Modern Portal Frame Barn Conversion

[Terryturf1]

Hi Everyone 

Ok im not a complete novice I actually built my own house but traditional build Bricks Blocks Block and beam floor attic trusses 7 yrs ago . Now after fighting with the LPA for 4 yrs I finally have permission to convert a Barn to 3 Houses . But im slightly nervous  ! I have to build round the rsjs  already in situ . I have to have a metal clad roof and walls . So this is like starting all over again to me like a novice ...

Im thinking of sips panels or blocking up between the steels ... I have some funds to kick it off then I have to sell my own.home  These houses are for my kids so I want it done right of course .

I would really appreciate some advice 

 

18-212 - 02A Proposed Elevations (1)west lodge.pdf

18-212 - 01A Proposed Plans.pdf

[kxi]

Hello, congratulations on the planning.

 

Quick initial questions. Is the current plan to have the insulation layer (e.g. sips panels) on the inside of the existing steel frame? The plan implies so and I assuming planning will not allow the footprint extension of an insulation layer outside of the existing frame? There is another barn conversion on the forum where I believe the existing steel frame was outside the envelope (apologies can't find it right now as on phone). Have you got any 'cladding space' to have at least some of the insulation layer external to the steel?

 

The plans say timber cladding, but I assume the metal cladding you describe above was a later planning condition?

 

My initial thought was the panels don't necessarily need to be structural and one could use something like the probably cheaper steel faced kingspan insulated panels. But it may be that the idea is to support the new first floor on the sips? Is the existing steel not ok to support a first floor (I assume not). Building an internal facing wall (+ service zone?) Might be easier against sips than steel faced panels. But perhaps worth looking in to.

[Russell griffiths]

You will need some careful details at the sole plate if you fit sips down onto a cold slab. 

Lots of planning to make them work properly without lots of cold bridges 

[Terryturf1]

 

Yes indeed with the planning lets just say Ive had my total fill with the LPA 5 applications and 2 planning appeals to get what I should have had all along . The wall cladding is fitted on purlins overhanging the actual steels by about 4-5 inches. Im asking the structural engineer about how I d  like to block up in between the steels and fit cladding outside these . Then maybe in the future I can render onto this and remove the cladding . Also im in a mind to maybe build a floor internally with timber or steel so the weight of this isnt on these walls or the existing structure . I did want wood cladding like larch but they intimated that they would once again refuse this application as they implied not enough of the original structure wood remain!  Despite i may add approving other applications where both walls and roofs were totally removed 

[Tosh]

I'm doing a steel portal frame conversion of almost identical nature. The SE will be critical to the type of build you go with. The issue your SE will likely raise, at least the ones that we invited did, is the wind loading. We ended up having a design with a significant amount of additional bracing to overcome the twisting of the steel frame that he said the building would have to resist. We tried to argue that the floor and stairs (steel fixed to floor) would offer this restraint but the SE argued that wasn't enough. I didn't have a huge issue with the additional bracing but because we wanted a vaulted ceiling (the roof pitch is too low to make it worth while having a ceiling) it becomes an issue of aesthetics. We will work around that issue when we get to it though!

 

Unless you've investigated already the other thing to be mindful of is that the pad foundations that the stanchions sit on is an unknown. They may need underpinning!

 

Check the building for plumb on all the columns and that they are in line. Check the floor levels. A lot of agricultural buildings are built with a fall on the floor - ours had 80mm from e2e. Also check the depth of the concrete floor and that it can take any internal load bearing walls - ours varied between 100-125mm but SE specified 200mm. It often measured 200mm at the edge of the building but when we trialed a meter or so in the depth reduced as well as being inconsistent - jack hammer and sthil saw time and then pour new foundations!!

 

Another pita job will be digging the external foundations between the columns as the columns get in the damn way! A digger with a knuckle boom would be ideal solution.

 

I did consider at one stage of just taking the whole lot, frame n all, down and selling it so we could start from scratch. However I was advised against this and tbf I'd already had some successes with the LPA in changing some of the conditions of our planning so didn't push any more. I guess you wouldn't want to try this either having the battle you've had.

 

We're using ICF because we can straddle the columns (column is 203 deep so a Nudura unassembled module of 200mm will fit nicely either side of it). It overcomes the cold bridging and any issues of detailing the blocks/timber frame to column fixing as well. You'll probably need to use debonded fixings if you go with blocks.We looked at SIPS and TF but both were around £70-80k. The ICF solution is simpler and around a third of the price - yes we have to put a floor in and a roof but still will works out £10-20k cheaper.

[kxi]

I assume maximising the internal space is a concern, so @Tosh 's straddling ICF route neatly gets half of your insulation layer outside of the steel, with probably enough room left to fit some cladding support within your 4-5 inches currently used by the purlins - thus no footprint extension so staying within your Class Q.

 

I don't know what you had in mind for the party walls, but I would guess block is the easiest and thinnest way to meet the desired standard for noise, vibration & fire? Using the ICF for that as well would seem to add unnecessary width.

 

For the roof, do you have the same 4-5 inches of purlins on top of the frame? It would be nice to get the insulation layer above the steel (in contrast to the current plan), especially if it can be continuous with an outer face of the wall's ICF. For that to be feasible you'd probably need something like the quadcore foam used in Kingspan's Benchmark panels, or the full insulated roof panels like the KS1000. I don't know if your planning requires you to retain/replicate the exact corrugations of the existing roof?

