Soaking thermalite blocks before use??

[c***@gmail.com]

Hi All,

My wife came home yesterday, and wasn't happy with the builder's blockwork. Specifically she felt that the mortar wasn't bonded to the blocks properly as he hadn't soaked the blocks before laying them.

I've had a quick Google to see if this has been answered here before (as I seem sure it must have)), but can't find anything.

Should Thermalite blocks be soaked before use?

My wife says my FIL (who was an Architechtural Technican and knew stuff) used to soak his as this prevents them from immediately sucking all the moisture out of the mortar joints and messing up the bond.

I had a quick Google last night, and when I could find nothing here read a post in a less august forum.


The general concensus from most of the people (who mostly claimed to be brickies, etc). Was don't soak the blocks (as it can lead to cracking when they dry out), but use a wet mix and get them down quick (one or two did say they had been on site and seen them being soaked). But then, they may be more interested in how quick they can get paid and move onto the next job, rather than the longevity or otherwise of the structures they build.

What does the team think?

Tia

Chris

[Andrew Gabriel]

Post by c***@gmail.com
Hi All,
My wife came home yesterday, and wasn't happy with the builder's blockwork.=
Specifically she felt that the mortar wasn't bonded to the blocks properl=
y as he hadn't soaked the blocks before laying them.
I've had a quick Google to see if this has been answered here before (as I =
seem sure it must have)), but can't find anything.
Should Thermalite blocks be soaked before use?
My wife says my FIL (who was an Architechtural Technican and knew stuff) us=
ed to soak his as this prevents them from immediately sucking all the moist=
ure out of the mortar joints and messing up the bond.
I had a quick Google last night, and when I could find nothing here read a =
post in a less august forum.
The general concensus from most of the people (who mostly claimed to be bri=
ckies, etc). Was don't soak the blocks (as it can lead to cracking when the=
y dry out), but use a wet mix and get them down quick (one or two did say t=
hey had been on site and seen them being soaked). But then, they may be mo=
re interested in how quick they can get paid and move onto the next job, ra=
ther than the longevity or otherwise of the structures they build.
What does the team think?

Thermal blocks must be dry when used. They expand enough when
wet so that when they later dry, they will crack in half.
This happens when left uncovered out in the rain on building
sites before use. You can moisten the surface for plastering,
but don't soak the whole block.

Mortar does bond to brick and blockwork, but the main function
is to hold them apart, and blockwork itself doesn't have much
tensile strength, so there's little point in forming a strong
bond, as you would just pull the block apart under any
significant tensile forces (as happens above).

[Brian Gaff]

Assuming of course they really are the real mcoy so to speak. I recall
seeing somebody kind of painting water on the surface to be mortared many
years ago, so the wetting rather than soaking sounds about right to me.
Brian
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Blind user, so no pictures please!

Post by Andrew Gabriel

Post by c***@gmail.com
Hi All,
My wife came home yesterday, and wasn't happy with the builder's blockwork.=
Specifically she felt that the mortar wasn't bonded to the blocks properl=
y as he hadn't soaked the blocks before laying them.
I've had a quick Google to see if this has been answered here before (as I =
seem sure it must have)), but can't find anything.
Should Thermalite blocks be soaked before use?
My wife says my FIL (who was an Architechtural Technican and knew stuff) us=
ed to soak his as this prevents them from immediately sucking all the moist=
ure out of the mortar joints and messing up the bond.
I had a quick Google last night, and when I could find nothing here read a =
post in a less august forum.
The general concensus from most of the people (who mostly claimed to be bri=
ckies, etc). Was don't soak the blocks (as it can lead to cracking when the=
y dry out), but use a wet mix and get them down quick (one or two did say t=
hey had been on site and seen them being soaked). But then, they may be mo=
re interested in how quick they can get paid and move onto the next job, ra=
ther than the longevity or otherwise of the structures they build.
What does the team think?

Thermal blocks must be dry when used. They expand enough when
wet so that when they later dry, they will crack in half.
This happens when left uncovered out in the rain on building
sites before use. You can moisten the surface for plastering,
but don't soak the whole block.
Mortar does bond to brick and blockwork, but the main function
is to hold them apart, and blockwork itself doesn't have much
tensile strength, so there's little point in forming a strong
bond, as you would just pull the block apart under any
significant tensile forces (as happens above).
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

[Andy Burns]

Post by c***@gmail.com
What does the team think?

I think it varies depending if the blocks have been baking in the sun
for weeks, or left out in the rain - I'd expect the bricky to act
accordingly, only soaking them if necessary.

[John Rumm]

Post by c***@gmail.com
The general concensus from most of the people (who mostly claimed to
be brickies, etc). Was don't soak the blocks (as it can lead to
cracking when they dry out), but use a wet mix and get them down
quick (one or two did say they had been on site and seen them being
soaked). But then, they may be more interested in how quick they can
get paid and move onto the next job, rather than the longevity or
otherwise of the structures they build.
What does the team think?

The concrete foam type of light weight block is unlikely to benefit from
soaking. You may need a bit of dampening depending on how hot it is when
laying them, but I can't see it being an issue this time of year.

(all the load is in compression anyway, and the light weight blocks have
little strength in bending, torsion, or tension - so the strength of the
bond is relatively unimportant as long as the mortar was hydrated enough
to allow proper curing)

You can check various technical guides here:

http://forterra.co.uk/resources/downloads?product-groups=thermalite-aircrete-blocks
--
Cheers,

John.

