Self build extension - people's opinion

Dylan97

I have had two qoutes so far from builders ranging from 80k plus for a builders finish, this is for a 20 square meter extension to the rear of the property, which has no access issues.No special design or anything, just an open plan room at 4x5m, with a sliding door to the rear.

I'm supplying the drawings from an architectural technician, and will be built as an exempt development.

I know materials are bad etc, the prices just seem so high.

I'm an avid DIYer but this would be the biggest task to date if I took this on, dug foundations, block work and hired trades in when required ( installing RSJ, plumbing, electric etc). I would be employing a structural engineer to hopefully certify works / and provide a cert or opinion of compliance.

What's people opinions? Any one have any experiences or advice they can share ?

Based on my experience, materials are maybe 25% of the cost of getting work done on the house. Obviously that varies depending on what you want done.

Also based on my experience, it should be possible to DIY the entire extension except for the trades— this is assuming that you can use a current window as the doorway and therefore avoid the need for an RSJ. There's no great magic to plumbing & electrics either, but electrics do need to be certified— depending on construction method, the sparks could inspect when done & connect up to the mains while fixing any errors you have made. Same for a plumber balancing radiators etc. No hint of an issue with any DIY foundations I've seen done (including my own) years later.

So you could probably save €40-60k of that quote by maxing out the DIY element.

BUT (huge & enormous but)

It's a hell of a lot of work. And you'll need to spend nearly as much time researching the methodology as actually working. And many of the learning resources contradict one another. And obviously you're taking a risk by betting on your own competency— you will make mistakes, hopefully they either won't be critical or they well be fixable.

On the other hand, not like there aren't sh1te contractors out there with no effective comeback on their crappy work— a DIYer who puts the time & effort into learning how to do things mostly right will do most of the work as well as most contractors in my opinion. But it will probably take four times as long, and may be much worse than an average contractor (you may be vastly over or under estimating your competence; I've done both on different aspects of the same jobs...).

No risk, no reward. Have a think about your risk appetite Vs potential rewards, and make a decision accordingly.

Dylan97

Totally agree. I don't beleieve I am under estimating the time at all, it's going to be several months to a year at least depending on how much time I take off also.

There's some shoddy tradesmen alright, but also some brilliant ones that are hard to find. I would hope to think that by doing what I can myself it would be to a good finish, again having the time to do things slow and correct is my approach. For exmaple, if it ttakes a week to lay a course of bricks so be it.

I've probaly put in over 50 hours of research on this, but still havnt got everything write on paper in terms of the whole process. Once I have the plan right I am going to get the foundations poured and block work up to dpc.

awec

https://www.boards.ie/discussion/comment/120040844#Comment_120040844

Don't forget to factor in how long the room you are extending will be unusable. Also how long is it not going to be water tight (i.e. how long until you've walls / roof and window / door in).

Doing an extension as a spare time project does not seem feasible to me, purely for practical reasons.

Rows Grower

Go for it, I did something very similar 20 years ago with practically no experience and no internet and it's still the best room in the house with regards to layout and holding heat. Use plenty insulation.

You could save even more money by buying used or factory seconds windows and sliding doors and build around them rather than leave a specific sized opening. It'll be a great project to get stuck into, go for it.

enricoh

I done something similar a few years back. 4x5m room is a fairly simple job imo, 4k a square metre is nuts but obviously what the market can bear.

I didn't bother with a structural engineer and had a fair bit of steel in mine, was 2 storey. I got an old retired builder neighbour to throw his eye on it- 2 minutes later I was going shopping for 8x4 n 10x5 rsjs. I was able to put field stone n red brick exterior and oak stairs etc in as I had saved enough dough with direct labour.

Gusser09

I think you are over egging your savings with all due respect. In my experience there is no way the builder is making 40-50k profit. He's probably seeing 15-20k at most. That seems like a lot but take into account tax etc.

