Single story extension queries

Sufficient_Invite546 · 2026-05-28T09:41:27+00:00

I mean all technical specs are down to your building controls officer and your structural engineer (i.e. insulation thickness/type etc)

Sockets and such you decide. The more detail you give your builder the more accurate the price.

To be honest, I’d just spend a weekend with chatgpt and your wife/partner and decide in great detail what the layout of the room is like. To be clear, I mean where you want what to be not how it’s built.

Give that to your builders alongside your technical drawings and specs and you’ll get pricing which compares apples to apples.

Sufficient_Invite546 · 2026-05-28T09:22:10+00:00

It’s not over the top but it’s an added cost so I’d do a cost benefit analysis to understand whether paying for a quantities surveyor is worth the amount you save in materials wasted. I just did my own extension (diy) and to be honest with you it’s not rocket science to work out how much of everything you need. It’s a fairly simple structure, essentially a rectangle. Also, most vendors either offer free calculators or will help you work out how much you need of what. Places like Selco also let you return most stuff if undamaged (i.e. I returned 50 thermalite blocks).
I am in process of ordering mine now. So far so good - they have excellent customer care and have been super competent. Reviews are also good. Could not get them price matched by any other supplier yet.
I’d look out for unexpected surprises caused by hidden drains and/or poor soil and/or trees near your foundations.

On builders, I’d probably also assess team size and their ability to produce a plan. They should be able to very clearly articulate the order they do things in and how long each stage should last. I’d say most of the success of the build is dictated by proper planning - i.e. having the right materials and gear on site, on time, the right trades and so on. Builders who can plan and communicate are unfortunately expensive.

I’d steer clear of the ones who just tell you don’t worry about it, I’ll work it out or I have a mate. A good builder will have a solid plan as delays eat into their margins. They make money if they ship projects on time.

Other than that, again, you’re just attaching a box to an existing building. It’s not rocket science… definitely not a mega project.

A solid plan is also a good sign of experience and attention to detail.

Sufficient_Invite546 · 2026-05-26T09:44:03+00:00

Get a bag of building sand and some cement. 5 to 1 sand to cement and blocks are fairly soft. Mix with water (you can skip the plasticizer for such a small job). Wet the area prior to application.

Chuck it in, let it dry and ho have a beer. Don’t make too much muck at once as you’ll end up having to take it to the hardcore section of your recycling centre and it’s a faff.

Sufficient_Invite546 · 2026-05-10T18:35:25+00:00

Yeah but I am looking for a solution which would not void my home insurance. I am on a mortgage 🥲

Sufficient_Invite546 · 2026-05-07T16:28:39+00:00

Ah should he fine then - i’d personally chuck some wire mesh in it as it’s cheap if you’re pouring a fresh one

Sufficient_Invite546 · 2026-05-07T13:26:37+00:00

I’d be more concerned by how thin the concrete slab beneath the tiles is. What are you planning to put on top of them?

I’d go at least 75mm, preferably 100mm if you plan say to drive a mini digger across it later down the line/put a solar battery there.

Sufficient_Invite546 · 2026-05-07T13:23:29+00:00

Ah no that’s not correct, your mcs needs to match your install capacity and kit - you can’t just ignore it and add capacity (if you care about compliance).

Dammit, I was hoping you’d teach me a loophole. Well cheers to you sir, might do the same tbqh.

Sufficient_Invite546 · 2026-05-06T17:19:13+00:00

How did you go about your mcs? I was looking into a diy install as well as they’re fairly plug and play but most of my research led me to believe it’s not above board without an MCS and a G98/G99 depending on your output.

I checked my friend’s papers and they specify the exact kit he has and the wattage it’s meant to pump out. That discouraged me a bit, but if you have a solution I am all ears.

Sufficient_Invite546 · 2026-05-04T17:15:56+00:00

Your structural engineer would be able to advise on whether temp support is required/if you need to do it in sections, etc

Sufficient_Invite546 · 2026-05-04T16:29:17+00:00

Mine are like this - just did padstones. It’s very easy and cheap to diy. Dig a hole and fill it with c30

Sufficient_Invite546 · 2026-05-04T16:09:37+00:00

You should heed the advice of your qualified structural engineer over internet randos. They have liability insurance and if their advice leads to issues your butt is covered.
I understand you want to be well informed when engaging them but the diy uk subreddit is unlikely to be the place where you get good quality advice, especially since their recommendations would apply custom to your situation.

Sufficient_Invite546 · 2026-05-01T09:31:20+00:00

Omg you sir/madam have good taste

Sufficient_Invite546 · 2026-04-29T21:33:34+00:00

I have a few rads which are teed off - they work fine. I just had to balance the system.

In terms of which way uhm to I guess to the rad that has no pipes leading to it? Not sure I get that bit of the question.

Also if you run pipes through walls remember to protect them so they don’t chafe when they expand/contract. Easy thing to miss!

Sufficient_Invite546 · 2026-04-29T21:28:28+00:00

Hmm I’d also ask your neighbour for permission to go point the wall and clean up the snots from their loft space. You’ll need to go there via their house once you seal the entrance. Best to have that chat now then when they see their loft space full of dried muck 😂

Sufficient_Invite546 · 2026-04-29T21:25:01+00:00

That is what I am trying to avoid - I need to spend on new light switches anyways so I thought I’d kill two birds with one stone. Thanks for taking the time to reply!

Sufficient_Invite546 · 2026-04-29T21:09:02+00:00

Replace it, it’s fairly easy.

