Workshop Foundations

[Onoff]

But it isn't. What you might be quoting is a figure for a very efficient heat exchanger tested in ideal conditions with no accounting for the energy used pushing the air through the filters/exchanger/ducting. I am big fan of MVHR systems, I fitted one in my own self build but I am also realistic about them unlike some other self builders who having spent untold thousands paying others to install them tend to gloss over the true efficiencies/costs, especially in the real world where filters are left untouched for years, ducting clogs up with dust/fluff and efficiencies drop.

Have you built to or exceeded passive specs with your build? Are you airtight to well in excess of building regs? The people I know tend to install them themselves and are anal to the nth degree and well aware of filter issues.

 

[Screwdriver]

My cunning plan is to try and partially build the new workshop around and over the existing prior to removing them.

Sounds like a nightmare. It might be possible to "join" two slabs but there's no way of establishing how they might subside over the long term. One is bound to be stronger than the other and getting the new strip foundation to match is also a guessing game. The new slab will almost certainly crack exactly around the new area(s) and you'll never know how far they might go. Obviously the effect will be magnified by the time any settlement reaches the roof.

Best bet is to break it up in situ and use the rubble as a subfloor. Might be an idea to dig out the strips beforehand so you can fill them to the same depth as the deeper of the two existing slabs. If you have the room, even a large tent is cheap as chips, no planning required etc and you can weatherproof your goodies as they get stowed away. Some freestanding racking would also be a wise investment or bandstands with scaff boards.

 

[Agrismith]

Sounds like a nightmare. It might be possible to "join" two slabs but there's no way of establishing how they might subside over the long term. One is bound to be stronger than the other and getting the new strip foundation to match is also a guessing game. The new slab will almost certainly crack exactly around the new area(s) and you'll never know how far they might go. Obviously the effect will be magnified by the time any settlement reaches the roof.

Best bet is to break it up in situ and use the rubble as a subfloor. Might be an idea to dig out the strips beforehand so you can fill them to the same depth as the deeper of the two existing slabs. If you have the room, even a large tent is cheap as chips, no planning required etc and you can weatherproof your goodies as they get stowed away. Some freestanding racking would also be a wise investment or bandstands with scaff boards.

There is no reason that they should have different settlement rates if foundations are suitable.
Also using demo rubble as an infill Is highly inefficient. A concrete crusher is far more expensive to hire than a grab lorry of which you only pay haulage on clean concrete.
Breaking it up by hand or breaker is time consuming and produces poor quality material in comparison to correctly graded crush. Which is also harder to compact if any large lumps are left which will cause settlement issues. As opposed to type one blinder which is easy to gain a consistent compaction

 

[Onoff]

@willie.macleod hopefully this'll mean more to you than it does me! He just wrote me this:

"I removed both copies of the blog when I sold the house. The 13kWh/m2a was for space heating only but I can't remember for sure whether the energy for running the Genvex was included in that. I would have thought the PHPP would have included the Genvex energy used and the heat recovery though because I bought a version upgrade for PHPP from 2007 to 2010 that included built in compact unit data which included the Genvex Combi".

 

[willie.macleod]

Have you built to or exceeded passive specs with your build? Are you airtight to well in excess of building regs? The people I know tend to install them themselves and are anal to the nth degree and well aware of filter issues.

Yes, it's an ICF build so it's pretty airtight and likely to stay that way, did well during testing. PH levels of mostly secondhand insulation used for underfloor/over rafter and good windows/doors but nothing PH certified. The cost of some of the MVHR filters are significant, more than the cost of electricity used each year in most cases but the improvement in interior air quality is significant even in a rural setting. Building regs are a bit stricter here in Scotland so there's a decent amount of setups with homeowners that have little clue as to what the system actually does, so ignore any maintenance requirements.