Now it can be done. Self managed that is and remove his profit. But digging foundations yourself? What about when trades let you down? So you have the insulation and plasterer ready to go but the sparks hasnt shown up for first fix and the plumber has made a mess of something. Lads will soon get sick of amateur hour and not rerurn your calls. Also no shortage of work so it'll be hard to get lads too. You have zero comeback on their work.

What about removing drains and connecting new pipes to drainage? Not as easy as you think.

For example if you dont have the waste pipes installed correctly it will be to late to redo when you find out poo is backing up.

Just a few things to think about.

Doable but complicated.

scwazrh

80k for 20 Sqm straight forward extension is crazy money .Shop around and get a few more quotes .Under €60k is a realistic market price

Dylan97

https://www.boards.ie/discussion/comment/120046152#Comment_120046152

Yes I agree hundred percent. I'd have bricklayer and roofer lined up to minimise the time it is exposed. I wouldn't be planning to do everything myself

Dylan97

https://www.boards.ie/discussion/comment/120046223#Comment_120046223

Thanks appreciate it! Any pointers or tips that saved you a lot of time or avoid mistakes ?

Dylan97

https://www.boards.ie/discussion/comment/120046542#Comment_120046542

Most guys are quoting crazy money for smaller jobs, sometimes it's not worth their while. I have an electrician and plumber friend so no hassle on that.

I'm not sure why you think foundations would be complicated? I've done a few before for sheds and garages, its mainly labour intensive once you have everything planned out and level. A small digger and dumper and a spade, a few stakes or laser level and off you go.

If you can't put the plan together I don't think any one should be having a go at it, plus I'll be having a structural engineer sign off on all structural items ( Engineers ireland cert of compliance )

Dylan97

Yep and that was only for a builders finish. 80k for a shell. I'm not surprised as I know a few lads that are getting similar qoutes.

I know one guy who did it himself, managed it and got trades in when needed. Cost him 35k with electrics, plumbing and glazing. 20 square meter.

Some builders think people are stupid and will go ahead with these prices, yes materials have gone up, but the guys are charging nearly twice as much for labour in some cases as opposed to pre covid. I won't be feeling sorry for them when there is an abundance of workers once Intel and the other big objects are finished up.

Furze99

Basic domestic building work is not rocket science, but does take time and a bit of graft. It's the details that count and knowing where to be careful and get the detailing right. So as mentioned research is the key, look at buildings at similar stages of construction and ask if you have queries. Most tradespeople in my experience are more than happy to advise a DIYer when they see they are interested and getting stuck in. I did this when building sheds and extensions here - was often amazed when I looked at houses under construction. Everything from lovely neat work to downright shoddy stuff. Funny thing is when I saw the houses completed, the differences whilst still there are a lot less apparent. A good plasterer can hide a lot!!

Rows Grower

https://www.boards.ie/discussion/comment/120046704#Comment_120046704

Have a few measuring tapes and a couple of hammers/screwguns, a large barrell full of water and about two dozen pencils. Invest in proper work trousers that have pockets for knee pads. Shop around online for material prices obviously, the best tip I could give is tidy up the work area every evening before leaving. Not only important for health and safety but being able to put your hand on a tool when you need it is vital and it's just nice to come into a clean tidy work area the next time and appreciate what you have accomplished.

YouTube is unreal for helpful advice, enjoy doing it and best of luck.

A good point by awec about length of time the place will be in unusable while you're doing it— it you're doing it blockwork, it's probably not a big issue— make the extension weatherproof, and then break through the entrance from the main house (if you're not using an existing door/window). If you're planning timber frame, it's going to be an absolutely massive issue; you can easily leave blockwork exposed for a year or two, OSB not so much...

Gusser09 makes a fair point about the builder's margin on an €80k project— but if you're doing the blockwork, carpentry, and labour yourself you're saving a packet besides the contractor's margin— roofing can be done DIY also. Also good point about drains/sewer pipes though.

