Concrete Frame Barn Conversion - Kent - Hello!

[TLane]

After spending what seems to be the better part of 2 years searching for an appropriate plot, we're now ready to pull the trigger on what seems to be the ideal one. No better time to introduce myself and say Hi! 

 

In terms of the plot; 

 

- A 200m2 Concrete atcost frame barn, with brickwork to the front, and low-grade asbestos corrugated roofing / cladding. In all the building 'feels good' (I would say that!) and a basic structural report states it's suitable for conversion. It fits the bill in terms of the type of project we want to take on, and has the added benefit;

 

✔ - Couldn't be better situated

✔ - Full Outline Planning secured

✔ - 3 Phase Mains & Water already connected

✔ - Private access from road

✔ - Opp for a PV, ASPH set up - economical / environmental dream barn build

 

Now.. where to start? So far all the architect /  SE / Various ecological reports etc have done the minimum to satisfy the planning department. I'm totally new to all this, and although I've snooped through all your BuildHub posts and blogs over the last year, I'm still fairly confused where to go from. 

 

Forgive my complete ignorance, and for putting things so simply, but my basic outline is below; 

 

1. Employ QS (3 quotes) to outline estimated build costs and outline. If promising, move onto step 2. Currently I'm running some napkin calculations based on £200-£250 p/sq ft. 

2. Finalise plans and schemes to finally satisfy the planning dept's conditions

3. Employ a SE to do a proper assessment, ahead of drawing up more accurate / proper plans to take into the kick off stages. (Can I take the current architect's plans (basic design), and have them 'regurgitated' by an SE that would serve as the master plans that everything's built off?) Do I need to work alongside an architect to bring this to life? Or will a SE and builder be able to manage?

4 . Employ a project manager/ builder to kickstart the build and get to the first fix stage, at which point I can manage the 2nd fix. (Ideally I'd love to take on more of the management side myself, but that seems insane given I have no prior experience, and not much experience other than being handy with most DIY, which doesn't say much.. not to mention a full time job.)

 

I've started a good black book of potential suppliers, advisors etc - any suggestions on where else is good to source (outside deep diving through google). 

 

I'm aware I'm missing another 10,000 steps around that, but I'd love to get your guys' thoughts? I'd massively appreciate any tips, advice, thoughts, suggestions. 

 

In any case nice to post something after so long lurking. 

All the best!

[Tom]

Congrats, sounds exciting!

You say a basic structural report states suitable for conversion - I'm guessing this was as part of the application relating to Part Q PD rights, is that correct? Tread carefully, as such structural surveys can be pretty much useless. You pay the structural surveyor to essentially say what you want them to say for the purpose of getting the Part Q. I would prioritise getting your own full survey done. Some pictures would be great if you could post them!

[TLane]

Thanks very much Tom - exactly that - A full survey is one of the first things we're planning on getting sorted. Will get round to posting some pictures when I'm back on better internet!  

[IanR]

Hello & welcome.

 

On 01/12/2023 at 17:31, TLane said:

✔ - Full Outline Planning secured

 

On 01/12/2023 at 17:38, Tom said:

Part Q. 

 

On 01/12/2023 at 17:45, TLane said:

exactly that

 

What planning permission has the Barn got currently? Full planning for a Conversion, Outline planning (which I guess would be for a knock-down and rebuild) or Permitted Development Class Q Change of Use?

 

Each will have different levels of restriction on what you can replace and on whether you can move the walls out a little to get the frame fully within the thermal envelope of the developed building.

 

Assuming it's not OP for a knock-down and rebuild. Have you considered re-submitting planning to do so, using the planning you have as a fall-back?

 

Is it a concrete, portal frame "shed". That's what I'm familiar with from Atcost. It's a lightweight frame, for a lightweight roof and wall cladding (unless the walls are on their own strip foundation), and the columns will typically have small foundation pads that can't take much more than the lightweight structure the portal frame is designed for. All this means you've got some compromises to consider on how you will insulate, and support your new walls and roof.

