would be the first id say ,

A lot of these things you should have hammered out with him long before now though

just do it

Very unsatisfactory job. I'd call a halt asap and insist on it being remedied. I think for me that would mean removing the insulation, knock off all mortar snots, clean it cavity, and pump when finished.

Is there a building body such shoddy work can be reported to?