Undercroft conversion idea - openings change - regs approach etc?

[RichardL]

Project idea
I have an unused space facing the garden, pictured - currently with a window & door that would be ideal converted to a garden store with full width access.

Situation
Its about 3-4m wide and a 4m x 4m room beyond, 1.7m ish ceiling height (not measured accurately)

Sits below the main part of the house, side walls support the house, but otherwise unconnected.
Timber joists above supporting the floor of the room above in timber construction.
Looks like the joist across the front may sit on the pier between the window/door but there's no lintel as such over them & other floor joists further back span the full width (would need/get a professional opinion before any change)

Piers to left and right of the door/window are cavity/block construction.
No heating in this space & no access to the rest of the house.

Changes
Change the window/door wall into a full width door - pair of doors to allow easier storage etc.

Question re permissions
Who will have an interest in terms of officialdom - planning is a given because I'm changing the openings.

Building control - re the structural element?
Do I need to describe this clearly as outside/unheated/floor = thermal break to the house?

Really not sure on the last bit.

Any pointers gratefully appreciated.

Edited May 21, 2023 by RichardL

[ProDave]

Picture zoomed further out to give context and one from inside showing lintels above the door and window?

 

Are the lintels where the wall steps out?  The house wall steps out, how is that supported or is that external wall insulation fitted that makes it step out?

 

What are you hoping to achieve?  It looks fine to me as it is as a useful outside / work / storage space.  What to you need or want to get into it that requires a larger door opening?  

[RichardL]

Thanks for responding.

The step out above is 100mm of external insulation - polystyrene + render layers etc.
The front wall structure is flush with the window/door area, the load bearing for the room above either side - left edge to the door and right edge to where it steps back slightly vertically.

Its hard to see in the photo and IRL - but theres a floor joist visible - then another just past the door/window - i.e. the top of the door frame and top of the window frame dont have anything above them. The closeup pic is the top left of the door frame - there's nothing on top of it.

The door is tight ~standard 600-700mm,  ideally i'd open up the full width so I could park a ride on mower in there and drive out direct onto the garden. i.e. more of a mini garage.

[kandgmitchell]

Stil not entirely clear what is exactly behind the exterior insulation at first floor level. Thus the pier could be propping that using part of it's depth, the balance stopping at door head level. Some closer investigation is called for.

 

Building reg wise, if the pier is non-loadbearing then there's no alteration to the structure if it's removed. If the space is unheated and remains so then there's no change there either. It would appear therefore that your proposal is not "building work" as defined by the regulations.

 

As to planning, isn't this an "alteration" to a dwelling house and so falls within Class A of the permitted development rights afforded said dwellings and thus doesn't require a planning application? 

[RichardL]

@kandgmitchell Thank you for the response.


Pictured is before the EWI went on - and the block piers either side construction is visible.
Theres also still a slight overhang - but that is the layers (see other pic) outside the studs (I think)?

The second pic is a view down when new windows went in - inside at the bottom - plasterboard/stud wall/tongue and groove - then original exterior shiplap? + addon exterior concrete? render over wire mesh. The 100mm EWI and and its associate layers sits outside that producing the 1st floor overhang.

Actions
But I'm with you - I don't know if its resting on the middle pier either. I'll take professional advice.
 

Planning is tricky around here - I'm in an AONB + they like to charge £100 for advice now  ... I'll read up on class A too.

Appreciate the leads.

[kandgmitchell]

The restrictions within Class A for properties within an AONB (here noted as article 2(3) land) are as follows:

 

 In the case of a dwellinghouse on article 2(3) land, development is not permitted by Class A if—

(a)it would consist of or include the cladding of any part of the exterior of the dwellinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles;

(b)the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse; or

(c)the enlarged part of the dwellinghouse would have more than a single storey and extend beyond the rear wall of the original dwellinghouse.

 

You don't seem to be covered by any of those exclusions.

 

So that facade above your garden room is timber studwork covered by T&G and then shiplap? Presumably something is supporting that studwork across the space between the two block piers (whether or not the middle pier props it)?

[RichardL]

7 hours ago, kandgmitchell said:

Presumably something is supporting that studwork across the space between the two block piers (whether or not the middle pier props it)?

Presumably - its been there since at least the 60s, us for 5 years.

I can't see the structure beyond that joist from the inside underneath.
I can't see any block work or other ties across the width.

My expectation - based on seeing various parts of this end of the house - bathroom refurb etc - is its a single stud depth framework with the layers as per previous picture + EWI on the outside.

[RichardL]

7 hours ago, kandgmitchell said:

that facade above your garden room is timber studwork covered by T&G and then shiplap

Yes + EWI and its layers now.
Not just that room one half of the house is constructed like that.

[kandgmitchell]

Mmmm, so only a timber "joist" - what sort of size?

[RichardL]

7" x 2"   ~16" centres
Under the floor space at least - I've no way of assessing anything above that.

[kandgmitchell]

So the chances are then that the original studwork forming the front of the house was built off the outermost floor joist (although there could be a support beam within the studwork above the floor). Odds are the pier does help prop that joist so that it only has to span the window as the greatest opening which a 7" x 2" obviously does. In reality the loads from the studwork are quite low due to the large upper floor window. However, there are a couple of solutions; coach screw a steel plate to the back of that outermost joist to stiffen it up or have a simple steel box frame made to both act as your new wider door frame and support to the joist.

 

Once upon a time a small local structural engineer would charge you a few quid for an A4 sheet of calcs to prove either the joist without the pier or what plate/box frame would be needed. You'd toddle off to building control, pay a fee for a building notice and hand over the calcs. They'd make one visit when it was done and that would be it.

 

Now that engineer is a "multi-disciplinary" practice that will sell you the entire package including site visits at vast expense. Your local Building control has amalgamated with the rest in the county, relocated to posh offices miles away and no longer has time to deal with a small job like this. " please submit your application on line and our staff will respond the next time Jupiter aligns with Mars". And they wonder why someone like you will speak to the local steel fabricator buy a piece of steel say 8mm thick, 150mm deep, long enough to span past the outer piers, has it drilled and coach screws it to the joist with the pier out of the way and the joist supported by an acrow. But like a good citizen you wouldn't.

[RichardL]

@kandgmitchell Really appreciate the in depth responses.

Doubling up with either steel or another timber had crossed my (amateur) mind too.

The steel box opening frame is a nice idea!

As you say the trick is moving a potentially simple project forward without everyone getting excited about making it complex.
I'm certainly not taking that pier out as DIY on the offchance

Many thanks;