Dwellings are constructed speculatively. As a result how our houses look on the outside is often something we have little control over. Most of us don't get the opportunity to design our own house, myself included. So it's on the inside of our house that we get to express ourselves. This is where we make our mark. As such, this is the place that reflects and describes us best.

When we choose to express ourselves in interiors, we reveal something of ourselves.

When we invite people inside our houses, we share these revelations. Interiors expose clues about our lives and the way we like to live. They are an extension of our tastes and obsessions. When we visit other people's houses, or when they visit ours, things are read into these clues. There is always a story.

Interiors are like crime scenes without the crime. Some we like, others we hate. We all have our opinions.

Interiors provide a visual history. They are like time capsules. Stripping back wallpaper can be like peeling back years; but after you discard ornamentation, remove decoration and strip surfaces, you find structure and organisation. You find the beginning, a place from where you can start again. You find the interior, the blank canvas, the naked model. You find the architecture of the space.

In talking about interiors, I'm less interested in how houses are dressed; I'm more interested in their bone structure and the space that such structure encloses.

As we normally live inside buildings that other people have made, the spaces we inhabit are not specifically tailored to our needs.

Somebody else has imagined what we might require from a house. More often than not a house will not fit us perfectly, but what ever does? We hope that a house can accommodate us, that there is room for our lives. Frequently they don't. If we are lucky they provide a loose fit and there are ways that we can adapt them. We can knock a wall out, convert an attic or make a playroom out of the garage.

This looseness of fit gives us options. It affords us choices. What happens when things are too tight, when we have less room to manoeuvre, when we have more stuff than space, more life than style?

I have always been curious about how people occupy their houses. As an architect I get to observe these things, other people's things.

I try to sort them out and then I go back to my own mess to relax.

My own house is all over the place. I work from home but most of the time it can feel more like I'm living at work. It's quite like a workshop. I get to try things out. As my home provides almost no storage space and as I have no attic or shed, there are things in the house that should definitely be somewhere else.

One day I realised I just needed to buy a shed, but I'm a fussy sort and I couldn't find a shed that appealed to me. So I thought I'd try to make one.

Making a shed is probably an activity that is best carried out in the garden, but, for some reason I can't quite remember, I decided that I'd make mine right in the living room.

Not in my overgrown garden where it belonged but in my already overcrowded living room, right around the sofa in the middle of the room. It was as if I was too lazy to get up out of the sofa and instead just started to build the structure around me. It gave the impression that my idea had been acted upon so urgently that I didn't even have the time to take it outside.

Knowing that I wanted something shed-like but not a shed, I decided I would start with a greenhouse frame, a greenhouse without the glass. Buying a greenhouse and explaining why you don't want to buy the glass is a curious way to spend a morning. Telling them that you're worried about people throwing stones doesn't cut it. Apparently selling the glass without the frame can be more than your job's worth, as people who just buy the glass are only looking for cheap replacement glass for the greenhouse they already own and can't be bothered to pay a glass cutter the price for one off pieces. Thus shops can be left with an excess of frames that nobody wants to buy, except me obviously. The fact that I was alleviating the problem of these glass poachers was lost on the woman in the shop who viewed me more as a problem doubled than a problem shared. Anyway, it just goes to prove the old saying that people who sell greenhouses shouldn't sell the glass first. The transaction [eventually] completed, I was free to start. I had bought the outline of a shed without the walls. A peculiar afternoon later there was what resembled the ghost of a room in my living room. It had a sliding door and one window. But you could see out of it everywhere.

It was a room inside a room. I was playing Russian dolls with space. That evening, my son and I ate our tea sitting on the sofa inside the frame. It had the effect of transporting us to another place, and presented us the opportunity of spying on our own living room. It was our tree house and I was clearly out of my tree.

The next day when my son was at school, I went about fleshing out my prototype, cutting up plywood sheets to skin its naked torso. I finished two of the four sides and put part of the roof on. That night we watched television in our old living room through the unfinished gaps in the frame.

From this cramped television watchers hut I could see possibilities. It wasn't practical but it was exciting to be inside.

We had created no additional space but we had a new vantage point, one where we enjoyed how tight things had become. As a hut, ours was useless; it only kept us dry because it was inside, yet we had found a use for it. It lightened our lives. The whole experience was like camping in the living room. We had ventured to a strange place, with unusual proportions and a scale of its own. When we had dismantled the greenhouse and banished it to the outside we had our old room back, but it wasn't the same. Having been someplace extraordinary we realised how ordinary our plain old interior was. It didn't have the same sense of fun. The greenhouse had been a playful intruder. It managed to mock the conventions of the living room. The normality of the old space lacked the complexity we temporarily enjoyed. It suddenly felt patronising, like a bad movie script, one that thought we couldn't handle, something more difficult. I felt short changed. It was as if whoever had designed the 2.4metre ceiling height thought anything more intricate would just be lost over our heads so no further elaboration was necessary.

