Wall/whole house construction

[djh]

Your building inspector and /or warranty inspector is probably the best place to start as they will know how the local sub soils behave.

Very illuminating post Noel, thanks. And the advice above is probably the most important!

If the clay is unstable for considerable depth then piles or a raft have to be considered but these options are very expensive.

I'm curious about this bit. I've read that piles are expensive but I've also read that rafts are cheap. I just googled to confirm my memory and this was the first page that came up http://building4today.googlepages.com/13

I believe rafts are also easier to integrate with the type of wall beelbeebub is planning, as far as airtightness and continuity of insulation is concerned.

But a structural expert with detailed local knowledge sounds like a very good idea.

A friend of mine lives on a clay hill and some houses were just built next to him. They built brick garden walls around the houses and the first time it rained, the gardens turned into muddy moats! 

[noelsquibb]

Are rafts economical ?
Hmm you've put me on the spot as I do not have costings.

My wild and fanciful claim is based on 30 years of doing foundations large and small, including 2 years involvement with piling contractor Roger Bullivant.

Less than 1 in 100  founds are rafts and they are always a pain in the rse to do. Here's why -

You've got to achieve a downstand around the edge so the finishes are visible below the floor level and above the ground. This means accurate shuttering and steelfixing with an accurately located hanging shutter to form the step. You've got to create thickenings in the slab under any load bearing walls. So lots of expensive cut and bent reinforcement, fancy 'chairs' to keep the steel in the right location whilst trying not to damage the DPM they are sitting on. Every pipe and service duct needing precision locating before any walls go up with no second chance. Blinding concrete under the whole lot with sand over to protect the DPM from the concrete underneath. This is needed to ensure the steel reinforcing supports dint sink  or fall over whilst lard ar$ed groundworkers fight with a concrete pump hose... did I mention the structural engineers costs for calcs ?  hopefully you get the idea.

Whoever wrote that stuff on the building4today site has probably never shoveled concrete.

Piling by comparison is a piece of cake. A rough pile mat strong enough to allow a tracked rig and a fork lift to travel.

Set out the positions accurately. Displacement piles ( usually precast concrete) bashed into the ground until a 'set' is achieved so we can demonstrate that the carrying capacity of each pile meets the design load. Cut em down to required level, join em up with precast beams, park house on top.
Works brilliantly on reclaimed land, contaminated land, high ground water levels, through tree roots, possible ancient relics  and of course shrinkage soils. Doesn't seem to matter how far down the good ground is you just keep bashing em down till they reach hard or resist drive enough.

I guess all that sounds a bit biased. It is 

Trenchfill will always be my first choice if ground conditions permit though.

Noel

[djh]

Less than 1 in 100  founds are rafts and they are always a pain in the rse to do. Here's why -

You've got to achieve a downstand around the edge

The newly published Carbonlite vol 5 discusses these 'traditional' rafts versus thicker but simpler rafts that don't need reinforcement at the edges or under internal walls and that have the insulation under the raft. I know nowt but it might be worth a look.

[noelsquibb]

The newly published Carbonlite vol 5 discusses these 'traditional' rafts versus thicker but simpler rafts that don't need reinforcement at the edges or under internal walls and that have the insulation under the raft. I know nowt but it might be worth a look.

Yes. I always thought we did rafts the hard way but I could never get anyone interested in lowering the whole thing by 150mm.
Probably too simple and obvious with far less design fees attached.

One continuous slab with two layers of HD mesh. Top of slab to finish 150mm below the finished floor level.
Build up the walls two bricks deep around the outside and tank the 'well' as its all at ground level.
Now put in 130mm of insulation / UFH and cover with 20mm thick flooring of choice. Or 100 insulation and 50 screed.

Easier than piling and a whole lot cheaper.

Builders are generally traditional in their ways and do not like new ways of doing things.
Architects and Structural Engineers tend to encourage and support this approach.

When you go outside the 'normal' way of building, you find yourself in a very lonely place.
Now you've got to convince your builders and the building inspector that your untried ideas are going to work.

They will be openminded at best and looking much harder than they normally would and will delight in any small snag or setback.

Ive done plenty of 'outside the box' building and groundworks but I tend to revert to 'normal' when Ive got to get the boxes ticked by the experts.

So best of luck beelbeebub. You have my full support.

BTW - that drain discharging to the road at the front of the house is usually a big no no.
Private water must not discharge onto public land and vice versa. Sure there are plenty of examples of non compliance but as its a new build, it must comply.

Either you have to get discharge consent to send it into a controlled watercourse ( that includes a roadside ditch that eventually dumps into a recognisable stream ) or you soak it into the ground you own or have legal rights to soak into

The magic solution for discharges are the words INTO EXISTING OUTFALL DRAIN or INTO EXISTING SOAKAWAY.
Ive put 'existing' discharges / soakaways onto the drawings where none previously existed.
Obviously this approach works better on a redevelopment / brownfield site.
They all sit in offices and do desk studies and no one, apart from the building inspector,would feel the need to check.
Legal discharges are vital for completion certificates and conveyancing.

So that existing old pipe into the road ditch that was put there before the '68 COPA2 act,  is 'replaced' and everyone is happy. Got to be discreet though.

Noel

[Amy]

I was watching a piling crew working on sand, building footings for a 20 story condo in Jontiem, Thailand.

They had 12" square concrete pilings sharpened at one end but i couldnt see how they got them all the same level

[beelbeebub]

@noel:

There actually is an existing soakaway taking the runoff from the spring above and soaking it away on our side of the boundary. The water then soaks onto/under the road below (it's not a public highway, it's a private track).

