Workshop Foundations

[gaz1]

In the big scheme of things I'm looking to build a new workshop to replace two old ones.
My cunning plan is to try and partially build the new workshop around and over the existing prior to removing them. My thoughts are to dig new foundations along sides 1 and 2 on the attached sketch and then build walls on both. These would include steel frame stanchions. Unfortunately side 3 is against a boundary so here I was proposing to carefully break-out areas of the slab and cast local pads to suit steel stanchions. The roof would then be locally removed to allow the install of these.

you state side 3 is against a boundary

a boundary to what ?

 

[Onoff]

No there is nowhere to fit radiators hence installing underfloor heating.
I know insulation would be better but from first hand experience it is nowhere near as bad as some people suggest.
Although I'm not sure if it's because it's overlay so therefore hasn't got the thermal mass therefore the heat pattern is like radiators rather than what you would expect from heating fitted in a screed.

My mate heats his whole house for less that 1.5kW a day. Obviously DHW on top.

Timber frame with 16" thick, Icynene filled walls.

No UFH.

 

[Mikes]

you state side 3 is against a boundary

a boundary to what ?

Another building not owned by me.

 

[Agrismith]

My mate heats his whole house for less that 1.5kW a day. Obviously DHW on top.

Timber frame with 16" thick, Icynene filled walls.

No UFH.

It's a 1970's council house so never going to get that efficient but it could definitely be alot worse

 

[LiftedDisco]

Another building not owned by me.

I’m afraid I’m also in the ‘demolish and rebuild’ camp with the potential requirement of going through the planning process.

The boundary wall consideration needs to allow for potential boundary wall fire condition, thinking about both break out of fire into the neighbouring property but also thinking about the potential over-turning moments and risk of collapse.

I would expect your boundary bases and h/d bolt arrangements to be a fully engineered solution and this will be easier to achieve with a full-on new build scenario.

 

[Onoff]

fully engineered

Or as I do it:

 

[willie.macleod]

Worthless unless you have adequate insulation under the slab or can afford to burn money. Even in a passive esque build with 300mm of EPS someone calc'd you lose some 8% of your heat through the slab!

You need to know the perimeter/area of the slab to begin to calculate losses as in general the larger the slab area the less you are dependent on the the thickness of insulation sitting under it to achieve a decent performance. A small house slab is likely to need a decent thickness of insulation in order to achieve building regs compliance, a large slab inside a hall may only need perimeter insulation.

In the case of trying to use a slab to raise workshop temperature to a relatively low temperature I would certainly use some insulation underneath but I would focus on insulating the perimeter of the slab well, something that is rarely done properly but the insulation there is likely to give the best return on investment. If heavy machinery is expected to be installed then using extruded polystyrene would be my choice of insulation board as it has excellent compressive strength.

 

[gaz1]

Another building not owned by me.

have you asked if you can overlap your roof onto theres

or is yours going to be higher?

if youre going right up to the boundary wall have you still got your boundary wall up at the moment ?

if you have then you can join onto there roof to create a good seal between propertys as your boundary wall will give you both a good seal between the propertys

yet still fitting a steel frame with box profile roofing sheets for the side panels fasten to your uprights

 

[Mikes]

have you asked if you can overlap your roof onto theres

or is yours going to be higher?

if youre going right up to the boundary wall have you still got your boundary wall up at the moment ?

if you have then you can join onto there roof to create a good seal between propertys as your boundary wall will give you both a good seal between the propertys

yet still fitting a steel frame with box profile roofing sheets for the side panels fasten to your uprights

The roof will be slightly higher than the adjacent such that it can slope to a gutter along wall 1. The existing roof sloped the opposite way and the apex of it was much higher than the adjacent so I'm actually lowering the roof line so don't think there will be a problem.
There will be a gap between the adjacent building and the new workshop. Don't want any party wall issues especially as it's a workshop.
If I don't have a steel frame then I will have to incorporate some secondary steelwork as I'm looking to install a couple of chain hoist runners.

 

[Onoff]

Is that 36kWh or 1.5kWh? No such thing of power/day.

Dunno. He heats his house for a day for less than it takes to boil a kettle. Losses are that low. Saying that he hasn't got a kettle just one of those posh hot water taps!

 

[gaz1]

The roof will be slightly higher than the adjacent such that it can slope to a gutter along wall 1. The existing roof sloped the opposite way and the apex of it was much higher than the adjacent so I'm actually lowering the roof line so don't think there will be a problem.
There will be a gap between the adjacent building and the new workshop. Don't want any party wall issues especially as it's a workshop.
If I don't have a steel frame then I will have to incorporate some secondary steelwork as I'm looking to install a couple of chain hoist runners.

as a prewarning dont have a gap inbetween if you are then you will need to be 1m for access scaffolding for maintenence of it

if you had your own party wall you can create a seal for better as you make your party wall being the the wall valley

dont do it like this




this is the valley between both propertys

the valley is l shaped piece goes up your side and has a lip under those slates to create a valley





its a better seal between the propertys

the steel frame can still be built internally

your upright post + your angle iron or z purlin the box section is external to that

so lets say your z purlin is 150mm so you need that space away from the wall and then your warehouse frame

you should be able to make a concrete post pad with bolts

then you get to insulate between the party wall by using 6" insulation

 

[Mikes]

The adjacent building is only a couple of years old and I watched it being built (badly) and sits about 50 mm back from the boundary line so party walls etc are out of the question. That's also why I've opted to have that as the high side of the roof as it means the gutter will be easily accessible without going anywhere near the other building.
The wall will be either facing brick or cladding so will not need maintenance. The neighboring building was built close to the boundary by choice so I'm doing likewise. Maximum height of the new workshop will only be 3 m above ground level.

