Purlin supported by one brick?

[Somebody_on_Earth]

Hi.

I am buying a house which is a 1957 bungalow. It's a Hips roof and so there are 4 purlins. The longer purlins of the 4 are both supported by 2 corbels which are made up of about ~10 courses of bricks and seem to be about maybe 400-500mm wide. The weird thing is that the actual purlin is only supported by one brick. That brick has had a notch cut in it for the purlin to sit in.

I want to find out if anyone has seen it done this way before and is it OK? I thought it looked quite sketchy, and so did my surveyor, but I made the mistake of telling him my opinions of the house before he inspected it. I'm worried he is covering himself by agreeing with me in case there is a problem. I have searched the internet and can't find a picture of a purlin supported by a single brick like this. I am new to thinking about buildings though so maybe I didn't search in the right places. All 4 of the corbels are like this and then just have the single brick support.

Thanks for reading this. Any advice would be greatly appreciated.

 

[RandomGrinch]

I want to find out if anyone has seen it done this way before

Been like this since 1890. I'm not too concerned
...although this is a terraced house rather than a hipped roof bungalow.
What did the surveyor actually say about the supports?

 

[Somebody_on_Earth]

Thanks for your photo.

I looked up his Linkedin profile and he had only been a surveyor for 2 years after being a lettings manager, so I don't know how knowledgeable he is. I don't think he had seen anything like that before. But his report did seem comprehensive, professional, and well thought out. The issue which I didn't mention is that he thinks there has been roof spread. This is based on some internal light cracking in the upper walls and then one actual chunk of plaster about maybe 80mm by 40mm that has become dislodged slightly from an upper wall. The other clue about the house is that the bricks have been repointed with a dark mortar around most of the perimeter of the upper wall. It's the top 3 visible courses of bricks, with there being maybe a further 3-4 courses hidden by the soffits. Basically I had suggested to him that maybe they were trying to hide / fix something and I was suspicious of it. He came up with the idea that it is roof spread. I don't think there is actually visible bowing in any wall though so I am a bit uncertain about what is correct. I had essentially suggested to him that the single brick supports might have been a modification to brace the roof at the same time the darker top perimeter mortar was added. Possibly higher in concrete content to strengthen the upper wall. I have to admit to being new to building stuff though and I have just only in the last 3 months watched a ton of Youtube videos. So I fear I have affected his conclusion. The sellers claim there is no roof spread and they are unaware of a problem.

The other clue I have which the surveyor didn't know is that the owners before the current owners had cavity wall insulation retrofitted in 2005. I couldn't see any holes that had been filled in in any of the walls, and so I have wondered if they had repointed the top bricks as part of that process. I am afraid I have no idea what type of insulation it was. There is no documentation for it.

 

[Somebody_on_Earth]

Here is a picture of a section of the repointing. It is all around the front of the property, the left side and the back. It is not on the right side where there is a carport and a chimney.

The sellers surveyors claims the mortar at the top is a different colour because of shading and rain protection from the soffit. As you can see in the picture, on a sunny day in September this year more of the wall was shaded and there is a clear change in colour at one brick course and not a gradual change as you might expect if the colour change was caused by sun and rain.

What does everyone think? What should I make of my surveyors claim of roof spread, and the sellers surveyors claim of a bit of weather?

Thanks.

 

[ChrisJP]

The way the purlins are supported on just part bricks doesn't look very stable to me.
I'd be happier to see a full length brick doing the supporting, with it reduced in depth lengthwise if required, or any shortfall in thickness made up with something like slate packing

 

[Harry Bloomfield]

Here is a picture of a section of the repointing. It is all around the front of the property, the left side and the back. It is not on the right side where there is a carport and a chimney.

It looks to my eyes, as if the lower level has maybe been repointed, leaving the higher level not repointed.

Are photos 3 (with the vertical timber support) and 4 (with the one brick support), directly opposite each other? Both doing the same job, though by different means?

 

[Harry Bloomfield]

Been like this since 1890. I'm not too concerned

That looks like an over-lapped joint, between two sections of purlin?

 

[Dereekoo]

That looks like an over-lapped joint, between two sections of purlin?