As we won't actually be increasing the amount of water reaching the soakaway I doubt there'll be a problem.

It looks like the planner will allow us a modest hight increase, which will allow the floor to be higher and make our drainage issue much easier.  We still have to contend with the clay movement tho!

[noelsquibb]

beelbeebub,

Surface water run off into existing soakaway. That's all I wanted to hear.
Suspect you might increase the discharge if you are thinking of putting the roof water down that drain.

What about the dirty water ?

When do you actually start ? Its good to have a roof on by October.


Amy

They had 12" square concrete pilings sharpened at one end but i couldn't see how they got them all the same level

probably better that they were blunt one end 

They don't have to get to the same level. All they have to do is to resist the driving force enough to demonstrate that they can support a certain load. This might mean they drive through the soft soils and stop on an uneven layer of hard material or they become long enough to support the load using only skin friction.

The tops are then cut down to the required level using a hydraulic 'muncher'


Noel

[beelbeebub]

Foul water will run to the public sewer running along the road below (if we can ever find the bl00dy manhole).  The current building uses the same sewer, but due to a quirk attaches much further "upstream" so the fall is less and is actually too shallow causing problems so we'll be attaching much closer to get a better fall.

Rain water runs into the soak away, the total amount reaching the soak away will be about the same, though the peak flow will be higher with roof run off hitting it with no delay.  To counter this we may well enlarge the soak away.

We'll get the roof on by October, just not this October!

We're putting in the planning app this week so fingers crossed get planning approval by end of august (after the usual wrangling etc)

Then demolition of existing structure, site clearance material reclamation etc. though sept.

If things going well and weather is good, foundations and services in by end of oct and poss floor slab laid.

Then shut up shop for November and December (rubbish weather) and do project planning

Away jan & feb

March return and continue project planning and weather depending start on walls late march.

Roof on and weather tight sometime August, move on to fitting inside.

Move in for Christmas 2010.....

Best laid plans and all that!   

[noelsquibb]

Foul water will run to the public sewer running along the road below (if we can ever find the bl00dy manhole).  The current building uses the same sewer, but due to a quirk attaches much further "upstream" so the fall is less and is actually too shallow causing problems so we'll be attaching much closer to get a better fall.

Rain water runs into the soak away, the total amount reaching the soak away will be about the same, though the peak flow will be higher with roof run off hitting it with no delay.  To counter this we may well enlarge the soak away.

To track the foul drain you can hire a 'cat & genny' or 'cat & mouse' and follow it down from the manhole that you do have access to.
The 'genny' is a signal generator and I just used this system to successfully track some lost drains.

I taped some old leccy wire to a length of blue water pipe, stuffed it down the drain at the one manhole I had found.
Connected up the signal generator to the wire then tracked the signal above ground with the 'cat'  ( cable avoidance tool )
If you are lucky, the blue pipe will 'jam up' at the next manhole so you can get an idea where it is . Then use the metal detector option to sweep the ground and with luck you will find the hidden drain cover.

The 'mouse' is a transmitter that can be attached to drain rods and works on a similar basis but you've got to keep on top of it with the cat as it moves through the pipe. The other disadvantage is getting it stuck and pulling an end off the drain rods , leaving some of the rods and a very expensive transmitter in the sewer. 

Or you might know an old boy who is handy with the bent copper rods. No science of course but divining for pipes and wires before digging used to be a regular and very reliable occurrence.

If the sewer is in the private road below the site, you will probably be better off digging down onto the pipe and installing a new manhole. Hopefully tracking the line, as above, will get you digging in the right location.
You could let a manhole onto the pipe pretty quickly if its not too deep ( you can go up to 1.5m deep with a 450 dia plastic manhole ) then pull a connection from it on another occasion, if your window of opportunity is restricted to 'very early on a Sunday morning'.

For soakaways we often use  plastic void formers. These give you nearly 100% storage volume ( unlike brick rubble )
and surrounded in gravel, seem to do the job.
Best result comes from a discreet connection to a ditch.  ... no mate its that old land drain we found and followed to the ditch. we replaced the bit we followed cos it was pretty silted up.... seems to be running ok now .

Giving yourself plenty of time should help to reduce the stress of being in charge.
I rather like using the 12 weeks standard/ minium hire for the scaffolding though, cos its a way of pushing all the external trades for a quick waterproof outer skin. When the scaffold comes down it feels great, even though you are still only half way built.

Noel   ( dreaming about getting another site )

[beelbeebub]

We actually know the path of the sewer very accurately, unfortunately the man hole cover that is indicated on the plans and that was definitely there (I remember a metal cover being there from walking along the road as a kid).

However the road was resurfaced a few years ago and raised up about a foot in level, covering the manhole cover!

We're going to to get hold of a metal detector and to try and find the cover.  If we can find the cover it will be easier than having to connect to the sewer main.

Do you have a name for the void formers?  It sounds like an alternative to washed rubble, that being said we will have a fair bit of rubble left over from the demolition.

The idea is to make the time-scales fairly long to reduce the stress and number of rushed decisions.  That should result in a better end product, and a less stressed me 

 

[noelsquibb]

Do you have a name for the void formers?  It sounds like an alternative to washed rubble, that being said we will have a fair bit of rubble left over from the demolition

Not really able to give you product names. I usually only have to ensure the hole is in the right location and at the right depth. Then a few numptys turn up and fill the hole with large empty beer crates, leave a mess and disappear.
Specialist subcontractors apparently.

Here's link to a few ways of water retention and outflow control -


http://www.y-ess.com/brochures/product/1238000598_Versavoid%20Brochure.pdf

Noel