 

@Tosh how are you planning to do the roof in your conversion?

 

It may be relevant that our LPA were surprisingly relaxed about Non Material Amendments to the original Permitted Development design, once we got over the small hurdle that they insisted no changes were supported under the legislation. They are, but it's not well-known it seems. But I suspect you'd rather just avoid going back to them for any reason.

[Tosh]

As @kxi says just use a mixture of standard dense concrete blocks and timber studding for internal walls.

 

For the roof:

We had the option to bolt flat bar to the existing 175mm deep timber purlins or swap them for metal z purlins. We're going with the later as it actually worked out cheaper believe it or not. It will also be easier to fix the Quadcore roof panels to. We did look at SIP roof panels but the quadcore you can cut penetrations for flue, windows etc more easily as they're a structural deck. Also for the standing seam you can fix direct to the quadcore whereas with a SIP you'd have to counter batten and fix another layer of OSB all over to act as a vent. Just a few things to think about maybe.

 

I should've mentioned previously but we bought our place with existing PP that said we had to reuse the 'olive green' agri bldg profile or material of same colour/profile like yours. As soon as we purchased though we put in a variation to the LPA to alter the cladding to a to a zinc standing seam roof and timber clad elevations. Planners passed it without issue.

[Simplysimon]

you're going to have to remove the tin to do anything so i'd be tempted to remove existing slab (if there at all) cut out under each column and place armatherm or similar under them if pad founds,  new insulated slab, and then away you go with whatever build you you want and clad in the original tin. otherwise a new insulated slab ontop of what is there and insulate around the steelwork.

[scottishjohn]

my first thought 

have you checked pricing of modern composite   cladding as used in modern portal industrial buildings?

theres a reason why they used it and I bet its cost 

you can get it very thick and that would very easy -beef up on inside between pillars you will get mega insulation value,with what ever system you like TF -sips 

If it is an agricultural shed --then yes you will need extra wind bracing for non agricultural--for sure you do in scotland 

If you were building new and it was not classed as agricultural the even the main steels and rod trusses have to be larger than minimum you need for an agricultural build

I had this problem when wanting to build an aircraft hanger 

they would not accept farm spec for wind or snow loading for anything other than a farm building

walls between the 3 units will need to be fire proof --so ICF --durisol -isotex -velox  or block work --also these will be best for sound proofing

just 2 pence worth 

 

[Terryturf1]

Its an industrial spec building with very heavy duty RSJs . I bought it second hand yrs ago took it down and re assembled it . I only bought it to keep my equipment safe so its all purely luck really I managed to get planning. I had a team come out and put the main frame up with a crane . I don't remember how deep the pads were under each upright but I seem to recall bringing in a lot of concrete on a grab truck I think about 1cu M per pad ..To gain permission a structural engineer came out  and completed a visual inspection of the building saying it was capable of conversion . So now ive gone back to him to help with technical advice etc .. The floor is around 8-10 inches deep of reinforced concrete with   But its yrs ago . The roof steel purlins . I'm just wondering what benefit I have by not insulating within .  I am considering putting a loft in and doing away with any vaulted ceilings due to cost and convenience .

 

[kxi]

It was IanR who had the conversion with the insulation layer inside the existing steel frame:

https://forum.buildhub.org.uk/topic/1111-touchwood-homes-experiences/?tab=comments#comment-14294

 

Our conversion has no existing steel, so I've not thought through the pros and cons of insulating entirely inside vs external / straddling, but I would suppose it's conceptually simpler to build everything inside, but you then lose some floor space and head height to accommodate thick insulation (I'm sure plenty of other pros and cons each way). Also, if your steel is say 180mm deep, then the purlins 130mm, the windows will be deeply inset if the insulation layer is fully inside. This could be seen as a design feature though. Some of our windows will probably end up being inset over 500mm!

[Tosh]

I'm sure you've covered it in the conversations with your SE but the barn we bought had a SE report saying precisely the same i.e. that it was suitable for conversion BUT we still had to bring it up to a domestic dwelling spec. I was a bit suspicious of the SE claim of twisting under wind loading at first until one windy day I put a magnetic laser level on the columns and could see all the movement going on. Quite an eye opener. 

 

It will be interesting to see what the SE comes back with.

[albert]

Hi I am also doing a  steel portal frame class q now . I am an experienced timber framer and builder and the design has been a head ache to say the least. If I was to start again I would  drop the whole wall structure behind the steels by 100mm subject to the planners approval. I paid my SE a LOT  to design the steel work required and there is a lot of steel to go in with our TF panels acting as infill essentially. (we are in a high wind and snow zone ) I intent to drop the whole building and prep the existing steels whilst the groundworks are being done. I am also breaking out the slab and renewing. It is important to remember the planners want a conversion  but with so little structure it is difficult to  think of it as one.  I have also had issues with lenders on mortgaging this property to add to the complexity of the build.

[Terryturf1]

Im discovering this as i go.. Thats why im not doing sips or timber frame. In the plus side i have planning from this conversion which i wouldnt have gotten. 

[K78]

The barnhaus concept uses a portal frame on pad foundations.