Extensions in West Mersea

Extending in West Mersea

Just over seven thousand people on an island reached by one road, where the tide, the salt and the town’s own planning policy each have something to say about your extension.

West Mersea occupies the western end of Mersea Island, between the mouths of the Blackwater and the Colne. At the 2021 census the parish held 7,221 people, which makes it larger than several places that call themselves towns on the mainland. It is reached by a single causeway, The Strood, and that one fact changes more about a building job here than anything drawn on the plans.

Colchester City Council is the planning authority and its Building Control team is the one we notify. There is a second document in play here though, and it is the one that surprises people.

The town wrote its own planning policy

West Mersea has a neighbourhood plan, and one of its policies is aimed squarely at bungalows.

The West Mersea Neighbourhood Plan was made in April 2022 after a referendum, and once made a neighbourhood plan forms part of the statutory development plan. That means it is not advice. It is policy the council decides applications against, alongside the Local Plan.

The policy that matters most to a householder is the one protecting single storey and one and a half storey homes. Applications that would turn a bungalow or a chalet bungalow into a two storey house are not supported unless it can be shown that the proposal would not harm the character of the vicinity. Read that carefully, because it is a policy with a door in it rather than a prohibition. What it does is shift the burden: on the mainland you would argue about massing and overlooking, and here you have to make a positive case about character before you get to that conversation at all.

The practical effect is that going up is a harder argument on Mersea than going out, and a great many of the extensions built here are single storey for that reason rather than for reasons of budget. If your house is a bungalow and you want more space, the design work starts with whether the plot will take the footprint, not with whether the roof will take a floor. Our guide to extending a bungalow covers the structural side of both routes.

The housing stock, and why it is mostly low

An oyster village core, then seventy years of seaside plots. The two halves behave completely differently.

The old village runs down to the water around the church of St Peter and St Paul, which is Grade I listed and eleventh century in origin, and along Coast Road towards the Hard and the oyster pits on Besom Fleet. That core is the West Mersea Conservation Area, designated on 15 May 1989 and covering roughly eight hundred metres across.

Inside that boundary the property is article 2(3) land. Class A no longer permits a side extension or a two storey rear extension without an application, cladding needs consent, and Class B stops a rear dormer being permitted development. A rooflight sitting in the plane of the existing slope is a different class and remains permitted development, which is worth knowing before anyone redraws a roof. The larger single storey rear extension route that runs on prior approval is not available on this land either. No Article 4 direction is recorded over the town, so the designation itself is the whole of the restriction, though it costs nothing to have the council confirm that against your address.

Outside the conservation area, and that is most of West Mersea, the town is a twentieth century creation. Wide grid roads of detached bungalows and chalet bungalows on generous plots, laid out and filled in from the interwar years through to the 1980s, with later infill between. Roofs are mostly shallow and hipped, plots are wide rather than deep, and side access is genuine almost everywhere. That combination is unusual in this district and it is why the briefs here look nothing like the ones in Colchester itself.

Flood zones, floor levels and the test that does not apply

The low ground around the island is tidal flood plain. What that means for a householder is more specific, and less alarming, than most people expect.

The Environment Agency maintains a flood warning area covering the Essex coast at West Mersea, The Strood and the surrounding marshland. The low fringes of the island, the marsh edges and the ground behind the sea wall sit in the higher flood zones, while much of the built up area on the rising ground in the middle does not. The boundary is not obvious from the street and it is checked on the address.

Here is the part that saves people money and worry. The sequential test, the mechanism that steers new development towards lower risk land, does not apply to householder development. Your house is already there, so there is no alternative site to steer it to. What is still required for an extension in flood zone 2 or 3 is a site specific flood risk assessment, and for a minor extension that is a proportionate document following the Environment Agency’s standing advice rather than a modelling exercise.

What that assessment usually settles is the finished floor level, whether the construction below a given level needs to be flood resilient, and how people get out. Flood resilient construction is not a Building Regulations requirement, so where it appears it appears as a planning condition or as the conclusion of the assessment. In practice it means solid floor build ups rather than voids, closed cell insulation low down, services and sockets raised, and materials that can be dried rather than replaced. Setting a new floor higher than the existing one sounds simple and is not, because it puts a step inside the house, so it gets decided at design stage rather than discovered on site. Our guide to flood zones and extensions in Essex goes through the assessment itself.

