Wall plate replacement

[David]

In our property (bungalow), the wooden wall plates are rotting, leading
to the rotting of the joists and floor boards too.

New 100x50 isn't the same size as the original 4"x2", which is not the
real problem, but can I use concrete lintels such as:

http://www.wickes.co.uk/invt/220307

in their place ??

Also, what is the best method of holding / lifting the wall to replace
them ?

I have seen Acros used, but the walls are cracked both vertically and
horizontally.

I am looking to somehow lift the walls using a home-brew spreader in the
gap where the wall plate was, then wedging them whilst replacing the plates.

Thanks

David

[harry]

The question is why have they rotted? (No damp proof course?)
It's no longer the practice to build bits of timber into the wall for
the joists to rest on.
I would be tempted to remove the wood a bit at a time and put bricks
in or similar that will fit if bricks are too big.

Something will have to be done about the DPC, maybe a chemically
injected one. You can hire the equipment to do this.

You might well find the joist ends have rotted too much to be left.
Even more likely if the wall are solid rather than cavity. If so,
consider concrete floors rather then replacing the timber.

A lot also depends on the relative heights of the ground outside and
the floor inside.

You need to carefully consider all the work, it might actually be
better demolish the walls, even the entire building if the roof is bad
too.

These jobs can grow like Topsy. As you get into them, more and more
defects become apparent.

[Phil L]

David wrote:
> In our property (bungalow), the wooden wall plates are rotting,
> leading to the rotting of the joists and floor boards too.
>

Floorboards?

What are you referring to when you say 'wallplate'?
The wallplate sits on top of the completed brickwork and the roof is built
onto this, unless you mean the floorboards in your loft?

> New 100x50 isn't the same size as the original 4"x2", which is not the
> real problem, but can I use concrete lintels such as:
>
> http://www.wickes.co.uk/invt/220307
>
> in their place ??
>
> Also, what is the best method of holding / lifting the wall to replace
> them ?
>

You've lost me, there is no wall on top of a wallplate, just a roof

> I have seen Acros used, but the walls are cracked both vertically and
> horizontally.
>
> I am looking to somehow lift the walls using a home-brew spreader in
> the gap where the wall plate was, then wedging them whilst replacing
> the plates.

Is this a horizontal joist within the wall at floor level?

If so, then i'll wager my life that your bungalow was built between 1918 and
1935, crap like this was commonplace for a shortish period after WW1,
luckily the (bad) practice died out just before WW2.

Also, I assume that this 'wallplate' is just on internal walls seperating
rooms, not outside walls? - again, in this era, this was a kind of 'frame'
built and stood on the foundations then brickwork filled in between the
timbers, which is why you are seeing vertical and horizontal cracking, the
entire thing's fucked and I wouldn't be at all surprised if there's dry rot
knocking about too.
Easiest and best solution, provided my assumptions above are correct, is to
hack off the plaster on this wall and see if it's a timber framed affair, if
it is, knock it down and put it in a skip, then you can treat any remaining
timbers with dry rot treatment, after replacing any bad parts 500mm past any
visible signs of rot, then rebuild the wall in studding and plasterboard or
thermalite block

More info required:
How many walls are affected?
is there adequate ventilation to the underfloor void?
Is there a DPC, either physical or chemical?

[Kevin]

On 02/10/2012 13:39, David wrote:
> In our property (bungalow), the wooden wall plates are rotting, leading
> to the rotting of the joists and floor boards too.

I had exactly this problem in my last house. Further to Phil L's reply,
this was in internal half-brick (4 1/2") walls and the inner leaf of 9"
external walls of an Edwardian semi in the Midlands. 4x2 or thereabouts
had been layed on a bed of what looked like a black mortar, presumably
intended as a dpc. Ground floor joists were layed on the wallplate,
with brickwork infill, and the rest of the wall built up from there.
Lengths of it had almost disappeared, as had many joist ends, and the
dry rot showed every feature described in all the books. There was so
much white furry fungus it looked like a dead polar bear under there.

Starting with lengths where there was absolutely no support from the
wallplate, I chopped it out (mainly with my fingernails) together with
whatever of the next couple of courses of brickwork fell out with it,
and built short lengths of new brickwork on felt dpc (this was 35 years
ago). Once the new mortar had cured, I moved on to the next section.
The dry rot was so extensive I replaced the floor with concrete,
otherwise I'd have used joist hangers. In one area, the dry rot hyphae,
around the diameter of a biro, had spread right up the wall, under the
plaster, till they merged with those from the rotten 9x9 timber lintel
over the bay window.

