Suspended floor timbers bridging dpc
Graham Jones
We are having an extension built and I have some concerns over how the
joiner is constructing the suspended floor.
The house is constructed with a vented void where the dpc is about
three/four couses above ground level, then above the dpc are air
bricks. The extension has been constructed the same way with the
airbricks and dpc at the same levels as the house.
The joiner to make the suspended floor has bolted timbers to each side
of the extension, these timbers start below the dpc and finish above
the dpc, also the timbers cover the airbricks. He has however drilled
lots of holes where the airbricks are behind the timbers. Attached to
these timbers are joist hangers. This gives the same floor level as
the main house.
My concern is that the timbers bridge the dpc, surely this can't be
right?
Any thoughts?
Thanks,
Graham
Tim W
"Graham Jones" <grahamj...@gmail.com> wrote in message
news:30b29ffb-d31d-44e7...@f41g2000yqh.googlegroups.com...
It sounds like a balls up.
The person to collar is not the poor tradesman who has been forced to bodge
it to get the job done and for whom any delay is expense, collar the person
who drew the plans with insufficient detail, who isn't making himself
available to answer this kind of query, or the person who is overseeing the
trades whose job it is to examine the plans and anticipate any problem like
this before you get there.
Unless of course the carpenter is the builder and you don't have any plans.
In which case you need to stop everything immediately and call Building
Control.
Tim W
Graham Jones
> "Graham Jones" <grahamjones2...@gmail.com> wrote in message
Thanks for your reply, the builder is the joiner. I agree with you
that is sounds like a balls up, but will it work? Or will the section
of timber below the dpc soak up water and/or transfer it above the
dpc?
Graham
Jim K
news:30b29ffb-d31d-44e7...@f41g2000yqh.googlegroups.com...
sounds Fing awful - some pics will probly get you a detailed "how it should
be" response from, amongst others, Hugo Nebula (a BCO)
Jim K
Graham Jones
> "Graham Jones" <grahamjones2...@gmail.com> wrote in message
Thanks very much for everyone's help with this, I have posted two
photos here:
https://picasaweb.google.com/112976012416010700696/Floor
The first photo shows the corner of the room, you can see where the
airbricks are and that the dpc is directly under the airbrick. This is
exactly how it is in the original part of the house. But as you can
see the timber bridges the dpc. The second photo shows how holes have
been made in the timber where it covers the airbricks. The levels seem
correct, the top of the joist will give a floor at the same level to
the rest of the house.
If you need any other photos then please ask.
Thanks,
Graham
harryagain
"Graham Jones" <grahamj...@gmail.com> wrote in message
news:30b29ffb-d31d-44e7...@f41g2000yqh.googlegroups.com...
Nothing should span the DPC.
The timber should have been specified as treated, (usually green in colour).
The normal practice is for the hangers to be cemented into the wall and
above the DPC. The hangers used would be much thicker metal for this
puspose.
But anyway.
It's quite unsual to have suspended floors at ground level these days.
Haven't seen one for years.
Normal practice is to have concrete (with insulation and DP membrane below.
This a much better system, nothing to rot and warmer too.
Jim K
https://picasaweb.google.com/112976012416010700696/Floor
-----
mmmm I'll wait for the comments with interest..
also
1) where will the floor insulation go?
2) I know technically they don't allow joists to be built into walls anymore
(for air leakage reasons (but they let me on an internal conversion)) but
why didn't he just use hangers on the wall rather than the "bolted bodge
beam" (TM)? (as there's F off airbricks right behind it can't be for "air
leakage control" can it?!!
I suspect the airbricks are set too high and the rest is a bodge around?
Wait for the others & Hugo (hope he's online and not stuck on Google
groups?? anyone know?)
Jim K
Phil L
There's two problems here, the first being that the airbricks are at the
wrong height - they should have been 2 or 3 courses below their present
level, so that you get an unhindered crossflow of fresh air under the floor.
The second problem is the DPC is at the wrong level too, it shouldn't be
75mm below floor level, it should be at floor level, which inevitably means
that the joists are usually below the dpc, to get around this, builders
usually incorporated two dpc, one underneath the joists, then laid 2 or 3
courses, then the secondary dpc at floor level, are you sure there's not
another dpc under the one visible in the pictures?