 

Since it's a modern shed there's unlikely to be much architectural merit that the LPA can argue needs to be saved, and they may well be willing to let you build new, although likely in a similar style.

 

I've completed my own conversion of a steel portal frame (cow) shed, under Class Q, and at the time my LPA wouldn't consider a knock-down and rebuild, although now there is plenty of case-law that they'd struggle to argue against. Mine could have been a far more efficient build had I been able to lose the original portal frame.

 

With regards to next steps...if you have time, I'd not rush in. Consider your options and get a feel for what building methods you'd like to follow and what aspirations you have regarding energy performance and comfort. Once you know what you want, then find the professionals that can help you deliver it.

 

One Caveat though is that if the Barn has Class Q, then you have 3 years from the Approval to complete the conversion, so there may be a time pressure.

[Tom]

^^^ this

We went down the Part Q then full planning for knock down and rebuild route, made things a lot easier than they might have been. Especially as the "survey" for the Part Q was a little optimistic, to say the least.

[saveasteading]

Hi. Good luck.

Is say £200/ft2 is feasible with luck, design skills and  close management.

 

Atcost was purely a concrete frame system. Latterly they started using steel purlins instead of concrete. That is a big advantage in refurbing. What is yours?

 

The system was used for industry as well as agriculture so is not in any way less adequate.

I think the trading name may still exist. 

 

The SE has so far been employed to confirm to the planners that this is a structurally sound building, that can be converted. Ie it doesn't have to be demolished or otherwise replaced.

It is likely to need strengthening for domestic use. Mostly because safety factors need to be added, whereas agricultural buildings don't have them. That might include underpinning.

I'd contact an SE now for a walkround with comments. Try phoning the one who did the report. 

 

You won't get builders' quotes until you know what has to be done. That SE is priority again.

[TLane]

On 04/12/2023 at 19:46, IanR said:

What planning permission has the Barn got currently? Full planning for a Conversion, Outline planning (which I guess would be for a knock-down and rebuild) or Permitted Development Class Q Change of Use?

Hi IanR!, It's currently got full planning for conversion. I'd need to run through in more details with the architect that drew up the plans and application - but there doesn't seem to be any major restrictions on what needs to remain / what can't be replaced. 

 

Current conditions; 

 

- Needs to begin within 3 years of the notice (comply with Sct 91 of the Town and Country Planning Act)

- Shall be carried out in accordance with the approved plans (Site location, block, proposed elevations, proposed elevations, demolition plan, biodiversity etc)

- Submission of all materials to be used externally

- Trees etc remain 

- Ecological Mitigation (no evidence of bats, etc - and nothing within the cartilage of the building)

- Parking space is kept / area to turn vehicles

- Landscaping scheme submission

- Misc other (RAMS etc)

 

On 04/12/2023 at 19:46, IanR said:

Is it a concrete, portal frame "shed". That's what I'm familiar with from Atcost

Exactly that. Concrete frame & Purlins - with asbestos (low-grade) corrugated roof and cladding. Brick face to the front.

 

The only reference to keeping the current frame is in the structural report. Without any specific conditions set out in the planning decision notice regarding what has to be retained - does that give you some relative 'freedom' with what can be done? 

 

On 04/12/2023 at 19:46, IanR said:

With regards to next steps...if you have time, I'd not rush in.

Outside the restriction on needing to begin with 3 years, we're in no rush - and want to plan as much as possible before delving in. I'd assume (perhaps naively!) that it would be fairly straight forward to 'extend' the planning permission, if it's close to lapsing? The site is a bit dearer than we'd hoped (SE for you!), and I want to make sure we've enough put aside for the build - I'll have some wiggle room, but not much, for any unforeseen cost increases... So happy to take time planning it all. We'd work alongside a project manager for the main build, and manage the conversion of the adjoining annexe (ancillary) ourselves, which is a little less daunting, once we've learnt a bit more!)