/=================================================================\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

[t***@gmail.com]

Post by c***@gmail.com
Hi All,
My wife came home yesterday, and wasn't happy with the builder's blockwork. Specifically she felt that the mortar wasn't bonded to the blocks properly as he hadn't soaked the blocks before laying them.
I've had a quick Google to see if this has been answered here before (as I seem sure it must have)), but can't find anything.
Should Thermalite blocks be soaked before use?
My wife says my FIL (who was an Architechtural Technican and knew stuff) used to soak his as this prevents them from immediately sucking all the moisture out of the mortar joints and messing up the bond.
I had a quick Google last night, and when I could find nothing here read a post in a less august forum.
The general concensus from most of the people (who mostly claimed to be brickies, etc). Was don't soak the blocks (as it can lead to cracking when they dry out), but use a wet mix and get them down quick (one or two did say they had been on site and seen them being soaked). But then, they may be more interested in how quick they can get paid and move onto the next job, rather than the longevity or otherwise of the structures they build.
What does the team think?
Tia
Chris

It's normal for mortar on lightweight blocks to crack as it dries. For mediumweight blocks it's not.


NT

[Bert Coules]

I recently had to remove the top two courses of blocks from a four foot high
wall and was surprised at how weak the mortar bond was: it seemed as if only
the weight of the blocks (the dense kind) was keeping them in place.

I found myself wondering if a serviceable (if not too tall) block wall
couldn't be constructed by using adhesive rather than mortar.

[Andy Burns]

Post by Bert Coules
I found myself wondering if a serviceable (if not too tall) block wall
couldn't be constructed by using adhesive rather than mortar.

There are "landscape" adhesives sold for just that in America e.g.

<http://www.loctiteproducts.com/p/pl_ca_lndscp_voc/overview/Loctite-PL-500-Landscape-Block-Adhesive.htm>

I checked with Henkel if it was available over here, they said not and
nothing similar, which is when I ended up looking for (and eventually
using) CT1 to glue down the edge pavers on my driveway, it didn't have
quite the numbers in terms of holding pressure, but not far off ...

[Bert Coules]

Post by Andy Burns
I checked with Henkel if it was available over here, they said not and
nothing similar, which is when I ended up looking for (and eventually
using) CT1...

I wasn't familiar with CT1 and had to look it up: it's considerably more
expensive than most gun adhesives though I suppose the spec is higher. But
wouldn't any of the high-performance tube adhesives, Stixall and the like,
do an almost comparable job?

As someone whose skill with mortar and cement is approximately zero this
approach holds considerable interest.

[Bert Coules]

And here's someone building a block wall using Gorilla glue:

[Andy Burns]

Post by Bert Coules
http://youtu.be/WSNIzxkD450

Argh! I think I'm seasick ...

[Andy Burns]

Post by Bert Coules
I wasn't familiar with CT1 and had to look it up: it's considerably more
expensive than most gun adhesives though I suppose the spec is higher. But
wouldn't any of the high-performance tube adhesives, Stixall and the like,
do an almost comparable job?

Don't think they'd hold up to car traffic (especially steering wheel
turning against pavers) I only needed a couple of tubes, don't think I'd
want to pay for enough to build a wall, plus it dries with a lot of
rubbery stretch/give to it, so not ideal for a wall.

I did use solvent gripfill to put in a temporary paving slab "half-step"
for a neighbour who found the normal height had got too much for her,
and it held OK, though it didn't take much force when the time came
later to remove it.

[Bert Coules]

Don't think they'd hold up to car traffic...

Yes, I suspect you're right; I was thinking more of walling than paving.

[harry]

Post by Bert Coules
I recently had to remove the top two courses of blocks from a four foot high
wall and was surprised at how weak the mortar bond was: it seemed as if only
the weight of the blocks (the dense kind) was keeping them in place.
I found myself wondering if a serviceable (if not too tall) block wall
couldn't be constructed by using adhesive rather than mortar.

Yes it is done.
The idea is to reduce heat loss through mortar joints.
EG
http://www.starken.com.my/products-overview/thin-bed-adhesive/

[Tim Watts]

Post by c***@gmail.com
Hi All,
My wife came home yesterday, and wasn't happy with the builder's blockwork. Specifically she felt that the mortar wasn't bonded to the blocks properly as he hadn't soaked the blocks before laying them.
I've had a quick Google to see if this has been answered here before (as I seem sure it must have)), but can't find anything.
Should Thermalite blocks be soaked before use?
My wife says my FIL (who was an Architechtural Technican and knew stuff) used to soak his as this prevents them from immediately sucking all the moisture out of the mortar joints and messing up the bond.
I had a quick Google last night, and when I could find nothing here read a post in a less august forum.
The general concensus from most of the people (who mostly claimed to be brickies, etc). Was don't soak the blocks (as it can lead to cracking when they dry out), but use a wet mix and get them down quick (one or two did say they had been on site and seen them being soaked). But then, they may be more interested in how quick they can get paid and move onto the next job, rather than the longevity or otherwise of the structures they build.

Thermalite blocks are horrid things - seen exactly what you describe.

It seems they only get strong when 1/2" of plaster goes on them...