First floor side extension

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    First floor side extension

    Hi all,

    this is surely something the most expert of you can sink their teeth into.

    I am the owner of a first floor flat in a Victorian conversion, comprising four flats in total. Demised to the property (as shown on the plan in attachment to the lease) there is a flat roof, built over a ground floor extension (which belongs to the ground floor flat). The tenancy is "share of freehold" - i.e. there is a management company owning the freehold and each flat owner has an equal share of the company - and a lease.

    I am considering building a side extension to my flat, enclosing the flat roof and building a second storey. The lease states that any structural additions require the previous consent of the freeholder, and that's typical. Another clause specifies that the demised premises include floors and joists below the floor of the demised premises (i.e. the flat roof too), but not the boundary walls (there is a 600mm tall parapet all around). The demised premises include the interior faces (plaster) of ceilings and boundary walls, and windows too. In short, everything "external" belongs to the freeholder, whereas the "internal" parts are included in the "premises demised".

    The idea is to build a new floor whose joists would span between the existing parapets, erect new brick walls with windows on top of the existing parapets, and top it with a new flat roof. Would the fact that the parapets belong to the freeholder be a condition which would not allow the construction of the side extension? i.e. "can't build on something that is not yours?"

    The way I see it, if the freeholder consent is obtained, the new walls and the exterior of the new flat roof would still belong to the freeholder, and everything internal would belong to the leaseholder (me). Practically, I would be building something for the freeholder at my expense, and the freeholder would give me the right (through the lease) to make use of the demised premises, which would now include the "internal" parts of the extension. This way, the conditions in the lease would still stand.

    Does it make sense? Eager to read your comments.



    Sorry this doesn't sound right at all.

    If the flat roof is demised to you in your lease, it's just a roof (up to the parapets). Not sure what you might use it for though. Do you use it for any purpose?

    What you are proposing is to enclose the SPACE above the roof, which is not demised to you in your lease at present.

    There are several things to worry about
    1. You would need planning permission (there is no permitted development for flats)
    2. Freeholder would have to agree to your taking his space and, even if happy with it,would probably charge you about half the increase in value of your flat. All leaseholders would have to be in agreement for this to go ahead. You might be building "something for the freeholder at my expense" but you would be the only person to benefit, and the freeholder would have an obligation to maintain the new building again for your benefit, so might apportion service charges differently. You might very well have to build a new parapet top of the new flat roof, which would probably be demised to the freeholder again.
    3. You would have to meet building regs.

    In consequence of the second condition, your lease would have to be redrawn, your new lease registered. All legal expenses would have to be met by yourself.


      You need freeholder permission to do anything in your post, and from what I see, you will be refused.

      You, as you say, cannot attach anything to the freeholders walls / parapet.
      You will have to get a structural evaluation to test that the exiting ground floor extension is strong enough to support another level, at your expence.

      Only the freeholder can tell you if you are allowed to do what you want, as we cant't.

      You can put every excuse you want on here, even showing that it is legal to do so, but if the freeholder says no, then it's a no.

      You will no doubt have to knock a hole in the side of the building to access the side extension.
      Something a freeholder, if it were me, would be refused you also.


        It all depends on the relationship with fellow 'freeholders' i.e. those other shareholders in the freehold company.
        If they are happy to let the extension go ahead then assuming planning permission and building regs approval then I see no problem. Just needs formal freehold company consent and any adjustment of demise and proportion of charges, etc, and maybe a fee into the funds.
        You need to ensure good relationships with your fellow leaseholders/shareholders.


          1 Your tenancy, and ownership, is leasehold. You also have a share in the company that owns the freehold. No such thing as SoF.

          2 While the flat roof outside is within your demise, based on your post, the airspace above it which you intend to develop is unlikely to be so included.

          3 Similarly while the structural alterations clause will refer to the existing demise, that does not extend or imply any rights to make structural alterations to other premises, ie if the existing walls cannot take the load, nor any right to alter those parapets if part of the building and not part of your demise.

          That means that before progressing you need to have the lease looked at by counsel (a barrister) to check before risking your time and costs.

          It falls into two broad parts, one if the extension and related work is possible and can be done as part of your demise for which consent to the works and mechanics of it are required, and two if not obtaining agreement to do so.

          As in the latter case it will add value to your flat, the freeholders, the company even though you are “a part of it”, can ask for a substantial sum to sell the air space and related rights to you.

          As you intend to add the exterior and structure to the building and let it fall under the freeholders responsibility, the terms of the lease will have to altered for your lease to show the new area, and for charges such as your share of repair expenses and insurance to be recalculated on in most cases a floor area basis. This is problematic in the case of lease with fixed percentages and you may need to convince the freeholder to seek individual variations to leases, or you may have to accept long term responsibility for the new bit, inside and out.
          Based on the information posted, I offer my thoughts.Any action you then take is your liability. While commending individual effort, there is no substitute for a thorough review of documents and facts by paid for professional advisers.


            We have just sold a very small garden to a leaseholder for a sum of 10K. We all (11) hold various amounts of shares in the freehold company. It would be irresponsible for the directors of the freehold company to give away an asset for nothing. The money received was then divided up according to the shares held and a Deed of Variation drawn up for the leasehold flat to show inclusion of the garden in their lease plan and that they were responsible for the regular pruning of a large tree and the upkeep of the perimeter walls.


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