 

On 06/12/2023 at 16:27, saveasteading said:

That is a big advantage in refurbing. What is yours?

Hi Saveasteading! It's Concrete Purlins. I don't think these have to stay.

 

On 06/12/2023 at 16:27, saveasteading said:

I'd contact an SE now for a walkround with comments.

 

Exactly what I've done! 

 

A general question - Do I need to get an architect / architectural technician to draw up the main plans - or can I give to an SE / Similar to do instead? I'm just looking at ways to preserve the build budget - and want to spend as little as possible on fees outside the main build. I'm very happy with the plans drawn up to obtain planning - so would be a case of making those into more of a build plan. 

 

Many thanks all. 

 

 

 

 

 

[saveasteading]

57 minutes ago, TLane said:

It's Concrete Purlins

OK. You can't drill into these so it needs another solution. There are a few ways to deal with it. 

 

SE essential. Architect not but...

The SE can specify construction but may not be great on layout and appearance and building regs other than structure. Ask them.

[IanR]

4 hours ago, TLane said:

Hi IanR!, It's currently got full planning for conversion. I'd need to run through in more details with the architect that drew up the plans and application - but there doesn't seem to be any major restrictions on what needs to remain / what can't be replaced. 

 

That likely gives a little more freedom than a Class Q would do, but...

 

4 hours ago, TLane said:

- Shall be carried out in accordance with the approved plans (Site location, block, proposed elevations, proposed elevations, demolition plan, biodiversity etc)

 

The planning ties you down to what's in the submitted drawings. It's normal for the primary structure to be retained for a "Conversion", and as the planning included a structural survey my guess is that it's been stated the structure is capable of conversion and has been shown on the submitted drawings. Are the purlins also shown and are they called out as the original ones to be kept?

 

On the submitted drawings, how much space has been provided from the outside face of the concrete portal frame to the outside of the rain screen for the walls and roof? Are all the columns within the external walls, or are there any that come down internally within the building, ie. is there a lean-too on any part of the portal frame that then positions the columns internally?

 

The Columns of the portal frame are attached to concrete pads in the ground, which will sit at 8°C - 10° all year round, so the base of the columns will also be at that temperature. While reinforced concrete has a lower thermal conductivity than Steel, the columns will still act as a heat sink if they are exposed to the internal house temp and be a potential risk for condensation. Is it easy enough to get the portal frame and purlins outside of the thermal envelope?  The haunches where the roof portals meet the columns can be a difficult area due to the extra depth of section in this area.

 

What's your plan for the floor, are you keeping an existing solid floor are will you be installing new. This may also need some consideration on how it will dove-tail around the existing pads and be thermally broken from the portal frame, especially if you intend to install UFH.

 

4 hours ago, TLane said:

A general question - Do I need to get an architect / architectural technician to draw up the main plans - or can I give to an SE / Similar to do instead? 

 

From where you are now a combination of SE and Architectural Technician would see you through if you plan a standard building regs type build. If you have aspirations of a higher performance building and are consider PassivHaus principles, then you'll need someone with that skillset to tackle some of the compromises brought about by the portal frame.

 

For me, I'd consider approaching the LPA to see if they'd consider a knock-down and rebuild, and give yourself an easy route to a good thermal performance. If the LPA are insistent on the keeping the appearance there are lots of options. 

Edited December 8, 2023 by IanR

[TLane]

Thanks so much, hugely appreciate your kind input!

 

58 minutes ago, IanR said:

Are the purlins also shown and are they called out as the original ones to be kept?

No purlins appear on any of the plans. Only the concrete frame they rest on, so I'd think we can replace the purlins..

 

1 hour ago, IanR said:

On the submitted drawings, how much space has been provided from the outside face of the concrete portal frame to the outside of the rain screen for the walls and roof? Are all the columns within the external walls, or are there any that come down internally within the building, ie. is there a lean-too on any part of the portal frame that then positions the columns internally?