 

[Screwdriver]

There is no reason that they should have different settlement rates if foundations are suitable.
Also using demo rubble as an infill Is highly inefficient. A concrete crusher is far more expensive to hire than a grab lorry of which you only pay haulage on clean concrete.
Breaking it up by hand or breaker is time consuming and produces poor quality material in comparison to correctly graded crush. Which is also harder to compact if any large lumps are left which will cause settlement issues. As opposed to type one blinder which is easy to gain a consistent compaction

I stand corrected though it does depend somewhat on the precise composition and condition of the existing bases. It was the 300mm level difference that got me and around here, getting rid of construction waste costs an absolute fortune.

 

[Mikes]

Yes, getting rid of the buildings and the 300 mm extra digging to give one new level are going to be a major cost. It's heavy clay as well which doesn't compact well so will probably have to be taken away by a grab lorry. Walls are old crumbly bricks so not much use for rill so will be skipped. Roofing is asbestos sheet so will have to be wrapped and specialist disposal. Base as far as I can see is just a raft so will be broken-up for hardcore.

 

[Screwdriver]

Yes, getting rid of the buildings and the 300 mm extra digging to give one new level are going to be a major cost. It's heavy clay as well which doesn't compact well so will probably have to be taken away by a grab lorry. Walls are old crumbly bricks so not much use for rill so will be skipped. Roofing is asbestos sheet so will have to be wrapped and specialist disposal. Base as far as I can see is just a raft so will be broken-up for hardcore.

Oh err, in that case...

 

[Onoff]

Building regs are a bit stricter here in Scotland

If I rebuilt here in SE England I'd want sarking too!

For Peter's house above, wall and roof U values were 0.095 with airtightness of 0.47ACH.

Tbh I wish I'd never been inside or heard the word "passive". Makes me realise what a draughty, oil burning, plasterboard tent I live in. I'm destined to die in fuel poverty being eaten by rats here! Ignorance WAS bliss.

(I'm not joking).

 

[Agrismith]

I stand corrected though it does depend somewhat on the precise composition and condition of the existing bases. It was the 300mm level difference that got me and around here, getting rid of construction waste costs an absolute fortune.

In general building waste is expensive to remove but clean concrete breakout and rubble is f.o.c to tip so only haulage to pay on it. You can save a fortune by keeping all rubble mud and clay free because as soon as it's contaminated you have to pay to tip.
And 6f5 recycled crush can be as little as 15 quid a tonne, recycled type 1 about the same so far more economical to build levels with than muck around trying to reuse existing materials. Plus technically you need to fill out paperwork for the environment agency before reusing materials on site which can just be another hassle

 

[Screwdriver]

In general building waste is expensive to remove but clean concrete breakout and rubble is f.o.c to tip so only haulage to pay on it. You can save a fortune by keeping all rubble mud and clay free because as soon as it's contaminated you have to pay to tip.
And 6f5 recycled crush can be as little as 15 quid a tonne, recycled type 1 about the same so far more economical to build levels with than muck around trying to reuse existing materials. Plus technically you need to fill out paperwork for the environment agency before reusing materials on site which can just be another hassle

Might be the start of a great business plan right there because here in London, you can multiply those costs by ten. If it looks like "builders waste" here's what they have to say about that:

"Charges for DIY waste for residents
Anyone disposing of mixed loads of construction, demolition or DIY waste will have to enter the site via the weighbridge and will be charged at £23 per 100kg."

From: https://www.ealing.gov.uk/info/2011.../292/re-use_and_recycling_centres_and_sites/3

Yup, £23 per 100kg

You would hope there will be economies of scale but I am assuming those will be applied to commercial entities which already pay an additional set of fees which subsidise the cost per ton. I appreciate this concern may not even be relevant to the OP but it is certainly an aspect to research before assuming the costs for disposal will be negligible.

 

[Agrismith]

Might be the start of a great business plan right there because here in London, you can multiply those costs by ten. If it looks like "builders waste" here's what they have to say about that:

"Charges for DIY waste for residents
Anyone disposing of mixed loads of construction, demolition or DIY waste will have to enter the site via the weighbridge and will be charged at £23 per 100kg."