The house is still standing, so the method must have worked. I think
the main lesson was to do it in short sections. I didn't try to jack
the wall because walls seem to settle irreversibly in that once a crack
opens, mortar and brick dust fall in, then won't compress to allow it to
be reversed.



--
Kevin

[David]

Hi Harry,

Thanks for the response.

There is a DPC, and the wall is the inner leaf of a cavity wall
construction.

The cause of the rot is the Cavity Wall Insulation ( CWI ), glass wool
made by a reputable company.

A few years back, the bedroom floor collapsed and I investigated. I
found rotten wall plates, joists and floor boards. The CWI had soaked up
the water from the bottom of the cavities, and even at two feet higher
than the DPC, was just like a sponge full of water.
I got the BBA (British Board of Agrement, the body responsible for the
certification of building materials and techniques) out to inspect.
The inspector stated that the insulation material was certified
approved, and the installation was performed correctly, and that what I
had showed him could not have happened.

So i removed every third brick from the outside wall just above the DPC,
vacuumed out the CWI below this level and installed cavity brush
horizontally around the (detached) property, and installed extra air
bricks in both leaves, sometimes offset by one brick to prevent wind noise.

Ours is the only property round here with suspended floors, all the
others are solid.
The property was built in 1953/4, and there is a 100m clay bed beneath
the area leading to very poor drainage.

I have used bricks in the past as a temporary replacement before in
other parts of the property to 'prop' up the walls, but in this case, I
think the wall has dropped a bit.

Thanks again

David

[David]

Hi Phil,

Thanks for responding.

There are 4x2 timber lengths laid into the inner leaf that lay on a bed
of mortar, that lays above the DPC that the joists are fixed to (so it
goes, brick, mortar, DPC, mortar, timber, mortar, brick).
These are commonly called 'wall plates' around here. The rest of the
wall is built on top of these timber lengths.

Also, there are 4x2 timber lengths laid on shorter walls (called sleeper
walls) at equal distances supporting the joists and these are called
'sleeper plates' around here.

The property was built in 1953/4, and is not timber framed. It is of
dual leaf cavity construction, and as you say, there are no timbers in
the outside wall.

All the perimeter inner walls are affected to varying degrees.

The has been adequate underflloor ventilation for the last fifteen years
at least now.

The DPC is present and unbroken, but that does exclude poor building
techniques: I found one sleeper plate going into an inner leaf below the
DPC in one room....

The cracking is I believe due to uneven sagging of the walls as the
timber in the inner leaf has dried and shrunk at different rates since
the extra ventilation was introduced.

Thanks again

David

[David]

Hi Kevin,

Thanks for responding.

I'm not sure what you mean by "half-brick" walls.
Our inner walls are brick and mortar to the DPC, which I believe was a
liquid poured onto the mortar, then another bed of mortar, then timber,
then mortar again with brick infill, then big grey blocks that are
similer to 'breeze blocks' for the rest of the inner wall.

I do not have any dry rot, thankfully, but there is white furry fungus
nearly everywhere in the voids under the floor on, dead organic matter,
not the property construction materials.

I'm pleased that you had success with your problem.

Thanks again

David

[dochol...@gmail.com]

On Wednesday, October 3, 2012 1:17:09 PM UTC+1, David wrote:
<snip>

>
> I'm not sure what you mean by "half-brick" walls.
> Our inner walls are brick and mortar to the DPC, which I believe was a
> liquid poured onto the mortar, then another bed of mortar, then timber,
> then mortar again with brick infill, then big grey blocks that are
> similer to 'breeze blocks' for the rest of the inner wall.
>

The convention is that walls built of stretchers, i.e. 4 1/2 inches thick, are referred to as half brick. Discounting walls built with bricks on edge this is the thinnest you can do with regular bricks, and is the thickness of most of the individual leaves of cavity walls.
Before the introduction of cavity walls it would be normal for the external walls to be 1 brick (9 inches) minimum, with the walls of larger houses often 1 1/2 or 2 brick thick at lower levels.

[george - dicegeorge]

on myhouse the garden had built up higher,
covbering the airbricks
which then let in water.