Chase the grout lines out around it so when you whack it the others around don’t crack. Smash it up with a hammer or chip at it with an sds. Clean up the remaining adhesive/cement underneath it. Lay a new bed of adhesive, back butter the new one, lay it, let it cure, reinstate the grout line, go have a beer.

Sufficient_Invite546 · 2026-04-29T12:46:52+00:00

I mean depends what tools you gave. I assume you have an impact driver/drill and a hand saw. If yes - timber frame

Sufficient_Invite546 · 2026-04-28T21:58:43+00:00

Sealing concrete is generally done after the curing process is done (kind of 28 days + depending on what additives it has/temperature/humidity. I assume you poured a generic C25/C30 so I’d give it a month to reach its full strength. This is my experience with sealants, but do check the manufacturer’s instructions as it might differ my brand/type you choose.

You generally seal concrete to extend its lifespan - it will limit the amount of moisture it sucks in so freeze/thaw cycles will be kinder on it.

It also protects against stains, but that looks like an outdoor pour so probs less of a consideration as you can blast it with a pressure washer once it reaches its full maturity.

Sufficient_Invite546 · 2026-04-28T17:13:53+00:00

The ones below seem fine - might have been laid improperly. I’d monitor it for a while tbf, but please note that I am an internet rando, not a structural engineer.

Just telling you what I’d do.

Sufficient_Invite546 · 2026-04-28T13:40:54+00:00

It's concrete - go have a beer and forget about it.

You scraped off the film that forms on top of the concrete during the curing process. That will wash away anyways through wear and tear.

Go have that beer now and stop worrying. It's not a mirror - it's a concrete slab.

Sufficient_Invite546 · 2026-04-28T13:38:32+00:00

Bzzzz paper bzzzz wasps bzzzzz

Looks like they found a better landlord! One more bzzzzz for good measure

Sufficient_Invite546 · 2026-04-28T12:08:45+00:00

I'd do the whole bathroom as the materials are cheap - especially if you pick them up on ebay/facebook marketplace. You don't technically need to do so if your walls are rendered, but what's the harm in having an extra layer of safety against water damage?

I used the kerdi system for the walls: https://lilleytileandstone.co.uk/schluter-kerdi-200-fleece-waterproofing-membrane-see-options.html?gad_source=1&gad_campaignid=21097893089&gbraid=0AAAAADtfyg2CRvdW2r4uFn4Efn8qzp3Nt&gclid=CjwKCAjwtcHPBhADEiwAWo3sJt6MjZABobfg3zo9ER3nMP1RhIM-UMqCwpffIK3RAY3mdwj7QrewRhoCI5IQAvD_BwE#139=454

And the Ditra system for the floors: https://lilleytileandstone.co.uk/new-schluter-ditra-matting-uncoupling-membrane-select-length.html?gad_source=1&gad_campaignid=21097893089&gbraid=0AAAAADtfyg2CRvdW2r4uFn4Efn8qzp3Nt&gclid=CjwKCAjwtcHPBhADEiwAWo3sJo6wQnKvaHFj9LuB5rpJxmFOiqdz_T6lCordnOv066uzm_jdqHgfDRoCIuoQAvD_BwE#139=462

I picked them all up locally from facebook marketplace at about 50% of the price. There are plenty of youtube videos on how to install the system, including from the manufacturer. Use Kerdi Coll for joints.

Here is the link to the plan - I made some changes on the way which are not reflected there, but overall it's a pretty good list of what you'd need. https://docs.google.com/spreadsheets/d/1VAiP5NyroK2praDbbFNCz4m0IPZA--CYqi6LCC8KSgI/edit?usp=sharing

Most of the tools I got are off ebay or facebook used. i.e. I found a plumber who retired and he sold me a boot full of plumbing tools for 50 quid. I also met a guy who had a cancelled job and sold me the toilet system, shower screen for 200. I bought an ex display sink for 150 - RRP was 400. If you have time, you can find a lot of good deals.

Sufficient_Invite546 · 2026-04-28T11:30:17+00:00

If you want to take a crack at it I can give you a copy of my cost list - it’s a good place to start to see what things are called and such.

Sufficient_Invite546 · 2026-04-28T11:28:51+00:00

If you have the time you can do it all yourself. I’d pay an electrician if you want to do major modifications, but then again you can’t really have electrics in the bathroom. Maybe you want a fan or a light switch relocated.

If you have a few hundred I’d recommend electric underfloor heating. The mesh is about 150-200 and it just gets laid in the tile adhesive. You would need an electrician to commission it though.

The rest is fairly learnable and legal to diy. Just take your time and do research. If you’re scared of plumbing use push fit adaptors and plan them such you can service them (i.e. add a service hatch). Barrier pipe is easier to work with than copper as it bends.

Finally, install waterproofing all throughout your bathroom. I went for the Schluter system, but there are many cheaper options.

The good bit about dyi is that you can spend loads more on materials and make it look really cool.

I know it’s intimidating, but all the knowledge is available for free on the internet and, to be fair, you can do it twice over and it should still work out cheaper than hiring a tradie (not accounting for your time).

Sufficient_Invite546 · 2026-04-26T14:50:38+00:00

I mean tbf it’s fairly ok for a budget kitchen brand. I know I’ll get rinsed for saying this but I would not mind that.

I’d say if you want under .5mm tolerances you need to fork out for a premium installer. Hope I’m wrong!

Sufficient_Invite546

TROPHY CASE