Workshop Foundations

[Mikes]

In the big scheme of things I'm looking to build a new workshop to replace two old ones. The logistics of this gives me nightmares as both are full and I really can't face the idea of decanting everything to another site. The existing buildings are single story and the new replacement will also be but slightly taller.
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. Spanning roof trusses would then be installed between sides 1 and 3 and a metal roof fixed. This would at least allow the area to remain nearly water tight. Then the existing roof would be removed together with the old wall along side 3. A new strip foundation would then be dug along side 3 in between the stanchion pads. The scheme is further complicated as there is about 300 mm difference in the floor levels of the two workshops so this would also need addressing in stages. The un-numbered side will be mainly doors (access and pedestrian).
My questions to any of the members who do this sort of work are:
1. Does this sound a feasible way of working?
2. Are there any downfalls to doing the foundations in sections providing I allow suitable reinforcement starter bars between each?

Any genuine observations and comments welcome.

 

[8ob]

I think you will save a lot of time ,money and get a better end result if you bite the bullet decant/demolish what you have.

Bob

 

[bricol]

What he said -

I bought 10X8 shed, filled it, stacked benches and heavy stuff up, covered in polyethene sheets and tarps.
Demolished existing, ripped up the disintegrating base, had new base done, erected new, bigger garage, took advantage of snow to use some snowboards to very easily skid heavy stuff into new building.

Less hassle overall than trying to work around, and got one, level floor.

 

[Agrismith]

It will cost a lot more to do it like that
You could dig the pads for the steel frame to be erected on
Build the steel frame and roof over including sides
Demolish the current workshop
Then everything would only have to be removed for a few days to cast the floor and moved back in.

I think trying to do it your way would make it very difficult to not only get everything level, matching and joined up neatly but also getting damp proof course to do its job.

 

[mtt.tr]

I think the time lost to working around stuff plus the awkwardness and additional dangers added would mean decanting is the best option.

 

[Onoff]

You could dig the pads for the steel frame to be erected on

How would you incorporate the 300mm of EPS under the UFH heated slab (that every garage deserves) and avoid cold bridging through the columns?

 

[Mikes]

How would you incorporate the 300mm of EPS under the UFH heated slab (that every garage deserves) and avoid cold bridging through the columns?

There's no way that I would have UFH in a workshop as by the time you've left areas under machines etc clear then the remainder gives very little output. My heating will be electric radiant.

 

[Mikes]

I think the time lost to working around stuff plus the awkwardness and additional dangers added would mean decanting is the best option.

Trouble is I would need two 20' containers to be able to put everything in and continue to use it . A very difficult decision but I'm considering building the whole lot in a totally different position. I'd already planned a separate sheet metal workshop as this is something that can be readily hived off.

 

[Agrismith]

How would you incorporate the 300mm of EPS under the UFH heated slab (that every garage deserves) and avoid cold bridging through the columns?

Tbh I deal with agricultural buildings so rarely even put polystyrene down.
I doubt the cold bridging through the stations would actually account for very much but if you wanted you could put 150mm of kingspan round the columns at slab height before you poor.
Then clad the steel work completely insulating the columns from the work space.
But doing so would require bigger pads for the columns to sit on as they wouldn't be incorporated into the pad.
If you want well insulated I don't think steel frame is really the best option.

 

[James1979]

Another vote for decant I’m afraid.

It also gives You the chance to have a good clear out and set everything back in how you want it in the new place. You can also paint the floor and things.

 

[mtt.tr]

Another vote for decant I’m afraid.

It also gives You the chance to have a good clear out and set everything back in how you want it in the new place. You can also paint the floor and things.

And put some bits up for sale that we can all fight over.

 

[Onoff]

Be careful about knocking down an existing building as you can fall foul of an ar5ey council.

Once it's down you've not necessarily the right to rebuild and may need to apply for planning permission especially if it's outside the size for permitted development. Gets even worse in an ANOB...ask me how I know!

Could be worse and I could live in a national park or area of special scientific interest!

 

[Brad93]

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

 

[Agrismith]

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

You can on an engineer designed slab
Which would use the building columns as support and possibly a thickened centre beam pus a well reinforced slab
Insulating a slab is possible if you have the budget.

 

[Mikes]

Be careful about knocking down an existing building as you can fall foul of an ar5ey council.

Once it's down you've not necessarily the right to rebuild and may need to apply for planning permission especially if it's outside the size for permitted development. Gets even worse in an ANOB...ask me how I know!

Could be worse and I could live in a national park or area of special scientific interest!

Yes, one of the many reasons for putting the new building in place of the old. Can be done without planning as far as I can see from the Council's on-line guidance.

 

[Onoff]

You can on an engineer designed slab
Which would use the building columns as support and possibly a thickened centre beam pus a well reinforced slab
Insulating a slab is possible if you have the budget.

UFH is well worth considering, laying some pipe in the slab "now" is cheap as chips even if you never connect it up. 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!

Handy too if ever SWMBO kicks you out and you have to move into the garage with your beloved (machinery).

 

[Agrismith]

UFH is well worth considering, laying some pipe in the slab "now" is cheap as chips even if you never connect it up. 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!

Handy too if ever SWMBO kicks you out and you have to move into the garage with your beloved (machinery).

I have underfloor heating overlaid at home with no insulation underneath the slab as far as I'm aware and I don't think it's expensive to run infact I think our house is quite cheap to heat

 

[brightspark]

I have underfloor heating overlaid at home with no insulation underneath the slab as far as I'm aware and I don't think it's expensive to run infact I think our house is quite cheap to heat

may not be expensive but a big heat loss underneath. all floors apart from one in our house isnt insulated . the one that is is warmer even the dog can tell

 

[Onoff]

I have underfloor heating overlaid at home with no insulation underneath the slab as far as I'm aware and I don't think it's expensive to run infact I think our house is quite cheap to heat

Have you got radiators as well as UFH?

 

[Agrismith]

Have you got radiators as well as UFH?

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.