With the greenhouse gone, we had lost a friend and we were lonely. We missed the sense of adventure, but it turned out we weren't alone.

My neighbour, next door, was up to similar tricks. If you went into his house you'd think that he had just moved in, but he had been there a while. His stuff surrounded him but his furniture was nowhere to be seen. The lights were on but there was no furniture home.

Maybe it was having second thoughts about committing to this new place of abode, or maybe it had wandered back to its old residence like a cat.

It turned out he was just procrastinating. - just hadn't bought the stuff yet. Either way it was intriguing. He had loads of space but little by way of allowing him to occupy it. He had a table tennis table but no table. No table to eat at anyway. So he would sit on the stairs to dine with his son. He told me this knowing that it sounded odd but you could tell he enjoyed it.

His son's friends loved to call around to this liberating house, a place freed up from the usual obstacles linked with daily life.

It made me think of so many public buildings where the staircase is everything. Where it all happens. Where people meet, pass and linger. It's less common in a domestic interior. In a typical house the various rooms are often organised around circulation space. This space is often sparse, efficient and economical, but it can do so much to animate the mundane. The stairwell connects levels but its volume also allows light to pass through space that is often closed off from access to daylight. As a moment where drama may occur it is latent with potential. The stairs have a few knowing accomplices, fellow rule breakers. In this regard, landings are not to be trusted.

They conspire to force people to stand aside or brush past each other. However, where they expand people, find reason to pause. Anyone who knows art will know that landings are where a knight embraces a princess.

I remember as a child kicking a football around the hallway of our house and playing on the upstairs landing more often than in my bedroom or the family room. The first floor landing that wrapped around the stairwell was more interesting than the boxed off bedrooms surrounding it. It was narrow and had more junctions and since in my head it was actually a vast network of roads for matchbox cars it had attributes of geography that for some reason I couldn't conjure up in my head in the vast square-ness of my bedroom. My siblings rarely interrupted me in these intermediate spaces. No one ever said "get out of my landing", or "I was playing on that step first".

Looking back I can't recall how they all got from one room to another without tripping over me, but it's probable that they were constantly chatting to me, asking me what I was up to, whilst I was driving scale model cars around the freeways upstairs. Whatever else I forget, I remember that slide tackling in the hallway would leave skid marks on the carpet and carpet burns on your knees. There was no more competitive field, especially when you were playing against yourself.

I don't know if things are quite like that any more. Being a parent rather than a child, I find myself on the opposite side of the discipline line.

The extra-ordinary toys that exist now may have replaced more imaginative games, yet you still find kids setting up base camp under a table, or organising objects to define a space of their own; playing in the box their discarded birthday present came out of rather than with the present itself; climbing into somewhere different to hang out for a while rather than walking into the same old space.

I wonder how I can design to include these incidents in a schedule of accommodation. The box could instead be an alcove, a niche or an inglenook. Our bodies sit and shift differently in these spaces.

When we have occasion to move differently, by hopping, skipping and jumping, or just sulkily slumping into a chair, we cross invisible thresholds and enter places of our own.

In the external world these moments are abundant. They are the gap in the fence, the stairs that lead into the sea, the people on the roof, the shelter in the storm. In the interior they are rarer, encountering them gives us more cause for celebration. I look for moments of casually improvising in an interior, like a window ledge that is deep enough to sit on or a warm wall that is nice to lean against. I think these moments happen more frequently at the edges, like a fringe festival. You have to look out of the corner of your eye to see them.

They exist at the end of a sideways glance. Eating stew on the stairs or finding a shed in the room are both accidental acts that may give rise to something more deliberate.

As things become more cramped we need to investigate different ways of making the same old culation spaces in a house are like the words in a sentence between the punctuation marks; they explain how something works; they are full of action and they are where things happen.

Houses have become places of conformity.

There is a huge demand for them but they all seem to be the same. Slowly things are changing. Eventually our appetite for different vessels to live in will cause us to demand something that is different. Sooner or later developers will have to speculate in a more enlightened way. One day they may provide us with houses we desire not houses we simply need.

In the meantime it delights me when people use things differently, in an unexpected way; when the functional is elaborated to include the accidental; when boundaries are blurred; when we occupy the residual; when nothing is left over.

If you ever get the chance to hire an architect to renovate your house don't tidy up before they call around. Let them see how you live. Then tell them stuff. Then let them make you something made to measure. Tailor it to your needs. You'll be surprised how well the result will fit.