Either way, the vents will need moving - why they put them in the way of the
dpc remains a mystery.
Graham Jones
Thanks for your reply, I have uploaded two more pictures to:
https://picasaweb.google.com/112976012416010700696/Floor
The first new picture shows where the builders have knocked out an
existing airbrick to find the floor level, the original dpc is just
under this airbrick. They have replicated this in the extension with
the airbricks at the same level and the dpc under the airbricks. So
maybe this is OK?
The second new picture shows (hopefully) the position of the existing
joists, this is looking into the airbrick they knocked out. The joist
is sitting on top of the dpc.
So is the problem just that the new joists are of a different height
to the old and are too large to sit above the dpc and give the same
floor level?
Graham
ARWadsworth
.
>
> But anyway.
> It's quite unsual to have suspended floors at ground level these days.
> Haven't seen one for years.
I take you have not been on a building site then..
--
Adam
John Rumm
Is this a cavity wall?
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Graham Jones
Yes
Hugo Nebula
chimpanzee, Graham Jones <grahamj...@gmail.com>, randomly hit the
keyboard and wrote:
>Thanks very much for everyone's help with this, I have posted two
>photos here:
>
>https://picasaweb.google.com/112976012416010700696/Floor
Firstly, the air bricks should be below the DPC. It looks to me like
the DPC has been installed too high. It should be not less than 150mm
above the adjoining ground level, but below the joists. If it's gone
too far to get it rectified, I would suggest forgetting about a timber
joisted floor and going with a ground bearing concrete slab.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have I strayed"?
Graham Jones
> [Default] On Sat, 13 Aug 2011 04:28:40 -0700 (PDT), a certain
>
> keyboard and wrote:
> >Thanks very much for everyone's help with this, I have posted two
> >photos here:
>
> >https://picasaweb.google.com/112976012416010700696/Floor
>
> Firstly, the air bricks should be below the DPC. It looks to me like
> the DPC has been installed too high. It should be not less than 150mm
> above the adjoining ground level, but below the joists. If it's gone
> too far to get it rectified, I would suggest forgetting about a timber
> joisted floor and going with a ground bearing concrete slab.
> --
> Hugo Nebula
> "If no-one on the internet wants a piece of this,
> just how far from the pack have I strayed"?
Thanks very much for your reply. You say the air bricks should be
below the DPC, but this is not how it is in the rest of the house. As
you can see in the photos the house was originally constructed with
air bricks above the dpc. I suppose the builders have just done the
same. The fourth photo shows the original joists above the dpc at the
same level as the air bricks.
It has gone too far to rectify this, the roof is on! Is there no other
way around this?
I am going to ask the builders to stop work on Monday until the
inspector can come and take a good look at everything.
Graham
Hugo Nebula
chimpanzee, Graham Jones <grahamj...@gmail.com>, randomly hit the
keyboard and wrote:
>You say the air bricks should be
>below the DPC, but this is not how it is in the rest of the house.
>It has gone too far to rectify this, the roof is on! Is there no other
>way around this?
>
>I am going to ask the builders to stop work on Monday until the
>inspector can come and take a good look at everything.
Two wrongs don't make a right.
If ground and internal levels allow, it should still be possible to
install airbricks below the DPC and fill in those above, install a
telescopic vent in the cavity, and wrap the ends of the joists in DPM
if they are below the DPC.
In fact, looking at the photos, are the joists 200mm deep? You should
be able to reduce that to 100mm if you have sleeper walls. The joists
may then be able to fit on top of the DPC.
Graham Jones
> [Default] On Sat, 13 Aug 2011 13:37:56 -0700 (PDT), a certain
Thanks Hugo. Am I right in thinking that the BCO should be able to
come up with a solution and say exactly how it should be changed? I'm
going to ring him first thing tomorrow. The annoying thing is that he
must have already seen the air bricks above the dpc as I am almost
certain he inspected when the build was at this level. Maybe he missed
it.
Graham
Hugo Nebula
chimpanzee, Graham Jones <grahamj...@gmail.com>, randomly hit the
keyboard and wrote:
>Thanks Hugo. Am I right in thinking that the BCO should be able to
>come up with a solution and say exactly how it should be changed? I'm
>going to ring him first thing tomorrow. The annoying thing is that he
>must have already seen the air bricks above the dpc as I am almost
>certain he inspected when the build was at this level. Maybe he missed
>it.