I have dug a moat around the house,
and hope that future generations wont fill it in with earth
and repeat the sorry saga!
[george]

[harry]

On Oct 3, 1:03 pm, David <m...@home.org> wrote:

If it's that bad you are probably down to dismantling the inner leaf
and rebuilding. The roof usually rests on a wall plate on top of the
inner leaf & will have to be supported.
You can buy screw in wall ties to replace the existing which may well
be naff.
I would fill in the void under the floor with hard core and put down
concrete floors with insulation beneath.
You can also fix the cavity wall insulation. I suspect that you have
interstitial condensation in the insulation due to warm air from the
building getting into it. Check up on vapour barriers.

http://en.wikipedia.org/wiki/Vapour_barrier
http://en.wikipedia.org/wiki/Interstitial_condensation

The new inner leaf could be insulation blocks

Whatever you decide to do, it's going to be a big job.

[george - dicegeorge]

i suspect that if the insulation is soaking
over 90% of the water is coming from rain from a leak in the roof.
[g]

[David]

OK, thanks

David

[David]

Good thinking, our DPC and air brick are well above the ground level.

David

[David]

I know that it isn't coming from the roof, nor from leaking gutters, but
it was from the CWI 'sucking' up the water from the bottom of the
cavities, before the CWI was removed.
The cavities fill with rain water after prolonged rain. Wetness can also
be seen on the surface of the solid sub-floor (?) after heavy rain if
the floor boards are lifted.

It could also be penetrating damp though, bricks are not waterproof ...

I am having the South and West elevations re-pointed in a couple of
weeks as they have deteriorated badly, though the current wall plate
concern is on the other corner (NE) of the property.

Thanks for the suggestion


David

[george - dicegeorge]

as well as digging a moat around my house,
and installing french drains,
i left some pits
so i can look at the water level
at various times, after rain, after drought,
and see where the local water table is at.

Maybe Ill' put some plastic french drain vertically
in these holes
with a cover over it
so i can check this over the years
when i've tidied up the outside of the house.
[george]

[g]

[Phil L]

David wrote:
> On 03/10/2012 21:11, george - dicegeorge wrote:
>> i suspect that if the insulation is soaking
>> over 90% of the water is coming from rain from a leak in the roof.
>> [g]
>>
>
>
> I know that it isn't coming from the roof, nor from leaking gutters,
> but it was from the CWI 'sucking' up the water from the bottom of the
> cavities, before the CWI was removed.

This isn't possible I'm afraid, and whoever has told you such garbage has
been lying.
CWI is waterproof - completely 100% waterproof, it's tested and tested again
and cannot 'wick' moisture upwards, unless you got someone to fill the
cavities with shredded newspaper? - I'm sure I read earlier that they were
done with blown glass fibre?


I'm afraid you've done more damage than good by removing part of the CWI -
walls need to be 100% filled to be effective not just against heat loss but
water penetration too

[harry]

Yes above is correct. The fibres they blow in are treated to make
them water repellent (slicon I think)
I think you're back to interstitial condensation. Warm moist air
condensing out in the insulation. The problem is once the water is in
the insulation it remains there and may have caused/made worse your
rot problem.
The only way to dry it out is by removal. Wet insulation is pretty
ineffective anyway.

If you have water under the floors, you've got to get rid of it.
Either by a drain or with a sump and a pump. Best to stop it from
getting in if at all possible.

[David]

Thanks for the continued advice.

Imagine removing a brick / block from the internal wall two feet above
the internal floor, and finding the CWI soaking wet. It was literally
like a sponge. Squeezing it released lots of water.
Are you (Harry) saying that interstitial condensation can penetrate the
wall to that effect ?
What about penetrating damp from the outside ? I would have thought that
more likely.

I do not understand how if the CWI is treated to repell moisture, that
it can collect and retain moisture to the extent it has.

So possibly, I need to remove the CWI and somehow put a vapour barrier
on the walls that have outside components.

The area is situated on a clay bed of 100m depth, there is poor drainage
and the cavities are somewhat lower than the ground level, therefore
they are a collection point for the rain.
Should I approach the Water Authority about connecting to the sewer, or
storm drains in the road ? Then I might get subsidence as the clay dries
out and shrinks. I suppose then I need to get the place underpinned.

Phil, with regard to me making the problem worse by removing the CWI,
now the timbers do not have wet material touching them and also there is
now more ventilation to dry the sub floor voids, this would have been
better had I not ?
I cannot agree with that. The timbers are now dry and rotten (and have
shrunk), whereas before they were wet and rotting. Would it have been
better to leave them wet ?

Again, your inputs are much appreciated.

David