It's a point well made that a good plasterer hides a lot of mediocre work. Some things have to be right though, among them weatherproofing, foundations (and drainage if applicable). No point saving €40k by going DIY only to spend it fixing it.

Research research research: you can do it if you have time & motivation, but learn the right way before you do it not after.

Dylan97

https://www.boards.ie/discussion/comment/120047929#Comment_120047929

Thanks, very valid points on all of the above. Yes it will be built using 4 inch blocks, cavity wall with 100mm insulation.

I'm under no illusion how long this can take if I do take on a lot of the works. The roof is something I rather get trades in to do so I have that all planned out. Wall up, roof on, then knock out the existing wall.

Slow and steady will get me to the finish line

Padre_Pio

Trades are probably on 60-90k a year, so you're paying that kind of money in labour alone.

Add in tax and materials and you can see how the costs add up.

If it was me then I would DIY it, but I know what I'm capable enough. The most important step is preparation.

Write a step by step list of what needs to be done, then tick off the tasks when you're confident you can tackle them. Arrange you're tradesmen for those you're not confident with.

Don't break the weather tightness of your house until you have to, that's your point of no return. Best of luck!

iwillhtfu

Another alternative OP is to just project manage it yourself. You will find lads to do the donkey work (foundations,walls) then a carpenter for the roof although if not a difficult design this is relatively easy. I wouldn't worry about adjoining rooms if you don't plan on changing layout and plan on repurposing the opes that are in play already. You can knock through once you've the extension weather tight.

The only issue will be interest and stamina because it will be expensive/difficult to had over something half finished. There's plenty of one man bands that'll take on adhoc work just keep an eye on what they're doing and as with everything don't pat with large sums of money in advance.

It's definitely achievable either way. Also couldn'e agree more. €80k is just a stupid amount of money for a pristine finish never mind a builders finish.

Dylan97

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Dylan97

Thanks I have all of the above, probaly too many at this stage !!

Yes, youtube is a wealth of information, anything I'm not sure of that's where I go, or the to old Collins manual. I'm a mechanical engineer so the maths / trigonometry stuff is simple for an extension. Having a structural Engineer also sign off is good reassuranc

Dylan97

https://www.boards.ie/discussion/comment/120048079#Comment_120048079

Prep, prep and more prep is what I'm currently doing. The misses thinks I'm gone off my head.

Measure thrice cut once 😉

Thanks for the advice on the weather tightness and breaking through. I'll be taking the week off when getting the beam in and wall knocked out.

I will be either having some one do this or get enough acrows and needles and over engineer it enough so I have nothing to worry about ( I'll be asking the structural engineer to determine the load)

Dylan97

https://www.boards.ie/discussion/comment/120048091#Comment_120048091

That's what I intend to do, foundations, block work and most woodwork I'll do myself.

I'll get roofers in so they can get it up in a quick turn around, and assistance getting the beam in also.

The issue is people are paying 80 to 100k and I think its madness for what your getting. Although it will take me at least 4 to 5 times longer by doing and managing it myself, but I'm well aware the work it's going to take.

Padre_Pio

https://www.boards.ie/discussion/comment/120048197#Comment_120048197

So long as your happy your garden will be a building site for a year and your house will be a site for 2 or 3 months.

Best time of the year to start is now though. Days are only getting longer.

Dylan97

https://www.boards.ie/discussion/comment/120048573#Comment_120048573

Ye I have cones and fences set aside so everything is set up correctly. I'll have the site properly fenced off etc for health and safety

frankkkiiiie

Dylan97 - Did you end up moving ahead with this? Have been thinking of doing a self-build too.

Dylan97

https://www.boards.ie/discussion/comment/121829826#Comment_121829826

I did some and hired a local builder to help on other bits - but he was so slow and caused a lot of stress… there is a lot of work if your working full time, but it is doable.