It's not his job to design it for you, but he may be able to offer
suggestions. If you have a worked-out solution that meets all the
guidance, then he's likely to agree with that.
I was going to post that it should have been noted at DPC inspection,
but I thought that may have raised more questions than it answered.
Such as, was it inspected? If so, were the airbricks in? On the first,
it's not uncommon for builders, if left to their own devices, not to
notify Building Control at any stage, or at least any stage after the
first foundation inspection, and lie to the owners that everything has
been passed by the Building Inspector, guv.
Or, he could well have missed it. That doesn't excuse it being built
wrong. If I get pulled over by the Police for speeding and he doesn't
spot a bald tyre, it doesn't mean my tyres are roadworthy.
Graham Jones
> [Default] On Sun, 14 Aug 2011 02:35:04 -0700 (PDT), a certain
Thanks I understand.
Not wanting another sleepless night I've just phoned the builder, he
is confident that there will be no damp issues and that the BCO will
pass it. In your opinion will this ever be passed? If the BCO does say
it is OK then what comeback do I have?
Thanks,
Graham
Grimly Curmudgeon
drugs began to take hold. I remember Graham Jones
<grahamj...@gmail.com> saying something like:
>Not wanting another sleepless night I've just phoned the builder, he
>is confident that there will be no damp issues and that the BCO will
>pass it.
He would say that, wouldn't he? Keeping his fingers crossed you believe
his bullshit and don't call the BCO in.
Graham Jones
Just to let you know the conclusion to this.
BCO was happy with position of airbricks and dpm, external ground
level means air bricks can't be any lower, builder needs to change
them to telescopic air bricks. Instead of timber bolted to wall use
embedded joist hangers.
He also had a good look around, no other problems. Had a private chat
to him after, says work is OK, in some places builder has gone further
than he needed to. Would recommened not changing builder but to keep a
close eye on him. BCO will make extra inspections before plastering.
Quite happy now.
Graham
Man at B&Q
> If you need any other photos then please ask.
One of his horse, please!
MBQ
Jim K
Quite happy now.
Graham"
result ;>)
Hugo Nebula
chimpanzee, Graham Jones <grahamj...@gmail.com>, randomly hit the
keyboard and wrote:
>BCO was happy with position of airbricks and dpm, external ground
>level means air bricks can't be any lower, builder needs to change
>them to telescopic air bricks. Instead of timber bolted to wall use
>embedded joist hangers.
Which would suggest to me that the adjoining ground level is only
150mm below the DPC. If so, you need to watch out that the sub-floor
is not below the adjoining ground level.
Graham Jones
> [Default] On Tue, 16 Aug 2011 04:02:28 -0700 (PDT), a certain
>
> keyboard and wrote:
> >BCO was happy with position of airbricks and dpm, external ground
> >level means air bricks can't be any lower, builder needs to change
> >them to telescopic air bricks. Instead of timber bolted to wall use
> >embedded joist hangers.
>
> Which would suggest to me that the adjoining ground level is only
> 150mm below the DPC. If so, you need to watch out that the sub-floor
> is not below the adjoining ground level.
> --
> Hugo Nebula
> "If no-one on the internet wants a piece of this,
> just how far from the pack have I strayed"?
Hello Hugo, by sub-floor do you mean the concrete on top of the dpm
sheet, or the suspended timber floor. Either way what are the
consequences of the sub-floor
being below the adjoining ground level?
Thanks,
Graham
Hugo Nebula
chimpanzee, Graham Jones <grahamj...@gmail.com>, randomly hit the
keyboard and wrote:
>Hello Hugo, by sub-floor do you mean the concrete on top of the dpm
>sheet, or the suspended timber floor. Either way what are the
>consequences of the sub-floor
>being below the adjoining ground level?
The sub-floor is the covering over the ground; in your case, concrete.
If it is below the adjoining ground level, there is the risk that any
water that gets inside cannot drain away and will sit under the floor.
If the ground around the building is sloping, part of the sub-floor
can be below ground level provided it falls away to the lowest edge of
the building where it can drain away. I have accepted a 'french drain'
around the building or offending part that is able to drain away,
i.e., to a gully or a soakaway.
jgharston
> It's quite unsual to have suspended floors at ground level these days.
