Garage refurb project - advice sought

newfhouse

Resolutely on topic
I have a tired old prefab detached garage that I need to fix up. It’s made of concrete panels slotted into concrete verticals with a bonded asbestos sheet roof to the rear and a short but steeper tiled front. I live on a slope so the rear of the garage is effectively buried the best part of a metre deep. It measures 5.9 m x 2.8 m.

The metal frame that held the bottom square has completely rotted away but nothing moves and I’m pretty confident it won’t. The steel frame that holds the roof up is surface rusty but not rotten so I expect I should be able to brush the worst off and Hammerite it.

I’m comfortable with removing the existing roof sheets and wrapping them for the council to take away. They should come off whole despite there being lengthwise cracks in a couple.

There are two windows, both rotten, and a wooden side door which is disintegrating from the bottom up. I’ve thought about replacing the windows if I can find suitable cheap replacements of the correct size to slot in. I’m less bothered about the side door and thinking of filling the gap with concrete panels. First question: does anyone know where I might be able to buy replacements? They are shaped to overlap top and bottom. I thought of buying concrete gravel boards and cutting to size but I don’t think I’m sufficiently skilled with a grinder to make a good job of the overlap.

The next question is about the roof. As I see it I could board it and then felt it, board and bitumen sheet, or use plastic coated corrugated steel sheet, with or without a board underneath. I should say that it would be useful to be able to walk on the roof when complete as I need to be able to cut back trees and ivy that are otherwise inaccessible. I’ve not used the steel sheet before. I see it comes in different gauges but is there anything I need to know? I intend to retile the front part of the roof, but I’m not sure how best to fix the ridge tiles at the transition from front to rear.

I’m not looking to spend a fortune on this but I do need it to be waterproof and look presentable. I had a quote of £2500 from a local builder which doesn’t feel like value for money as I could get a new prefab garage installed for not much more. If I could do the job myself with reasonable but not stellar DIY skills for less than £1000 I would be happy.

What does Team CC think?
 

Archie_tect

De Skieven Architek... aka Penfold + Horace
Location
Northumberland
When you say it is retaining up to a metre of ground... anything over 600mm [edit!] difference in level requires an engineered retaining wall... be very careful if the frame has rotted - what's holding the concrete panels in place? Might need a structural engineer to give you some advice [is there one on CC?]

The roof is the least of your worries, unless it is genuinely asbestos sheeting... in which case the Council will need to know before they collect it as disposing of it properly normally gets charged for.

Photos would help.
 
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bruce1530

Veteran
Location
Ayrshire
Asbestos - depends where you live. My own council have a "catch 22" system for disposal of "domestic" (ie non-trade) asbestos cement sheet. No charge. They won't uplift, but f it's double-bagged, they'll accept it at the main waste site and put it in the asbestos skip.
However, they also say that, while they'll accept domestic asbestos, you're not allowed to transport it there unless you're a licensed waste carrier. And that make it non-domestic..... :-)

In practice, I took some asbestos flue pipe there a few months ago, double bagged, no problem - the guy couldn't have been more helpful.
 
OP
newfhouse

newfhouse

Resolutely on topic
When you say it is retaining up to a metre of ground... anything over 650mm difference in level requires an engineered retaining wall... be very careful if the frame has rotted - what's holding the concrete panels in place?
I will have a proper measure tomorrow. It’s been there a long time and doesn’t look like it’s going anywhere.

asbestos sheeting... in which case the Council will need to know before they collect it as disposing of it properly normally gets charged for.
Asbestos - depends where you live.
My understanding is that the Corporation of London deals with hazardous waste for most of the London boroughs and will collect domestic quantities of asbestos cement sheets if double bagged.
https://www.croydon.gov.uk/sites/default/files/Asbestos-information2017.pdf

Photos would help.
I will post some tomorrow.
 

Archie_tect

De Skieven Architek... aka Penfold + Horace
Location
Northumberland
That's an incredibly generous service that London Boroughs provide and even more incredible that it's totally free to collect up to 15sq metres of asbestos sheeting!
 

Drago

Flouncing Nobber
Location
Poshshire
I'd be inclined to steer clear of bitumen sheet. In my experience it sags over a couple of years, no matter how many beams and purlins support it from below.

Box section galv steel is more expensive but is solid as a rock once fitted. I can highly recommend... www.cladco.co.uk

It cost me just under £500 for the 0.7mm box section sheet to do my 18 foot garage.

Good luck.
 

the snail

Guru
Location
Chippenham
I agree with drago, used steel for my shed, probaby you can reuse the supports from the cement roof, and it's quick and easy to install. I used the plastic coated sheets, still looks good as new. You'd have to use crawler boards to walk on it though.
 
Whenever I remove suspected asbestos I spray with diluted PVA to reduce dust. Use a quality mask and disposable overalls.
It wont hurt to do removal on a rainy day.

Are the wall concrete panels loaded with asbestos?
 
OP
newfhouse

newfhouse

Resolutely on topic
Box section galv steel is more expensive but is solid as a rock once fitted. I can highly recommend... www.cladco.co.uk
Thanks, that looks good.

I agree with drago, used steel for my shed, probaby you can reuse the supports from the cement roof, and it's quick and easy to install. I used the plastic coated sheets, still looks good as new. You'd have to use crawler boards to walk on it though.
I hope I can just drill and screw the sheets to the existing roof frame. Not sure if I need to use a timber batten between the new and the old metal. Point taken about using crawler boards, that would still allow access. The frame members are 33“ / 84 cm apart.

How is a metal roof with condensation? Does it need an underfelt?
 

Drago

Flouncing Nobber
Location
Poshshire
Thanks, that looks good.


I hope I can just drill and screw the sheets to the existing roof frame. Not sure if I need to use a timber batten between the new and the old metal. Point taken about using crawler boards, that would still allow access. The frame members are 33“ / 84 cm apart.

How is a metal roof with condensation? Does it need an underfelt?
That I don't know for sure. No condensation yet, but mine has only been up for the warmer months. I my case its a large, well ventilated area so im gooing my calculations are correct and won't have a problem, but you're wise to consider the matter.

You can pay an extra couple of quid and the sheets come with a dripstop backing.
 
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OP
newfhouse

newfhouse

Resolutely on topic
Hows this project coming along @newfhouse
I think I've settled on how I'm going to do it and I'm about to order the materials. Annual leave is booked for two weeks time so weather permitting I'm hoping to make good progress then.

The renovation of the house itself is substantially complete now, externally at least. Scaffolding is coming down tomorrow if my less than reliable contractors turn up as promised.
 
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