Salt, and what it does to a specification

Essex is one of the driest counties in England, so wind driven rain is not the problem here. Salt in the air is.

Building within a few hundred metres of open saltwater changes the materials schedule in ways that are invisible on a drawing and obvious ten years later.

• Wall ties and lintels. Galvanised steel is standard inland. In a marine atmosphere the sensible specification is austenitic stainless steel for ties, and stainless rather than galvanised for the lintels over openings. Ties are not something you can change afterwards without taking the wall down.
• Brick and mortar. Facings are chosen for frost resistance and low soluble salt content, and the mortar designation is picked for exposure rather than for workability. Salt crystallising in a soft brick is what produces the fretted, crumbling faces you see on older seafront property.
• Coated aluminium. Powder coated windows and doors carry different warranty terms in coastal locations, generally requiring a marine grade pretreatment and a regular wash down. That is a real maintenance obligation and it is worth knowing about before the guarantee is the thing you are relying on.
• Roof fixing. An exposed island site takes higher wind uplift than a sheltered suburban one, which means more mechanical fixing of tiles and dry fixed ridges and verges rather than mortar bedding.

None of this is exotic and none of it is expensive as a proportion of the job. It is simply a set of decisions that a quote written for a house in Prettygate will not have made.

The Strood, and building to a tide table

The causeway floods on high spring tides. Everything heavy that arrives on this job arrives between those tides.

The Strood carries the only road on and off the island and it goes under water when tide heights are high enough, for a couple of hours either side of the peak. Most of the time it is irrelevant. On the days it is not, it governs the programme.

Ready mixed concrete is the sharp end of it. Concrete has a working life measured in a couple of hours from batching, so a pour has to be booked against the tide as well as against the weather, and a wagon that cannot get across is not a wagon that arrives late. The same logic applies to a crane lift, a beam delivery, a scaffold drop and a skip exchange. It is entirely manageable and it is the reason a Mersea programme is planned rather than assumed.

The compensation is that once material is on site, conditions are good. Plots are wide, drives take a skip without a highway permit, and there is room to stand a mixer and stack materials off the road.

The ground under the island

Not the clay and trees problem that governs foundations in Colchester.

Mersea sits on London Clay with river terrace sand and gravel capping the higher ground, and alluvium along the creek and marsh edges. On the gravel capped ground the seasonal shrink and swell that dictates foundation depth in the Colchester suburbs is much less of a driver, and depths can be more modest. On alluvium near the water the material is soft and variable and the answer is usually to found through it rather than on it.

Which of those you are on is not something to read off a map. It is a trial hole at survey stage, and on this island it is the single cheapest way to find out whether your budget is realistic. The general mechanics are in our guide to extension foundations.

Questions we get asked in West Mersea

Can I go up on my bungalow?

Sometimes, and it is a policy argument rather than a technical one. The neighbourhood plan does not support turning single storey or one and a half storey homes into two storey ones unless the character of the vicinity would not be harmed, so the case has to be made on design and context before anything else.

Do I have to pay a coastal mitigation charge?

No. That tariff applies to net new dwellings across the whole district, not to extending an existing house, and it is not specific to the coast.

My road floods on big tides. Does that stop me building?

No. Householder extensions are exempt from the sequential test. You will need a proportionate flood risk assessment if you are in flood zone 2 or 3, and it will set the floor level and the construction below it.

Does the tide really affect the price?

It affects the programme more than the price. Deliveries and pours get booked around it, which takes planning rather than money, though a job that ignores it will find the delays expensive.

Getting a price for a West Mersea extension

We are based at West Bergholt on the other side of Colchester, and Mersea is a place we plan for properly rather than treat as another postcode. The neighbouring mainland villages work differently again, and you can read how in extensions in Peldon.

Our team comes out and looks at the ground, the exposure, the access for deliveries, the flood position and the conservation area boundary, and tells you what the job depends on before telling you what it costs. Most people who call us already have drawings and permission and want a builder to price the work and build it. That is the ordinary job here, and we are glad to work to somebody else’s plans. Where the drawings do not exist yet, we bring in the technician who draws it and the structural engineer we work with, we handle the planning route with Colchester City Council, we notify Building Control, and we run the job as main contractor.

We carry £2m public liability cover and build to current Building Regulations, through to the completion certificate. The survey and the quotation cost nothing.