A bugger on your knees and you can't nail/screw anything to it or get
underneath it. I like wooden floors.
JGH
chris
> Hello,
>
> We are having an extension built and I have some concerns over how the
> joiner is constructing the suspended floor.
>
> The house is constructed with a vented void where the dpc is about
> three/four couses above ground level, then above the dpc are air
> bricks. The extension has been constructed the same way with the
> airbricks and dpc at the same levels as the house.
>
> The joiner to make the suspended floor has bolted timbers to each side
> of the extension, these timbers start below the dpc and finish above
> the dpc, also the timbers cover the airbricks. He has however drilled
> lots of holes where the airbricks are behind the timbers. Attached to
> these timbers are joist hangers. This gives the same floor level as
> the main house.
>
> My concern is that the timbers bridge the dpc, surely this can't be
> right?
>
> Any thoughts?
>
> Thanks,
>
> Graham
Graham
I concur with the majority here that this is a builder who most
certainly has not a clue about new build or even how to repair old.
He could have
a) put the joists in joist hangers or even BAT Joist angles (Jangles)
if he could find any
b) put a vertical DPC against the wall before installing the so-called
wall plate
What he should have done and what I would now absolutely insist on is
1) 4" concrete on the oversite ( a building reg or used to be )
2) brick or concrete block piers or honeycombed sleeper wall inside
the line of the room at the perimeter at about 8 ft intervals
intermediately (depending on size of joist)
3) the wall plate laid flat on a polymeric or LL dpc
the airbricks are in exactly the right place - under no circumstances
move them but do put in a telescopic connection to under the
insulation (to be)
What really concerns me most is the apparent lack of use of tanalised
timber . Is it even VAC VAC treated? which is not so good as
tanalised due to the absence of combination of the preservative with
the hydroxyl groups on the timber
My advise is to swallow hard and
a) get rid of the timber floor with all the complications of having
air and insulation under and underneath put in 4" or bigger if you can
ducts to the outside vents from the existing vents to provide through
flow of air
b) If there IS concrete laid and it is rough determine if it is ok for
structural purposes either on its own or by adding to it - incorporate
ducts below such as to allow sufficient mass above
or
put in a reinforced 4" concrete floor with vent ducts below
c) put in as much insulation as possible not less than 4" preferably
more up to 12" max
d) a 3" screed with UFH
Chris
chris
> Hello,
>
> We are having an extension built and I have some concerns over how the
> joiner is constructing the suspended floor.
>
> The house is constructed with a vented void where the dpc is about
> three/four couses above ground level, then above the dpc are air
> bricks. The extension has been constructed the same way with the
> airbricks and dpc at the same levels as the house.
>
> The joiner to make the suspended floor has bolted timbers to each side
> of the extension, these timbers start below the dpc and finish above
> the dpc, also the timbers cover the airbricks. He has however drilled
> lots of holes where the airbricks are behind the timbers. Attached to
> these timbers are joist hangers. This gives the same floor level as
> the main house.
>
> My concern is that the timbers bridge the dpc, surely this can't be
> right?
>
> Any thoughts?
>
> Thanks,
>
> Graham
test
harry
What problem is there in screwing stuff to it?
Why would you want to get under it?
Andy Champ
>
> What problem is there in screwing stuff to it?
It's harder than wood.
> Why would you want to get under it?
All my central heating pipes are buried in the solid floor. One day
they'll need replacing, and the floor will have to come up.
Andy
Graham Jones
Hello Chris,
I think the problem is that there is no requirement for the builder to
do these things. For example are tanalised joists a requirement? The
BCO has seen timber used for the joists and didn't question it. "the
wall plate laid flat on a polymeric or LL dpc" again is this a
requirement? Why would any builder spend extra time and money on
things that are not required by the regs?
Graham
Hugo Nebula
>I think the problem is that there is no requirement for the builder to
>do these things. For example are tanalised joists a requirement? The
>BCO has seen timber used for the joists and didn't question it. "the
>wall plate laid flat on a polymeric or LL dpc" again is this a
>requirement? Why would any builder spend extra time and money on
>things that are not required by the regs?
The Building Regulations are only about health, safety and welfare.
