You spent months and a lot of money on the extension. The kitchen is finished, the bifolds open onto the garden, and it is where the whole family now spends its time. And the WiFi does not work in it.
Or the loft conversion is done: a new bedroom and ensuite, maybe a home office under the eaves. The rest of the house has signal. The new room has one bar, if that.
We get these calls every week across Windsor, Maidenhead and Reading. It is one of the most predictable WiFi problems there is. An extension or loft conversion adds a room in exactly the place WiFi has the hardest time reaching, and builds it from materials that block signal. This guide explains why, and the fixes that work.
If your problem is the upstairs rooms of the original house, read poor WiFi upstairs. If the whole house is large and patchy, how to fix poor WiFi in a large house is the better starting point. This post is about the new rooms.
Why rear extensions lose WiFi
Most extensions in our area are added to the back of Victorian terraces, Edwardian semis and 1930s houses. The router is almost always at the front, where the phone line or fibre comes in. The WiFi has to travel the length of the original house before it even reaches the extension.
Then it meets:
The old back wall
The extension usually attaches to what was the external rear wall. In period houses that is solid brick, often 225 mm or more. Even when the wall has been knocked through, parts of it remain as piers either side of the opening.
The steel beam
Knocking through needs a steel beam (RSJ) to carry the wall above. A solid steel section across the opening reflects signal. On its own it does not kill WiFi. With solid brick piers either side and a router twenty metres away, it often decides whether the extension works.
Underfloor heating and screed
Many new kitchens have underfloor heating in a thick screed with pipes and metal mesh. This matters less for a router on the same floor and more for a signal coming down from upstairs.
Coated glass and bifolds
Bifolds, roof lanterns and large glazed panels often have a metal coating for energy efficiency. That coating reflects WiFi. It mostly affects signal trying to go out to the garden, but in a glazed extension it also means less signal bouncing around the room.
Appliances
A kitchen extension is full of metal: fridge freezers, range cookers, dishwashers and extractor hoods. A router placed near them loses coverage in several directions.
Why loft conversions lose WiFi
A loft conversion is the furthest room in the house from a ground floor router, with two floors of timber, plaster and pipework in between. On top of that:
- Foil-backed insulation. Building rules require high levels of insulation, usually rigid boards with a foil face. Foil reflects WiFi.
- Foil-faced plasterboard. Some converters use it on the sloping ceilings.
- Dormers and knee walls. The room is surrounded by insulated walls and roof on most sides.
- Stair position. The new stairs often arrive over the original landing, which is the one path WiFi could have used.
The result is a room lined with reflective material, a long way from the router, reached mostly through floors.
What does not work
- Moving the router to the back of the house. Often not possible, and it moves the dead zone to the front bedroom.
- A plug-in extender in the hallway. It repeats a weak signal at lower speed. See why WiFi is slow with fast broadband for why.
- A more expensive router. The walls and the distance are the same.
- Upgrading the broadband. The line is not the problem if the rooms near the router are fine.
A quick test tells you which problem you have. Run a speed test next to the router, then in the extension or loft. If the first is fine and the second is not, it is coverage. That is our job, not your provider’s.
Fixes that work
Mesh, when the path is clear
A mesh system can fix an extension if one node can sit with a clear line to both the router and the new room. In a through-lounge semi, a node in the back of the original living room can often reach the kitchen extension well.
It works less well when the only path is through the old back wall and the steel beam, or up two floors into a foil-lined loft. Each wireless hop loses speed. Is mesh WiFi worth it for homes goes into when it is enough.
A cable to an access point
The most reliable fix is a Cat6 cable from the router to a ceiling access point in the extension or the loft room. The cable carries the connection past the walls, beam and insulation. The access point then fills the new room with full-speed WiFi.
This is the same approach we use across whole houses. Why wired access points matter explains the difference in detail.
Wired mesh
If you already own a mesh kit, running a cable between the main unit and the extension node gives you most of the benefit of an access point. It turns a weak wireless link into a solid wired one.
Getting a cable to a finished room
People worry this means chasing walls. Usually it does not.
Extensions. We often go through the floor void under the original house, along skirting routes, or through the ceiling void of the extension from above. Where there is a loft over the original house, a route down an internal wall is common.
Loft conversions. The eaves spaces behind the knee walls are often reachable. Stacked cupboards give a vertical route. Existing pipe or cable runs can be followed.
We go through these in detail in adding Ethernet without ripping up the house. The guide to Cat5e vs Cat6 vs Cat6a covers which cable to use.
If the work has not started yet
The cheapest time to fix WiFi in an extension or loft is before the plaster goes on.
- Ask the builder or electrician to run Cat6 from the router position to a ceiling point in the new room
- Ask for a second cable to where a TV or desk will go
- Have the cables labelled and left long at both ends
- Keep a photo of the routes before they are boarded over
A cable at first fix costs very little. The same cable after decoration costs a visit. Data cabling explains what we can fit alongside your builder.
Local patterns we see
Windsor and Eton. Victorian and Edwardian terraces with long, narrow rear extensions and solid party walls. The router is at the front bay. A cabled access point in the extension ceiling is the usual fix. Listed and conservation properties add route constraints, which we plan around.
Maidenhead. Many 1930s semis with wrap-around and side-return extensions, plus loft conversions with dormers. Often we fit one access point for the extension and one for the loft room, both cabled from a small switch near the router.
Reading. Victorian terraces in areas such as Redlands, Katesgrove and Earley with rear kitchen extensions and full loft conversions. Three storeys, solid walls and a ground floor router at the front is the classic setup for a dead top floor.
Our pages for whole home WiFi in Windsor, Maidenhead and Reading cover each town in more detail. For older houses in general, see WiFi in Victorian and period homes.
Get it working
Send us a photo of the floor plan or a rough sketch, where the router sits, and a speed test from next to the router and from the new room. We will tell you whether mesh will do or whether it needs a cable, and quote before we book.
We cover Berkshire, Surrey and West London. Contact us or read more about whole home WiFi installation.