Not a huge amount at all, and would estimate it's mostly just the external render / finish of the wall as opposed to anything structural. The plans have the exterior walls made up between the columns, with some additional internal walls that hold up the 1st floor.

 

1 hour ago, IanR said:

Is it easy enough to get the portal frame and purlins outside of the thermal envelope?

I don't think so now!

 

1 hour ago, IanR said:

What's your plan for the floor, are you keeping an existing solid floor are will you be installing new. This may also need some consideration on how it will dove-tail around the existing pads and be thermally broken from the portal frame, especially if you intend to install UFH.

 

Current plan is to take up the existing, and installing new - adding UFH. I had hoped to keep some of the concrete structure exposed on the interior. This is a really similar structure / build I have been aspiring to a similar build as this https://www.thegrainstorelewes.com/our-story. Ugly to some, but I quite dig the industrial aesthetic of the concrete columns, and funny when you compare to the exposed beams in a listed threshing barn!..

 

1 hour ago, IanR said:

This may also need some consideration on how it will dove-tail around the existing pads and be thermally broken from the portal frame, especially if you intend to install UFH.

That's an incredibly good point, thank you!

 

1 hour ago, IanR said:

If you have aspirations of a higher performance building and are consider PassivHaus principles

Considering the principles, but not aiming for the certification. Want to include PV, ASPH, triple glazing, air tight as possible etc (within budget)

 

1 hour ago, IanR said:

For me, I'd consider approaching the LPA to see if they'd consider a knock-down and rebuild, and give yourself an easy route to a good thermal performance. If the LPA are insistent on the keeping the appearance there are lots of options. 

Potentially the way to do it, and I'd assume cheaper in the long run. Really appreciate the advice!

 

5 hours ago, saveasteading said:

OK. You can't drill into these so it needs another solution. There are a few ways to deal with it. 

These don't appear on any of the plans, so I'd hope they can be replaced altogether! 

[IanR]

2 hours ago, IanR said:

Is it easy enough to get the portal frame and purlins outside of the thermal envelope? 
 

1 hour ago, TLane said:

I don't think so now!

 

The example you linked to shows one of the compromises you'll need consider. The depth of the column is, on this build, greater than the thickness of the wall, so the plasterboard adjacent to the column has no insulation behind it and in January will be sitting a few mm off a concrete column that will be close to 0°C. And those exposed roof portals are attached to that column drawing out the heat from inside the building and possibly compensating.

 

  

I do also like the industrial look this gives, but for me I'd want bring the portal frame within the thermal envelope and get a reasonable thickness of insulation around the outside. I'd then just live with the cold bridge from the base of the column to its concrete pad, as long as I kept warm moist air away from the lower parts of the column.

 

1 hour ago, TLane said:

Considering the principles, but not aiming for the certification. Want to include PV, ASPH, triple glazing, air tight as possible etc (within budget)

When following PH principles, once you've added sufficient insulation and got the air tightness within target, the cold bridges are where you will leak your energy. 

 

1 hour ago, TLane said:

Potentially the way to do it, and I'd assume cheaper in the long run. Really appreciate the advice!

 

Like for like, it has to be cheaper. You could perhaps spend some of the money you save on a Glulam portal frame to give a similar (but less industrial) internal appearance.

 

...and park them inside the thermal envelope.

Edited December 8, 2023 by IanR

[saveasteading]

3 hours ago, TLane said:

hope they can be replaced altogether! 

I've done  a similar conversion, but for an office. I think we clamped timbers to the purlins, so they stayed.

[saveasteading]

If you wanted to, you could expose the pads and insulate them. It's diminishing returns though for a smallish benefit a few days per annum.

I can't see that replacing with glulam is cheaper, but it's certainly  easier. 

A builder would prefer to replace the whole building. A self builder is converting and working around issues, and surely was attracted to the building as it is?