They are not about property maintenance or longevity of materials, and
are certainly not about the quality of materials or workmanship,
except so far as is needed to ensure continued compliance with the
requirements.
Its not the builder's time and money being spent on these things, it's
yours. You've either contracted for a reasonable quality of work or a
legally minimal job. Either way, you should get what you've paid for.
Graham Jones
> [Default] On Fri, 19 Aug 2011 14:49:51 -0700 (PDT), a certain
>
> keyboard and wrote:
> >I think the problem is that there is no requirement for the builder to
> >do these things. For example are tanalised joists a requirement? The
> >BCO has seen timber used for the joists and didn't question it. "the
> >requirement? Why would any builder spend extra time and money on
> >things that are not required by the regs?
>
> The Building Regulations are only about health, safety and welfare.
> They are not about property maintenance or longevity of materials, and
> are certainly not about the quality of materials or workmanship,
> except so far as is needed to ensure continued compliance with the
> requirements.
>
> Its not the builder's time and money being spent on these things, it's
> yours. You've either contracted for a reasonable quality of work or a
> legally minimal job. Either way, you should get what you've paid for.
> --
> Hugo Nebula
> "If no-one on the internet wants a piece of this,
> just how far from the pack have I strayed"?
Thanks Hugo, I understand. Can you tell me in your experience the
percentage of jobs you have seen that use treated timber (joists/roof)
as opposed to untreated.
Thanks,
Graham
Hugo Nebula
chimpanzee, Graham Jones <grahamj...@gmail.com>, randomly hit the
keyboard and wrote:
>Can you tell me in your experience the
>percentage of jobs you have seen that use treated timber (joists/roof)
>as opposed to untreated.
Don't know, 'cos it's not something I check for. I would imagine it's
approaching 0%, which is more to do with the quality of the work I
have to deal with. A properly constructed floor or roof shouldn't need
treated timber; it shouldn't be getting damp enough, or be ventilated
enough to get rid of it.
As we always have to tell people; we're not Clerks of Works. we only
control enough to ensure the health & safety of the finished work.
chris
Answers
There is a general requirement that the product be fit for purpose.
Tanalith treatment is not a requirement but would be considered normal
good practice. It would depend on what was the essence of the contract
as to whether or not this could be enforced in court - unlikely in the
extreme but just possible if the contract was, say, "please build me
a high quality extension in accordance with the best practice" . If,
however, it was "Please build me an extension as cheaply as you can
that will not fall down but be ok" then there would be no obligation
to use tanalised. As a matter of simple competence, given the nominal
price difference and the huge increase in quality, any builder that
did not automatically use tanlasied is demonstrating his lack of
competence.
BCOs are generally almost as ignorant in matters of preservation as
builders and should not be relied on. When they got rid of the proper
old DSs in the mid 90s they put in young lads who were clueless and
paid them peanuts.
Wall plate on a dpc has been in building regs since about 1886!!!
Answer to your last question >Why would any builder spend extra time
and money on
> things that are not required by the regs?
a good builder would do so as a matter of competence and protection of
his reputation
a bad one will do a cheapskate job
I refuse to work for clients that want a botch job done
I can afford to do so because clients appreciate it done right and
luckily I have plenty of them
chris
chris
> [Default] On Sat, 20 Aug 2011 01:23:21 -0700 (PDT), a certain
>
> keyboard and wrote:
> >Can you tell me in your experience the
> >percentage of jobs you have seen that use treated timber (joists/roof)
> >as opposed to untreated.
>
> Don't know, 'cos it's not something I check for. I would imagine it's
> approaching 0%, which is more to do with the quality of the work I
> have to deal with. A properly constructed floor or roof shouldn't need
> treated timber; it shouldn't be getting damp enough, or be ventilated
> enough to get rid of it.
>
> As we always have to tell people; we're not Clerks of Works. we only
> control enough to ensure the health & safety of the finished work.
> --
> Hugo Nebula
> "If no-one on the internet wants a piece of this,
> just how far from the pack have I strayed"?
You obviously don't work in the Camberley area where it is a
requirement to have all house timbers treated and has been since just
after the last war
or
on properties where the client specifies treatment
Where I work which is mainly the SE and home counties, I guess that
over half the properties are with treated timber but my clients tend
to be rich
chris
All properly constructed floors should be pre- treated for insect
attack as this can affect any well constructed site