From: https://www.ealing.gov.uk/info/2011.../292/re-use_and_recycling_centres_and_sites/3

Yup, £23 per 100kg

You would hope there will be economies of scale but I am assuming those will be applied to commercial entities which already pay an additional set of fees which subsidise the cost per ton. I appreciate this concern may not even be relevant to the OP but it is certainly an aspect to research before assuming the costs for disposal will be negligible.

It's the same in London but it has to be clean and it has to be large quantities such as grab lorry loads
Which the op will most likely have if breaking out a pair of concrete bases.

Domestic waste disposal bears no resemblance to commercial in terms of price. Also it depends how mixed up the waste is.
As I said concrete is free. Clay is I think 10-15 a tonne but someone may correct me.
Wood is similar. Mix all three together and it is going to be £150 a tonne and will have to go through a recycling center for processing

 

[Onoff]

Yup, £23 per

That's cheap! It's £6 per rubble bag here. £4 for a bag or sheet of plasterboard.

Charges at HWRCs - Kent County Council

Find out about the HWRC charges on non-household waste items and for non-Kent residents.

www.kent.gov.uk

 

[Screwdriver]

Domestic waste disposal bears no resemblance to commercial in terms of price.

Just out of interest, how much would it cost to be able to use commercial waste disposal centres? I assume a regular Joe can't just turn up and get those prices.

 

[Pete.]

I have got rid of crushable material (concrete, stone, concrete block) for as little as 60 quid a load (8 wheeler) right in central London. That's about 4 quid/tonne.

 

[Screwdriver]

I have got rid of crushable material (concrete, stone, concrete block) for as little as 60 quid a load (8 wheeler) right in central London. That's about 4 quid/tonne.

Is that the same place you found a Bridgeport in a skip?

 

[Agrismith]

Just out of interest, how much would it cost to be able to use commercial waste disposal centres? I assume a regular Joe can't just turn up and get those prices.

They charge by the tonne
I think it's around 125-140 for mixed waste a tonne but not entirely sure now. Anyone can go in you just go over weighbridge empty your vehicle
Back over weighbridge and pay by card.
Clean concrete free tip will be in aggregate yards. its free as it will be crushed to make a saleable product. Although a few more diversified skip places take it foc and have a crusher of there own.
Some also do a cheap rate for clean wood with no roof felt or anything on it as it can be chipped and sold for biomass
Some places round here let anyone in but the bigger places it's 7.5t vehicles and up

 

[Pete.]

Is that the same place you found a Bridgeport in a skip?

That never happened. Must be someone else.

 

[Mikes]

Just as an update, I've decided to move as much as I can into a 20' container and do the job in one go. I've started a cull of the easiest stuff to get rid of. With scrap prices high it's an easy option to quickly clear space so much of the offcuts are going together with a lot of rods, a couple of old welding sets and a load of miscellaneous junk that I thought might be useful one day. Also clearing another shed that was full of electrical crap and will use this for a temporary workshop. Surprising how the weight soon adds-up and the cash raised will buy a few tonnes of concrete. Going to be a long and painful job but much overdue and will be worthwhile in the end.

 

[Screwdriver]

Just as an update, I've decided to move as much as I can into a 20' container and do the job in one go. I've started a cull of the easiest stuff to get rid of. With scrap prices high it's an easy option to quickly clear space so much of the offcuts are going together with a lot of rods, a couple of old welding sets and a load of miscellaneous junk that I thought might be useful one day. Also clearing another shed that was full of electrical crap and will use this for a temporary workshop. Surprising how the weight soon adds-up and the cash raised will buy a few tonnes of concrete. Going to be a long and painful job but much overdue and will be worthwhile in the end.

If you want to knock up a baggie of useful steel offcuts, I'm in! I'll pay more than scrap plus postage of course.

Say 30kg baggies? Ideally 500mm lengths of <whatever> but 150mm for larger diameters/thickness. Any little bits which are square and self similar (like say half a dozen identical offcuts) are ideal for my purposes.

Just a thought...