TV Aerials and Satellite Dishes Fixed to a Chimney Stack

Why the stack ends up carrying the aerial

A television aerial wants height and a clear line of sight, and the chimney is usually the tallest, most solid thing on the house. A bracket strapped or bolted to the stack gives a firm-looking fixing without needing a separate mast, so it has been the default choice for a long time. Satellite dishes are sometimes added to the same stack for the same reasons.

The trouble is that a chimney was built to carry its own weight and the weather, not an extra structure at its top. Every addition changes how the stack behaves in the wind, and the changes are not always obvious from below. A pole, a dish and a bracket together add weight, wind area and a lever arm, and the stack feels it at its weakest points.

It also matters that many aerials are put up by a different trade from the one who looks after the stack. The installer's priority is a good signal, not the long-term condition of the brickwork, and nobody is asked to think about what a bracket does to a joint ten winters later.

How loads and fixings work on the brickwork

There are two kinds of load. The first is dead weight, which is usually modest. The second is wind: a pole with an array or a dish catches the wind like a flag, and that force is passed into the brickwork through the bracket and its straps. Because it is applied high up, it bends the stack, and the straps act like a spanner on the joints.

Fixings add a second problem. Straps are tightened round the stack, and in time the brick expands and contracts while the metal does not follow, so the strap loosens, or digs into the brick and mortar. Bolts and expanding anchors drilled into a joint or a weakened brick can split the masonry when the fixing is loaded. Moisture then runs in beside the metal, rusts it, and the rust swells and opens the crack further.

Pots and flaunching are affected as well. A pole that is lashed through or beside the pots can rock them in their bed when the wind blows, and cracks in the flaunching near a bracket are an early sign of exactly that.

Cracks and loose joints to look for near brackets

From the ground, a few signs are worth noting. Look for rust trails running down the brick beneath a strap or bolt, for a bracket that has visibly shifted or tilted, and for joints near the fixing that have gone dark with damp or lost their pointing. Hairline cracks that radiate from a bolt hole, or that follow a bed joint from one strap to the next, suggest the brickwork is being worked by the load.

Inside, there may be no visible clue. But if damp stains appear on the chimney breast or in the loft below a stack that carries an aerial, the fixings may be letting rain in. Our guide to Damp on a Chimney Breast: Leak, Condensation or Salts? explains how to tell stack damp from other causes.

It is easy to assume that a bracket which has held for a long time must be fine. That is not always so. A fixing can look steady in calm weather and still be moving in a gale, and the damage tends to appear as a slow loosening rather than a sudden failure. Please do not climb or lean a ladder to test one; a picture from the ground is enough for a roofer to assess it.

Removal, repointing and making good

If the aerial or dish is no longer needed, or if the stack is being repaired, the usual approach is to take everything off properly before repair work begins. The pole, bracket and straps are removed, and any bolt holes and damaged joints are cut out and refilled in a mortar that suits the brick. Where a fixing has gone through lead, the flashing has to be corrected too, not simply sealed over.

Repointing around old fixings needs care. The mortar is raked out to a sensible depth, cleaned and filled in layers, and any cracked or loose bricks are replaced rather than packed with filler. Repointing a Chimney: Why the Mortar Mix Matters More Than the Finish explains the mortar choice. If the cracking is more than skin deep, a part rebuild may be wiser; Repoint, Rebuild or Remove? How the Decision Gets Made sets out how that decision is made.

Take photographs or ask your roofer to note where the fixings were, because the repair should deal with every hole and not only the obvious ones. We work on the outside of the stack in and around chimney repairs in Heswall, and we are fully insured.

If you want the aerial back: fixing it elsewhere

Reinstating an aerial is a separate decision, and it is worth thinking about it before the scaffold comes down. A wall bracket, a short mast fixed to the roof structure, or a mounting on a gable wall can often provide the same signal without putting load on the chimney. An aerial installer can advise on the signal; a roofer can advise on how to fix through or beside the roof without letting water in.

If the property is listed or in a conservation area, or the dish is on a wall facing the street, planning rules may apply. This is general information and not legal advice, so check with your local council before you decide. The same applies to rented or leasehold homes, where permission from the landlord or freeholder may be needed.

If the stack is going to be reduced or taken down to roof level, the aerial has to move in any case, and it is far easier to plan that at the quotation stage than to find out later. For disused flues, see also Capping a Flue You No Longer Use, and Why Sealing It Solid Causes Damp.