Supported by about 40bricks and made of wood covered in dust?

 

[RandomGrinch]

That looks like an over-lapped joint, between two sections of purlin?

Apologies to OP - yes, two separate purlins, one is mine, one is the neighbours. It's how all the terraces around my way are built - open to each other.
I have since repointed the brickwork and built a firewall to next door... and vacuumed!

 

[Somebody_on_Earth]

It's a hips roof with 4 sides, with the bungalow having a simple rectangular floor plan. By drawing lines on the floor plan I estimate 2 purlins are 6 meters and the other 2 are 3.5meters. the longer 6 meter purlins are both supported by 2 corbels built up from the internal walls and then the purlin is resting on the single brick. So there are 4 corbels in total. The other shorter purlins are supported I think by maybe 1 piece of wood, but I'm not sure. Can't remember. The photographs only show one of the corbels, it's just it shows it from 2 different angles. All the other 3 are the same design. The photos were taken by the surveyor. I looked in the roof, but didn't take my own photos.

I spoke to 2 roofers, and they haven't seen the pictures, but they didn't seem to think the single brick thing was unusual for a 1950s house. I will not disturb these bricks but probably do something like build up some more bricks around them and pack it with 3:1 mortar and hope for the best. I might do some form of metal bracing/screws that fix the bricks I add to the wall, but that might be overkill? Not sure.

 

[Dereekoo]

It's a hips roof with 4 sides, with the bungalow having a simple rectangular floor plan. By drawing lines on the floor plan I estimate 2 purlins are 6 meters and the other 2 are 3.5meters. the longer 6 meter purlins are both supported by 2 corbels built up from the internal walls and then the purlin is resting on the single brick. So there are 4 corbels in total. The other shorter purlins are supported I think by maybe 1 piece of wood, but I'm not sure. Can't remember. The photographs only show one of the corbels, it's just it shows it from 2 different angles. All the other 3 are the same design. The photos were taken by the surveyor. I looked in the roof, but didn't take my own photos.

I spoke to 2 roofers, and they haven't seen the pictures, but they didn't seem to think the single brick thing was unusual for a 1950s house. I will not disturb these bricks but probably do something like build up some more bricks around them and pack it with 3:1 mortar and hope for the best. I might do some form of metal bracing/screws that fix the bricks I add to the wall, but that might be overkill? Not sure.

Build up some more bricks around the single brick for what purpose? The single brick takes the point load put on it from the purlin and then dissipates it downwards and outwards at a nominal 45 degrees to the bricks below it which then carry on dissipating the load downwards/outwards so on and so forth to the lower bricks till the edges of the pier contain any further dissipation. Surrounding the single brick with other bricks will do nothing to aid the load distribution. In theory you could have a single brick pier all the way down to the support wall if their crushing strength is large enough to take the load imposed on it from the purlin but, unfortunately, the slenderness of the support then comes into play and any load placed on the brick off centre brings eccentric forces into play which would cause the pier to bend/collapse hence the need to thicken the pier to take the load down to the supporting wall. Imagine if the supporting wall was one brick below the purlin, you would quite happily put one brick underneath it without thinking you need to surround this one brick with other bricks? If you look at your existing pier the greater dimension is orientated in the direction that any flexing force from the purlin is likely to occur as opposed to the shorter dimension that needs to resist forces that would occur due to the purlin trying to move sideways (along with the roof!!!) How the dimensions of the pier were originally designed is anyones guess and is probably based on "we have always done it like this and have never had any problems" which 60 years of use appears to back up.

 

[Somebody_on_Earth]

Yes that is true and you are right.

My concern is that the surveyor thinks there has been some roof spread or movement. I'm not sure he is right and I am getting a structural engineer so he can tell me what he thinks. I'm just imagining scenarios where the roof moves. But yeah thanks for your help.

 

[robinbanks]

"Purlin supported by one brick?"

I wouldn't worry too much about it; nearly every brick in every house in the country is supported by only one other brick, in total

 

[blup]

You could always add a strut if there is a suitable load bearing wall available. Surveyors are increasingly covering their backs because of insurance claims, so even tne slightest risk is highlighted. I came across one the other day which mentioned that the staircase creaked when they walked up it.