 

[Onoff]

We have two kettles. One draws 1kW and the other 2.4kW. If I used 1kW to heat my house it could use ad much ad 24kWh. If I used the larger wattage kettle value, it could be as much as 55kWh.

The small kettle will boil a mug of water in less than two minutes, costing less than one new penny.

You can understand, maybe, the subjectivity of his claim - without the full information being provided and using a ‘bogus’ measure of energy that does not exist!

Basically he uses less energy to heat his house in a 24 hour period than it takes to heat 1 kettle full of water.

 

[Onoff]

OK.

My larger kettle holds 1.5 litres of water.

One kettle-full will require approx 550kJ of energy to raise that water to 100 Celsius (assuming cold water at 15 Celsius - but it may only be 10 Celsius).

With losses,etc, lets say 600kJ. One kilowatt, for one hour (one unit of electricity) is 3.6MJ. That means that kettle of water, at boiling point, requires about 1/5 of a unit of electricity - costing around 5p or less (if boiled on current standard day-time rates)

As the standing charge is the best part of 25p/day, I would suggest your friend likely doesn’t know precisely how much heat he uses, or lives in a PassivHaus - or is using an alternative form of energy.

Of course, I am thinking, here, of any one single day - not the average for the whole year (when summer heating costs are zero - or even considered negative, if it is air-conditioned).

There are houses that use very little heating energy, but sadly not enough of them.

Oh, where does he live? How big is his house? Does he run several servers, by any chance? Does he have a heat recovery system for ventilation air? How many occupants (we are all 100W ,or more, even at resr?)?

I really questioned your facts because “1.5kW per day” is not a sensible unit of anything. I could easily boil 6 kettle-fulls of water with 1.5kWh. Now I am wondering which is - 6 times more or only 1/6th…

His house, well actually he's just sold it. Down near Canterbury. His old house on the left:

"We have 300mm insulation under the concrete slab and warm air heating which keeps the house at 23C. The slab is always going to be very close to 23C unless of course the sun is shining on it when it can be warmer. With bare feet it will feel cooler because we have porcelain tiles all over the ground floor but if you had for instance cork tiles it would feel warm".

&

"I have 350mm I-beams as my main frame filled with Icynene and OSB3 racking on the outside. I then have the membrane and 50mm RW6 Rockwool batts followed by a 50mm cavity and cedar cladding as the rainscreen".

&

"a Genvex Combi 185L which is a ventilation system with a built in EASHP which heats my DHW and provides warm air which supplements the normal heating provided by electric towel rails in the bathrooms. The towel rails keep the bathrooms at around 24C and the ventilation system transfers the heat around the house. This type of system only works for space heating because the house is very highly insulated and airtight".

 

[willie.macleod]

Basically he uses less energy to heat his house in a 24 hour period than it takes to heat 1 kettle full of water.

What he'll have neglected to inform you is that he forgot to include the energy cost of running the MVHR system (pushing all that air around takes significant amounts of energy) and although heating may not cost much getting rid of excess heat is the next issue and that can be harder. No point in building a house that you overheat in every time the tumble drier goes on or someone cooks a meal both of which pump a lot more heat out than a kettle full!

 

[Onoff]

What he'll have neglected to inform you is that he forgot to include the energy cost of running the MVHR system (pushing all that air around takes significant amounts of energy) and although heating may not cost much getting rid of excess heat is the next issue and that can be harder. No point in building a house that you overheat in every time the tumble drier goes on or someone cooks a meal both of which pump a lot more heat out than a kettle full!

When an MVHR can be around 90% efficient it's FA.

 

[willie.macleod]

When an MVHR can be around 90% efficient it's FA.

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.

 

[Pete.]

You can't put polystyrene under a floor you're going to put a few tonne of machine tools on

There's no question that it'll support the weight we have used it a few times in our work but the slab will probably bend a bit if you move plant around.

 

[brightspark]

thats what reinforcement mesh is for

 

[gaz1]

The adjacent building is only a couple of years old and I watched it being built (badly) and sits about 50 mm back from the boundary line so party walls etc are out of the question. That's also why I've opted to have that as the high side of the roof as it means the gutter will be easily accessible without going anywhere near the other building.
The wall will be either facing brick or cladding so will not need maintenance. The neighboring building was built close to the boundary by choice so I'm doing likewise. Maximum height of the new workshop will only be 3 m above ground level.

brick or cladding will need maintenance as its higher and can take the brunt of bad weather rather well

even if you built it 2 walls with a gap between them the outside can leak through but drops down between the gap

becareful i suspect because your building a new structure they may want good insulation for that building your building as there is a real big push to being energy efficent